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1983 Summer - American Radio History

1. A TET 7 x JEI 2 25 ecironics sue 1983 SYNDLE The Electronic Candle that flickers like z a Wax Taper The magazine fzr people who Wy build electronic projects X MAKE PRO CABINETS ss for Home Brew Projects Build it for FUN ST Aad aiae E 3 Band Shortwave Converter Electronic Slot Machine Preamplifier for moving coil Phono Cartridge is Soundbox 80 for Computer Game Sounds Prototyping Power Supply See pag2 4 Test Gear Projects Ribbon Cable Tester Meg O Dapter for DVM Sn A DDI Mini Audio Generator Scope Calibrator Single Sweeper One Blanker Tl 71896 48784 CPLUS JBL Sound suse for the musician See page 4 sclder version s Als and rainbow in Brand New Low Cost tIDC A bly Tool and Cable So sensationally low priced it gine put a crimp n your budget A P has it all far you S Connectors pes E a y ea k Ais we T a i P kan A a 2 one ar bn a ea z p ai lt j ae ot 4 Re G T CIRCLE 801 CN FREE INFORMATION CARD OOO eee 7 chs The Magazine for people NY ho build electronic gadgets You made us believers Editors sit inivory palaces and conjure up ideas stories features and everything else that goes into magazines Far too often an editor will forget a
2. EVERY ISSUE OF SPECIAL PRO IF YOU RE THE KIND OF READER that doesn t want to wait you can order your next copy of Special Projects now Special Projects is crammed full of electronic projects that you won t be able to wait to build for yourself You can expect top notch digital projects fun to play electronic games valuable add on computer projects BCB and shortwave receivers photographic darkroom gadgets devices to improve your car s performance test equipment ideas and more in every jam packed issue of Special Projects TO HELP YOU TO BE SURE that you don t miss any future issues of Special Projects SUBSCRIPTIONS ARE NOW AVAILABLE E YOU CAN HAVE THE NEXT FOUR ISSUES of Special Projects delivered directly to your home for only 9 00 We pay the postage If you want the next eight issues you can even save a dollar off the newsstand price Get eight issues for 17 00 JECTS will continue to contain a variety of construction articles to suit every taste In addition feature articles on electronics fundamentals test equip ment and tools will round out each issue Of course we will continue to provide new product and literature listings to keep you up to date on the latest de velopments in electronic technology GET IN ON THE ACTION Order your next issue of Special Projects to day Use the convenient order coupon below CASH WITH ORDER ONLY SP 7 Allow 6 8 weeks for the first issue to arrive
3. LEGAL REQUIREMENTS techni cal specifications and how you the home constructor can meet them Find out what mechanical and elec tronics skills you need RECEIVER CHARACTERISTICS technical details and specifications ong with examples of actual re snars built at comparatively low cost ANTENNA DESIGN and x actly how you can build a spherical antenna while keeping total earth station cost for the complete system under 1 000 THE FRONT END is critical when you build your own system We help you explore several different ap Name ie Satellite TV Reprints Radis 45 East 17th Street Electronics senyor nY 10003 want dling amp Postage add sales tax reprints 7 00 each plus 1 Han jerseragaressy I have enclosed _ N Y State residents must City CIRCLE 824 ON FREE INFORMATION CARN Proaches to making one that will work for you M RECEIVER SYSTEM hardware and how it goes together to bring you di rect from satellite TV reception in your own nome To order your copy Complete coupon and enclose it with your check or money order for 7 00 plus 1 00 for postage and handling We will ship your reprint within 6 weeks of receipt of your order All others add 4 00 for postage New York State residents must add 58 sales tax State i g Zip 1 can be printed on an 8 inch line with um derline capability The user can se
4. clock The software always maintains a perfect 3 1 ratio at any speed That is ideal code By connecting a transistor to pin 36 of the CPP1 it is possible to turn on and off a relay connected to a transmitter Since IC3 is also connected a side tone is also available Conclusion The CPP Code Practice Processor is a very powerful tool for the person just starting to learn Morse code or for those who are trying to increase their speed Practicing 15 to 30 minutes a day is all that will be necessary to learn the Morse code However as with any learning experience to become really proficient there is no substitute for practice It is advisable to practice with the CPP then listen to an actual Amateurbands right away That will reinforce your learning experience At first only freshly memorized letters will be recognized but in a short period of time whole conversations will be copied with ease In no time you will be ready for your Radio Amateur license SP 1000uF 15VDC GND j OUTPUT 2 COMMON 3 INPUT 1 861 YAWANNS pa SPECIAL PROJECTS fe oO Here s a simple crystal oscillator count down circuit that helps you tune to the carrier with accuracy LES KUHN TUNING A DIGITAL DISPLAY RECEIVER FOR A STATION ON A known frequency is a simple operation Determining the exact frequency of an unknown station isn t necessarily that easy It is a test of operator skill to find the center of
5. Fp NO amp If you can buy it you can install it Shopping wise and installing it yourself may cut the radio s final cost in half Courtesy of Cadillac Cimarron 83 equipment Also some cars such as those from Chrysler require a special mounting bracket if the car wasn t sold with a radio Usually the special bracket was available from the same people that made the radio In a sense the aftermarket radios were truly universal because they came with mounting and trim hardware At the very worst the installer might have to purchase a special mounting bracket Today you get none of the special hardware with a univer sal radio The average person can t even get the mounting bracket if it s needed because most stores that sell this item are only wholesale or for the trade If you re stuck for a bracket or trim panel try a junk yard Generally they ll let you have either for acouple of dollars which is a lot less than you would pay a dealer for the item For example the final trim panel shown in the photographs was obtained for 1 from a local junkie In some junk yards you have to do the Stripping so bring your tools What you get OK Let s get on with an installation When you open the radio you ll find it s packaged with assorted mounting nuts perhaps a few screws knobs a strong metal strap a trim panel possibly some electrican s wire nuts for splic
6. High impedance voltmeter places more than 500 000 ohms between readable voltages as low as 2 millivolts and the meter expensive 0 1 milliampere meter connected to an op amp IC1 which raises the voltmeter s effective input impedance and offers the opportunity for amplifying low voltages in high impedance circuits The input impedance in this case is one million ohms With RI R2 Megohm l volt input gives volt output at pin 6 of IC With R4 adjusted for just under 2000 ohms then 2 volts input will give full scale deflection on the meter also only 2 microamperes are drawn from the circuit under tests That 2 microamperes could be cut down by making resistors R1 and R2 10 Megohms each but it really isn t necessary So far we have improved the loading characteristics of the basic meter We can take advantage of the op amp s gain by making R2 larger that R1 Resistors R1 R2 and R3 Fig 4 are lower in value which reduces the input impedance some what You may wish to make R5 larger and keep RI as a fixed value To roll your own SSSV you need to know that the gain of the system in Fig 4 is the ratio of R5 R1 That means that if R5 is 10 Megohms and R1 is 1 Megohm then 0 1 velt input gives Q volt output That is a practical but not theoretical limit for what is being done here The overall sensitivity of the SSSV may be increased by adjusting the basic meter for 0 2 volts That is done with the aid of S3 and
7. January 1982 not available LU How to Make PC Boards 2 00 Write in issues desired L All About Kits 7 2 00 Modern Electrics Vol 1 1 Parol 25 Aprii 1908 Wireless amp Electrical Cyclopedia at 4 95 To order any of the items indicated above check off the ones 1918 176 pp you want Complete the order form below include your pay ment check or money order DO NOT SEND CASH and mail ARTICLE to Radio Electronics Reprint Department 200 Park Ave South New York NY 10003 Please allow 4 6 weeks for li you need a copy of an article thal 1s In an issue we indicate 1s unavailable you can Order it directly from us We charge 50 PAGES per page Indicate the issue month amp year pages and article desired include payment in full plus shipping and handling gale ee Se each charge TOTAL PAGES TOTAL PRICE MAIL TO Radio Electronics SP 7 Reprint Department 200 Park Ave South New York NY 10003 All payments must be in U S funds Total price of order TR Sales Tax New York State Residents only Shipping amp Handling US amp Canada only includes FIRST CLASS POSTAGE 1 00 per item oes Alt other 2 00 per item sea mai NOR eye 4 CO Der item aiima vod ee a a a 2 4 beats Total Enclosed ES U a a a a ee ee a S Address ee ee ee State Zip CIRCLE 820 ON FREE INFORMATION CARD and comes with plastic carrying case velcro Square for attachmen
8. Several different products can be used for the panel mark ings In the golden age of construction 1950 1975 most hobbyists used the panel decals shown in photo 7 These were sheets of preprinted standard and not so standard panel markings titles legends and alphabets The user cut out the desired marking as shown in the photograph soaked the Strip in water until the paper backing floated free leaving the title on a strip of a gelatin like substance then placed the strip on the panel The excess water was squeezed out from under the strip with a cloth and when the strip dried the marking was permanently affixed to the panel Of all the various types of panel marking products it s the easiest to handle and apply The labels were sold under various brands throughout the U S The major supplier was G C Electron ics and Audiotex though there were many regional brands WHEN USING TRANSFER TYPE protect as much painted surface The stuff is still available from some electronics parts dis as is possible with paper shields Transfer type tends to come off when you don t want it and it s difficult to remove tributors a T 7 al A e palau mae 4 ratte A a vir Tor p A a SPECIAL PROJECTS wo AN EXTRA SHIELD has been positioned to cover the word Scope which pre ceeds Calibrator Protect any area that might be covered with the transfer type sheet as you add new mar
9. i Detach and mail today to Special SPECIAL PROJECTS Projects SUBSCRIPTION DEPT 200 PARK AVE SOUTH SUBSCRIPTION new york NY 10003 O want to be sure don t miss any issues Send me the next four issues of Special Projects for 9 00 starting with 8 Postage is free in U S For Canada add 3 00 Foreign add 7 00 want to be sure don t miss any issues and want to save 1 00 too Send me the next eight issues of Special Projects for 17 00 Starting with 8 Postage is free in U S For Canada add 6 00 Foreign add 14 00 D Send me __ ______copies of Speciat Projects 8 at 2 25 plus 1 00 postage and handling for US Canada and Mexico U S funds only All other countries add 2 00 r l l l l l i l i l I l l l l i l l i l i l l l I t t l l t l l l i l l I I I l t l l i l l l l l l l l l l I t I j Please print Name Street Address City State Zip oO an af Mla m m me Yd Sy ee s 861 YSAWWNS SPECIAL PROJECTS LETTERS RAVE REVIEW love your plans on building the 10 step 0 1 voltage calibrator Voltage Calib rator Special Projects 6 page 42 that have breadboarded from the plans you published found the unit to be rock stable when tried it out on my 6 digit F
10. l I l J2 0 FIG 6 SEEMS SCREWY to use an ohmmeter to calibrate a voltmeter but that s exactly the case The ohmmeter is used as a constant current source to provide a selectable scale deflection on the volmeter s HiGH range setting of S3 Then switch S3 is flipped to Low and adjustment is made See text for details MINI AUDIO JOHN PORTER Here s an one chip test gear project that s worth its weight in Herizs BUILT FOR USE IN TROUBLE SHOOTING AUDIO SYSTEMS THE simplicity and low cost of the Min Audio Generator should make it of interest to anyone involved in servicing audio and radio equipment Built around a single inexpensive inte grated chip this little generator will provide many of the functions found on instruments costing 20 times as much Contained in a 2 2 X 2 xX 4 inch aluminum chassis box the generator is capable of putting out a signal ranging from 2 Hz to 18 Khz at a strength of up te 0 volts peak to peak It will easily drive a speaker directly making it ideal for signal injection testing The circuit Uuilizmg only the VCO section of the 4046 chip the outpu frequency is controlled by the amount of voltage fed to pin 9 that being controlled by R1 See Fig 1 C1 and R2 determine the operating frequency range of the VCO Potentiometer R3 acts as a voltage divider to contro the amount of signal available al output jeck JI The syuarewave output will be rcunded off at the
11. universal they are anything but The photographs show the highlights of an in dash radio installation Universal what Before we proceed let s straighten out the word univer sal because most of the car radios are sold as either a universal or DIN type DIN simply means it will fit directly into the dash of European cars Europe has a standard for virtually everything It might also mean the radio of your choice won t fit at all It appears that given any two measure ments the Europeans will use the most difficult and ex pensive size as a standard On the other hand the term universal generally means the distance between the two sets of controls volume tone tuning etc can be adjusted Nothing else other than the shafts are guaranteed to fit into your car s mounting holes The term universal came about this way Up until a few years ago aftermarket radios generally were packaged with an assortment of hardware and front panel accessories specifically matched to a particular car At worst the in staller could use some of the supplied panel accessories such as filler panels to make it appear the radio was factory PENCIL POINTS TO the clamp and chassis holes that permit the control shaft spacing to be easily and rapidly adjusted for your particular dashboard Clamp should not be discarded It is the only truly universal part of a universal radio u Ma Lu F Q x a lt Lu a
12. Inc P O Box 27038 Denver CO 80227 Price is 29 95 plus 1 50 for handling anc UPS shipping Price for printed circuit board only is 10 00 plus 1 50 Master Card and VISA orders may be called in to 1 303 781 1589 or 1 303 781 5750 FIG 2 SAME SIZE FOIL PATTERN simplifies the planning of a circuit board or wire wrap hookup when running But alkaline batteries are expensive the price of a single set will almost pay for a 9 volt battery eliminator rated about 250 mA that will handle the power require ments at no further cost Construction The Electronic Slot Machine is assembled on a 5 16 X 76 inch printed circuit board Any type of copper clad board can be used The foil pattern see Fig 2 1s more or less wide open so there are no special mounting problems as long as you use a soldering iron with a pencil tip rated at 25 to 60 watts Take careful note that potentiometers P and P2 are the subminiature type while P3 is the miniature type If the potentiometers you use are another size make certain you modify the printed circuit board s template If you purchase the kit from the source given in the Parts List the supplied potentiometers will match the PC foil s pattern All component holes in the printed circuit board except for switch PB can be made with a 58 or a 56 bit A string SOME SOLID STATE DEVICES used for the Electronic Slot Ma chine are CMOS types which are very sensitive to static electric ity Th
13. No not when the design is made to eliminate extra crystals and special switches Here are three squarewave reference voltages that can also serve as the calibration test signal for your oscilloscope s low capacity input probe H DAVID HERMAN A LABORATORY OSCILLOSCOPE WITH ALL THE BELLS AND WHIS tles is probably high on the wish list of every electronics hobbyist and experimenter Unfortunately they don t come cheap and many of us must make do with a general purpose scape from the old days But even if your scope ts the original Heathkit 0 1 with a variable vertical sensitivity there s no reason you can t en joy the modern advantages of a calibrated input sensitivity and a properly adjusted low capacity probe All you need is a pre type oscilloscope calibrator such as you might find in the latest lab scopes and you can build just such a device mostly with parts from your junkbox Virtually every modern scope with a calibrated input also includes a calibrator a square wave signal output of known PC BOARD misne by su 2 z tS P ji Wvevr Orr Ot pwet f aa precise voltage amplitude To check the calibration of the scope s input the user touches the test probe to the calibrator test point or output jack If the CRT doesn t display the correct reading the user simply tweaks the vertical gain adjustment until the CRT display is correct For example assume that the oscilloscope calibrator
14. but nice to see PNT ACTIVE HIGH TTL J1 R4 C 12 274 SWEEP GATE OUTPUT 100K y B Q1 te 2N2222 OPTIONAL 2N3904 R6 SPECIAL PROJECTS P HA FIG 7 SO YOU ARE DEALING WIT4 high level sweep and Ssweep gate circuits Here s how you can cope with the high levels and still use the circuit in Fig 4 SEE TEXT INPUT 5VDC FROM S1 ON REGULATED SV OC C1 C3 REGULATED 100 4 POWER SUPPLY IC4 7805 5V REG QUT INPUT FROM 12VI9C BATTERY ELIMINATOR trol the blanking amplifier on the deflection circuit board additional AND or NAND gates may be used to take control of the blanking amplifier Now virtually any scope where you can pick off the sweep time base and which has Z axis control intensity modulation and or blanking can be modified for single sweep blanking control with the Single Sweeper One And we ve only covered a few specific cases here however with a working knowledge of how your particular oscilloscope operates the circuit in Fig 4 can generally be modified to work Power option You could either outboard a 5 volt DC supply that is regulated or pump in approximately 12 volt DC from a plug in battery eliminator and install a regulated 5 volt DC circuit within the unit Additionally you could use a 9 to 2 volt DC battery pack with the regulator circuit Refer to Fig 8 for the schematic diagram The parts for that circuit addition have foil leads and holes provided
15. came up on an unusual tool cabinet Item A mar keted by Concept 2001 Inc that gave him visions of a tidy workbench at home where the tools he used most often would always be in reach He dug into his pocket and made the purchase on the spot that s in pulse buying When I saw the tool cabinet I experienced impulse larceny However the best I could do was borrow the unit for the cover shot of this issue of Special Projects The photo reveals that decorative wash able plastic tool cabinet with an assortment of brackets and clips holding all sorts of tools many of which you ll recognize Should you care to obtain more information on the Concept 2001 cabinets and accessor ies circle number 872 on the Postage Paid Free Information Card bound in the back of this issue OK industries Inc was kind enough to loan to us their model SA 3 Temperature Controlled Soldering System Item G Ht looks like something that NASA designed and works as well as their space shuttles so I decided to use it on this issue s cover A fingertip control on the SA 3 permits accu rate and useful temperature regulation of the soldering tip whereby the experimenter has the required heat necessary to solder IC s onto boards and remove 14 solid copper wire from chassis ground lugs Now the need for more than one soldering iron on the bench or the dangerous replacement of hot screw in soldering tips has been elimin ated What I like best a
16. has an outside diameter of Ys inch TI is cemented to the circuit board with five minute epoxy glue The high pass filter coils are self Supporting and are close wound using No 22 magnet wire A quarter inch drill bit shank is used as a winding form A drop of airplane glue will keep the coils of LI and L2 in place Testing Check your wiring carefully before powering up the unit Check the operation of the crystal oscillator by monitoring the current in the positive 2 volt lead to the converter The current reading should dip from about 14 mA to about 8 mA when a crystal is plugged into its socket Be sure S1 is set correctly The dip indicates that the oscillator is working You could monitor each crystal frequency with a calibrated receiver to check the oscillator operation and frequency accuracy Tuning the bands All you have to do now is to switch to the proper crystal TRE HIGH PASS FILTER BOARD ASSEMBLY mounts those corr ponents used to eliminate as much of the broadcast band sig nals as possible without attenuating the shortwave fre quencies designed to pass through the converter to the AM auto receiver One single screw mounts the board on the chas sis Be sure to place lockwash ers on the screw between the board and the chassis to pre vent the board from rotating Use two nuts as spacers to eliminate the possibility of a short circuit between the flea clip terminal tie points and the metallic chassis M
17. mount directly to the board Refer to Fig 3 Begin construction by installing all required jumpers on the PC board including J2 if the switch is to be omitted Follow by mounting the diodes resistors and capacitors observing polarity where important Note that some resistors are mounted vertically to conserve space The IC s should be mounted last along with trimmer R13 and the fuse clips Four wires may be connected to facilitate connecting the completed board to the battery and charger jack with a fifth wire required if it is desired to mount I external to the assembly The board can be mounted on standoffs or held in place by double sided foam tape The latter method is often used by manufacturers of smal circuit board accessories that are designed to be mounted in commercial communications equipment where a wide varety of installation variations may be encountered Dress it up The electronics completed the builder must ponder the nature of the enclosure used to house Syndle Such enclo sures may be as simple as a plexiglass pyramid build around the circuit board or as ornate as desired The author chose to PEEK INSIDE THE BASE of Syndie and you ll see the printed circuilt board mounted on two brass standoffs leaving room to mount or stuff the batteries too Be sure to tape all exposed metal parts on the batteries to avoid an accidental short circuit The foam pad glued to the inside base cover at right presses against
18. s output is a 400 mV peak to peak square wave signal If the vertical input is set to 100 mV per vertical division the display height should be precisely four divisions 100 mV X 4 400 mV peak to peak If the CRT display isn t pre cisely four divisions the user can adjust the vartable gain control on the scope if there is one or the vertical calibration adjustment until the display height is correct From then on the CRT vertical graticule is precisely cali brated If the user switches to the x 10 range each division would represent four volts and so on for each setting of the vertical input sensitivity selector range If your oscilloscope is a basic model with only a con tinuously variable gain adjustment oscilloscope calibration can be somewhat difficult if the calibrator has only one Output voltage That problem is avoided by the Scope Cali brator shown in the photographs because it has three outputs 0 05 0 5 and 5 0 volts peak to peak Also instead of a 60 or 120 Hz test frequency the calibration frequency is the professional value of approximately 1000 Hz which permits precise adjustment of low capacity test probes To explain Low capacity probes must be adjusted to match the specific scope with which they re used Generally THE ASSEMBLED PRINTED CIRCUIT BOARD just fits in side the specified aluminum chassis box The connecting wires between the printed circuit board and the output terminals J1 J4 are sold
19. the power wire etc To use the wire nuts you must cut and strip the existing wires This has produced many heartaches for installers who found the wires were too short FOLD THE PLASTIC HINGE over and squeeze the Quick connect with pliers to drive the metal gizmo through the wires insulation Since everything is encased in plastic you can make the power connection while power is on if necessary but don t do it Q am m D h Te oe N nn SPECIAL PROJECTS N mH THE CIGARETTE LIGHTER power wire or the vehicle s original radio power wire is a good place to splice in radio s power wire Should you make a mistake Quick connect comes apart easily tape the original wire where the gizmo cut through the insulation too fragile or whatever A more secure and easy to use connector is something called a Quick connect or Scotch lok the plastic device shown in the photos The beauty of the Quick connect is that it s fully insulated and you can make a Splice with power on the circuit The device is a sort Of plastic dual tunnel with a small metal gizmo in the center and a hinged plastic cover You place the wire to be tapped in one tunnel insert the connecting wire in the other tunnel fold the plastic cover and squeeze with pliers thereby driving the metal gizmo into the pair of wires where it pierces the insulation when making the connection without cutting the wires This device work
20. 000 ohm R3 2200 ohm R4 5600 ohm terminals is at 12 volts DC Turn the ignition switch off before making any connections to the automobile The project s Vin wire will plug into that terminal The output wire from the project will plug into the remaining terminal The third and last wire from the project is a ground and may be connected to any metal part common to the negative terminal of the battery support braces etc Make sure the device is mounted so that the transistor cases and heat sinks for Q5 Q8 don t touch any metal parts in the car If they do you blow the 12 volt fuse to the turn signal line Atter the project has been installed turn on the turn signals and make sure that all the car s signal lamps operate properly Set the frequency and volume of the turn signal on warn ing tone by adjusting RS and K7 respectively If you wish to change the flasher speed the values of R and R2 must be changed on the workbench and not in the car The formulas to do that are listed in Table A With the values of RI and R2 shown in the schematic diagram Fig 1 the flasher speed TABLE A ELECTRONIC FLASHER TIME CONSTANTS Time for one cycle in seconds 685 R1 2R2 C3 Turn lamps on in seconds 685 R1 R2 C3 Turn lamps off in seconds 685 R2 C3 Where R1 and R2 are in Megchms and C3 is in microFarads Example When R1 is 33K and R2 is 100K and C3 is 4 7 pF Then R1 033 Megohms R2 100 Megohms C3 4 7 pF
21. 75 C RADIO CONTROL FOR BEGINNERS 4 50 C ART OF PRO GRAMMING THE tK ZX81 5 00 How to use Ihe fealures of the 2X81 in programs that fit the 1K machine and are still fun to use C INTRODUCTION TO BASIC PRO GRAMMING TECH NIQUES 5 00 Based on author s own experi ence in learning BASIC and helping others to learn to program C A MICROPROCES SOR PRIMER 4 50 Painless approach to computing for the be ginner Step by slep explains compuler op erations and assembly C ELECTRONIC PROJECTS FOR BE GINNERS 5 00 C ELECTRONIC MUSIC amp CREATIVE TAPE RECORDING 5 00 C ELECTRONIC SECURITY DEVICES 5 00 O HOW TO BUILD YOUR OWN SOLID STATE OSCILLO SCOPE 5 00 C SECOND BOOK OF CMOS IC PRO JECTS 4 25 C PRACTICAL CON STRUCTION OF PRE AMPS TONE CON TROLS FILTERS AND ATTENUATORS 3 75 C BEGINNERS GUIDE TO DIGITAL TECHNIQUES 3 75 0 ELECTRONIC HOUSEHOLD PRO JECTS 4 50 C ELECTRONIC MUSIC PROJECTS C FIRST BOOK OF HI FI SPEAKER EN CLOSURES 4 50 J SOLID STATE NOVELTY CIRCUITS 3 50 L 28 TESTED TRAN SISTOR PROJECTS 4 25 O SOLID STATE SHORTWAVE RE CEIVERS FOR BE GINNERS 4 50 O 50 PROJECTS US ING IC CA 3130 4 50 C 50 CMOS IC PRO JECTS 4 50 O HOW TO BUILD ADVANCED SHORT WAVE RECEIVERS 5 00 C BEGINNERS GUIDE TO BUILDING ELECTRONIC PRO JECTS 5 00 ESSENTIAL THEORY FOR THE EL
22. IC ER eaeN bes we Ee A rt THE SOUNDBOX 80 looks like a haven gt for roosting integrated circuit chips Sockets are used to mount the IC s Make up your mind before you pur chase the sockets as to the technique for wiring the unit Wire wrapping is best and calls for special sockets If you prefer to interconnect and solder wire wrap sockets with their long posts may still be a good idea you could always Snip off the excess lengths after the unit is wired The plastic box is a garden variety that s available almost everywhere You may prefer a sturdier plastic box that most experimenters can buy at local elec tronics parts stores 3 579545 MHz xi ig IC2 FIG 4 HERE S A HANDY CLOCK CIRCUIT that filis the bill for Soundbox 80 and just about any TTL and CMOS circuit requiring clock pulses in the megaHertz s Since the 4013 is a dual inte grated circuit unit you may want to divide again to reduce the More information on the operation of the programmable sound generator is available in the AY 3 8910 data manual as well as a more detailed explanation of the logic required The circuit may be built on a circuit board or wire wrapped Using Soundbox 80 The programmable sound generator ICI can be easily accessed from a BASIC program The sequence for shipping data to one of the chip s registers is show in Table 2 Note that each time the data is to be transferred to or from a Cee ee ee ee L
23. Pilot Light blinks That friendly colorful wink from LED you pick the color could be enough of a reminder to save you the loss of perfectly good batteries and the use of valuable equipment when you need them most SP PARTS LIST FOR EXTRA LOW POWER PILOT LIGHT C1 G2 47 nF S0 WVDE disc or tubular capacitor LED1 Light emitting diode your choice a eaor do Q1 Q2 N3904 2N2222 ECG123 or most any suit able replacement types of NPN general purpose low power transistor Ai 180 000 chm 4 watt composition resistor R2 18 000 ta 22 000 chm Yee wwettt composition fe sistor AS8 17 to 4 7 Megohm s walt composition resistor A4 470 4o 620 ohm va watt composition resistor N te Resistors may be either 20 10 or 5 toler ance Perfboard or portoersiecul board materials wee 31 coment solder hardware ete i THE FIRST STEP IN ACQUIRING AN AMATEUR RADIO LICENSE IS learning the Morse code For some people that is but a stepping stone to an exciting world of global com munications To others it is a Step into quicksand and they go no farther Learning Morse code by traditional means can be more of a frustration than an enjoyable experience It s hard to find dedicated partners with whom to practice Using cassettes and records is irritating because of the time consumed search ing fora particular practice group In addition one s concen tration is constantly interr
24. R sti leek PA a L l i i PUSH RELEASE 1C1 a PIN 6 0 AND IC1b PIN 11 0 J Fa nR 7 l IC1 b PIN 9 0 AND IC1 b PIN 12 D ne g EN RANDOM SCOPE TRIGGER SLI Uti a SS A gy at bh T INTERNAL SCoPE SCOPE SWEEP GATE I gt i SIGNALS IRAMP SCOPE SWEEP RAMP NE RETRACE i SUPE SMEER HO LOGER U rp FIG 5 TYPICAL TIMING DIAGRAM for a triggered oscilloscope with a single sweep IC2 b PIN 8 Q AND IC1 b PIN 13 R RESET IC1 b blanking circuit Take the time to fully un SINGLE SWEEP UNBLANKING Din IC2 b PIN 9 0 AND 1C2 a PIN 1 R Wy at iC2 a PIN 6 AND 1C2 b PIN 13 R 1 mini box and plugged or switched in circuit as in Fig 1 In the case of scopes like the Tektronix T 921 T922 with a TTL active high and active low sweep gate IC U2234D pin I and IC U2234A pin 3 respectively the blanking circuit in Fig 4 could be switched in when needed requiring no input pre conditioning However in other scopes using TTL logic on the sweep time base and or horizontal ampli tier boards those signals can generally be located by reter ring to a schematic diagram or user manual Also a 5V signal into the Z axis Input on the Back of this particular scope will cause a noticeable decrease in intensity where the maximum Input 1s 50 volts Theretore a low level input into the Z axis with front panel intensity adjustment might be used or a voltage translauion circuit with output level adjus
25. Two independent tuning CIRCLE 821 ON FREE INFORMATION CARD contrals are provided for selecting the sub carrier channel desired in the range of 5 5MHz to 8 0MHz A selectable IF filter al lows reception of high fidelity programming with low distortion For tuning favorite stations easily four in dependently pre set positions may be selected using the PROGRAM Switch Popular Sub carrier frequencies have been pre programmed at the factory on all four of those positions The TUNE position on the switch allows the user to select alternate sub Carriers The model 6740 has a suggested retail price of 359 00 Channel Master Divi sion of Avnet Inc Ellenville NY 12428 VIDEO SWITCH model VS 6004 provides an inexpensive way to control all TV or Video signal sources connected to a TV set from one convenient location By simply flipping a switch up to four signal sources may be attached to a TV set and two to a VCR View ers will have easy access to off the air or cable programs video games VCR s Videodiscs satellite receivers or home com puters at their fingertips The model VS 6004 also allows the viewer to monitor and edit programs being recorded ona VCR or copied from one VCR to another High isolation switching circuits reduce in et 3 is yt Cae we Be aes eae rate E a eg Beam AR hcg Bros iw CIRCLE 822 ON FREE INFORMATION CARD Oe teraction between Signal sources and pre vent inter
26. after cleaning and drying Three different model multimeters were tried requiring from 660 to 780 volts DC This was the open circuit voltage after zeroing The first multimeter model was calibrated in Megohms multiplied by three the second calibrated in Megohms divided by two and the third calibrated directly in Megohms All models were accurate over the entire scale with center scale readings of 15 Megohms and full scale reading of 2000 Megohms The Meg O Dapter must be calibrated for each model but requires only one calibrating resistor All capacators excluding electrolytic types should show an almost infinite leakage resistance within their rated voltage With the ZERO control on the Meg O Dapter adjust able from zero to 1000 volts DC any selected voltage may be used Resistance readings at reduced voltages will be incorrect but this is not important for insulation leakage tests This handy little box permits your direct reading of Megohms from the face of your DC voltmeter 86 YAWWNS d on SPECIAL PROJECTS D THE MEG O DAPTER IS A COMPACT UNIT Removing some screws and lifting the front cover reveals the two circuit board low voltage and high voltage Box sides have slots to hold printed circuit boards in place Small capacitors even below 50 pF will show a charge kick on the meter All capacitance which includes wiring motor windings etc can store high charges when there are no leakage
27. are subsequently fed to a phono preamplifier and to the tone control and power amplifier stages Over the last few years however there has been renewed interest in another type of cartridge the moving coil car tridge Some dedicated hi fi enthusiasts claim that the mov ing coil cartridge offers advantages in terms of transient response frequency response and phase response at high frequencies Whether or not those claims are valid is a matter for some argument suffice to say that we do not intend to enter the debate here So how does a moving coil cartridge differ from a moving magnet type The answer is that the positions of the coils and magnets are reversed although the principle of operation remains essentially the same In the moving coil cartridge the magnet is held stationary while two miniature coils are mounted on the cantilever assembly and move as the stylus tracks the groove hence the name moving coil Since the coils are attached to the cantilever they must be kept extremely small to keep the tip mass to a minimum As a result the output level of a moving coil cartridge is extremely low typically around 200 uV That is around 27 dB below the output level of a moving magnet cartridge which is typically around 5 mV or more Because the output of a moving coil cartridge is so low considerable voltage gain is required before the signal is fed Original project appeared in Electronics Australia Au
28. as to conform to the parts supplier s nomenclature When the button is released the tone will sound if you hit a winner Like the mechanical slots the Electronic Slot Machine can tease Two digits can lock while the third one rolls in The tone might sound for an instant as if you have won but then it ceases as the third display rolls to a loser Alternately you might lose only to have the third display roll in as a winner And typical of the mechanical slots you can more or less program whether a winner will come up frequently rarely or almost never It just takes a bit of playing withthe adjustments and we ll tell you more when we get to the final alignment Though the project can be powered by a 9 volt battery see Fig 1 its total operating life isn t all that much Normally two parallel connected alkaline batteries are suggested but even they don t provide extended life That s because the project idles at about 100 mA and consumes almost 250 mA 2 86 YAaWWNS SPECIAL PROJECTS J FIG 1 SCHEMATIC DIAGRAM fof the Electronic Slot Machine gives the reader a clue as to the complexity of the printed circuit foil pattern PARTS LIST FOR ELECTRONIC SLOT MACHINE SEMICONDUCTORS D1 D6 1N4454 silicon switching diode DISP1 DISP3 MAN74 light emitting diode display IC1 IC2 555 timer integrated circuit IC3 IC7 4023 triple 3 input NAND gate integrated circuit LED Light emitting diode j
29. certain the leads are in the correct holes Make certain that D is installed with the correct polarity the anode end connects to ground the cathode end the one marked with a black band connects to Q3 s collector None of the resistors and capacitors need be precision tolerance the only thing really critical in the project is the output voltage which is determined by DI see Fig 2 The Squarewave output however probably won t be symmetrical or close to symmetrical if C1 and C2 aren t matched and they won t be matched because Mylar capacitor tolerance is very broad If you re fussy and you want squarewaves to look like squarewaves trim the value of either CI or C2 by connecting a rest 0 01 mF capacitor in parallel with one or the other Tack solder the test capacitor to the foil side If it makes the condition worse move the test ex i bo he ae A We EG THE BUSINESS END of the completed Scope Calibrator It s only necessary to touch the scope s probe to the test terminal when calibrating the vertical input hence any kind of terminal can be sub stituted for the multi way binding posts J1 J3 gt jo Y be erereth erent Capacitor to the other circuit capacitor for example if you connected the test capacitor across C move it to C2 A few tries should give you a reasonably symmetrical output wave form For example the waveform shown attained using very cheap Mylar
30. conducting That configuration provides an alternating on and off warning tone only when the turn signals are on C2 pin 9 ts the turn signal lamp flasher output which is zan nected to IC3 an LM339 quad voltage comparator at its inverting inputs pins 4 6 8 and 0 Resistors R8 and R9 form a voltage divider that provides a 2 5 volt reference to the non inverting inputs of IC3 pins 5 7 9 and 1 In that configuration C3 inverts the input signal from IC2 pin 9 IC3 also splits the input signal into four outputs and ccnverts the TTL input levels to the voltage levels needed by the output transistors to turn the signal lamps fully on and off O and 12 VDC The outputs from IC3 pins 1 2 13 and 14 D1 1N4003 12V 5V REGULATEO LEN FRON i BATTERY SEE TEXT AUTO FRAME 6 EOUNO R4 VOLTAGE A 5 6K C5 COMPARATOR 49 01 LM339 R5 55 1MEG C4 01 R13 1 5K EMITTER 3 RASE 283906 COLLECTOR SPKR Doci 01 04 ae 2N3906 3 2W3055 TAIL EMITTER LIGHTS p SEE COLLECTOR TEXT g r BAND 3 1C2 O Ore iC1 996 7805 gt ME ano bare i ak CATHODE _ 14 Saag 05 08 1 1 3 p 01 02 IC3 2N3055 COMMON 1N4003 LMI FIG 1 SCHEMATIC DIAGRAM FOR THE ELECTFONIC FLASHER uses several semiconductors pact aged in five different type cases or moldings The dual 56 timer IC2 determine the turn signa on and off periods Circuit constants determire exact periods as siated in Table A The quaz voltage com
31. finds both shorts and opens in Cables and does it with nothing more fancy than a 6 3 volt transformer six LEDs four diodes and four resistors Further all the parts are available from your nearby electron ICS parts store How it works The secondary winding of T1 refer to the diagram pro vides a voltage that is rectified by D1 D2 D3 and D4 sa that four voltages VI V1 2 and V2 are pro duced The voltages actually provide two pairs of voltages and two independent current loops Those voltages are wired to one side of a connector P1 which is attached to the ribbon cable under test A dummy connector P2 attaches to the other end of the cable under test so that not one of the four voltages is adjacent to itself in the cable Thus by tracing the voltages shown in four different colors through the cable and associated connectors P1 and P2 the following will occur If all wires in the cable are continuous LED and LED will light And since the voltages VI and V2 are 180 out of phase LEDI and LED2 will alternately light at a 60 hertz rate which to the eye appears as a steady light However if the wires in one current loop or the other is not continuous LED or LED2 will fail to light indicating an open loop as opposed to closed loops Further which may not be obvious a short between any two adjacent wires in cable under test will form an alternating current path between the two current loops mentioned
32. functioning of reader bulit projects based upon or from plans or information published in this magazine 861 YANWNS SPECIAL PROJECTS ecjal Volume 1 No 7 DIGITAL sj ge04 SYSTEM Are your TRS 80 computer game programs as quiet as electrons hitting the monitor s screen Well here is a gadget that ll interface with your com puter and add sounds as you shoot down aliens Here s the benchtop project for you It delivers 5 volts DC that s rock stable has a LED bar cur rent monitor two logic probe cir cuits and 12 clock frequencies from 0 01 to 170K Hertz 34 ait A EA oe RIBBON CABLE MOCO 980 naa ee P SINGLE TESTER PREAMPLIFIER 9 SWEEPER ONE That new flat ribbon cable may look real good but somewhere in one of the end connectors or in between may lurk a shor or open circuit that ll put your computer on hold Our gadget tests the biggest of cables 51 MINI AUDIO GENERATOR We tout this one chip test gear project as one that s worth its weight in Hertz s It can dever from 2 to 18 000 Hertz with an Output up to 10 volts peak to peak And it goes together fas ter than you can imagine Is your golden oldie oscilloscope lacking a built in single sweep blanking circuit Then have we got a winner for you All that the old scope need have is a gate or ramp output and a Z axis input and away you ga Have you been staying away from mo
33. graphics capability is based ona single IC CRT display controller and time Sharing of main memory between the CPU and the video display controller That pro vides faster access to screen memory by permitting it to be anywhere in the 12 amp K main memory High resolution graphics is pro vided via a 640 x 312 pixels display Two versions of the Vector 4 are available the 4 20 with two 54 inch 630K floppy disk drives priced at 4495 and the 4 30 with a Single 630K floppy and a 5 inch 5 mega byte Winchester drive priced at 5995 Both versions use Vector s proprietary Dualmode disk controller which has automatic error de tection and correction circuits Vector Graphic Inc 500 N Ventu Park Road Thousand Oaks CA 91320 SP 7 m J p SS oe lim oe 7 a2 y _ or meti n le a ar i a SYNDLE The Electronic Candle that fickers like r a A a Wax Taper 4 z SS ae Tg magamne oO poopie who See bikia procs Build it for FUN Band Shortwave Converter Bectronic Stot Machine Rreamplifier for moving coil Phono Cartridge Soundbox 80 for Computer Game Sounds Prototyping Power Supply for HomeBrew Projects ingle Sweeper One Blanker JBL Sound System for the musician Subscribe Today MAKE PRO CABINETS INTRODUCING OUR NEW SUBSCRIPTION OFFER Become a Charter Member Subscriber Get every issue SUBSCRIBE TODAY Use the order form below
34. has traversed one half the remaining distance to the radar source As each indicator illuminates the au dible beep becomes faster and faster When the last indicator illuminates the sound is Steady warning that the radar source is near The Bearfinder Quest receives both X and K band signals from all types of radar includ ing moving and hand held pulse types it is designed for installation on the sunvisor or on the dash of a motor vehicle The small com pact case is just 5 inches wide 1 inches high and 4 inches deep is made of extruded aluminum and weighs approximately one pound It is available only from the factory REPRINT BOOKSTORE C Build Your Own Satellite TV Receiver 7 00 LJ Radio Electronics back issues 1981 3 50 C 8 Ball Satellite TV Antenna 5 00 March December 1981 nat available C Build Your Own Robot 12 00 Write in issues desired _ TV Descrambler January February 1981 3 00 l C Video Entertainment January 1982 2 00 J Special Projects Winter 1980 4 00 C Your Own Computer October 1981 300 LJ Special Projects Spring 1981 4 00 Radio Electronics back issues 1963 3 00 H Special Projects 4 Summer 1982 400 January February 1983 not available Special Projects 5 Winter 1983 3 00 Write in issues desired Special Projects 6 Spring 1983 3 00 _ Radio Electronics back issues 1982 3 00 H Radio Electronics Annual 1983 2 50
35. how to assemble your own multi lead cables in cluding those very expensive pre assembled ribbon jobs with the greatest of ease SUPER SENSITIVE SIMPLE VOLTMETER Did you ever think that you could measure the voltage on ing the receiver s circuit action This test circuit can do it and let you read as low as 2 millivolts THREE BAND SHORTWAVE CONVERTER Pull in the hottest shortwave bands 49 41 and 31 meters plus U S time station WWV with this all FET tunable converter 455 kHz BEAT FREQUENCY OSCILLATOR Crystal controlied count down circuit helps you tune to the carrier with accuracy providing BCB listeners with a new tool f CONTENTS INDEX TEST EQUIPMENT PROJECTS 9 Digital Prototyping System for bench top Experimenters 32 Ribbon Cable Tester 42 Single Sweeper One step up your oscilloscope 48 Super Sensitive Simple Voltmeter 51 Mini Audio Generator for all sound systems 75 Meg O Dapter checks out insulation resistance 83 Scope Calibrator PROJECTS FOR THE FUN OF IT 20 Soundbox 80 add sound to TRS 80 games 24 Custon Sound for Your Car 61 Syndle the Electronic Candle 69 Electronic Slot Machine 98 455 kHz Beat Frequency Oscillator COMPUTER PROJECTS 28 Make Your Own Computer Cables 54 Retrofitting the Sinclair Timex Computer for a Standard video output 93 CPP1 Code Practice Processor for new and stepping up Hams PROJECTS YOU CAN T P
36. in spacers wire etc that is done in the lower cast probes by adjusting a smal trimmer capacitor for a perfectly square CRT display In the more expensive probes such as those from Tektronix the barre of the probe itself is the capacitor adjustment and 1s rotated for optimum squarewave form A properly adjustec probe will produce the CRT display shown in A of Fig the actual Output of the Scope Calibrator project If the probe s capacity is set too low there will be an overshoot of the leading edge of the waveform as illustrated in B of Fig 1 If the probe s capacity is set too high it will attenuate the high frequencies illustrated in C of Fig bya rounding of the squarewave signal s leading edge While it s possible to get in the ballpark with a 60 or 120 Hz squarewave calibration signal derived from the powerline more convenient and precise adjustment is attained from a 1000 Hz waveform the usual calibration frequency of lab grade scopes The output frequency of the Scope Calibrator shown in the schematic diagram and photos is 1000 Hz How accurate The project is intended to be primarily a junkbox special and most component parts typically found lying around will be close to the specified output values For example the 5 volt output will actually be nominally 4 8 volts If you adjust the scope s sensitivity so that the outer edges of the trace is 5 volts peak to peak the graticule will be acc
37. in a plastic candle sleeve which is designed to slip over a standard light socket Make your connections inside the socket to the lamp and circuit board mounted in the base of the brass lamp fixture Neatness counts for impact when unit is completed Here are Hy a lou ae design Husky ant n is particularly lead guii a F ai na 4 le oS E ae et Fs ils for scially u sicians att project se with pyboards _ E Ps g h R Tni ET ae T ae Se Teg r NEVILLE WILLIAMS WHEN THE LADY OF THE HOUSE WANTS TO DUST UNDER THE rafters what do you do You lift the roof That may be easy to do provided you are a musician and have need for a 30C watt home made loudspeaker enclosure To help you out with the housework and your musical performance we are providing the complete plans for the Just Blast Loudspeaker System or as we call it for short JBL System As a matter of fact the JBL System uses the JBL E130 bass middle range driver which has a continuous power rating of 300 watts and a sensitivity of 105 dB The optional treble driver packs solid oomph also but more on that later The E130 is fitted with a metal cap over the voice coil which sustains the response to a nominal 6 kHz JBL says that it is commonly used on its own for lead guitar vocals and keyboards Where there is a requirement for a more prominent upper register one or more separate tweeter loudspeakers can be used But
38. input A semi transparent black grille cloth provides the necessary professional lock finish while giving a hint of the hefty JBL drivers behind The final job is to fit and wire the loudspeaker or speak ers In the case of a single E130 leads need to be run from the terminals to whatever output connection is required on the rear of the enclosure It is conventional in music circles to use a standard 4 inch phone socket connecting the red plus speaker terminal so that it will connect to the tip and the black terminal to the shank of the input plug Where a high frequency driver is used as well that will have to be interconnected along with its splitter or crossover network In the prototype unit black wires run to the respec tive speakers negative terminals a white wire to the high frequency driver plus and a red wire to the E130 plus For those planning to build their own enclosures the lumber oddments and finishing materials would have to come from the usual lumber supply sources Right now we do not know of any pre cut panel kits for the particular JBL system described here JBL loudspeakers can be obtained from or ordered through JBL dealers in the United States and Canada For specifications and data write to Professional Division JBL Sound Inc 8500 Balboa Boulevard North ridge California 91329 SP Three sevens is a winner and you will win for sure when you finish wiring this enjoyable game BY LARRY GLEN
39. jack J2 should be polarized to avoid accidental voltage rever sal Otherwise poof go the IC s AUDIO FIG 3 THE AUDIO OUTPUT CIRCUIT pro FROM duces up to one watt of audio power That is too much for the small speaker built into Soundbox 80 Keep the volume setting down to avoid damage to the speaker If you wish the LM386 can power a heavy duty speaker externally connected or to Spare the ears of those around you con nect a headphone ground pins of ICI through IC 10 circuits if the noise is still a problem and can be heard on the output of the audio ampli fier pin 5 of IC8 Fig 3 The power supply plugs into the unit via J1 The audio output of the programmable sound generator IC can be used to feed an external amplifier or the circuit of Fig 3 may be used as a one watt internal amplifier for Soundbox 80 The potentiometer R4 is used as the volume control and the output of the LM386 is fed through the 470 uF capacitor to an 8 ohm speaker IC1 PINS 3 4 38 SEE FIG 1 N C1 2200uF 3 5V TO FIGS 1 3 AND 4 p D1 D4 T 1N4004 RE In Fig 4 a standard 3 579545 MHz color burst crystal X1 is used as the basis of the oscillator circuit The 4011 CMOS NAND gates IC9 are used to develop the 3 579545 MHz frequency and IC10 a 4013 CMOS dual D flip flop IC10 is used to divide the clock frequency by two te 1 7897725 MHz That is within the 1 2 MHz range required by the PSG circuit in
40. leading edge somewhat at the higher frequencies The strong output is parthy due to C2 which charges up o ore kalf of the cycle only te discharge on the second helf adding its charge to the COVER OFF VIEW OF THE MINI AUDID GENERATOR reveals a miniature circuit board which mounts the IC and several other small circuit parts pulse coming from the L C That makes it possible to obtain a 10 volt peak to peak signal although the generator is only powered by a 9 volt battery Of course that amount of signal is only available with very light loading The 4045 was chosen because it doesn t require a dual voltage power supply nor does it need a regulated supply Also CMOS chips draw less power than TTL chips con tributing to battery life The reason why RI is not calibrated in the Mini Audio Generator is that output frequency varies as the battery ages That could be eliminated by adding a 7 5 volt DC regulator ato een a OO ee Te ee ae a r ee Z 4 K LEDI Ja i C1 sF Ra L G0 AFE 4702 H FIG 1 PHASED LOCKED LOOP CHI 4046 is the heart of the Mini Audio Generator CAP CAP However only the voltage cantrolled oscil ae ke PRET vco i lator VCO section is used Enough soup ma Mm i comes out of the chip fo power a small 500K iL cp cag a ea 4 loudspeaker although the intent of the cir ale LW GND INH i La a hey OUTPUT cuit design is to provide a signal for injec eyo R3
41. makes a turn or lane change Those can be very dangerous situations The solid state turn signal Electronic Flasher described in this article has none of the disadvantages mentioned above The flashing speed of the unit wil not change unless the input voltage drops below about 7 volts in which case the car will not start anyway nor would it run in all probability The circuit will drive from to 7 signal lamps per side which makes it ideal for trailer towing or add on lamps for vans It also provides a warning tone when the turn signals are on instead of the sometimes inaudible clicking Turn signal flashing speed and the frequency and volume of the warning tone may be adjusted to suit your particular taste The circuit is designed to replace two terminal turn signal flashers only which are used in abcut 90 percent of the cars on the road today The Electronic Flasher cannot be used in cars with 6 volt electrical systems or in cars with a positive ground both of which were not used in most cars after the 1950 s The Electronic Flasher also should not be used to replace 4 way emergency flashers because parts of the circuit are on whenever voltage is applied iz ea a About the circuit Voltage regulation for the circuit is provided by 5 volr regulator chip ICI Diode DI helps protect the circum against reverse voltage spikes generated by turning off in ductive devices such as starter motors and alternator kick back
42. markings to avoid overlaps Planning ahead makes for a better project iS iS 2 NEA os 1 feet alll he Ss Lae Oe Py 7 i u wOTtice Tt t NOT QrERA ING nt ALL BANC c y OFF Tris EQUIPE 4 HIGH FREQUENT HANDS Axum METER Me RECEIVER ADJUSTMENT nee mCRP ns juste DNE RUTOMATY MODE MIC MOO ices o t oa ATOMal aie S be ANL ee mute NORMA o i amni fet o ATu RADIO Ai MOX M on THE ref H T Gi Anos ansus tmar peos a oT Rene gan ne anes AU no osc ora i PY se ANALOG snay FFAPON maori AF un AMPER y BANDSET TGV TRLOAD Ot Sen Toe ano HO BEFERENCE ht AN ents AMPS nose a CILATO AUR pane saunas REGHVER a iar oA BANDS NCE BAL a ate smany ainaty sock samme SEM AUR epetan og pab MONES fam Spun rt i Caina non x sranpay SAHS 5 power ny a int BUFFER Day PHONE OF s CHANNELS CHAN CHAN SIII SHUNT sean ano PASS p omi OA WEA MA eatin aps Ase cowvanTag Cst SPARE sunTRaCi or oppak UPER a cenit CONVENT PASTS AETA v9 Somruran aaO Fora sanh pp Lowe nveRten co t COMMON eec UV A 1tO st PANEL MARKING DECALS are complete phrases EROU pataki Ea rose reas CATAN Y SNI COMS e EN cots wog i 2 MO vest rape f st ice G et ge eet em characters or letters on a gelatin base You cut out Guseeinmial avi oa wom woso wom Pomme Camon COUP Ri a ie DIGNA OIGITeL paum Fener zero greo COUPLING 5 the marking you need soak it in water to float off M S o n 678 Ovings civ ose Cw c the paper backing and transfer to the
43. most of the components for this circuit Board size is critical should you use the Pomona case specified Should you use a different size case you may want to resort to a perfboard or wire wrap techniques it s up to you Megohms times 3 One model produced readings in Megohms divided by 2 After adjusting the ZERO control to read the precision resistor value short the input leads and adjust R13 for a zero meter reading on the ohms scale If meter fails to reach zero reduce the value of R11 and R12 Should the meter go beyond zero increase the vaues of R11 and R12 These values are not critical as long as R13 is in adjustment range It will be necessary to repeat this several times Accuracy will depend on the calibration resistors and the meter itself With the VOM calibrated open circuit voltages can be selected Connect the microampmeter to the test jumper and set ZERO control R4 for the desired current For example 3 3 microamps through the 30 Megohm bleed resistors would equal 100 volts with the input open Now short the input leads and record meter readings in Megohms This can be done for any value selected up to and including the zero set point As mentioned above resistance readings will be in correct but are not important for insulation tests FIG 4 PARTS LOCATION DETAILS for both circuit boards Note that the boards are electrically isolated except RE am i DOE for common transformer T1 and switch S1 All
44. of WWV is on 1500 kHz For indoor use an antenna of 25 foot wire strung about a room along the ceiling is good enough If too long an antenna is used without an external tuner you may begin to receive unwanted local broadcast signals depending on your loca tion For automobile use tie into the car s AM radio s an tenna An unloaded full lengfh CB antenna will serve very well A 12 volt power supply with a one ampere capability works fine to supply voltage to the auto receiver and the converter for indoor use Here s a tip The crystal socket used was an octal tube socket out of the junkbox Otherwise you ll have to buy crystal sockets Capacitor C6 is one section of a 3 gang 350 pF per section varlable capacitor sold by Poly Paks for about 1 00 The series circuit of CS and C6 makes a maximum value of 105 pF That system was used to save money and space Any 100 pF variable capacitor may be substituted THE COMPLETELY ASSEMBLED Shortwave Converter illus trated here fits neatly inside a 54 x 3x 2 inch aluminum box On the 49 meter and 31 meter bands the local oscillator frequency is subtracted from the higher shortwave frequency producing an AM band signa that increases with station fre quency On the 41 meter band the oscillator frequency is higher than the shortwave signat producing a mixed signal on the AM band that is flipped as the shortwave station fre quency increases the AM tuning diat setting is decreased Unusual
45. of the cabinet Note that a ground lug is installed under the mounting screw The lug is generally supplied with the jack when purchased STANDARD MONTOR STANDARD MONTOR III 4421731111111111 fo Dob bt dd od od ad ed rd Dd Bed dt pH TL LLL a alg Pee eales Lakako AITEITE NPETE DDDDDIDIDDIDDDDDDDDIDIDD d D 4 D D c z z 9 2 An ARO STANDARD MO a PIPETTE ppan papapa papa ba pa pn y amp 11 2 Bs Bs isskourr ke oe He OsBweBecwnwes By mu 2 Bo Ee a efs Bo BF eBGeBtams Ba Et E oge Bx Bc ay Be Bn Bu E E in addition to the normal TV broadcast output all that s needed is a bridge connection across the computer s video at the input to the TV module By routing the low impedance video output to a standard phono jack the output cable sup plied with the computer can be used for either the low Z video or TV outputs No hassle retrofit The actual modifications to the computer aren t difficult to do and the photographs show how it s done without damage to the computer First step is to open the computer s cabinet which is easy 86l YAWANNS Sz Sz SPECIAL PROJECTS on mH if you know about the old hidden screw trick shown in Fig 2 Flip the computer over on its keyboard On the bottom of the computer you I see two screws and four rubber mount ing pads that are used as anti scratch feet Three of the pads concea
46. order and to make your own cable at a Savings of at least 23 you simply crimp connectors conventionally to both ends of a length of ribbon cable and the whole thing works In most instances cables for modems being the exception ordinary ribbon cable is the best thing to use Though connectors tor ribbon cable are the easiest to install they are also the easiest to damage or completely foul up and you usually don t get two chances with ribbon connectors Unlike solder type connectors with some form of channeled terminals ribbon connectors have nasty little razor sharp knives euphemistically called insulation dis placement terminals The connector itself has at least two components possibly three the main body a pressure bar that secures the wires and possibly an orientation bar that guides the wire out of the connector straight up straight down or out the back The main body which is usually a plastic material has V shaped razor sharp terminals moulded into the body The ribbon wire is placed on top of the terminals and the plastic bar is placed over the wire When the bar 1s squashed down by squeezing the connector ina vise the wire 1s forced down on the V knives The knives simultaneously pierce the wires insulation When the bar is fully seated each wire 1s sitting at the base of the V shaped terminal with plastic insulation between the terminals There is no difficulty in assembling a
47. previously So when a short of that nature takes place one or more of LED3 through LEDO will light Going further The diagram features a 32 conductor cable assembly and It might seem that only even numbered cable assemblies the most common can actually be tested using this testing de vice However the procedure can readily be extended to larger or smaller cables and you can test both even and odd numbered cables The simplest and most flexible method to test all of the cables mentioned above is use a modular IC breadboard socket or experimenter s PC board as opposed to actually That new flat ribbon cable may look OK to the eye but hidden shorts and open circuits will put your computer on hold and put you in a straightjacket hardwiring sockets Then a wide variety of cable assemblies and types can be tested allowing quick reconfiguration for various units And as far as testing odd numbered conductor cables goes it s a simple matter to test 48 lines of a 49 wire cable and pull the cables or plugs shift them over one space or so and pick up the oddball wire Further using that shift procedure it s possible to test cable assemblies which are larger than your test jig is set up to handle Construction hints You may use fixed plugs at the ends of the cable assem blies but that limits flexibility and requires a lot of setup time when testing cables of varying numbers of conductors Fixed test jigs are re
48. relate to the power supply battery check circuit in Fig 2 THIS INSIDE VIEW is slightly different from the other photo because of the addition of a metallic shield within the metal case The added shielding will greatly reduce noise pickup a common fault with many low level high gain preamplifiers signal This was exactly the measured result on the finished protvpe One point which also emerges is that the base noise cur rent is well below the other noise sources Hence we could have increased the collector current of Q1 Q2 and thus re duced the emitter base voltage noise considerably If we use the formula for optimum collector current for lowest noise we find that the current is around 20 mA which is much greaier than the 3 mA we chose We did that for two reasons however lower distortion and lower power consumption Power for the unit is obtained from six 5 volt D size batteries See Fig 2 A battery check function is provided consisting of a front panel light emitting diode LED 220 ohm resistor R12 and 5 6 V Zener diode D1 When the front panel switch S1 IS set tO BATTERY CHECK power is applied to the circuit If the battery voltage exceeds the 5 6 V drop across the Zener and the 1 6 V drop across LED 7 2 VDC then LED will turn on If LED glows very feebly or not at all a new battery is required ADDING A REGULATED SUPPLY You may decide to power the MoCo Preampli fier with a regulated DC power s
49. require alteration of the charging circuit however to insure that they receive the proper current Putting it together Construction is not critical as there are no high frequen cies involved and perfboard wirewrap and printed circuit board construction methods are acceptable Following the C7 220 pf 12 WVDC electrolytic C8 1 uf 100 WVDC Mylar ADDITIONAL PARTS AND MATERIALS B1i 6 VDC 1 2 AH NiCd battery F1 25 A 3AG fuse l1 No 1850 lamp bulb see text Ji Miniature open circuit jack P1 Minature plug to mate with J1 S1 SPST miniature toggle switch T1 117 VAC pri to 12 6 VAC 250mA transformer Jimpak AC and NiCd power versions type AC250 or equivalent Printed circuit board materials fuse clips 2 socket for l1 wire mounting hardware enclosure hardware solder etc The following are available from Hiawatha Electron ics Inc P O Box 442 Winona MN 55987 Circuit board and all parts which mount on board 24 95 postpaid USA Circuit board only 9 00 postpaid USA Please include applicable state and local sales taxes PC board pattern shown in Fig 2 results in a neat functional project and greatly reduces the chance of a wiring error I can be mounted directly to the board if desired by using a PC board socket or may be remotely located to facilitate mounting the electronics in prefabricated housings All other components with the exception of Bl SI and J
50. resistors R8 and RY See Fig 4 Although the op amp is still delivering volt to its output terminal it has to deliver a little more current than before The additional current drain is well within its capabilities R7 IC1 i B2 2 3 THE FLIP TOP COVER of the card file box makes for easy assem bly of the SSSV With the heavy components on the cover the unit is a bit top heavy You may want to mount a burned out transformer in the bottom of the light top heavy plastic case to reduce the tip ability and increase the heft ability The net result of that last maneuver is a meter with six ranges covering 50 millivolt to 2 volt full scale and an input impedance of at least 500 000 ohms As little as 2 millivolts may be read on the lowest range of SSSV That makes it a handy null indicator for Wheatstone bridges and other DC nulling devices Putting it together The cabinet for the SSSV is a4 X 6 inch plastic card file box Use a plastic case unless your meter states that it is calibrated for use on steel panels If all you are going to make is the amplifier part and use it with an existing voltmeter then the smaller 3 X 5 inch card file box will be big enough Most of the smaller parts were mounted on a piece of surplus perfboard That in turn was hung on the back of the meter movement as shown in the photo Of course we re talking about wiring up the schematic diagram in Fig 4 The meter switches bindi
51. ribbon connector If you take your time The wire must be trimmed straight across and a large scissors beats most other kinds of cutter Then the wire must be positioned precisely over the ter minals and held in place while the bar is positioned and the first pressure is applied If the wire drifts out of position you can end up with some V knife terminals cutting through a few wires a short or two or some open connections If possible just force the bar down by hand to hold it in position then place the whole connector in a small vise as shown in the photograph and close the vise until the bar ts completely seated It s a lifetime connection so don t attempt to salvage a used or detective ribbon connector because it usually won t work One of the terminals is bound to get bent askew and won t seat around its wire you J connect everything together and then spend hours troubleshooting inoperative equipment If you re lucky the other end will take a matching ribbon connector or if it s a different connector it will use the exact same wire order If you re unlucky which ts more than likely the wires on the other end won t be in the same order What you must do is use a cable type connector which was initially intended for multi wire round cable the stuff with which we re usually familiar Cable type connectors usually have solder terminals 86t HIWWNS Ga i SPECIAL PROJECTS Q3 N though some
52. s CRT After a one sweep cycle the negative trailing edge of the sweep ramp or sweep gate fires the one shot which resets the flip flap via its clock input And the flip flop holds the scope s CRT blanked once again until the next manual reset However EXTERNAL BUFFERED SWEEP RAMP OR SWEEP GATE SCOPE OUTPUT MANUAL FIG 1 MOST MARGINAL single sweep RESET mbane MANUAL blanking designs are based on scopes with O O RESET an external buffered sweep gate or ram L ODEBOUNCE Pg Pp 5V i isda GATE R gt N SWEEP RAMP outputs and Z axis In the drawing at left E y the scope s CRT is held blanked via its Z MOOULATION axis by the flip flop s Q or Q outputs De pressing the RESET sets the flip flop and un blanks the scope s CRT After one sweep cycle the negative trailing edge of sweep ramp or sweep gate fires the one shot flip flop which resets the flip flop via its clock input with J tied low the flip flop hoids the scope s CRT blanked once again until the next RESET However that scheme works when the scope s ramp generator is being triggered only occasionally otherwise the asynchronous reset causes partial display and lock problems This design cannot be used with free running synced scopes end it s sensitive to ramp or gate rates VOLTAGE _ TRANSLATION IF NECESSARY nn Here s a sweet acting single sweep blanking circuit packaged to cope with the limitations of yo
53. that firm and may be damaged doing a task they are not designed tc do for your hands a tool or even a screw for the strap In some vehicles the strap can be routed under the radio to a metal support plate for the dash or the reinforcement for the ash tray Whatever simply bend the strap so it comes from under the radio The strap is iron and not the easiest thing to bend that s why it makes a good bracket Use a vise to hoid the strap and hammer it to shape Try to get the strap in place before installing the radio it might not be possible later Either attach the strap to the radio saving the support connection for last or vice versa There s more Then install the radio in the dash using a deepwell socket wrench to secure the shaft nuts Don t try to force a standard socket wrench on the shaft it s not deep enough and don t use pliers that will just chew up the controls You have most likely spent at least 100 on the car radio possibly 200 or 300 spend a few dollars for a deepwell socket wrench and do the job the right way By the way don t try to use long nose pliers for the shaft nuts You ll probably ruin the pliers and they cost more than deepwell socket wrenches In many instances you re going to find the trimplate doesn t fit properly because there is no such thing as a universal trimplate Most likely there will be holes and FINALLY RE INSTALL the ash tray or glove box if they were rem
54. the received signal An AM station s very strong signal is au dible for several thousands of Hertz on either side of its carrier frequency Sometimes more On a receiver you tune for highest S meter reading and or best audio fidelity For an AM station s signal that is weak rapidly fading or suffering from strong interference that tuning procedure is difficult to do By mixing or beating the output of the 455 kHz BFO Beat Frequency Oscillator with the station s intermediate frequency IF carrier signal you can tune rapidly to the exact station s carrier frequency And as a bonus if you already have not guessed the 455 kHz BFO comes in very handy for tuning in CW sta tions and providing the missing carrier for SSB and DSB stations that sound like monkey talk without this handy gadget Circuit operation Fig l is a schematic diagram of the circuit for the 455 kHz BFO Transistor QI is a 3 65 MHz crystal controlled oscil COMAARGCATIONS RECEIVER vaesu FAE 7700 Sa et ean M AT a vona ae T sae m AN Beet CEG a a a gt e AD lator The oscillator output is coupled to ICI and IC2 which are 4027 CMOS dual JK flip flop integrated circuits used as divide by two flip flops The output at pin 1 of IC2 is a 455 kHz squarewave The output frequency may be adjusted slightly by changing the value of capacitor C1 If you have a frequency counter available you may want to substitute a vari
55. the batteries holding them in place Note the on off switch and battery charger jack also mounted on the base cover Once assembled Syndle looks like the old fashion candle holder Grandma used 86 YAWNWINS epi Q3 SPECIAL PROJECTS mo gt FIG 3 PARTS PLACEMENT looks simple enough until you try to mount a resistor with its axis parallel to the surface of the board That cannot be done in some cases because the holes are too close together Then do as the pros do mount the resistor with its axis per pendicular to the board s surface and bend the top most lead to the mating mounting hole build the prototype using a plastic simulated candle mounted in a decorative table lamp typical of those found in restau rants See photos The battery and electronics are mounted in the base along with S and Jl The resulting combination presents a very realistic effect Similar lamps may be found in gift shops or hardware stores however careful selection is necessary if it is desired to fit all the components within the case With the exception of R13 there are no adjustments re quired to cause the circuit to operate Connect a variable power supply in place of the battery with the voltage set to approximately 6 volts and adjust R13 fully clockwise The lamp should light and begin to flicker Verify the random nature of the flickering by observing the device s operation for a few moments The proper functioning of IC
56. the jack will be secured to the board without need for a drop or two of adhesive or epoxy You apply power to the Electronic Slot Machine by simply plugging in the battery eliminator or connecting the battery There s no need for the extra expense of a power switch Checkout and adjustment Set all three trimmer potentiometers to the mid position then apply power to the Electronic Slot Machine That should cause some form of indication on each of the three display devices and the LED located near switch PB should pulse There will be no sound from the speaker If you don t get those coniditions it s more than likely there is a wiring error Check the orientation of the LED and the IC s the diode polarities and capacitor polarities and finally the battery eliminator polarities Take particular care to check the in Stallation of the two type 555 timers IC and IC2 the dot on one faces the bottom of the board while the dot on the other faces the top of the board Potentiometer P3 controls the brightness of the display and therefore has a substantial effect on the total current drain If you re using batteries set P3 for the minimal usable birghtness If you re using a battery eliminator you can set the brightness at maximum THE SPEAKER CAN BE SECURED to the board by placing a thin bead of RTV silicon rubber adhesive around the rim of the speaker and then placing the speaker face down on the board un
57. the probe s trimmer capacitor or calibration adjust ment for a perfect squarewave as shown in A of Fig SP FIG 3 BELLY UP VIEW of the printed circuit board foil pattern Location of parts can be de termined from the photographs Positioning of transistors Q1 Q3 is given in text PRO CABINETS HOMEBREW A well prepared box or cabinet protects the circuit components and incourages the builder to employ the project HERB FRIEDMAN BACK IN THE EARLY DAYS OF RADIO WHEN GRANDPA WOUND HIS receiver coils around old Quaker Oats oatmeal boxes radios were built on wood bases either the proverbial kitchen breadboard or slabs of mahogony maple oak or anything else with an attractive grain The wood was usually sanded glass smooth and then finished with several layers of stain and hand rubbed varnish The finished product was a work of art often surpassing the appearance of store bought equipment which was also made of wood in them thar days Today we generally build our homebrew projects in alu minum or plastic cabinets because they are inexpensive materials easily worked with home workshop tools But although metal and plastic don t have the beauty of wood grain a homebrew project can still be attractive In fact spray paint and some decal labels and letters are all that s needed to make a Plain Jane homebrew project look like something that came out of a high technology hi tech fac tory
58. they must be of a type with sensitivity and power handling to match that of the E130 otherwise they would be completely useless More about that point later But why the distinction vocal lead guitars keyboards Surely a good system should be good for anything hi fi guitars electric pianos organs public address systems and what have you It s a point that may puzzle hi fi fans and one that warrants clarification The long and the short of it 1s that there are important distinctions between optimised hi fi and optimised music Original project appeared in Electronics Australia January 1981 Edition and reappears here by permission loudspeakers involving such qualities as frequency re sponse distortion sensitivity and overload characteristic A loudspeaker intended for a hi fi system has to be capable of reproducing a wide variety of sound from the deepest notes of a grand organ to the shimmering near supersonics of a cymbal It should have no obvious peaks or troughs in its frequency response otherwise it will impart its own colora tion to instrumental or vocal sound Distortion must also be as low as possible at all likely power levels from a whisper to full volume in the particular listening situation almost in variably a home environment About hi fi loudspeakers To meet those needs designers of hi fi loudspeakers have tended to favor the use of voice coils much longer than the magnetic ga
59. transistor RESISTORS All resistors are Ya watt 5 unless otherwise specified R1 R4 1 Megohm R5 R13 R14 1000 ohm R6 1000 ohm trimmer potentiometer R7 R8 R19 R20 33 00C ohm R11 R12 100 ohm 12 watt R15 R18 R21 R23 270 chm R24 500 000 ohm potentiometer R25 3 300 ohm R26 0 5 ohm 20 watt use two 1 ohm 10 watt resis tors in parallel CAPACITORS C1i 10 nF 35 WVDC electrolytic C2 C3 47 uF disk C4 001 uF disk C5 01 uF disk C6 4700 F 35 WVDC electrolytic C7 1000 uF 35 WVDC electrolytic ADDITIONAL PARTS AND MATERIALS E1 6 terminal barrier type screw mount Strip F1 v2 A fuse and holder 11 Neon panel indicator tight with built in dropping re sistor J1 J2 Quick connect disconnect color coded binding terminals type used for rapid connect to speaker leads J3 J4 Multi way binding posts black S1 DPST power switch S2 S3 SPST miniature toggle switch T1 Low voltage power transformer 117 VAC primary winding 12 6 VAC 3A secondary winding with no cen ter tap 3 Cables ribbon type with 16 leads terminal one endin 16 pin DIP jack to mate with 1 pin DIP IC type socket 1 Heatsink for IC7 50 watts dissipation minimum Radio Shack 276 1361 Printed circuit fabrication materials mounting hard ware knob case heatsink conpound terminal strip solder wire line cord with moulded 3 prong AC plug P1 etc An etched and drilled printed circuit board i
60. very fussy as to what you re trying to Stick it on It will not adhere directly to many of the greasy aluminum cabinets nor to most high gloss enamel paints it might not even come off its carrier sheet when rubbed with a stick Asa general rule the inexpensive paints provide better initial adhesion of transfer type If you find yourself stuck with a cabinet paint job to which the markings won t stick apply a very thin coat of matte finish or non glossy clear paint such as DATAKOAT over the paint and let it dry for at least 24 hours The transfer type will stick like glue to the matte Surface Making it all permanent Virtually all panel marking material is very fragile when first applied though the decals are many times tougher than transfer type Often just brushing them with your fin gers will cause parts of characters or complete characters to flake off the cabinet The markings are made permanent by applying a light coat of DATAKOAT or an artist s protective clear spray Both products very slightly dissolve panel mark ing material so it merges either with the cabinet paint or the protective clear spray paint When it all dries the markings are actually part of the paint coat itself and are immune to damage from normal handling See photo 11 You d have to scrape the paint off the cabinet to remove the markings Customize Naturally you probably have your own ideas as to how you would like to custom
61. we only show noise generators at the input of the amplifier and not noise generated in later stages In most cases that is quite valid because the amplifier is most sensitive at the inputs and following stages will operate at higher signal levels Looking at each noise source individually Shot noise or quantum noise occurs because of the discrete nature of electric current which is actually pockets of individual elec trons comprising the current flow and not ahomogenous flow like water from a tap The mechanism involved is analagous continued on page 38 Everybody s making money sellin Now NRI Trains You At Home To Make Money Servicing Repairing and ing Personal and Small Business Computers Seems like every time you turn around somebody comes along with a new computer for home or business use And what s made it all possible is the amazing micro processor the tiny little chip that s a computer in itself Using this new technology the industry is offering compact affordable computers that handle things like payrolls billing inventory and other jobs for business of every size perform household functions including bucgeting environmental systems control indexing reci pes And thousands of hobbyists are already owners exper imenting and developing their own programs Growing Demand for Computer Technicians This is only one of the growth factors influencing the increasing opportunit
62. when the ignition is turned off Cl and C2 filter the input and output voltages respectively and also improve the stability of ICI The turn signal lamp on off timing signal and the turr signal on warning tone are both produced by IC2 a 556 dua timer chip RI R2 and C2 are timing components that s t the turn signal lamp flashing speed The flashing speed can be changed to suit your needs by changing the value of Kl and R2 The formula for doing that is shown in Table A R3 R4 R5 and C4 are timing components that set the frequeacy of the turn signal on warning tone The warning tone re quency may be adjusted between 72 Hz and 10 8 KHz by potentiometer R5 C5 and C6 help keep the 556 timer C2 stable in the harsh electrically notsy environment The turn signal on warning tone output from IC2 pin 5 is sent through diode D2 which blocks any voltage that may de fed back through the loud speaker SPKR R6 limits tke current that can be drawn from C2 and potentiometer R7 will adjust the turn signal on warning tone volume to an accept able level The speaker is a small 1 5 in 8 ohm speaker which will provide more than enough volume for most ap plications The return line of the speaker SPKR is con nected to the emitters of Q through Q8 Ground Is prc vided to SPKR through the signal lamps only when the turn siznal switch in the car is on left or right and only during the off cycle of the flasher when Q5 Q6 Q7 and Q8 are not
63. which is OK considering that the heat sink was taken from the junk box Fuse location is satisfactory and strain relief on the power cord is very good construction practice pa D e oo 3 PRONG temperature The checkout of the logic probes is simple With the power supply turned on touch one probe to the 5 terminal The HIGH LED LEDI1 should go on and the puts E LED LED15 should stay on for only about 250 msec Touching the probe to ground should light the Low LED LED 13 and the puLSE LED should flash when the probe is removed from ground With the memory switch S2 on touch the 5 bus and then ground the probe The pulse LED should go on and stay on even after the probe is removed from the signal When the switch ts turned off the puLse LED LED 5 should extinguish about 250 microseconds later Both probes work PARTS LIST FOR DIGITAL PROTOTYPING SYSTEM SEMICONDUCTORS C1 LM324 operational amplifier Op amp integrated Circuit IC2 LM3914 bar dot display driver integrated circuit C3 74LS123 dual one shot integrated circuit IC4 74LS04 hex inverter integrated circuit ICS LM555 timer integrated circuit IC6 4060 CMOS 14 stage driver integrated circuit C7 78HOS 5 volt DC regulator integrated circuit BR1 6 A 50 PIV bridge rectifier module Radio Shack 273 1180 or equivalent LED1 LED16 Light emitting diode red 20 mA forward Current Q1 Q2 2N3904 NPN transistor Q3 Q4 2N3906 PNP
64. 04 s02 A LOW M F LEDI3 LOGIC PROBE S LED 14 CABLE TERMINATES AT qi 1 S01 AND FRONT PANEL Ky 2 S02 AND FRONT PANEL PINT 3 503 AND FRONT PANEL 861 HSWWNS a ml SPECIAL PROJECTS gt N TABLE 1 CLOCK RANGES Sa n it Bi SU Tap No High Frequency Low Frequency A 170 kHz 1560 Hz B 11 kHz 100 Hz C 1395 Hz 12 Hz D 174 Hz 1 5 Hz E 21 H2 19 Hz F 10 H2 01 Hz 5 7 pulses min and R19 preventing the capacitor from charging and holding the one shot in its triggered state with puLsE LED LED15 on Opening S2 causes C2 to charge and after 250 msec Q goes high and the puLse indicator LEDI5 goes out Tick tock The clock circuit is made up of IC5 and IC6 See Fig 2 ICS ts a 555 timer connected in its astable mode The fre quency is adjustable by range potentiometer R24 The output of the timer is fed to IC6 a 4060 CMOS 14 stage binary divider chip The input signal is divided down and tapped off at five different stages That allows the clock output to be available at six different frequencies simultaneously The available range is from 170 kHz to less than 1 Hertz The clock ranges are listed in Table 1 Construction The main circuit can be assembled using an etched printed circuit board or a wire wrapping technique on a perf board A foil pattern of the wiring side of the PC board is shown in Fig 3 Component placement is shown in Fig 4 Mount all PC components t
65. 2 a pin 3 IC2 Q output pin 6 will go low resetting C2 b via its reset input pin 13 blanking the scope s CRT again Also the C2 b Q output pin 9 going low resets IC2 a via its reset input pin 1 The scope will remain blanked until a new sweep com mand is received by manual operation of SI or a pulse is applied at IC1 b s set input pin 10 See the typical timing diagram for a triggered scope using the single sweep blank Ing circuit in Fig 5 Operational status LED indicators see Fig 6 may be added and driven by the unused outputs of the flip flops or unused inverters which are used as butfer drivers LED driven by ICl a s outputs would indicate a manual reset LED2 driven by ICl b s outputs would indicate when the circuit was ready for a new command And LED3 driven by IC2 b s outputs would indicate blanking status Interface Where high level sweep gate or ramp inputs were used the input signals might be pre conditioned by a current limiting resistor followed by a two transistor scheme See Fig 7 However the pre conditioning circuit could be used to amplify a signal but the use of low level sweep ramp ADDITIONAL PARTS AND MATERIALS S1 DPDT momentary pushbutton switch RESET S2 SPST toggle switch ON OFF Jt J2 BNC connector to mate with oscilloscope s patch cable J3 open circuit miniature jack power Connection Plastic cabinet 4 X 2 2 X 1 a in printed circuit board materials
66. 4 c tion to a circuit under test VW 100K eat R2 C2 JI gt 100K 2 a errand il 861 HAWWNS on pes SPECIAL PROJECTS ol N FIG 2 FOIL SIDE VIEW of the printed circuit board copper foil This illustration can be used as a pattern to making yours If you wish use pre etched standard layout boards to construct the circuit and save the etching mess Otherwise you may consider wire wrapping the circuit a Zener type circuit but when originally designed the plan was to try for the least amount of parts within the circuit Building it The Mini Audio Generator if built exactly as shown should cost less than 10 00 including the etchant for mak ing the printed circuit board Fig 2 is a same size toil pattern used on the author s printed circuit board The circuit is so simple you may choose point to point wiring using the wire wrap technique There s nothing wrong with that idea Fig 3 shows the printed circuit board with an X ray view of the foil surface and the parts mounted on the board Placement of parts is not critical so you may design your own printed circuit board Since the 4046 1s a CMOS chip the proper handling precautions relating to static electricity should be observed Furnishing such a healthy signal requires a fairly large supply of current at least by CMOS standards so LED is used as a power on indicator and reminds you to turn the Mini Audio Generator off when you are not usi
67. AND OTHER low level voltages without loading down the circuit or your budget Here is an instrument we call the Super Sensitive Simple Voltmeter SSSV that will measure from 2 millivolts to 2 volts DC with an input impedance of 500 000 ohms or higher The circuit may be added to your present voltmeter or built as a separate instrument All of that is yours for the price of an op amp a few resistors and an inexpensive meter movement Theory The primitive DC voltmeter shown in Fig 1 is good for checking batteries and other similar low impedance circuits All of the current needed to move the meter s pointer comes from the circuit under test In the low voltage circuit of Fig 2 the 1 millliampere that the meter needs for pointer move ment represents more current than the circuit would deliver under normal operation Since the meter s current loads down the circuit the meter indications would be in error by a 100082 E 0 1 MA FIG 1 THE TIME HONORED voltmeter circuit that serves well in testing low impedance voltage sources accurately Ideally suit able for checking batteries power supplies and low impedance circuits This is not the voitmeter to check low AGC voltages FIG 2 DISASTER STRIKES when a low impedance voltmeter attempts to measure the base bias of this transistor circuit The meter Circuit radically alters the resistive biasing network Caus ing abnormal operation and an incorrect and worthless voltage r
68. ASS UP 34 MoCo Moving Coil Preamplifier for audio Buffs 58 Electronic Flasher for Your Car 65 JBL System for Musicians you build the enclosure 79 Three Band Shortwave Converter 87 Pro Cabinets for Home Brew Projects 92 Extra Low Power Pilot Light DEPARTMENTS Editorialt news on how to Subscribe New Products 4 5 Coverage Cover 8 Advertising Index 8 Letters from our Readers 101 Postage Paid Free Information Cards w 8861 H3IWWNS SPECIAL PROJECTS NEW PRODUCTS ADAPTER is an RS232 interface adapter for the Zenith mode Z7T personal information terminal The Z7 terminal contains an inte gral 300 baud modem for communicating with computers over telephone lines This new interface allows it to function also as an RS232 terminal to communicate with com CIRCLE 818 ON FREE INFORMATION CARD puters at the user s site The interface plugs in between the ZTI keyboard and power supply supporting all data rates available from the Z7 110 through 2400 baud The retail price of the RS232 adapter is 69 00 Magnolia Microsy stems Inc 2264 15th Ave West Seattle WA 98119 RADAR WARNING The Bearfinder Quest provides a four step relative distance in formation display using LED signal strength indicators The first indicator and accompanying slow audible beep announces the acquisition of the radar signal The second third and fourth indicators each illu minate when a motor vehicle
69. E eet n E E pi a ako Lees g 3 m ki ee oe ee ee FERE em O a he P K output clock pulse to one half different register than the time before the new register num ber must first be latched The sequence for reading informa tion is shown in Table 3 A wide variety of sounds can be generated using that chip The PSG can produce sounds ranging from explosions and laser fire to music with three part harmony The only way to get really familiar with it is through trial and error and the manufacturer s data manual The circuit can be built with relatively little cost or know how It will provide a new dimension for your TRS 80 and much entertainment for you Now you can look toward a happy BOING ZAAAAAAAP and PINGGG SP SPKR e yy Be a a m a E BELLY UP VIEW of Soundbox 80 illustrates the rat s nest wiring that makes the programmable sound generator circuit do its thing Jack J2 is for connection to the external power supply You may want to add a closed circuit jack to hook up an external loud speaker If you prefer to connect a stereo headphone use a closed circuit stereo jack and connect both channels to the audio output so that both ear pieces produce sound N e86l HINWNS GUSTOM SOUND FOR YOUR CAR LARRY GLENN WHILE DETROIT AND TOKYO MIGHT HAVE PRICED THEIR IRON well beyond what you can afford you don t have to wait for new wheels before you upgrade
70. ECTRONICS HOB BYIST 5 00 C FIRST BOOK OF TRANSISTOR EQUIV ALENTS amp SUB STITUTES 3 75 T PRACTICAL COM PUTER EX PERIMENTS 4 50 O ANTENNA PRO JECTS 5 00 Covers practical antenna de signs including active toop amp ferrite types that are easy amp inexpensive to build O RADIO STATIONS GUIDE 4 75 Com prehensive isting of transmitters around the world Presents toca BUY 12 PAY FOR 10 TAKE 2 FR ENGINEERS amp MACHINISTS REFER ENCE TABLES 2 00 _ SECOND BOOK OF TRANSISTOR EQUIVALENTS amp SUBSTITUTES 4 50 C 52 PROJECTS us ING IC 741 4 00 C BEGINNERS GUIDE TO nPROCESSORS a COMPUTING 4 50 C VMOS PROJECTS C HOW TO USE OP AMPS 5 75 AUDIO PRO JECTS 5 00 C MODEL RAILWAY PROJECTS 5 00 C CB PROJECTS 5 00 C HOW TO GET YOUR ELECTRONIC PROJECTS WORK ING 5 00 O MULTI CIRCUT BOARD PROJECTS 5 00 C ELECTRONICS SIMPLIFIED CRYSTAL SET CONSTRUCTION 4 50 ELECTRONIC HOUSEHOLD PRO JECTS 4 50 lary Gines Sure ieeed E 8 ee re i ee he An Wi ac tect be Mada DS orey Q CB PROJECTS 5 00 A number of useful and interesting designs for CB accessories Speech Processor interference filter amp more C CRYSTAL SET CONSTRUCTION 4 50 Packed tuil of easy to duplicate de signs for crystal radio POWER SUPPLY PROJECTS 4 50 Contams designs and construction details
71. ECTS on E Remove the stone age thermo mechanical signal flasher from your car and add a beeping solid state device whose flash frequency is always constant TERRY A WARD THIS ELECTRONIC FLASHER CIRCUIT IS A SOLID STATE REPLACE ment for the thermo mechanical turn signal flashers used in almost all automobiles Thermo mechanical turn signal flashers have severa disadvantages which may be dangerous to the car and passengers The speed at which the turn signal lamps flash is affected both by changes in the car s charging system voltage and by changes in flasher load current The higher the voltage or current through the flasher the faster the turn signal lamps will flash The opposite is also true For instance on a cold winter night engine idling with lights heater and other accessories on the charging system s voltage may be very low Under those conditions the turn signal lamps may flash too slowly or not at all Another example would be in the case where a trailer s turn signals are wired to the car s signals Current draw may increase to a point that the turn signals flash so quickly they appear to be about half brightness constantly You see the lamps have a thermal lag Another disadvantage to thermo mechanical flashers is that many times the clicking of the flasher may not be heard over the road noise That may cause the turn signals to be left on accidentally for several miles after the driver
72. H HEFIU FEHSI USEF l B YTD N6KBY KTD6 TYNKD BKNT DY6D TBOKT YKTND 6KYK BN TB KYTDN 6 KYD D6YTK YBTND K6NYT C V4R2A 3R42 A VR3 24VA 3A V3 A23 3 24RAV RRVV 4374A V A23 RAV42 3R2V4 AVR 2 V4R2V RV42 D X QGC MXG XGCM M XM C X CGM X GXCM OMGX l X C MXCGM X C GM C CXN G M 0 X E J L1P WPJ1 LW1 LiJWP PJWL PPE 1J WW LPJ1W WL1J al LV LJWP1 JPL 1PWJL LJ P1 W 1J5P l F 0 ZO 798Q ZQ087 09 8 0Q9Z 0 78Z ZQ8 9 80 Q 9Q90 07ZO ZOQ9 Q 9 Z 90270 QZ0 9 807 Q G 92837 46510 49628 53709 96821 13579 25680 95062 13467 53751 KEYER ae 1j n 2 Oe wins ei Wes 2 of IC2 The software will then test for the one shot to time out by testing pin 3 of IC2 through pin of the ICI If for example a dash is being sent IC will first turn on the 00 Hertz tone generator by pulling pin 4 of IC3 high through pin 36 of the ICI ICI will next trigger C2 and wait for it to time out It will do that three times After the third time it will turn the tone off by pulling pin 4 of IC3 low again The actual dot timing is based on fixed resistor R6 SPEED potentiometer R7 and capacitor C8 Pulling pin 39 to ground through sTARt sTop switch S3 will start the practice sequence or start the electronic keyer function if selected Pulling pin 6 to ground through START STOP switch S3 will stop the practice sequence To leave the keyer mode requires powering down of ICI This can be done with a simple ON OFF switch i
73. IC 1 is plugged in connect the batteries to the SSSV and check with a voltmeter to be certain that pin 7 is positive with respect to pin 4 Refer to Fig 4 If that is OK turn S2 oFF and plug in ICI Set the range switch S3 for the highest voltage 2 volts in this case Connect a voltmeter and a PARTS LIST FOR SSSV RESISTORS All fixed resistors are Hewat 4 values unless other wise noted Ri 2 Megohms 2 1 Megohm units in series R2 A4 R5 1 Megohm R 500 009 0 ms 2 1 Megohm units in parallel R6 1000 ohms R 1500 ohms potentiometer Ra 47 ohms RAI 100 ohms potentiometer SWITCHES S1 DPDT miniature toggle or slide switch Se 3 pole 4 pasition rotary switch s3 SPDT miniature toggle or slide switch ADDITIONAL PARTS AND MATERIALS B1 B2e 9 VDC transistor battery IC1 CA3140E or TLO8 BIFET operational amplifier Jt J2 Multi way binding post one red one black M1 0 1 mA panel meter 2 to 3 in circular or rectanqu lar face Plastic 4 x 6 1n card tife box see text battery clips perboard scraps wire hardware solder tc O TO 30y Q1 Q2 GENERAL PURPOSE NPN SILICON TRANSISTORS FIG 5 LOW POWER PILOT LIGHT is an optional feature in SSSV Consider it a project all by itself with application not only in SSSV but in many other projects where pilot light indication is necessary and a transistor 9 volt battery is used as the pawer supply The low drain does not shorten the bat
74. IC2 and IC3 can be checked by monitoring the output of each device in dividually A voltmeter or oscilloscope connected between pin 3 and ground will show a pulse of several second s duration occurring every 20 to 40 seconds at IC and IC2 IC3 will exhibit a continuously verying pulse train of approx imately 4 Hz If improper operation is observed check the wiring and component placement for the affected stage 2 A P ANS ve S ee E i Tre Qa d z La 5 i d i 4 T sie Oe s P b q i b a f F a i aj E 1 4 4 G t i r s da f j J 3 j Ea IIGS HY z l cee ein g Q aA a ak a After determining that Syndle is functioning properly reduce the power supply voltage slowly until the lamp is extinguished Note the power supply voltage It should be very close to 5 6 volts If it is not increase the voltage to again light the lamp readjust the setting of R13 up or down as required and repeat the process until the lamp goes out as the decreasing voltage reaches 5 6 volts Due to the hysteresis in the comparator circuit the voltage level needed to turn the lamp on will be higher than that at which it switches off Once properly adjusted the trimpot can be fixed in place with a drop of nail polish and should require no further adjustment If a 47 type bulb is used in place of the 1850 B1 should have a potential of 7 2 volts 6 cells and the proper turn off voltage
75. IXER PI TD AUTO Qt RADIO HIGH PASS FILTER TM Cope ANT INPUT DOE O0taF OOF p 1002 ANT o Ti Js Ji a 5 O5uF RG 47K 470K et a RGSBALU C6 100K OPTIONAL GNO CONNECTION FOR INDOOR USE fe SpF 2 i X1 Ss 5000kHz 49 METERS Q2 O 23819 x2 o a on 8500kHz 3IMETERS cuime SEE TEXT C1 C12 50pF 005uF G2 o N oN N G BOTTON VIEW FIG 1 THE THREE BAND SHORTWAVE CONVERTER schematic diagram looks like this and is simple enough to build The high pass filter section is constructed on a separate circuit board primarily ta simplify construction The remaining portion of the circuit mounts almost entirely cn a circuit board ina neat layout as shown in the photos No on off power switch is supplied because the power shculd be controlled at the power source PARTS LIST FOR THREE BAND SHORTWAVE CONVERTER SEMICONDUCTORS Q1 3N211 N channel silicon dual gate MOS field effect transistor Radio Shack 276 2045 or equiv alent Q2 2N3819 N channel silicon junction field effect transistor Radio Shack 276 2035 or equivalent RESISTORS All resistors are watt 5 units R1 R7 47 000 ohm R2 470 000 ohm R3 100 ohm R4 100 000 ohm R5 1000 ohm R6 4700 ohm R7 220 000 ohm R8 47 ohm R9 330 ohm CAPACITORS All capacitors are ceramic 50 WVDC units unless otherwise noted C1 C3 001 pF C4 50 pF C5 150 pF C6 350 pF variable Po
76. LELLU z 1 A PRO CABINET starts out with properly drilled panel holes and openings You don t want the panel components hanging half in and out of oversize holes Use a drill press or a stand mounted hand drill if possible Be sure to clean out the burrs Paints also aren t all alike As for the type of paint to use you will need at least two of the three products similar to those shown in photo 4 The center product in photo 4 is ordinary spray paint a some what inexpensive private brand paint Funny thing adout the spray paints price is not necessarily indicative of quality when it comes to adhering to aluminum I ve had no luck with Rustoleum brand paint it takes several coats to cover Krylon tends to run or peel depending on the aluminum and how well it s been scrubbed with stee wool For single coats I ve had best results with cheap private brands If your project is going to get rough handling and you would like the paint to stick like glue use a primer paint as the first coat it if you plan on painting the cabinet you can keep the spray paint out of the inside of the cabinet by taping over the holes from the inside Actually careful spraying will limit interior paint cover ing A surface must be scraped clean later at ground tie paints will just take an extra night to finish the paint job The Krylon Matt Finish used by artists is an excellent aluminum primer Apply evenly but spa
77. N SOMETIMES A PROJECT CAN BE A LOT MORE TROUBLE THAN IT S worth For example an Electronic Slot Machine can be a lot of fun at parties or at a School Fair or at a Las Vegas Nite for your local charitable organization The problem is that it s usually not easy to come by the required parts from one source and by the time you re finished paying for several shipping and handling charges most of the pleasure is gone Well we ve put some of the fun back in building relatively complex projects by making almost all the parts needed for an Electronic Slot Machine available from a single source If you don t have the parts in stock or can t locate a few items locally you can purchase almost the whole kit and kaboodle from Chaney Electronics Inc you ll get everything except one small power jack that we ll cover later The Electronic Slot Machine is a modern version of the old one armed bandit You bet your money and press a but ton Three seven segment LED digital readout devices show whether you ve won or lost The devices can display either the numeral 7 a dash or the letter L for you lose If you hit three sevens or three dashes a tone sounds from an internal speaker to indicate you have won Should any other combination of sevens dashes or L s appear you lose The small internal speaker sounds rapid ticks as long as PB the push button operating switch is depressed Note we used PB instead of SI so
78. ORS Q1 Q2 LM394 Super matched pair NPN transistor QS 04 2N4250 or AST4250 low level low noise sili con transistor RESISTORS All resistors are 2 watt 5 fixed composition type R1 47 0hm F2 68 000 ohm F3 19 ohm F4 220 000 ohm F5 R11 10 000 ohm F6 47 009 ohm F7 470 ohm F8 1500 ohm R9 220 0ohm CAPACITORS Ail capacitors are 16 WVDC electrolytic type C1 100 uF FX1EIS bead and in conjunction with the 47 ohm resistor R1 following prevents RF interference from being rectified by the input stage and passed to the amplifier Q4 A 100 uF electrolytic capacitor C couples the input signal to transis tors Ol and Q2 Because of feedback to the emitters of Q1 and Q2 the input impedance of the stage is quite high at around 35 000 C2 C4 10 yF ADDITIONAL PARTS AND MATERIALS J1 Ji Phono jack RCA type RFC1 4 turns of 28 wire on Phillips FX1115 ferrite bead Metal case printed circuit m terials hardware wire Saider etc PARTS LIST FOR BATTERY POWER SUPPLY B1 6 1 5 VDC D cells connected in series C5 100 uF 16 WVDC electrolytic capacitor Di 5 6 V 400 mW Zener dicde LED Light emitting diode red diffused lens S1 Single pole 3 position toggle switch center off one throw position may be pring return to off R12 200 ohm s watt 5 resistor Battery holders tor D cells wire hardware etc ohms The recommended load for most moving coil car tr
79. RAMMABLE SOUND k GENERATOR AY 3 8910 TD AUDIO AMP 3 i SEE FIG 3 f Si dh FROM CLOCK G 00 CIRCUITRY IC SEE FIG 4 OCTAL BUS TRANSCEIVERS 14 14 14 IC3 IC4 Ics 74LS30 74LS32 74LS02 TO REG 5 VDC POWER SUPPLY SEE FIG 2 191181 7116 15 1411312 11 74L 245 DIR DO D7 DATA BUS D0 D1 02 03 04 05 D6 07 ICt AY 3 8910 1C2 74LS245 IC3 74LS30 IC4 74L 32 ICS 74LS02 QA IC6 74LS04 K IC9 4011 B IC10 4013 1 FIG 1 SCHEMATIC DIAGRAM FOR THE PROGRAMMABLE SOUND GENERATOR section of Soundbox 80 the noisy addition to your TRS 80 The text takes you by the hand through the schematic diagram which in effect isa basic course in logic theory The associated power supply circuit audio circuit and clock circuit are provided in the following figures all of which are part of Soundbox 80 are summarized in Table 1 The BDIR signal pin 2 must go low whenever writing or latching to the internal program mable sound generator IC1 Since the BC2 input pin 28 does not need to be used it is tied tothe 5 volt supply The BC signal pin 29 only goes high during the read and latch operations The logic to create those enable functions begins with the address decoder made of IC3 and I C6 a which is an inverter used to select the desired port It can be replaced by any combination of inverters on the address lines A2 through A7 The ouput of IC3 goes lo
80. S ARE EXTENDING THE life of home appliances electrical tools test equipment and salvaged parts This can be done with considerable savings but is it safe Many technicians depend on their volt ohmmeters VOM even for insulation testing For AC line operated equipment the potential used in the ohmmeter circuits are not high enough compared to Megohmmeters or meggers which have potentials from 500 to 1000 volts DC Now a simple adapter we call it the Meg O Dapter can be used with most analog multimeters without any modifica tion to the meter circuits This adapter provides an open circuit output varable from zero to 1000 volts DC Although these high potentials sound frightening current levels are only 50 or 60 microamperes Any charge on capacitances in the unit tested is dumped or discharged through normally clased contacts of the momentary contact power switch Speaking of Megohms Insulation resistance of an appliance may vary depending on age moisture corrosion and dirt Resistance will vary from several Megohms to infinity Most low readings are caused by moisture and can be corrected by drying the appliance ina low temperature oven Heat will also cause lower readings so a second reading should be made after cool down In cases involving grease or carbon from brushes washing the appli ance with a cleaning solvent and re drying can help For harsh environments insulating varnish can seal motor or transformer windings
81. ST FOR SINGLE SWEEPER ONE SEMICONDUCTORS IC1 IC2 7474 dual D edge triggered flip flop inte grated circuit IC3 7404 hex inverter integrated circuit 1C4 7805 5 voilt regulator integrated circuit LED1 LED3 Light emitting diode with red diffused lens Q1 2N2222 or 2N3904 NPN transistor Q2 2N2907 or 2N3406 PNP transistor RESISTORS All resistors are fixed composition watt 5 com ponents R1 R2 R3 4700 ohm R4 100 000 ohm this value is suitable for sweep gate or ramp voltage levels of 30 volt approximately Use 1 Megohm value for higher values R5 1000 ohm R6 470 ohm R7 R9 470 ohm CAPACITORS C1 100 pF electrolytic 10 WVDC C2 1 uF disc C3 04 uF disc manual reset or new sweep command signal and may also be used to store or hold an external pulsed reset command applied at ICi b pin 10 But whether by pulse or manual command Cl b s Q output pin 9 going high enables IC2 b D input pin 12 IC2 b is the single sweep blanking control flip flop which will set on the low to high leading edge of the sweep gate or similarly derived pulse applied to its clock input pin 11 When IC2 b gets set it unblanks the scope s CRT via its Q pin 9 or Q pin 8 outputs Also IC2 b s Q pin 8 going low resets Cl b via its reset input pin 3 At the end of one scope sweep cycle the sweep gate will go low which ts inverted high by C3 a and applied to the clock input of 1C
82. Time for one cycle in seconds 685 x 233 x 4 7 750 second Turn lamps on in seconds 685 x 133 x 4 7 428 second Turn jamps off in seconds 685 x 100 x 4 7 322 second WITH THE COVER REMOVED you can easily notice the sim ple packaging technique to assemble the unit Any packaging technique is usable providing that the space available under the dashboard is sufficient Instead of using four heat sinks you may use two or one big one That all depends on the design you come up with R5 1 Megohm potentiome er PC board mount R6 150 ohm R7 5000 ohm potenticmeter PC board mount R8 R9 10 000 ohm R10 R13 1500 ohm CAPACITORS C1 100 yF 35 WVDC electrolytic C2 1 yF ceramic C3 4 7 uF 15 WVDC electrolytic C4 C5 01 yF ceramic C6 47 uF metal film ADDITIONAL PARTS AND MATERIALS SPKR 1 2 2 in diameter speaker 8 10 ohm Plastic case heat sinks to handle 35 50 watts total perfboard RV cement hardware wire solder etc will be cycle 75 seconds signal lamps off 32 seconds and signal lamps on 43 seconds The Electronic Flasher unlike thermo mechanical flash ers is not dependent on a number of lamps to continue operating Thermo mechanie al flashers stop operation afte one or two lamps burn out thus warning the driver of the lamp failure but leaving him without turn signals The Electronic Flasher will stop operating only if all the signal lamps on one side are burned
83. To illustrate what can be done for even small junkbox projects we ll show how the cabinet for the Scope Calibra tor project shown elsewhere in this issue was given a laboratory instrument appearance The same procedures can be used for other projects large or small Drill all holes and cutouts first First step is to select your cabinet and drill the necessary 861 YAWWNS J SPECIAL PROJECTS holes you want to avoid drilling or cutting the cabinet after it s been painted When you ve decided on the cabinet to use lay out the cabinet hardware and cut all the necessary holes and openings cleanly nothing looks as sloppy as a beautifully finished project with screws and other hardware hanging half in and half out of oversize holes If possible use a drill press photo 1 and or chassis punch s for the larger openings If you don t have a drill press at least use an inexpensive small stand that converts your electric hand drill into a miniature drill press For holes 16 inch diameter and smaller a Whitney hand punch available from the better hardware and tool stores does a fantastic job on aluminum PC boards Bakelite plastic or whatever See photo 2 It leaves a clean burr free precision hole If you need a little extra oomph for some what heavier metal you can clamp the punch in a vise If you re lucky enough to have a decent parts store in your area you might be able to pick up a cabi
84. WVDC C1 C2 22 pF ceramic disk C3 1 uF electrolytic C4 C6 1 nF C5 C8 1 uF C7 C9 100 pF electrolytic ADDITIONAL PARTS AND MATERIALS J1 Stereo jack for phone plug input S1 S8 SPST toggle switch S2 8 position single pole rotary switch non shorting type SPKR 8 ohm 2 3 inch PM loudspeaker X1 3 57 MHz crystal 1 to 6 MHz usable Printed circuit board cabinet or case 2 knobs for control Shafts wire solder 5 volt power supply etc KEYER OPTION J2 Phone jack Q1 2N3904 NPN silicon transistor R10 4700 watt composition resistor The CPP1 Code Practice Processor Chip is available from Micro Digital Technology PO Box 1139 Mesa AZ 85201 for 19 95 postpaid The printed circuit board sells for 5 00 postpaid Checks VISA and Mastercard accepted On credit card orders please include card number expira tion date telephone number and full name Phone orders call 1 602 897 2534 Complete kit of parts less case are available fom Green brier Marketing International Inc 509 S 48th St Suite 105 Tempe AZ 85201 Priced 49 95 postpaid SPEAKER OUTPUT KEYER by 2 4 to get the number of words per minute Example 2 4 x 5 dots sec 12 WPM This technique will be a lot easier by using a longer time period say 5 to 10 seconds and counting the dots with the aid of a digital counter device Another method to determine dot time and to set up a predetermined speed is to replace po
85. a SELECT SPEED Actually wiring is not ciritcal but pride in construction dominates here C86 YAWWAS wo on TABLE C INTERNATIONAL MORSE CODE A N 1 B ia apma J oes ee CG tia P sp 5 Taky a D p Qa 4 ees er A ea TTT F ec G B amarai G T 7 H U 8 V 9 J W 0 J L Y M Z period ee Comma a a question mark IMI fraction bar colon semicolon parenthesis parenthesis apostrophe WG hyphen or dash DU dollar sign VU quotation mark open quotation mark close Error sign 8 dots FF ee ee ee ee ee ee gt ar eh oe 2 wa SPECIAL PROJECTS ie Q Separation indicator BT ee End of transmission AR er Invitation to transmit a Wait AS ne End of work SK i 5 me ae Starting signal S Pan Tap otf what you need from a bench top power supply or steal some from another project Of course there are those who want a complete project with internal power source To the latter we suggest you look at Fig 5 which offers a straight foward line isolated circuit that will do the job This circuit is optional and the parts for it are not specified in the Parts List The advantage of the 7805 chip is that it s exactly 5 volts DC which makes the circuit safer to use than ad
86. a singie Printed circuit board All are powered by a SV battery C IC PROJECTS FOR BEGINNERS 5 00 Inexpensive digi tal and inear IC s are used to assemble this selection of circuits in tended for the be ginner O HOW TO MAKE WALKIE TALKIES 5 00 Descnbes equip meni for tow power handheld operation 112 pages of must reading for the gedi cated experimenter O ELECTRONIC CALCULATOR US ERS HANDBOOK 3 95 Prasents formu lae data methods of calculation conversion factors amp more from the 0 AAT OF PRO GRAMMING THE 16K 2X61 6 25 Topics in clude full screen scroll ing PEEK amp POKE plus actual working programs C THE 6809 COM PANION 5 00 Wri ten for the average assembly language programmer A discus son of 6809 features amp relerance work tor the 6809 programmer O PRACTICAL COM PUTER EX PERIMENTS 4 50 Fills in background to rmeroprocessor by Con structing typical compu ter curcuits using dis crete logic components C ELECTRONIC SYNTHESIZER PRO JECTS 4 50 50 CIRCUITS US ING GERMANIUM SILICON amp ZENER Dt ODES 3 75 T 50 PROJECTS US ING RELAYS SCR S amp TRIACS 5 00 50 FET FIELD EFFECT TRANSIS TOR PROJECTS 4 50 50 SIMPLE LED CIRCUITS 4 25 7 50 CIRCUITS US ING 7400 SERIES IC S 4 50 50 SIMPLE LED CIRCUITS BOOK 2 3 95 _ PROJECTS USING 555 IC S 5 00 PROJECTS USING LM3900 IC S 4
87. able capacitor for the fixed 300 pF capacitor Inside the 4027 The dual JK flip flop integrated circuit chip is a low current CMOS device used in this project to divide the input clock signal from the 3 64 MHz oscillator circuit by 2 in three separate steps to produce the 455 kHz squarewave output Each flip flop is used independently in the clock mode which requires that pins 4 7 9 and 12 be grounded Pin 8 is the chip s power and signal ground circuits to the power supply Inputs to the J and K pins decide what the flip flop is going to do In this project both the J and K pins are tied to 9 VDC so that the flip flop outputs alternate from 9 VDC to zero volts The positive edge of the 3 64 MHz clock signal to pin 3 of IC causes the flip flop to change its state at pin say from low to high The next positive edge of the clock signal causes the flip flop to change its state again Thus for every two cycles of input signal at pin 3 one cycle of an output squarewave is produced at pin effectively dividing the input frequency by 2 The same occurs at pin 13 and 15 respectively for the other flip flop in the 4027 The circuit draws little current and is usually on for only short periods a 9 volt transistor battery is used for power As the battery ages the voltage drops and lowers the oscillator s output frequency To alert the user a low voltage detector was built into the 455 KHz BFO When LED and LED2 are of equa
88. added to prevent wire lead clutter and to make it hard to misplace the probes Each probe can detect pulses as short as 40 nanosec An adjustable clock with several divided down outputs is included to help streamline breadboarding time and to eliminate wasted space on the block The power supply circult The power supply circuit is shown in Fig 1 Transformer Tl bridge rectifier BR1 and filter capacitor C6 form a full wave power supply regulated by IC7 a 78H05 high current regulator integrated chip and capacitor C7 The output is rated at 5 volts DC into a 3 ampere load maximum The current monitor uses a 5 ohm 20 watt resistor R26 to cause a voltage drop equal to 5 millivolt per milliamp of ALAN BRADFORD The next time you undertake to design your own digital project let this unique device provide you with regulated 5 VDC power with LED current monitor two logic probes and 12 clock frequencies from 01 to 170K Hz 861 YIWWNS 1 P1 BLACK a ma VAC RH 15 i l i a rear gt RI R3 ee i ox E 1MEG 1MEG TESES T 13 K 2 2700 AN IN 1c 13 17 Y 9e LM78H05 4 2100 LM78HV05 lt BOTTOM VIEW i6 y NI ry fe o To IC2 ma P 55 BAR DOT ic a DISPLAY H4 lt O LM324 1MEG M DRIVER 7 Pi R2 N 1200 1MEG 13 w 14 8 900 1 12 wW 11 w 10 300 10 JUI 9 J BAR DOT FIG 1 THE POWER SUPPLY PORTION of the Digital Prototyping System uses a simple bridge rectifier to
89. alog Mail Card Today Send the postage paid card for our 104 page catalog showing all courses with equipment and complete lesson plans There s no obligation other than to yourself See how NRI can help you take advantage of the exciting job and earnings opportunities in the exploding field of microcomputers If card has been removed please write fo us Education Center pR 3939 Wisconsin Ave e 4 Washington DC 20016 Hii We ll give you tomorrow NRI Schools McGraw Hill Continuing SPECIAL PROJECTS G continued from page 34 BASE SPREADING RESISTANCE EMITTER BASE NOISELESS THERMAL VOLTAGE TRANSISTOR NOISE R Ry NOISE MOVING COIL CARTRIDGE FIG 1 SIMPLIFIED MODEL of a noisy transistor amplifier The noise generating elements from the transistor which actually cannot exist The text provides detailed circuit description to rainfall in that individual raindrops striking a tin roof create noise From that you can see that shot noise actually increases with collector current Another feature of shot noise is that it is white in character that is the noise amplitude is constant with frequency Referred to the input of the transistor the shot noise 1s called base current noise and is modelled by a current gener ator at the input see Fig 1 Emitter base voltage noise is modelled by a voltage source in series with the base That is also a white noise source but unlike base curren
90. and the ouput wires use No 12 AWG from the project wiring will be needed In some cars the flasher plugs into the fuse panel so use a burned out fuse to terminate the wires To install the Electronic Flasher three connections must be made to the automobile Two connections will be made to the automobile s turn signal flasher socket and the third will be made to the car s electrical ground First make sure that the car is in gear or in park with the emergency brake on and the ignition switch in the off position Remove the turn signal flasher trom its socket Turn the ignition switch to the on position but do not start the engine Move the turn signal lever to either the right or left turn position The turn signals should not be functioning if they are the 4 way hazard Hasher has been removed and not the turn signal flasher With a VOM find which one of the car s flasher socket E86 YAWWNS SPECIAL PROJECTS a2 PARTS LIST FOR ELECTRONIC FLASHER SEMICONDUCTORS D1 D2 1 N4003 silicon rectifier diode IC1 7805 5 volt DC regulator integrated circuit IC2 556 Dual timer integrated circuit IC3 LM339 quad low pcwer low offset voltage com parator integrated circuit silicon Q1 Q4 2N3906 silicon switching and amplifier tran sistor Q5 Q8 2N3055 silicon high power transistor 15 amperes 115 watts RESISTORS All resistors are 12 watt 5 values unless otherwise specified R1 33 000 ohm R2 100
91. andard terminal numbering Then there was Heathkit with an RS 232 terminal 20 connection known only to Heathkit But does anyone every learn Never The latest version of the Osborne computer instruction manual has a completely erronious set of parallel printer connections after you blow your mind and a few days work most users wind up spending 40 to 60 tor an approved cable And let us not torget that if you use a standard reversed modem cable between an Osborne and a professional RS 232 modem the computer will lock up Or how about Radio Shack s Color Computer The rest of the world uses a D connector for a serial iniertace the CoCo uses a 4 terminal DIN connector When you come right down to it in many instances there 1s no such things as a standard cable H one end is standard the other probably isn t but that s no reason why you still can t save big bucks by making your own cables Mast computer cables can be easily assembled trom a smalfassortment of parts some ribbon cable press fit ribbon connectors multi wire round cable with solder connectors or some combination of ribbon and solder connectors At most it s simply a question of using the easiest cable and connector for a given job Ribbon cable is usually preferred because the connectors clamp on they are not soldered Ribbon cable consists of may individual plastic insulated wires moulded side by side It s usually available in spec
92. are very sensitive to static electricity until they re connected into the circuit The static electricity built up in your body from simply walking on a carpet or wearing a FIG 3 PARTS LOCATION is shown here in this diagram with a photo of the actual unit for comparison Your board should look like the photo when the Electronic Slot Machine is completed synthetic fiber sweater is enough to zap a CMOS device and you ll never know it until you try to run the project The CMOS IC s are easily identified because they are supplied wrapped in aluminum foil or pressed into a piece of conductive foam a thin black porous plastic material Don t remove them from the foil or foam until you re ready to install them To avoid damage caused by static electricity which ts instantaneous there is no seconc chance handle the CMOS IC s only if you are groundec through a ground strap All you need to make a ground strap is about six feet of insulated wire any light size a 1 Megohm watt resistor SPEAKER CONNECTION BATTERY CONNECTION BATTERY CONNECTION and a small alligator clip Connect the wire resistor and clip in sertes then connect the free end of the wire to an electrical ground such as the small screw that secures the metal cover plate of a 120 volt AC convenience outlet Make certain that the screw is really at electrical ground if the cover plate is plastic there s a good chance that the wiring
93. ary tweeters would be adequate because both sensitivity and power rating would be far below that of the E130 JBL s answer to that need is what JBL refers to as the 2901A High Frequency Power Pack The term power pack is explained by the fact that itis a three element package comprising a high frequency driver a high pass network and a treble contro intended to be mounted in a location which will provide access as necessary when acoustical adjustment is required The tweeter is a high efficiency compression driver with integral horn loading and a frontal high frequency lens to ensure wide dispersion of the sound With aluminum voice coil and an impregnated phenolic diaphragm it has a normal impedance of 16 ohms but is suitable for use with either 8 ohm or 4 ohm circuits and with power rating up to 300 watts continuous program Treble response The crossover network is designed to take over above 1 5 kHz and the manufacturer s curve suggests that the 2901A treble driver is flat from 2000 to 15 000 kHz and about 8 dB down at 20 kHz While the treble driver can be mounted separately from the base driver JBL suggests that it should most logically be mounted high up on the baffle of the main enlcosure Since the 2901A driver is sealed off at the rear it will not suffer any pumping by pressure in the main enclosure from the E130 unit So much for the design philosophy behind musical instru ment loudspeakers and the parti
94. at ellite digna multiplex radio amp telegraphy h DIE Eh PARAE uio SPECIAL PROJECTS So diodes in use today view of the calculator 4 50 tion frequency power receivers ona user 7 ELECTRONIC Circuitry C INTERNATIONAL GAMES 4 50 O LONG DISTANCE AN INTRODUC TRANSISTOR EQUIV LINEAR IC EQUIV EOT ULAN pe TV RECEPTION TION TO RADIO DX MICROPROCESS ALENTS GUIDE BLENTS AND PIN O SINGLE Ic PRO Higa ae PROJECTS TVDX FOR THE EN ING 5 00 Listen in ING SYSTEM amp CIR 7 50 Products of JECTS 4 25 75 THUSIAST 5 00 your home to broad CUITS 7 50 A truly CONNECTIONS 8 25 more than 100 man Shows equivalents amp pin Practical amp au casts onginating nomprehensive guide ulacturers are listed amp connections of a popular C PROJECTS IN thoratative introduction thousands of miles to all of the elements of cross referenced with user onented selection of C RADIO CIRCUITS OPTO ELECTRONICS to this unusual aspect away Tells how you a microprocessing possible replacements Ape CS USING IC S 4 50 5 00 of electronics can do tt system ELECTRONIC TECHNOLOGY TODAY INC SP 7 P O Box 83 Massapequa Park NY 11762 Number of books ordered Name TOT RICO OF BOOKS crates au ait eek eaten tre nts Sales Tax NY State Residents Shipping 75 1st two books 30 ea additional aes SS a a ae State________ ZIP POT AMENCLOSED thc n enone cet ah Prices go
95. ations The circuit Let s now take a look at the actual circuit we have used See Fig 2 The basic configuration is one we have taken from the National Semiconductor Linear Applications Hand book and uses just four transistors Briefly Q and Q2 are connected in parallel as a common emitter amplifier with Q3 as a constant current load That drives Q4 another common emitter amplifier which in turn drives the output and the feedback network to QI and Q2 Looking at the circuit in more detail now we have in cluded a small RF choke RFC 1 at each input you need two for stereo It consists of four turns of No 28 wire on an R6 a on 47K a 9 DC RB 1 5K heey Q4 2N4250 J2 OUTPUT LM394 3 04 a1 02 2N4250 e B OFF y eS an ny B B E A 9VD0C ky NE w E E i BATTERY TS BOTTOM VIEW BOTTOM VIEW REO An cs LEQ LED FIG 2 ONE CHANNEL of the necessary two cnannels for the 100 gt R12 FT stereo amplitication of a moving coil stereo cartridge Each au 22082 1 9V dio channel except for the common power surply and phono a1 cartridge is electrically apart and independent Transistors Q1 5 6V F and Q2 are physically Iccated in one metal top hat can and 400mW appears as a Single transistor in the unit should you nct spet the Lis Fap ZENER 3 six leads coming from th2 base POWER BATTERY CHECE CIRCUIT PARTS LIST FOR MOCO PREAMP Note double quantity for stereo SEMICONDUCT
96. ay booth from a large cardboard carton an egg crate is a good choice Cut away the front as shown in photo 5 so you can spray from almost any angle Place the chassis on a small support a tray box or a scrap chassis salvaged from an old project and spray lightly with broad sweeping mo tions Two thin coats are always better than one thick coat thick coats tend to run and crinkle when the paint dries Two thin coats will come out s m o o t h except of course for the dust that settles on the wet paint If you must turn the cabinet you re spraying turn the support If you touch the f p4 rive Sre QULCK DRY Lt tahoe Spray Enamel w DRY TRANSFERS a7 he amp i Tile Fike F Pa a TweRPRoor TOU Wit wor veLto TANS OF YOROCAAE CAS UNGE a up R EXTREMELY gm d Sa i cara F pa s SPRAY ENAMEL PAINT can in center is an inexpensive kind that works best The Dataxoat clear matte spray at left protects mark ings you apply on the panel The spray can on the left is artist s protective spray sold in many local art supply houses TO PREVENT THE SPRAY PAINT from coating everything in the shop make a spray booth from a large cardboard box Position the cabinet on a wooden klock or small box so it can be moved USING THE CABINET as a guide make a drawing of how you would like the finished product to look Indicate the distances from the panel components to the edge of the panel
97. bill check must be enclosed If you like to make things work and then find out why they work ou coum be Learn electronics right on up to an Associate Degree in your own home without giving up your present job or income People who reaily like their work get ahead faster And when your natural abilities match the job requirements you have an extra advantage When you use practical training to sharpen your skills your odds are better for keeping your job even if others are losing theirs So if you find satisfaction and interest in making things work a career in electronics may be for you WHY ELECTRONICS IN THE 80 s Oppcrtunity The field of electronics simply offers more career Opportunities and more job se curity than most other fields today Take digital technology for example Much of the new telecommunications data processing and production equipment depends upon sophisticated microprocessors to receive sort and send digital signals in micro seconds Two of CIE s newest home study courses combine digital electronics theory with actual experience on digital equipment Successful completion of either one of those courses is creditable toward CIE s Associate Degree program That s right you can earn an Associate Degree without attending a single class session MAKING THINGS WORK Many of CIE s Career Courses stress hands on training We believe textbo
98. bout the SA 3 is the feature of reducing the heat on the tip to a low value when the soldering sequence is interrupted and then setting the tempera ture to the desired level for getting back to work quickly The SA 3 makes sense and OK makes it Want more information Then circle Number 873 on the Postage Paid Free Information Card and mail it today The other equally attractive items on the cover are projects made by our authors What is more important We give you the complete construction details so that you can make your own Here s the lowdown on each Syndle a battery operated electronic candle Item C that looks like the real thing it flickers and dims at a random rate it is the kind of mood setter you would add to any room in your home to create an atmosphere That is the Editor s Choice for this issue Digital Prototyping System a clever packaging of two probes clock outputs and power supply Item B for the test bench designer Single Sweeper One an advanced proj ect Item F for the digital experimenter and serviceman who still is using yesterday s oscilloscope that does not feature a single sweep blanking circuit 455 kHz BFO a mini project Item D that you ve talked about but never really undertook to assemble Now you have no excuse we give you the complete plans Mini Audio Generator At last a pocket size device Item E for troubleshooting audio systems providing frequencies throu
99. bout the real world his readers live in and drift off into some fantasy world that is not meaningful to them Here at Special Projects we realize that human attribute and work hard to avoid the pitfalls that grow in every editor s path In an editorial discussion period two issues back it was decided that our readers wanted to receive Special Projects via subscription tet the mailman do the walking We had no hard facts to back up our dream but we believed we were correct in that assumption After a few inquiries via the telephone we asked our readers in the last issue to advise us as to what we should do You made us believers in ourselves You voted overwhelmingly for the subscription option So be it lf you wish to subscribe to Special Projects we suggest you turn to page 7 where complete subscription information and a coupon to facili tate ordering is available For the remainder of 1983 Special Projects will be a quarterly maga zine We are still looking into the possibility of publishing more frequently but that move has to be based on so many facts and inputs from so many corners that the decision to remain quarterly will have to stand for the present One source of input is you our readers Let s hear from you Should we continue to publish quarterly Or should we step up to bi monthly six issues a year Your input makes our decisions meaning ful Please help us Now all we ask you to do it turn the page and get into th
100. cabinet Disnar DORI EVEN 1333355 e 0 8 Ona OYT PACIA TON ENTEOS t 2 5 ferrets Sua LOCK Vector FAN FUSES PUNCTIONS 52345279292 newn tte GATED GENERATONGIN aaCDEiGmiin eo DSTT OM gy GROUND GND NAF FFAA AAE P ouaLta D MIGH SPIO MYER N ARCO ESO MT TRIN DNIDES a mor Re NOPORSTUVWHYE HECRON ANOTHER FORM OF PANEL MARKING is transfer or Weltewal INIEENAL INT NOPORS UVR YT xen katte A poua press type The letters are on the back of a clear iene mare AON ay A a r S MOn ELS en Cymer r gt UNOR ev t nT p oat wet Kev plastic sheet Rubbing the sheet with a burnishing ATMIR MEMOUT MODE we a Y AE AC TOMeTON eno SO Danon IAT art ARIPAURA MINIMUM m OR T atA amt Nt tool causes the wax character to transfer to cabinet OU ET SRDUCTANCE aet SE A LO artens NANO Cog AY Al a sad 4 LOA aG MOC sav amp is as 1 MA paasite ded vat quot ies A Mase Me 6 7 8 9 O eae eo ec vor oat 1 1 CDir onn taa rS p Ola MAS Soret SEA When you need large big or giant markings you ll use what s known as transfer or ruboff type This consists of a Clear plastic sheet with letters or symbols on the back which transfer to the under surface when rubbed with a stick ball pen or burnishing tool Notice in the sample shown in photo 8 how individual letters have been used up As a general rule transfer type comes in upper capitals and lower case aaret si sets up to about 20 point The type you are reading now is 10 wee Le
101. capacitors required a marked value of 0 02 uF for Cl and 0 0l uF for C2 To simplify the final assembly solder four 5 inch in sulated leads to the output foils they will be cut to size after they are connected to the multi way binding posts J1 through J4 Note that J4 is grounded it s the common or ground connection The printed circuit board 1s installed in the cabinet using Y4 inch spacers or a stack of washers between the board and cabinet at each of the three mounting screws Make certain that no component or wire lead sticks through the board and shorts to the metal cabinet don t depend on the standoffs without checking visually Note There is no power switch none is needed Simply plug the calibrator in when you need it It uses virtually no power so it can be left connected whenever the scope is on Using the calibrator If possible check the output voltage on a lab type or quality scope To calibrate the CRT graticule connect your oscilloscope s vertical input ground or common test lead to J4 the common or ground binding post Connect the os cilloscope s hor test lead to JI the 5 volt peak to peak out put Adjust the oscilloscope s vertical gain so that the wave form fills the number of graticule divisions you want to represent 5 volts Or as you may require use the other calib rator Outputs To adjust your oscilloscope s low capacity probe connect it to any of the calibrator s outputs and adjust
102. commended only when testing large numbers of cables of the same number of conductors or if you only have one type to test A better solution is to use or adopt breadboard socket strips or experimenter strips designed for that purpose where it s a simple matter to set up for most commonly used cables in a few minutes by sticking in a few jumpers D E PATRICK The configuration of the actual test jig for the Ribbon Cable Tester to suit your particular purposes may require some ingenuity But try to keep things uncomplicated for best results Some useful options such as colored LEDs might be added OK we have got you thinking now so go ahead and design your own test setup We did not include a Parts List with the Ribbon Cable Tester project because you should adapt and design to your testing needs One tip Prepare dummy plug P2 for installation at remote cable end loca tions In our editorial office we have 40 wire ribbon cables snaked throughout the office interconnecting many rooms Thus the cable installation may remain unaltered with the test hookup made possible by a two part test unit SP RIBBON CABLE UNDER TEST USE 4 1N4002 OR 1N4003 P DUMMY PLUG l g V2 15022 ALL VALUES 29 e 4 28 rt ae 26 ho 24 23 22 2e THE LED S TELL THE WHOLE STORY When LED1 and LED2 are 20 both glowing the circuit indicates that the ribbon cable under ae test is OK It ll be a good idea to use gre
103. cular pair of drivers chosen for the system described here Boxing it Now let s get down to the construction of the enclosure Overall dimensions of the enclosure are 30 inches high 24 inches wide and 12 2 inches deep The surface material is 4 in void free plywood or high density particle board Internal volume neglecting cleats padding and speaker dis placement came out at about 3 8 cubic ft Incidentally the extra cleat around the inside lip of the cabinet of the JBL System is optional its purpose being partly functional partly cosmetic It does lock and seal the baffle firmly in position and it does increase the thickness of the exposed front edge as a precaution against abuse It also makes the enclosure look a lot more massive than it really is While it would be possible and even convenient to cut the holes with the baffle already fixed in position it may be wiser to prepare the baffle fully beforehand to guard against the possiblity of an inadvertent error Cut the holes as speci fied taking particular care with the respective diameters so that everything will fit neatly and firmly into position Expe rience has shown that with heavy systems constantly being 861 YHAWWNS mo N SPECIAL PROJECTS oD Lee moved around things soon loosen up if the fit and the fixing is not to the highest standard Whether or not you fit the high frequency horn will de pend on your requirements and your checkb
104. cur rents For safety a momentary contact power switch built into the Meg O Dapter ts used to discharge or dump this capacatance The Meg O Dapter is powered by a 9 volt transistor bat tery and will operate between 6 5 and 10 volts with a current drain between 15 to 25 milliamperes With only two con trols power ON OFF and ZERO control operation of the adap ter is simple Plug output leads into the VOM and set to selected DC voltage range 2 Short input leads depress power switch and adjust ZERO control for zero reading on meter s ohms scale 3 Release power switch and connect leads to circuit or component to be tested 4 Press power swtich on for direct meter readings For lower voltage testing controls are set as above except for ZERO set in step 2 With leads shorted adjust ZERO control for pre determined point on meter which will give the desired open circuit potential External capacitance depending on value will require time to reach full charge This can range up to several seconds for large values Circuit description The schematic diagram for the Meg O Dapter Fig 1 is shown with the momentary contact pushbutton switch S1 in REMOVE THE BACK COVER and you ll discover that the trans former and battery are mounted on it Be very careful when laying out the parts location before you drill holes check clearances the OFF position This switch a double pole double throw type is wired with Sl a in the nor
105. d which is similar to the configuration used in the Tektronix T922R The T922R is the rack mount version of the T922 but unlike the T922 it has external ramp gate and a single sweep option Now in Fig 3 we can see that IC1 b sets on the positive edge of IC1 a s Q output at time tl At time t2 the oscillo scope s trigger circuit produces a pulse which in turn causes the sweep gate to go low The bar symbol indicates an active low signal Sweep gate going low resets ICI b and the scope s sweep cycle begins However when ICI b gets reset the scope s trigger circuits are disabled Therefore alter the completion of one sweep cycle there won t be another sweep displayed until the manual RESET or sweep command switch S1 is depressed again because the trigger circuit itself cannot retrigger the sweep circuit Obviously the difference between Fig 2 and IB is the fact that the former ts inherently synced up and asynchronous reset is an impossibility However the partial single sweep disable circuit s Fig 2 deceptive simplicity belies the fact that it cannot be generally applied One that really works In order for a single sweep blanking circuit to be as effective as a single sweep disable circuit the former must sync up the unblanking of the scope s CRT with the start of a sweep cycle Only one complete sweep cycle with each RESET Or new Sweep command request must be allowed Partial displays and l
106. e For the remainder of the retrofit the circuit board will be folded back on the keyboard and there will be a broad bend in the ribbon Take extra care that vou do not lean into the ribbon and crease it The cable isn t all that delicate but it wz break if you press it hard Refer to Fig 4 and note that the module at the upper right labled UM 1082 That is the TV modulator Fig 5 shows a close up of the left side of the TV module The three wires coming out of the module are the video input closest to the far edge of the printed circuit board the DC power supply the center wire and the channel selector wire nearest you The metal frame of the module itself is the A FIG 4 PENCIL POINTS TO the flexible ribbon cable that connects the main circuit board to the keyboard This is how it appears when the citcuit board is folded up against the keyboard Take extra care that you don t squish or Squarsh the cable by pressing against it The TV mod ulator transmitter is at the upper right of the board q FIG 5 THE TV MODULATOR has three wires at one end The one closest to the edge of the circuit board is the video input There is a ground foil on the circuit board directly below the video wire to which the shield will connect FIG 6 THE VIDEO WIRE to the modulator is pointed out by the pencil point A shielded output cable is tack soldered to this wire The shield lead is connected to the ground foil immediately below t
107. e PC board layout is for the Radio Shack 276 1161 bridge rectifier If you substitute any other integrated recti fier make certain that the printed circuit connections match If not modify the PC template You can Substitute a bridge consisting of four discrete silicon rectifiers such as the THE SCOPE CALIBRATOR S CIRCUIT is assembled on a printed circuit board for which a same size template is provided Note that even power transformer T1 is mounted on the board JUMPER BR1 C1 i IIRS b ki OTOT ewsns AMSZ O4W00S oy ei C2 Q1 R1 R2 a2 86 YAWWNS ee on SPECIAL PROJECTS eo Lep PK PK VOLTS Scope Calibrator 1N4001 family Again modify the printed circuit template Fig 3 accordingly Transistors Q1 Q2 and Q3 are the 2N3391 or its equiv alent NPN hfe of 300 to 500 The specified transistors have an ECB not EBC lead arrangement make certain they are installed correctly Some TI and other make transistors may be configured for an EBC lead arrangement depending upon their prefix or suffix designation So be extremely careful Holding the printed circuit board so that you are looking at the component side with Zener diode D at the bottom position Q1 and Q2 so that the flat on each transistor faces the bottom D1 Install Q3 the transistor nearest the bottom of the PC board so that the flat faces to the right edge If you substitute transistors make
108. e problem is essentially eliminated if your body is grounded when handling the CMOS IC s Connect one end of a wire in series with a 1 megohm resistor and connect the free end of the resistor to an electrical ground Connect the free end of the wire to a small alligator clip and secure the clip to your metal watchband or the metal buckle of a leather wrist strap of holes enlarged into a slot is required for PB s terminals The speaker can be any 1 or 1 inch 8 ohm type Though there is no indicated position for it on the printed circuit board as shown in the photos it can be cemented to the board using silicon rubber RTV adhesive Before actually cementing the speaker in place mark the location of the speaker on the printed circuit board and then drill two holes near the speaker terminals The speaker s connecting wires will be passed through those holes to the underside of the board and routed to the solder pads that provide the speaker PRT iv 861 HIWWNS N SPECIAL PROJECTS i nS output While you re cementing the speaker in place also cement four rubber bumpers or mounting feet on the un derside of the board near each corner CMOS chip installation Install all the other components before you install the four CMOS integrated circuits they are installed after all other components and wires are soldered in place see Fig 3 The reason for using extra care with the CMOS IC s is that CMOS devices
109. e require ments the simple cost of candlelight is surprisingly high A restaurant may easily use 50 00 worth of candles per year at every table simply to insure that the proper atmosphere exists The same susceptibility to moving air currents that gives the candle its charm and warmth makes it somewhat less than totally reliable in windy environments a fact that movie makers have exploited for years How many times has a faintly flickering point of light been coughed into nothing ness by a well timed draft leaving our horror movie hero heroine frantically fumbling for that elusive last match The circuit described in this article does away with those problems by substituting a low voltage filament for a flame and electronics for the effects of the surrounding atmosphere The result is attention getting hypnotic and fascinating Once built Syndle can eliminate the difficulties of replacing burned out candles and nursing faint hearted flames forever Filmmakers take heart however the batteries could still fail About the Circuit IC3 a 555 timer chip see Fig l is configured as an astable multivibrator operating at a nominal frequency of 4 Hz with its output directly driving a 1850 incandescent lamp Il IC and IC2 are similar astable multivibrators Operating at much lower frequencies typically 03 and 04 Hz respectively The pulse waveform produced by IC is integrated by R7 C9 and buffered by one section of IC4 The resulti
110. e same unless you salvaged parts from the junkbox then the price is right The circuit Fig 2 consists of a simple cross coupled free running oscillator with an LED in between the battery and the collector of Q2 As the transistors Ql and Q2 are alternately switched on and off so is LED The values of resistance and capacitance are chosen so that minimum cur rent is drawn in the off mode and LED is off longer than it is on during each cycle An added feature of that design is that electrolytic capacitors are not needed The values for the resistors specified in the Parts List express a wide range of ohms because the circuit is not too critical and the ex perimenter may select those values he currently possesses different from those in Fig 2 so that project cost may be kept very low Also the chances are that you may be able to 5 30 VDC FIG 2 THE EXTRA LOW POWER PILOT LIGHT circuit is noth ing more than a free running multivibrator designed to kee power consumption down way down Values are not critica and most any NPN transistor can be used in this project assemble the project this very evening from parts presently i your junkbox Typical current drain using a 10 volt power supply runs from less than one half mA 5 mA in the off mode to about 14 mA during the on mode or light burst At 5 volts DC the drain is a quarter of amA 25 mA and 3 mA respectively The higher the voltage the faster the Extra Low Power
111. e the cooling will be the best Measure the four 000 000 ohm resistors R1 R4 with an ohmmeter Use the one with the highest value for R4 for best circuit operation Measure the output of the op amp ICI with no load on the power supply The offset should be less than 11 mV Some experimentation with the value of R4 may be necessary It must be higher than R1 to ensure a low enough offset NOTE MAKE SURE R26 HAS ROOM FOR HEAD DISSIPATION R26 CONSISTS OF TWO RESISTORS GROUND TO REGULATOR CONNECT TO CHASSIS GROUND RL TO PC BOARD 5 VOLTS TO DC TO PC BOARD REGULATOR amp FRONT PANEL 5 VOLTS FROM REGULATOR RH TD PC BOARD FIG 4 PARTS LOCATED on the PC board are shown along with wire jump ers and the bar dot jumper JU1 With JU1 connected the light emitting diodes will remain illuminated for a bar display The foil pattern is shown in an x ray view A grounded three wire electrical cord with molded plastic plug PI is necessary to insure personal safety The ground should be bonded good elec trical contact to the chassis with a nut lock washer and bolt The transformer or terminal strip mounting bolt is a good place for the ground The power supply ground return should also be connected to the chassis at the same point All the front panel parts are connected to the PC board by DIP jumper cables The wires are soldered to the front panel parts and the PC board ends plug into 16 p
112. e unit You will have to fabricate the steel box yourself if you cannot find some suitable steel box The PC board is mounted inside the box using four to 2 in tapped brass spacers Before mounting the PC board however make a cutout on the back panel for the 4 way RCA connector and drill holes and the back panel earthing ter minal and the front panel switch and LED bezel The back panel ground terminal must be connected to ground lug and there to the ground terminal on one of the output sockets The RF chokes at the inputs are made by passing four turns of No 28 enameled copper wire through a small ferrite bead type FX1115 from Philips One end of each choke is soldered to an RCA input terminal and the other end to the inner conductor at the shielded cable The outputs from the MoCo Preamplifier are also connected via shielded cable If you are using batteries to power your unit then you will require one 4 X D cell battery holder and one 2 x D cell battery holder They are wired up in series to give the requisite 9 VDC Alternatively a plug pack power supply and the regulator board can be used Finally check all wiring carefully and then switch to the battery check position The front panel LED should come on to indicate that battery voltage is present Now switch to the ON position and check the preamplifier for correct operation simply by connecting it to a moving coil cartridge and amplifier and try
113. eading Even worse the transistor may be destroyed Super SENSITIVE large magnitude and the circuit would not operate normally while it is being tested There are several simple remedies for those ills By putting a simple high impedance amplifier in front of the basic voltmeter the circuit under test will not know that there is a voltmeter connected to it The power needed to move the meter s pointer comes from the batteries and is controlled by the amplifier The circuit continues to function in its normal manner and you are able to read voltages under working circuit conditions There are many good voltmeters on the market that will not load down the circuit but they don t go down below 1 or 2 volts which means that the reading is just barely seen as a flicker of the pointer coming off the zero mark The high impedance amplifier permits the use of a low sensitivity 1000 ohm volt VOM or an inexpensive meter movement Furthermore voltages less than 10 millivolts may be read on a meter that normally needs or 2 volts just to kick the pointer slightly Getting advanced The simplified voltmeter circuit in Fig 3 shows an im BIT 9VDC 0 1 MA FIG 3 BASIC CIRCUIT from which the SSSV grew This one range voltmeter measures 0 to 2 volts DC accurately with usable increments of 0 05 volt The input impedance of this circuit is one million ohms and draws Only 2 microamperes maximum from the circuit under test
114. elp you decide where you want to start and how far you want to go For your convenience we ll try to have a school representative con tact you to review the various educational programs and assist in course selection Just mail the postage paid card or write men tioning the name and date of this magazine We want to help you make things work so send for your FREE school catalog today CIE s Microprocessor Training Laboratory an integral part of the Associate Degree program lets the advanced student apply digital technology in many of the same ways electronics professionals do Cl Cleveland Institute of Electronics Inc 1776 East 17th Street Cleveland Onio 44114 Accredited Member National Home Study Council SPECIAL PROJECTS NO ROBERT MURR If your TRS 80 game programs are as quiet as an end term examination then think what sounds like Booiiinnnggg Zapppp Whizzzzz will do to keep your play action popping MANY READERS HAVE ENJOYED PLAYING GAMES ON THE TRS 80 Model I Yet something definitely felt missing as we brought the alien within our sights pressed the fire button and simply saw the word bang on our screen Now witha little hardware and some programming practice we can make these games come to life with sound from Soundbox 80 Though the integrated circuit behind all that has been around a while and has been used in other computers it has not been interfaced specifically to
115. en LED s here If one or E e both green LED s LED1 and LED2 are not glowing then there are on2 or more open circuits in the cable Should one or more of LED3 through LED6 glow there s one or more shorts between the wires in the cable It ll be a good idea to use red LED s here Once you have a good cable under test disconnect one of the LEDS wires in the test jig and see which LED goes off Try several and attempt to determine which LED will go out Then short a few pairs together one pair at a time and try to determine which LED s will come on With a little practice you will be able to figure out the logic and pinpoint the trouble quickly 861 YAWWNS amp w amp SPECIAL PROJECTS MoCo Prea Super matched pair of low noise transistors pom i a E a ee a0 zs a Ee Sn es eT ea ee aB a m aa a h Jo N E le c fa ots fh rt E MOVING COIL i ij UM Hatten i CHEDE 1 provides the needed audio boost for your super fi moving coil phono cartridge RON DE JONG BY FAR THE MOST COMMON CARTRIDGE CURRENTLY IN USE IS the moving magnet cartridge In that design a tiny magnet is mounted on the remote end of the cantilever and provides a magnetic field cut by two fixed coils mounted close by When the magnet is set in motion as occurs when the stylus tracks the record groove the magnetic field moves and small electrical signals are generated by the two coils Those sig nals
116. equipment the HERE S HOW you handle a cable that can use a ribbon con nector on one end bottom con nector but needs a solder type connector top connector on the other At the solder type connector fold the sides of the ribbon inward to form what is best described as a flat tube then wrap the tube with several turns of plastic tape where it enters the connector s cable clamp If the cable clamp doesn t bite down hard into the tape add a few more turns the wire s must be secured by the clamp not by their soldered ter minal connections Note how the top of the ribbon connector has been labled to prevent it from being installed the wrong way Centronics type printers and RS 232 extensions are the easi est to make because the terminal connections were intended for flat ribbon cable hence they match on both ends even if the connectors are different By match I mean that the order of the wires is the same even if the connectors and their numbering aren t For example if wire 1 on one end is ground it s ground on the opposite end If wire 11 is the printer busy on one end it s in the same order on the other end even if the connector terminal isn t 11 Except for the CoCo Radio Shack computers are a good example of wire standardization while a Radio Shack computer s parallel printer output connector isn t necessarily the same as the connector used on the printer the wires are in
117. er a point Larger sizes are available in either all caps or all lower case There are many different brands available though art supply stores The best for electronics experimenter use is the Letraset brand because most of the sizes have a spacing and alignment guide located under each letter on the sheet 3338 er LE In photo 9 we show how transfer type is applied The letter 5 vee is positioned over the painted cabinet and rubbed with a wood e o oe 67717 are E S a stick pen or whatever When the paper is lifted off the letter will remain on the cabinet Special Letraset style transfer type is available with complete titles for electronics panels It is applied the same way except the stick is rubbed over the entire title or word cabinet you ll leave your fingerprints in the paint While the paint is drying allow at least a full 24 hours refer to the drawing of the panel layout you made prior to drilling the holes If you did not make a drawing do so now and indicate all spacing between the components and the 9 panel markings Use the actual panel components for the measurements don t guess Try to keep the drawing to scale See photo 6 The spacing between the panel markings and the panel components must be accurately indicated in your draw ing Keep in mind that it s difficult to make changes later if you find that some control nut or knob half covers your solidly affixed labels
118. ered to the foils before the board is installed in the cabinet and later they are trimmed 861 HAWWNS fee w SPECIAL PROJECTS o a C FIG 1 THE TOP AND BOTTOM EDGES of the Scope Calibrator s output A are flat and this is how it should appear on the oscilloscope s CRT when fed through a properly adjusted low capacity probe If the oscilloscope probe s capacity is set too low the leading edge of the waveform will overshoot 8 producing a picket fence type of CRT display If the oscilloscope probe s capacity is set too high C the high frequencies will be attenuated producing a rounding of the trace s ieading edge PARTS LIST FOR SCOPE CALIBRATOR SEMICONDUCTORS BRi lIntegrated silicon bridge rectifier 25 PIV or wher same as Radio Shack 276 1161 D1 5 1 V Zener diode see text Q1 Q2 Q3 2N3391 NPN transistor RESISTORS All resistors are Ye watt 5 R1 R3 R7 100 000 ohm R2 R4 33 000 ohm R5 1000 ohm R6 1500 ohm R8 910 ohm R10 10 ohm CAPACITORS C1 C2 01 uF ceramic C3 1 uF ceramic C4 500 nF 25 WVDC electrolytic ADDITIONAL PARTS AND MATERIALS Jt J2 J3 Insulated multi way binding post red Wii Insulated multi way binding post black discard fiber wash ers and mount directly to metal chassis P1 AC power 3 prong plug with power cable attached Alu minum 3 x 2 x 5 in chassis box LMB type prirted circuit board materials hardware
119. es HERE IS THE ONLY metal part of an electrical Quick connect It taps wiring without actually cutting through the copper wires Wires are placed in tunnels or grooves plastic hinge placed over them and gently squeezed by pliers to make connection acti ne m and possibly some wires attached to a connector that provides the speaker and power connections or a separate wire might be used for the power Depending on the price of the radio or how greedy the manufacturer wants to be the connector s might be attached to little stubs of wire which must be spliced into your existing wiring or wiring you install or the connectors might be attached to a wiring harness that will stretch from the rear deck speakers to the dash with a few feet left over to spare A really decent harness will also have push on connectors for the speaker so you don t have to lie flat on your back in the car s trunk trying to solder wires on the speaker terminals The harness will also be color coded so you get the speaker phasing correct the first time Regardless whether you re using a harness Supplied with the radio or one you have made yourself run the wires up to the radio s location before you install the radio There probably won t be room for your hands behind the dash after the radio is installed If the kit is provided with wire nuts don t use them for any connections already in the vehicle such as existing speaker wires
120. essories ACTIVE ANTENNA _ New Technology for your VLF receiver Ft e TV WONDERS FOR YOUR a aR FUTURE Back to school Series Te Latest Receivers and POWER AMPLIFIERS 734 ee ee rj e e Entertain Inexpensive and versatile A P fers TV Toda rojection y 2 DVM CIRCUITS DESF satellite TV Receivers you can build rA a j Jack Darr s Monthly f i PECENE O SS Service Clinic PLUS Es ig ae 6 Service Problems and a oS as Solutions MEF Wir o Videogames yx Hobby Core we Computer Corner Dum i i e AND you also get these AS Sine Ot Solid State H Equipment bepora sh toglar MONTHLY Es LOOKING AHEAD by Dave Lachenbruch Radio Electronics covers all HOBBY CORNER IC Applicati zs PAT aspects of the fast moving by Doc Savage e FASCINATING electronics field featuring oe asec HOW TO DO IT ARTICLES COMPUTERS VIDEO STEREO i a a eo TECHNOLOGY SERVICE Toh ies obs Make Your Own PC COMMUNICATIONS PROJECTS Se a ae Boards and NEW IDEAS STEREO Wiring Techniques 4 PRODUCTS NEW Soldering and COMPUTER PRODUCTS Descldering FOR HOME JOB and Design and Prototyping MUCH MORE 3 i ig G Subscribe today to Radio Electronics Dont miss a single issue and you save as much as 7 03 off the newsstand price When you select one of the subscription offers listed on the handy coupon you ll be assured of having your copy reserved even if it sells out on the newsstand Ma
121. ets the words minute rate for Morse code character generation SPECIAL PROJECTS R8 15K R9 15K DI 1N914 C5 1 START IC will become an electronic keyer with S2 at KEYER If switch S is closed and 2 is open set at KEYER the chip will execute the punctuation practice group Complete de tails are given in Tables and 2 Every character in Morse code is based on a dot time One dot time on is a dot three dot times on is a dash Fo produce proper repeatable dot timing with IC requires an external one shot multivibrator IC2 See Figs and 2 IC will produce a very short pulse from pin 35 of the CPP to pin FIG 2 CPP1 pin terminal signal and power func tions are identified here to make circuit board sig nal tracing a bit easier Treat the CPP1 chip as you s oO TABLEA l Fa would a typical CMOS chip tenderly and with x OTABLEGB treme care not to pass a static charge through it ONE SHOT INPUT T vec START KEYER DASH INPUT I KEvER DOT INPUT T TONE ENABLE KEYER OUTPUT T ONE SHOT OUTPUT 7 s26 S2F XTAL XTAL LL RESET SPEED Sie 2 MEG aa T s2c J2 KEYER S28 OUTPUT S2A N C j Si VCC D2 N C 1N914 GND TABLE B SELECTABLE CODE PRACTICE SUB GROUPS Switch S2 Setting Code Practice Sub Groups S1 Closed HEFSU 5IEUH H5EIF USH5H ISSFE EI5S5 FEIHS SUI5F UEFHE FUI5SE SIFHE 5UES
122. ewed in place however the sides top bottom and the inside of the panel itself should be lined with a layer of acoustically absorbent material typical ly about l inch thick Heavy duty carpet underfelt not foam fiberglass or bounded acetate are all suitable for the purpose glued and or stapled firmly into position so that they will not droop against the inner ends of the port tubes Do not pad the surface areas on the rear of the baffle In fact some musicians tend to argue against fully padding the inner surfaces of a music enclosure on the grounds that it tends to dull the sound Others compromise by padding only one of each pair of facing surfaces to permit more build up of standing waves inside the box to be heard through the cone as extra mid range brightness Surface finish About now the surface finish will have to be added Painting or staining is easy but dubious in terms of eye appeal and durability Veneers or laminates don t really belong to the pop music scene Thin black carpeting is a with it finish but difficult and expensive to organize Good quality cloth backed vinyl is probably the best all round choice glued over the entire surface FITTED WITH CORNER PROTECTORS flush side handles and 2 inch castors the enclosure takes on the pro appearance The enclosure is rigid rugged and is no more bulky thanit needs to be for the job of making a really big blast from lead guitar or keyboard
123. fabulous discounts most of the profit is in the cables For example an ordinary Centronics type printer cable that you can assemble yourself for about 18 costs between 40 and 60 at your local computer emporium And ordinary R 232 extension cables for a mocem printer or a terminal are a literal gold mine a 5 foot length with something like 5 3 worth of parts sells for 4C and up while a simple gender reverser you can throw together from some junk connectcrs Starts at 30 The best way to overcome the greed of the computer shops and save a bundle at the same time 1s to simply make your own cables Sometimes it s a snap 10 minute ob to assemble the equivalent of a 60 printer cable other ti nes it takes a little more effort because some of the manufactt rers throw a hook into their connections to force you to buy their cables For example the non standard Apple paralel printer connections are legendary The quixotic numbering THE CONNECTORS Specifically made for ribbon cable have razor sharp insulation dis placement terminals When the ribbon is pushed against tie terminals the knives slice through the insulation and the wire makes contact with the ter minal s No soldering of any kind is required of Radio Shack s original printer port connections led to many repairs during the warranty period and many users believe it was innumerable freebie repairs that convinced Radio Shack to use st
124. ference The completely passive device requires no AC power to operate and is compact and lightweight Bandpass is Channels 2 through 83 all connections are 75 ohm type The model VS 6004 is priced at 41 75 Winegard Company 3000 Kirkwood Street PO Box 1007 Burlington IA 52601 COMPUTER POLLUTION CONTROL The Magnum Isolator is designed to control se vere electrical pollution Electrical pollution drves microcomputers bananas and many systems even create their own pollution Dis ks and printers often create enough electrical interference to disrupt an entire program nearby electronics equipment can be affected as well CIRCLE 823 ON FREE INFORMATION CARD The Magnum Isolator incorporates heavy duty spike surge Suppression and features four individually quad Pi filtered AC sockets It will control pollution for an 1875 watt load each socket can handle a 1000 watt load The Magnum Isolator is priced at 200 95 Electronic Specialists Inc 171 So Main St PO Box 389 Natick MA 01760 More on page COVER COVERAGE LProbably the most exciting phase of pre paring a magazine for publication is the generation of a suitable cover picture to tell our newsstand magazine readers what we have to offer them in the issue And that 1s exactly what we have done on our cover However we did use a few props to dress up the photographic scene and I d like to tell you adout them Our publisher Larry Steckler
125. for almost any power sup ply the experimenter ts likely to need C REMOTE CON TROL PROJECTS 5 00 Radio contro infra red visible light amp ultrasonic systems are all inctuded along with methods of applying them C ELECTRONIC TEST EQUIPMENT CONSTRUCTION 4 50 Construction de tails of a wide range of test equipment the ex perimenter can build at home ELEMENTS OF ELECTRONICS Special C ELECTRONIC PROJECTS USING SOLAR CELLS 5 00 Simple circuits that have numerous ap plications around the home C ELECTRONIC TIM EA PROJECTS 5 00 Timing circuits tor almost any application the experimenter might need A most valuable reterence C COUNTER DRIVER amp NUMERICAL DISPLAY PROJECTS 4 50 Features ap plications amp projects using vanous types of numerical display de vices shod aE Tuini l aiden Prepare 6 volume set C THE SIMPLE ELECTRONIC CIR CUIT amp COM PONENTS 5 75 All the fundamental theery needed to lead to a full understanding of the simple atectronic circuit and its components C ALTERNATING CURRENT THEORY 5 75 Alternating cur rent theory without which there can be no comprehension of speech music radio or Television O SEMICONDUCTOR TECHNOLOGY 5 75 Everything you always needed to know about solid state devices in one volume O COMMUNICATIONS 7 50 Covers most modern communication syslems Line micro wave submarine s
126. ghout and beyond the listener s frequency range with output level control That covers the projects found on the cover but there s so much more in this issue that I m sure you ll be involved with project building until we publish our Fall 1983 issue of Special Projects Till then happy build ing Julian S Martin wm 86l YAWANS SPECIAL PROJECTS PRINTER model DMP 100 is a dot matrix printer with graphics capability It prints 50 characters per second at 10 characters per inch and has a bit image mode to allow print ing of fully addressable high density graphics Using an optional screen print pro gram the model DMP 100 can produce de tailed black and white graphics printouts similar to those on the TRS 80 Color Compu ter screen display W PRODUCTS The model DMP 100 has 80 upper and ee lower case 5 x 7 dot matrix characters which SPECIAL REPRINT i Flee tron ics Corn OPED Pantha rt tbe m ao a BUILD A BACKYARD SATF LITF TV RECEIVER Don t miss out again Send away today for your 36 page booklet containing a complete reprint of all seven articles in the series on Backyard Satellite TV Receivers by Robert B Cooper Jr This all inclusive report gives you all the data you need to build your own Backyard Satellite TV Receiver TELLS ALL ABOUT domestic satel lite communications with full details on how you can pull those elusive TV signals from space
127. gic low whenever the lowest 8 bits of the address buss are decimal 126 or 127 That output is combined separately with the inverted and non inverted AO The lowest address line is used to select whether the opera tion is latching to or writing to the chip IC5 a b and c are used so that the circuit will only respond during an input or output instruction They are again combined and are used to feed the master enable of C2 Soundbox 80 needs only a regulated 5 volt power supply you cannot power it from the 5 volt pin on the TRS 80 edge connector a clock and an audio amplifier Schematic di agrams for each of them are illustrated in Fig 2 3 and4 The schematic diagrams for Soundbox 80 Figs through 4 may be built on a circuit board or wire wrapped The con nections to the TRS 80 are made via a 40 pin card edge connector J1 The power supply of Fig 2 uses a6 3 VAC transformer a full wave bridge rectifier and a 7805 five volt regulator chip The 2200 uF electrolytic capacitor is used to filter the DC before the input of the regulator and the 0 1 uF capacitor used to reduce the noise on the 5 volt output Additional 0 uF disk capacitors may be tied directly across the Vec and 86l YAWWNS N SPECIAL PROJECTS NO NO eee ee ee eee SS See eer p O O n 117 VAC FIG 2 THE POWER SUPPLY CIRCUIT is p the usual regulated 5 volt DC supply that powers so many projects built by ex perimenters Plug P1 and
128. gust 1981 Edi tion and reappears here by permission into the phono inputs of a conventional hi fi amplifier One solution is to use a transformer but those are quite expensive and difficult to manufacture The alternative solution is to use an additional preamplifier stage and the design presented here has performance equal to or better than most com mercial units for a fraction of the cost We call it the MoCo Preamplifier for obvious reasons Before taking a look at the circuit however it may be as well to point out that the requirement for a separate preampli fier is one reason why moving coil cartridges have not gained widespread popularity in the past Commercial units tend to be expensive and that coupled with the high cost of the cartridge itself 100 or more has been sufficient to deter most hi fi enthusiasts This project will help overcome that problem as far as the cost of the preamplifier is concerned Design considerations Perhaps the most important specification of a MoCo Pre amplifier is the signal to noise ratio Let s first take a look at the various sources of noise and find out how they may be minimized in a low noise preamplifier design There are four main sources of noise in a transistor ampli fier shot noise emitter base voltage noise 1 f noise and thermal noise Those individual noise sources are illustrated in Fig 1 which shows a simplified model of a noisy transis tor amplifier Note that
129. h voltage board is a bit different from drawing be low because of last minute changes Use the diagram T1 gt PRI WIND Od i I Raar ey Sere i im N d i i y A iiia n Den Ba pot B f 2S ae ed he gp a Li r ie Photos by MEI Linse JACK SPILLANE HERE IS A SHORTWAVE CONVERTER AND AUTOMOBILE broadeast band receiver combination that provides reception in the 49 meter 5950 to 6200 kHz 41 meter 7100 to 7300 kHz and 31 meter 9200 to 9700 kHz shortwave broadcast bands and also WWV the Bureau Of Standards time signals at 10 000 kHz Put it all together it spells highway SWL DX ing Before we get to deep into this article lets talk about highway SWL DX ing Yes you can use the Three band Shortwave Converter to listen to distant shortwave stations as vou wing down the road but the term used implies listening at home too You see what we are advocating here is the acaption of an auto car radio of AM vintage coupled with a hame brew converter to pull in DX from the shortwave bands Those two units can be installed in your car or they may be set up on your desk with an external power supply to replace the car s battery The supply need only be a l ampere regulated 2 volt supply of the variety used in many of the projects found in power supplies commen to other projects you have read in Special Projects The circuit The input SW signal is fed from the antenna through ANT
130. he hot video lead h ground For clarity in Fig 6 the pencil points to the video input wire the wire you will bridge for the low Z video output Carefully prepare the end of short length of thin coaxial catle such as RG 174 U or even standard audio shielded cable Just be certain that it s thin about inch di ameter Twist and tin the shield and strip the center con ductor insulation within 4 inch to inch of the shield Locate the video input wire to the TV module and tack solder the cable shield to the ground foil directly under the module s video input wire Carefully cut away all excess strands of shield wire to ensure they don t short to adjacent foil then wrap the cable s center conductor around the mod ules video input and solder Flip the circuit board over route the cable to the phono jack and cut it to length Be certain that your routing will not cause the cable to interfere with re installing the circuit board If necessary you can snake the wire around the plastic supports sticking up from the cabinet Again prepare the tree end of the coaxial cable then connect it to the phono jack Finally secure the circuit board with its two screws install the cabinet cover secure the five mounting screws then place a dab of fast drying adhesive or rubber cement on the feet and secure in place Fig 7 shows how the installation will appear when you plug in the cable from the monitor Using a video mo
131. her a standard TV or a video monitor Simple theory Fig shows a simplified block diagram of the Sinelair Timex computer The computer s composite video output is fed into a TV modulator module actually a miniature low power TV transmitter that broadcasts the comput er s display to the TV receiver through a length of shielded coaxial cable The module s output is on TV channel 2 or Computer video output HERB FRIEDMAN 3 the user selects the channel that is not in use in his or her local area The actual transmitter output connection ts a phono jack built into the modulator module To provide a low Z low impedance video monitor output LOW Z COMPOSIT VIDEO OUTPUT ON TV CHANNEL 2 0R 3 TV COMPUTER MODULATOR FIG I SIMPLIFIED BLOCK DIAGRAM of Sinclair Timex computer s The low impedance compositve video out put is fed to a TV modulator module which is actually a miniature transmitter It provides an RF output on TV channels 2 or 3 The internal video load resistor is 390 ohms The low Z output is taken from across the 390 ohm resistor at points A and B with A being high 4 FIG 2 THREE MOUNTING SCREWS are concealed be hind the cabinet s rubber mounting feet The pencil points to one of those screws Simply pull or peel the feet off the cabinet to gain access to the screws FIG 3 THE PHONO JACK used for the low Z video output is mounted at the rear right
132. hing about it You guys are in the dark ages When is the editorial policy going to change RoD LESTER Northbrook IL My wife tells me that she is giving up her subscription to her favorite knitting magazine because the editorial is almost 100 computer theory and soft ware discussions Well maybe l m mak ing that up but it seems to be the case nowadays It appears as if every elec tronics magazine is changing its name to some computer type title to pull in the big bucks they can earn in the computer field in so doing they forget about their faithful and loyal readers Well faithful and loyal readers who are electronics experimenters stick with Special Pro jects because we are sticking with you Yes we will have some computer pro jects in every issue but the bulk of the issue will cover the varied interests of alt our readers Electronics experimenters dont change their spots solder burns just because a new fad is in the scene Remember how everyone ran to CB radio Try to find someone who wili admit to owning a CB rig today No we don t follow fads we serve electronics experimenters TELL ME WHY Our teacher wants us to pass the FCC Radio Cperator s second class license examination in order to get a passing grade for the term don t plan to use the license yet l m forced to take it Is there a better way CHARLES NETTLE New York City There is a better way and that is to take the exam prove to yo
133. idges is merely stated as being greater than 10 ohms but if it is too high the leakage inductance of the cartridge will create unwanted bass boost It is for that reason that we have included the 47 ohm resistor R1 on the input Incidentally that resistance is the standard input impedance of most mov ing coil preamplifiers C861 YSWWNS Ww amp SPECIAL PROJECTS FIG 3 FOIL SIDE PATTERN of the printed circuit board used to assemble the MoCo Preamplifier Physical isolation of the left and right audio stereo circuits greatly re duces possibility of crosstalk The collector load of Q1 Q2 is transistor Q3 used here as a constant current source delivering about 3 mA We have used it in preference to a simple resistive load because it permits us to adjust the collector current of Q1 Q2 in dependently of gain In addition it increases the open loop gain and linearity of the amplifier to give very low distortion figures and increases the supply rejection ration important if the unit is to be run from a plug pack Following Q and Q2 we have another common emitter amplitier consisting of transistor Q4 The emitter is de coupled to ground rather than to the supply which again improves the supply rejection and the emitter voltage is used to bias QI and Q2 on The arrangement is a variation on collector biasing because the emitter voltage of Q4 tracks the collector voltage of QI and Q2 However it has an advantage over conven
134. ies for qualified computer techni cians The U S Department of Labor projects over a 100 increase in job openings for the decade through 1985 Most of them new jobs created by the expanding world of the computer Learn At Home to Service Any Computer NRI can train you for this exciting rewarding field Train you at home to service not only microcomputers but word processors and data terminals too Train you at your convenience with clearly written bite size lessons that you do evenings or weekends without going to classes or quitting your present job Your training is built around the latest model of the world s most popular computer Its the amazing TRS 80 Model III now with disk drive and the capabilities and fea tures to perform a host of personal and business func tions No other small computer has so much software available for it no other is used and relied on by so many peopie And it s yours to keep for personal and business use You get plenty of practical experience Under NRIs carefnlly planned training you even install a disk drive verifying at each step its operation Using the NRI Discovery TRS 80 is a trademark of the Radio Shack division of Tandy Corp Somebody s servicing t i E l m OT Se AI Lab that also comes as part of yo ir course you Fuild and study circuits ranging from the simplest to the most advanced You ana lyze and troubleshoot using N the profes
135. ific wire widths such as 20 26 30 36 or 40 wires If you need something like 38 wires you Simply strip away 2 wires from a 40 wire ribbon cable Ribbon cable can be either all one color with one single wire on either side a different color or every filth wire might be a different color to help you count trom either end or every group of wires might have individual colors say all colors of the rainbow repeated in sequence Regardless how it s done the two outside wires are never the same color unless someone has deliberately gone out of their way to be stupid by stripping multi color wire in such a manner the two outside wires are the same color The outside wires are polarized tracers and must be a different color If you use conventional ribbon cable one side wire will be red or black or blue while the other wires are one other color If every fifth wire is color coded only one outside wire will be color marked To save yourself the heartache of an inadvertently blown periperal standardize and use the color coded wire as the 1 lead connected to the 1 terminal Regardless of what the manufacturers of your computer and peripherals do your cables will be OK if you use one and only one cable wiring standard Ribbon cable comes in several different gauges The stuff from Radio Shack however is the easicst to locate and 1s among the least expensive it works just fine because its insulation appears to be the exact thic
136. in IC sockets Calibration and checkout The only adjustment is for the current monitor The volt age at pin 6 IC2 should be set equal to the voltage at pin 5 during full rated output 3 A A simple calibration load is shown in Fig 6 Connect a DC ammeter capable of display FIG 5 PICTORIAL DIAGRAM FOR THE POW ER SUPPLY wired to a terminal strip in the de vice s metal box enclosure Be sure to space parts so that a flow of circulating air will cool those that tend to heat up hese A GROUND ee ed TO PC BOARD ay amp FRONT PANEL oS DQ 12 6V AC FROM TRANSFORMER T1 a 86l HIWWNS SPECIAL PROJECTS pan STRAIN RELIEF GROMMET ing 3 amperes in series with the calibration load as shown Adjust R until the meter reads 3 amperes Using a DC voltmeter measure the voltage at IC2 pin 5 Record the voltage and disconnect the load Now move the voltmeter to pin 6 and adjust R6 until the voltage reading is the same as at pin 5 All voltage measurements are taken with reference to ground Be cautious around Q Fig 6 as it is dissipating 5 watts and will get very hot without a heat sink Severe burns could result if the transistor is touched f not using a heat sink then disconnect the positive lead that goes to the power supply every 15 seconds to allow the transistor to cool to a safe A PEEK AT THE BACK of the unit shows the 5 volt regulator chip mounted on an over sized heat sink
137. ind this issue to your liking TIME CUTTER You have no idea how much time your Story Tracer Tone Special Projects 5 page 36 saved me when ran into a short circuit problem in my firm s com puter cable hook up had buiit the Trac er Tone a few months earlier on a lark It was a simple circuit required a few parts most of which were within reach of my workbench and it worked like a charm put the gadget aside consider ing It to be a novelty until that God awful short in the ribbon cable rat nest in the false ceiling Today placed the plans for Tracer Tone up on the bulletin board for all to see and noticed a few technicians collecting parts to make their own That s OK with me as long as they don t take my back copies of Special Pro jects PREFER TO BE NAMELESS Silicon Valley CA Thanks for the letter Nameless Now dig your toenails into the carpet be cause when you turn to page 32 in this issue you may just leap into the over head with excitement We have an equally simple circuit that tests ribbon cables for shorts and opens This one is a winner and if your plant is creeping with ribbon cables as our office is this project is for you Let me know what you think of it COMPUTER BUFF UNSATISFIED Come on you guys get with it The way to go is computers There is so little in each issue of Special Projects on the greatest thing since sex computers and the editors are doing next to not
138. ing it out Happy listening SP 861 HIWWNS ss oh SPECIAL PROJECTS gt nN ONE MANY SINGLE SWEEP BLANKING CIRCUITS HAVE BEEN PRO posed as add on options to oscilloscopes like older Dumonts and the Philips PM3210 which have external sweep ramp or gate outputs and Z axis inputs Fig 1 However none match the performance of the built in circuits they are attempting to mimic based on disabling sweep or trigger circuits after one sweep in Fig 2 Most add on designs unblank the scope s CRT for one sweep cycle via its Z axis or intensity modulation input after a reset or new sweep command then blank the CRT again by Z AXIS OR INTENSITY MODULATION SCOPE INPUT SWEEP Z AXIS IN OuT ort Qion Bus SINGLE SWEEPER ONE triggering off the trailing edge of a sweep ramp or gate output Fig 1 But most add on designs have partial display asynchronous reset and lock out problems Further little effort has been made to apply those circuits to scopes like the Tektronix T921 T922 or Heathkit 10 4510 the former has a Z axis input but no external ramp or gate output and the latter has neither external sweep output nor Z axis input Taking a closer look With the typical marginal sweep blanking circuit in Fig the oscilloscope s CRT is held blanked via its Z axis by the flip flop s Q or Q outputs Depressing the RESET Switch sets the flip flop and unblanks the scope
139. ion and the reduction of resistors re quired in the calibration circuit the VOM is set to a DC voltage range Depending on the VOM selected a range of 50 to 100 volts or more can be used Once calibrated to a particular VOM recalibraticn would be necessary for use with any other make or model Construction and calibration All parts and components are standard off the shelf items Layout ts not critical and can be made point to point on LOW VOLTAGE 117V 12V er 2N1711 HIGH VOLTAGE 01 R A K3081 C5 10MEG R10 N yu H E 4 R8 R12 10 MEG E LCG R9 R12 01 02 01 10MEG 2N1711 02 2N3439 5K 3081 R13 1MEG TEST CAL JUMPER R14 4 IK ANODE SK3081 1N4007 CATHODE INPUT JI FIG 1 COMPLETE SCHEMATIC DIAGRAM for the Meg O Dapter clearly illustrates the isolation be tween the ow voltage circuit and the high voltage circuit The 7555 CMOS integrated circuit is identical in function to the common 555 chip but draws very little current greatly extending the useful life of the transistor battery B1 power supply The Stancor transformer specified for T1 in the Parts List should not be replaced or substituted Switch S1 is a spring return type shown in the schematic diagram in the at rest position Check out transistor and dicde connections perf board A model 3301 Pomona case was used measuring 4 4 inch long by 2 M e inch wide by 1 16 inch deep Two circuit boards we
140. is issue of Special Projects Enjoy reading it and enjoy building projects as much as we have enjoyed preparing the issue for you The Editor s Choice for this issue is Syndle the Electronic Candle which appears on page 61 lf you d like to learn Morse code turn to page 93 fer complete plans fora code practice processor that we call CPP7 And there is lots more to pick from that ll make Special Projects your benchside manual for many months to come Happy building Julian S Martin KA2GUN Managing Editor Radio Electronics Special Projects ISSN 0730 7616 published quarterly by Gernsback Publications Inc 200 Park Avenue South New York NY 10003 Phone 212 777 6400 Four issue Subscription rate is 9 00 U S funds only Canada and Mexico subscribers add 3 00 for postage All others add 7 00 Mail all subscription orders address Changes correspondence and Postmaster Notices of undelivered coples Form 3579 to Special Projects resale Service Suite ublications Inc All 1101 200 Park Avenue South New York NY 10003 Single copy price 2 25 1983 by Gernsback rights reserved Printed in U S A A stamped self addressed envelope must accompany all submitted manuscripts and or artwork or photographs if their return is desired should they be rejected We disclaim any responsibility for the loss or damage of manuscripts and or artwork or photographs while in our possession or otherwise As a service to readers Radio Electr
141. is ungrounded Romex so the box won t be at ground As a general rule of thumb If you can get a 120 VAC meter reading from one side of the outlet to the screw in the wall plate the screw is at electrical ground If the convenience outlet box isn t grounded connect the free end of the wire to a cold water pipe To ground yourself secure the clip to any metal part of your watchband that also contacts your skin If your watch has a leather strap the buckle is probably metal so that s where you place the clip After youre grounded you can unwrap the CMOS IC s and install them CMOS IC s also require a grounded soldering iron it must have a three wire power cord one wire is ground You run a good chance of zapping CMOS devices if you use an un grounded soldering tron Battery eliminator modification There s plenty of room on the left bottom edge of the board 861 YAWWNS J w SPECIAL PROJECTS Ta for the power jack of a battery eliminator Select any type of printed circuit jack that will match the connector on your 9 volt battery eliminator Mark its position on the board making certain that you are clear of any foils on the underside of the board Drill or cut the matching holes pass the jack s terminals through the holes and then connect them to the appropriate positive and negative power foils which you ll find are immediately adjacent to the jack If you use solid 20 or 22 wire for the connections
142. ists and keyboards 92 EXTRA LOW SCOPE CALIBRATOR FOR HOME Here are three square BREW Bree wave voltages 5 0 0 5 and 0 05 volts peak to PROJECTS For once someone has consid The old breadboard Mom s chopping board and the oat meal box are no longer used to assemble projects ered the battery drain that pilot lights place on projects Now a simple circuit flashes a light emitting diode peak that serve as a Calibration signal for your scope s low Capacity input probe The Magazine for people who build electronic gadgets CUSTOM SOUND FOR YOUR CAR That Detroit or Tokyo hunk of iron and plastic you Call trans portation could stand an up lift in the radio audio department considering that the old heap is going to pile up more than six digit mileage 61 SYNDLE The flickering light of a candle has fascinated man throughout the centuries Now you can do the same without fear of burning your self or Icsing the house by using an electronic candle that simulates the flame s characteristics To turn it off you may try to blow it out CPP1 CODE PRACTICE PROCESSOR Now you can learn the differences between the dahs and dits and pick up the required code speed to J get your Amateur Radio ticket from a single chip processor i the AGC bus without interrupt MAKE YOUR OWN COMPUTER CABLES We tell you
143. iver s frequency display at the zero beat position It must be re membered that the BFO output mixes with the IF carrier signal which is present all the time when an AM station is tuned properly A non carrier signal such as a SSB with suppressed carrier will not work with this device SP 86 YAWWNS ate wo Pewee ee ee ee eee ee ee a a Electronics Paperback Books Quality Paperbacks at Affordable Prices 30 SOLOEALESS BREADBOARD PRO JECTS BOOK 1 5 75 Whenever possi bia the same parts are used in several pro jects Even a first time builder can complete these circuils O HOW TO GET YOUR ELECTRONIC PROJECTS WORK ING 5 00 Helps you troubleshoot and repair home built projects of avery description C MINI MATRIX BOARD PROJECTS 5 00 A variety of pro jects that can atl be buit upon a muni matex board that has 10 strips and is 24 holes long C PRACTICAL ELEC TRONICS CALCULA TIONS AND FORMU LAE 7 50 A basic reference work thal bridges the gap be tween complicated technical theory amp cut and tried methods C INTERNATIONAL DIODE EQUIVALENTS GUIDE 5 75 Helps you find substitutes for the many different types of semiconductor MODERN OP AMP PROJECTS 5 00 Wide range of special ized op amp circuits im ciuding lo noise k distortion uftra hy input impedance etc MULTI CIRCUIT BOARD PROJECTS 5 00 21 fairly simpte Projects that can all be duit on
144. ize your projects We have touched on the basic principles of decoration the precise type of materials you use will depend primarily on what s available in your neck of the woods Actually just about anything that will stick to the cabinet until you can get a protective clear coat to hold it down can be used If you re not certain a product will work try it on a small piece of scrap aluminum or a cabinet salvaged from an old project Whatever you try the key to success is to always be certain the surface is absolutely dry before you work on it If in doubt simply wait 24 hours before you apply each coat of paint to the cabinet or the panel markings or whatever SP HERE S WHAT THE FINISHED PROJECT looks like on your test bench What makes the packaging effort worthwhile is that the home brew project looks good enough to use and clearly in structs the user as to its connection and application with other devices Beauty takes the beast out of your project 12 l 2 f Sat ts Sey T A Taz j H 91 SPECIAL PROJECTS wo nN Extra Low Power PILOT LIGHT This flashing light telis you that it is time to turn off the power switch BY EVERT FRUITMAN HOW MANY TIMES HAVE YOU REACHED FOR A PIECE OF battery operated equipment only to be disappointed upon finding the batteries drained because someone had forgotten to turn it off Some kind of pilot light might have saved the day and the batteries Bu
145. jack J1 to a high pass filter consisting of CL L1 C2 L2 and C3 See Fig 1 That filter is used to reduce broadcast band feed through RF transformer TI is the combination of an untuned input primary winding and the tuned secondary winding The latter is parallel with the series capacitors C5 and C6 and tunes from 5950 kHz to 10 000 kHz The signal is coupled to gate G1 of QI a dual gate MOSFET transistor used as an RF mixer QI mixes the incoming signal from the antenna with the output of the crystal oscillator Q2 Small signal N channel FET Q2 operates as a Pierce oscilla tor Switch SI switches in either crystal X1 5000 kHz to crystal X2 8500 kHz for band switching purposes The output of Q2 is coupled through C7 to gate 2 G2 of QI The mixed output of Q2 is coupled from the drain D of QI and its load resistor R6 through C10 to a 16 inch length of RGS8A U coax cable That cable is terminated by a Motorola type bayonet connector PI to match the antenna input jack on the automobile receiver The circuit board The circuit board is a standard prepunched perfboard with 042 inch holes spaced 100 inch apart Push in terminals with 042 inch diameters were used to mount the circuit components The main circuit board is 5 10 inches by 1 30 inch and the filter board is 1 50 inch by 1 10 inch The wiring of the boards is done with No 30 insulated wire wrap wire and soldered to the terminals on the bottom of the board The
146. justable types that can be incorrectly set and destroy the CPPI chip IC1 Consider heat sinking the 7805 integrated circuit chip as a precautionary measure Operation Using the CPP is quite painless Table A contains the code practice tables for switch S being open Table B contains the code practice table for switch S1 being closed Table C gives the dits and dahs of the International Morse Code First determine which practice table you want and set switch S1 to either an OPEN or CLOSED position Turning power on will reset the processor Then set S3 at START Adjust R7 for a comfortable code speed The selected sub group will continue until 3 is set at srop That s all there is too it Determining code speed can be done in one of two ways The simplest way is to go to the keyer mode and press START Hold the dot input to ground pin 37 and count the dots for one second Take the number of dots counted and multiply it f FIG 3 FOIL SIDE LAYOUT of the printed circuit board is shown here actual size Considering the number of closely spaced wires it is wise to go the PC board route PARTS LIST FOR CPP1 SEMICONDUCTORS D1 D2 1N914 silicon switching diode IC1 CPP1 code practic2 processor integrated circuit IC2 IC3 555 timer intecrated circuit RESISTORS R1 5 R8 9 15 000 ohm watt R6 220 000 ohm 1 4 watt R7 2 Megohm potentiometer CAPACITORS All capacitors rated at 10
147. k ora zingy solo sound more sustained treble is desir able but a bass roll off at 50 Hz might be acceptable T FE EE HEr i i THE E130 DRIVER is a large and heavy loudspeaker requiring a 14 inch diameter cutout The metal dome cap is not just de corative it holds the frequency response to about 6 kHz The driver is available in 4 8 and 16 ohm versions The 2901A treble power pack is compatible with all three Bass guitar Bass sustained to about 40 Hz treble response not important above 2500 Hz Hawaiian steel guitar Bass sustained to about 50 Hz treble about 5000 Hz Lead and rly thin guitar Bass sustained to about 50 Hz strong middle response 6000 Hz at least Electric piano Broadly similar requirements to lead and rhythm guitar above If a brighter than average sound is required the response can be extended to 10 000 Hz or more by the addition of one or More tweeters having an appropriate power rating Thus voice vocals can be reproduced with a smooth response fram 50 to about 7000 Hz The setup can be a system like that for lead guitar or electric pian provided that the middle end treble is not too peaky rendering the voice harsh or sibilant Looking at those requirements it is evident that the loud speaker system for a recital organ or bass guitar must have a fundamental response down to the 30 40 Hz region com bined with the ability to generate acoustic power appropriate to the environment F
148. ke sure you get all the excitement in every issue of Radio Electronics every month by filling in and mailing the coupon today Mail to Radio Electronics Every Month i PO Box 2520 Boulder CO 80322 Get the Best Mail Today O 1 year 12 issues only 14 97 You save 3 03 off newsstand price O Payment Enclosed O 2 years Save More 24 issues 28 97 Save 7 03 off the newsstand price O Bill Me Name a es please print Address PE E State o ip Code Canada Add 3 00 per year BST aih is oe cise en bt om Aw 9 en SPECIAL PROJECTS oi Retro fitting the Now you can cut out the middleman by driving the video monitor directly from the bargain computer for maximum picture clarity the idea is expandable PERSONAL COMPUTERS THAT USE A STANDARD TV SET AS THE monitor all suffer from reduced resolution because of the inherent limitations of the TV itself But feed the very same video display to a standard TV monitor even a6 MHz model made for closed circuit television and the increased sharp ness and resolution is astounding A case in point is the Sinclair ZX 81 and its twin sister the Timex 000 The very same display that is best described as passable on a TV set becomes razor sharp on a monitor What s that You thought a TV was a monitor OK let s take time out to explain At best a TV set has a 4 MHz bandwidth because the American TV standards only require a 4
149. kings to the painted cabinet Notice the paper shields taped to the cabinet in photo 9 Often unwanted transfer type symbols will transfer to the cabinet wherever you touch the sheet The markings that stick with the most tenacity to the painted surface are of course the ones that flake off accidentally You simply avoid a good part of the problem with the paper shields most unwanted markings will flake off on the shields Photo 10 better illustrates the user of paper shields Note the large shield to the left of the word Calibrator It covers the word Scope Without the shield you would find that fresh transfer type sheets might actually lift previously applied markings off the cabinet Also note the small THE FINISHED CABINET S front panel is now ready for the panel components to be mounted The cabinet has been sprayed with clear Datakoart to protect and secure the panel markings dashes on the lower shield They provide the reference line for the larger type used for the word Calibrator The dashes which are the guide marks from the Letraset transfer sheet are a lot easier to use than juggling a ruler as a straight edge and better than marking the panel with a China type grease pencil grease pencil doesn t always rub off com pletely particularly from light color paints One word of caution regarding transfer letters and titles The stuff is
150. kness required for most ribbon type connectors If the wire is too heavy you can easily damage a connector during assembly Unfortunately while I have always been able to purchase the wire in a Radio Shack store have never been able to find it in the catalog though it must be there somewhere At times you ll have had no choice but to use solder connections and you ll create the least problems if you A use a light iron about 22 watts with an ultra thin 1 6 inch soldering tip B use the so called wire type solder of 22 or 24 gauge and C you twist the wire ends very very tightly and tin them solid from the insulation to the tip before you try to install them on the connector s terminals 86t YAWANS N wo SPECIAL PROJECTS ww So Is it really standard The first step in making your own computer cables is to determine if the things you want to connect together are standard whatever standard is supposed to mean If you re connecting to a Centronics type printer the con nections at the printer itself are standard or at the very least the eight signal lines the ground the strobe the busy and the ACK connections will be standard It you re making up an ordinary RS 232 extension cable which usually sells for between 40 and 60 depending on its length both ends are usually standard unless its a modem cable which reverses pins 2 and 3 on one end If there are any
151. l a mounting screw The pad directly above the TV channel selector switch does not conceal a mounting screw Pull off the other three pads If they re stuck puli hard vow ll glue the pads back when you re finished Remove the three screws concealed by the pads and the two screws that are in the clear Gently separate the case You Il be looking at the back of the main circuit board and the keyboard The two are connected by a section of ribbon cable Locate the two assembly screws holding the main board and remove them Gently flip the board over on the keyboard sectton that will expose the entire cabinet area under the circuit board There ts one safe area for tnstalling a video jack that will not interfere with any future peripherals for the Sinclair Timex computer It ts located at the top right side near the memory expansion edge connector Carefully drill a Y in hole for a phono jack the type that mounts with a single nut threaded on the body Make certain that you use the supplied ground lug as show in Fig 3 Although the inside of the plastic cabinet is flashed with a metallic coating to pro vide a shield ground for the computer use the jack s ground lug if you want to ensure a stable TV display Both before and after installing the phono jack take ex treme care not to damage the ribbon cable that connects the kevboard to the main circuit board In Fig 4 the pencil points to the ribbon cabl
152. l intensity the battery voltage is usable As the voltage drops LED2 begins to dim rapidly as the voltage across D1 falls below the Zener s rated breakdown potential and the current passing through R6 D1 and LED2 de creases It is easy to detect a decrease in battery voltage before there is a detectable change in output frequency The circuit is built on a small piece of scrap perfboard Point to point wiring works nicely or a simple printed circuit board may be designed and etched Layout is not critical Keep all leads as short as possible 1C2 1 2 4027 1 2 1 2 4027 Using it The 455 kHz output signal must be coupled loosely to the receiver s 455 kHz intermediate frequency amplifier sec tion To do that begin by removing the receiver s top cover Tune your receiver to a local station and move the 455 kHz BFO output wire across the receiver s circuit board That wire is insulated and must not make electrical contact Signal transfer is by capacitive coupling When the wire comes near the 455 kHz IF circuit a beat note or whistler should be heard in the receiver s audio output Secure the wire with masking tape in a position to give the receiver a comfortably loud beat note To determine the station s exact frequency tune the re ceiver for a zero beat A zero beat signal cannot be heard However as you rock the receiver s tuning knob from side to side the whistling tone will reappear Record the rece
153. ld not be ready to build into the cabinet While we have assumed the use of cleats the main enclo sure can be assembled in any way that will ensure that it is completely rigid and airtight except for the deliberate air path through the twin ports That is important accoustically because with the internal pressures generated by a speaker of such power rating panel rattles or air whistling through cracks can be very obvious Furthermore a relatively bulky enclosure manhandled frequently into vehicles and onto platforms will soon loosen up if not put together rigidly For that reason all joints should be glued and screwed at the time of assembly For homebuilders we would suggest propping the cabinet at various angles running a line of PVC glue along each joint in turn and leaving it to set Not only will that add strength but the glue will also form a meniscus seal wherever it is so applied Where the baffle is a fixture some may prefer to have the back panel removable Alterna tively if the bass driver is secured by bolts and captive nuts access to the inside of the enclosure could be through the base driver cutout However assuming the former the back panel must fit snugly against its own cleats with a generous number of screws to hold it in position We would suggest that it be bedded down against a strip of adhesive foam to take up any slight discrepancy in the mating surfaces Internal Damping Betore the back panel is scr
154. lect 10 characters per inch 80 columns at 27 lines per minute or expanded at 5 characters per inch 40 columns The printer measures 516 x 16 8 4 inches and weighs 8 pounds It operates from 120 volts AC at 60 Hz uses 15 watts and is U L listed A ribbon cartridge is included The model DMP 100 is priced at 399 00 Tandy Corporation Radio Shack 1800 One Tandy Lane Fort Worth TX 76102 MICROCOMPUTER the Vector 4 in corporates both 8 bit and 16 bit microprcces sors and presents a choice of several operat ing systems It calls on 16 bit commands to Speed up selected 8 bit operations To pro vide maximum program development flexibility multiple operating systems are available for the Vector 4 including CP M MS DOS and OASIS The Vector 4 includes a detached key board conveniently located integral lapry disk drives and a green phosphor video display screen that is treated optically to elim inate reflection and glare With a single board microcomputer design for compactness and reliability the Vector 4 comes standard with 128K of internal RAM expandable to 256K Memory mapping logic allows the Z 80 to access the entire main memory in 64K increments There are also three S 100 card slots for accommodating p EARARARAARARRAR I i t D r E L ee ie E CIRCLE 825 ON FREE INFORMATION CARD communications interfaces peripheral con trollers or other specialized input output boards The
155. loormat switches to the circuit as an addition to the intrusion alarm sys tem already installed by professionals Thanks for a great project PaT DEARBORN salt Lake City UT l m glad you called it a dinky little cir cuit because that is what it is should you not have the imagination to adapt it to the needs of your home and Office One reader wrote to us telling how his office complex uses 12 separate circuits as an annunciator to alert executives to call the operator at the front desk for an important message The signal LED s are placed at strategic parts of the office complex corridors so that executives can spot at a glance when their particu lar LED indicator is lit The bell buzzer circuit is not used because silence is golden in that office setting BUDGET TEST GEAR enjoy making test equipment from proj ect plans in magazines and books l m sure that there are many more like me so that the editors of Special Projects should consider coming up with an en tire issue on test equipment projects Bos ANDERSON Commack NY Bob not everyone is a test equipment project builder True from time to time most experimenters will build a test equipment project but we cannot ignore all the hobbyists by devoting an entire issue to just one specialized aspect Nevertheless in this issue of Special Projects we have devoted a consider able portion of our editorial space to test equipment projects Hope you f
156. luke DVM According to the article the kit was to be offered and would have ordered the kit as opposed to the fuss and bother of picking up the parts and breadboarding it from scratch Where and how can get kits so can make a few more voltage calibrators HARMON HAaDDIK Toms River NJ Well Sol we re sorry about leaving out the pricing and kit information from the article However you can order the kit from Electronic Technical Consultants P O Box 29278 Denver CO 80229 for only 40 00 with standard reference di ode and 60 00 with Analog Devices super stable and spec ed reference di ode Be sure to include 4 50 for post age and handling By the way when the author checked the article he missed a connection that was omitted from the diagram Terminal 13 clock enable should be tied to ground Wed like to thank the builders of that project who wrote and told us of their experiences with it Your letters encour age us to prepare more stories like the voltage calibrator for publication FEELS SAFER Your Fire Alarm Module project Special Projects 6 page 23 is a dinky little project that s worth its weight in CMOS chips after you build it Every one in my family feels safer now that the fire alarm module is installed in my home Of course had to modify the project as always like to do have two 6 inch alarm bells sound off instead of the buzzer that you specified Also tied in two f
157. ly Paks 7060 or equivalent C7 5 pF C8 C9 05 pF C10 C11 50 pF C12 005 pF COILS L1 L2 13 and 10 turns respectively of 22 magnet wire wrapped tight wound on in inside diameter air core use a in drill Dit shank and slide coil off after winding Keep leads shorn T1 Use coil form with outside PVC water pipe as air core form it has an in outside diameter Wind 9 turns tight wound of 22 magnet wire for primary winding Wind 27 turns tight wound cf 22 magnet wire for secondary winding Leave approximately 3 turn space between both windings Drill holes inform and pass all winding erds through core with lencth of about three inches Trim unnecessary wire lengths on transformer installation ADDITIONAL PARTS AND MATERIALS J1 Antenna terminal tse any convenient type Au thor used push in loudspeaker terminels red for ANT and black for GND Ground terminal not necessary for auto installation P1 Motorola type auto radio antenna pug Connect to 16 in length of RG 584 U coaxial cable S1 SPDT miniature toggle switch X1 X2 5000 and 8500 xHz racio crystal FT 243 fun damental type Perfboard cut to size Dush in terminals for periboard Radio Shack 276 1394 and 270 1392 chassis box approximately 5 4 x 3 gt 2 in crystal socket 1 in length of in L D PVC hot cold water pipe epoxy knob hardware crystal socket graund lugs hardware wire soldar etc Crystals a
158. m 2 wait resistor S1 SPST switch mount2d on shaft of R3 optional toggle switch replacement may be used Printed circuit material to abricate 1 x 2 in printed circuit board 9 VDC transistor battery connector 4 X 2 X 2Ya in aluminum chassis box 16 pin DIP socket knobs hardware wire solder etc IT S WHAT S UP FRONT THAT COUNTS when you are ready to Operate the Mini Audio Generator as a test device LED is a power on device serving to prevent accidental battery drain This will be coming to you when you subscribe to Radio Electronics e HELPFUL CONSTRUCTION ARTICLES Test Equipment Hi Fi Accessories Telephone Accessories Music Synthesizers Computer Equipment Automotive Equipment Intruder Alarms Home amp Car Video Accessories e NEWS ON NEW TECHNCLOGY Computers Microprocessors Satelite TV Teletext Automotive Electronics Speech Synthesizers City Offer Valid In U S Funds Only 5 HOW TO REJUVENATE Radio oo 1 50 MAR 198 E leclronics e HOW YOU AND THE COMPUTER CAN BE FRIENDS COMPUTERS VIDEO STEREO TECHNOLOGY SERVICE Getting Started Programs Circuit Design Games A D D A Interfacing SHORTWAVE RECEIVER Peripheral Equipment Buyers guide es ee I e NEW AUDIO DIMENSIONS nn FOR YOUR PLEASURE inside the new tay es Noise Reduction Devices 767 COCKPIT he gt g How to Connect that Build ai Ra i gt 71 Extra Add On aiana a Re 3 Hi Fi Acc
159. mHz bandwidth The fact that we might call a TV set a monitor if it s used to display anything other than a TV broadcast signal doesn t change the fact that it remains a TV set with a 4 MHz bandwidth Now 4 MHz might be fine fora TV picture but it s not all that good for small minute characters they tend to get fuzzy unsharp and run together To get around the lack of definition when displaying charact ers personal computers intended for use with TV moni tors generally use relatively large characters Real computer monitors are not TV receivers They are only the business end of a receiver the video amplifier s and CRT and they are relatively wideband As a general rule even the lowest cost video monitor intended for use with closed circuit surveillance TV cameras has a bandwidth of at least 6 or 8 MHz Then there are real computer video monitors with a bandwidth of 9 12 MHz 18 MHz or even 20 MHz They can put up to 80 characters across a CRT with razor sharp outlines Today you can pick up a wideband video monitor for as little as 100 from the discount stores The problem is that most computers that are designed to utilize a standard TV asa monitor such the Sinclair ZX 8 and Timex 1000 are designed on y for use with a standard TV set Yet with less than a worth of parts and about 30 minutes work both the Sinclair and Timex computers can be modified to work with eit
160. mally open position and S1 b normally closed In the off position S1 b will dis charge any capacitance across the input through R14 a 1000 ohm resistor When depressed S1 b opens and Sl a closes to supply power to transistors QI Q2 and IC and their associated circuits IC a 7555 timer operates as an astable multi vibrator producing a nine volt squarewave output This out put connects to ZERO adjust potentiometer R4 The variable output from the wiper of R4 feeds through capacitor C3 to the base of QI Emitter current from Q1 passes through R6 to the base of Q2 which drives transformer T A high voltage develops across the secondary of T1 which feeds a voltage doubler composed of D1 D2 CS and C6 This high voltage DC controlled by zero control R4 can be varied from zero to over 1000 volts DC Three 10 Megohm bleed resistors R7 R8 and R9 con nect across the high voltage connected in series with a test jumper For open circuit voltage measurements the jumper is removed and replaced by a microampere meter The open circuit voltage will equal the microamperes x 30 Megohms The positive high voltage also passes through resistors RIO RII R12 and calibration potentiometer R13 to the INPUT jack J Any leakage current from the circuit under test returns to the negative inpuT jack J2 and is connected in series with the VOM before returning to the negative side of the high voltage source in Meg O Dapter For meter protect
161. n engi neering degree or special equipment Radio Electronics want to order Robot Reprints 200 Park Ave South New York N Y 10003 BUILD YOUR OWN ROBOT The robot is fully mobile with minipu lator arms to grasp lift and carry E MANIPULATOR ARMS and end effectors hands are what enable the robot to perform useful tasks Details of construction techniques and con siderations are fully explored MOBILITY BASE is not a lunar space station It is the drive system that permits the robot to move from here to there Full construction de tails along with a discussion of power sources is included Please print reprints 12 00 plus 1 00 postage and handling for U S Canada and Mexico Name Add 96 sales tax for New York State residents only U S Funds only want to order _ reprints 12 00 plus 3 00 Street address Air Postage and handling for all other countries U S Funds only Allow 6 8 weeks for delivery City E THE BODY FRAME AND ROTA TION MECHANISM This is the part that makes Unicorn 1 look like a ro bot Wood and Formica are the ma terials for the body Motors and gears are what make it function COMMUNICATIONS How you can tell your robot what to do Prepio gramming techniques radio contro computer control are all detailed E SENSORS How to add sensors so your robot doesn t bump into things SP 7 State Zip We do not
162. n the power supply circuit Two jacks are provided See Fig 1 for connection to external Circuits KEYER INPUT jack J1 is a standard stereo type jack The DOT circuit connects to either hot contact and the DASH circuit connects to the other hot contact The ground connection is the shaft panel contact and need not be isolated from ground KEYER OUTPUT jack J2 can be any audio or polarizes two terminal jack with one lead used as the hot or signal lead and the other is the ground return circuit Construction The circuit has been tailored to be straightforward enough to be constructed by a beginner in just one evening All of the parts except the CPP chip are available at any electronics parts house Parts layout is not critical As a general rule the crystal and associated capacitors Cl and C2 should be located as close as possible to the 1C1 An additional caution Capacitor C7 should not be omitted That capacitor will prevent the pro cessor from being glitched when the tone is activated Figs 3 and 4 show a same size foil pattern and parts location drawing for a small printed circuit board that can be used Capacitor C7 is located off the board either at the battery or at the power supply Powering up with regulated 5 volts DC ts a simple matter SPKR IC1 BY POSITIONING THE PARTS in tine l with some relationship to the printed circuit board you will be able to keep y lead lengths short and uncluttered STAR ne
163. nd crystal sockets available from CW Crystals 570 North Buffalo street Marshfield MO 65706 Write for prices and availability enclose stamped addressed envelope 86 YHAWWNS oo SPECIAL PROJECTS co MN CIRCUIT P1 BOARD HIGH PASS FILTER BOARD COMPLETE INSIDE VIEW of the Three Band Shortwave Converter Author s consiruction is to be admired because the construction is very neat construction The author used an 8 pin octal tube socket to mount the two crystals X1 and X2 You could do the same or use sockets specially designed to hold the FT 243 type crystal holders Its up to you frequency and tune variable capacitor C6 to the proper band to receive the shortwave broadcast signals and convert them to a broadcast band frequency All station tuning is done with the dial of the auto receiver On the 49 meter band the 5000 kHz oscillator mixes with the 5950 kHz to 6200 kHz input signals to produce a tuning range on the auto receiver of 950 kHz to 1200 kHz On 41 meters 7100 kHz to 7300 kHz the tuning range is 1400 kHz to 1200 kHz Notice that the tuning is upside down on that band That is because the crystal oscillator frequency ot 8500 kHz is above the incoming signal and you are tuning in the difference signal On the 31 meter band the 8500 kHz oscil lator signal is mixed with the incoming signals of 9200 kHz to 9700 KHz and the auto receiver tunes from 700 kHz to 1200 kHz The 10 000 kHz signal
164. net prepainted in Hammertone Grey or you might be able to get a plastic 2 SMALL HOLES are punched cleanly and in perfect position with a Whitney hand punch that can be secured in a vise for extra heavy metal Do not apply pressure to the case as you punch the hole Punches do not work well on plastic chairs or boxes cabinet in the desired color All you ll have to do to finish these cabinets is add the proper labeling for the panel com ponents More than likely however what s available will be an unpainted aluminum cabinet or a plastic cabinet in a dull color and your first step wil be to paint the cabinet Unfortunately all aluminum cabinets are not alike In particular the aluminum cabinets sold by Radio Shack have some form of coating that detergent and acetone won t re move and the paint with its panel markings flakes off almost as soon as you put it on You tend to get a better paint adhesion from the BUD Par Metal and LMB aluminum cabinets However whatever you use wipe it down with a strong detergent and then scrub all surfaces to be painted with a medium to coarse steel woo available from hardware and paint stores just before you re ready to paint the cabinet If you don t want to get paint inside the cabinet when it s spray painted you might need a clean surface for a ground connection cover the opening with a strip of electrical or masking tape from inside the cabinet See photo 3 Wut L
165. ng so battery life should be approximately 12 hours when using a 1 2 ampere hour battery FIG 2 SYNDLE S CIRCUIT BOARD is designed with the novice in mind Heavy copper foil paths can take a bit more soldering iron heat than can the fineline layouts PARTS LIST FOR SYNDLE SEMICONDUCTORS D1 D2 1N40C1 50 V PRV 1 A Silicon rectifier D3 D5 1N914 silicon switching diode D4 1N5226 amp 3 V watt silicon Zener ciod gt IC 1 IC3 NE555 timer integrated circuit IC4 LM358 low power dual operational amol fier RESISTORS All resistors are Ya watt composition 5 types unless otherwise specified R1 1 Megohm R2 R4 100 000 ohm R3 R9 470 000 ohm R5 2 2 Megohm R6 120 000 0hm R7 R8 4 7 Mecohm R10 R14 R15 10 000 ohm R11 R12 3300 ohm R13 10 000 ohm PC mount trimmer potent iameter R16 18 ohm 2 watt 5 wire wound resistor CAPACITORS C1 C9 1 uf 50 WVDC ceramic C2 C3 22 pi 12 WVDC electrolytic C4 C5 C6 914f 50 WVDC ceramic Fuse Fl protects the device from damage that could be caused by the potentially large current that E can supply due to its low internal resistance While the author chose to utilize a NiCd battery pack in the prototype other types of cells are available and offer advantages in many cases Gelled electrolyte batteries such as Panasonics 6M1 2 offer high current capabilities and freedom from the mem ory effect that plagues NiCds Those batteries may
166. ng it So as to conserve the battery For best circuit results alkaline batteries are recommended Parts values are not at all critical and close substitutions are permissible The Mini Audio Generator is a tough and versatile circuit The author has used the generator and stored it in his travel ing toolbox for more than a year during which time it performed as required SP BATTERY RUBBER CLIP FOOT PRINTED CIRCUIT BOARD INSIDE THE MINI AUDIO GENERATOR shows plenty of room for the positioning of circuit parts No problem here squeezing in all the parts Note that rubber foot on printed circuit board was added so as to eliminate the possiblity of board touching the side of the chassis box cover and shorting the circuit R i 7 i sae a eee pe es FIG 3 HERE S AN X RAY VIEW of the printed circuit board with the parts mounted on the flop side of the foil surface Nothing is too critical so that the novice could re layout the design successfully to suit his own requirements PARTS LIST FOR MINI AUDIO GENERATOR Bi 9 VDC transistor battery C1 002 uF 25 WVDC ceramic capacitor C2 2 nF 15 WVDC electrolytic capacitor 1C1 4046 phased locked loop integrated circuit J1 RCA phono jack LED1 light emitting diode red diffused lens R1 500 000 ohm to 1 Megohm potentiometer R2 100 000 ohm 2 watt resistor R3 100 000 ohm potentiometer with SPST switch see 1 below R4 470 oh
167. ng posts and if you like the low power pilot light mount on the box The layout may be anything that you like when you wire up your SSSV The low power pilot light Fig 5 draws very little power and its friendly flicker is a good reminder to turn off the batteries That is necessary because the meter normally sits on zero and requires no electrical zeroing As a result there is RANGE SWITCH O m FIG 4 BUILD THIS version of the SSSV By setting switches S2 and S3 to desired positions you can measure full scale DC voltages from 50 millivolts to 2 volts Input impedance is related to the selected resis tor made by switch setting of S2 thus selecting either R1 R2 or R3 ST 52 R1 500K REVERSE R5 1MEG 86 YAWWNS A SPECIAL PROJECTS a COMPLETED SSSV looks as if it belongs on a lab bench You may want to change location of switches and that presents no problem in construction Location of J1 and J2 is ideal because test leads will not lay over switches and meter M1 Also a slight tug on the test leads will not tip over the meter case no real indication that the unit is turned on and slowly draining the batteries Use one of the BIFET op amps such as the CA3140 or the TLO81 for best results in your SSSV The input offsets in the 741 op amp won t allow its use on the extreme low ranges Checkout and calibration After evervthing is wired and before the BIFET chip
168. ng ramp is applied to the timing network of IC3 via D3 and R11 altering the latter s output frequency and duty cycle Pulses produced by IC2 are similarly integrated by R8 C6 and further vary IC3 s duty cycle by means of pulse width modulation via pin 5 The interaction of the two control signals provides a random continuously varying pulse train which modulates the intensity of I1 Due to the thermal hysteresis inherant in the lamp this random series of pulses is smoothed resulting in a flickering effect which continually varies from a subtle undulation to occasional deep pulsations and dimming effects giving the impression of a flame disturbed by air currents The overall effect can be tailored to suit individual tastes by altering the time Constants of any or all R C networks associated with the circuit howev er R5 and C8 affect the character of the flicker most directly and should be selected to give the desired effect e861 HAWWNS Oo 86l YAWWNS fo ND DI 1N4001 R3 470K R4 100K D1 D2 ae 1N4001 03 D5 1N914 1N5226 s I E e I al 1850 01 220 FIG 1 HERE S A DIAGRAM that has timer on its hands Three 555 timer chips are used to flicker control a lamp bulb with frequencies of 03 Hz and 04 Hz Put them all together they spell flickering light the mystique of Syndle the electronic candle The second section of IC4 see Fig 1 is used as a com parator monitoring
169. nitor Most video monitors have switch selected 75 ohm low Z and Figh Z about Megohm inputs See Figs 8 and 9 The Sinclair Timex computer doesn t have sufficient output to drive both its modulator and a video monitor to best pic ture so set the video monitor switch to HIGH Z or whatever designation is used for the high impedance input That s the total extent of your adjustment Bcth the TV monitor and video computer outputs will be available and you select the one you want by simply plug ging the phono jack patch cord into the appropriate jack You plug into the original TV modulator phono jack if you re using a standard TV receiver for the monitor If you plug into the jack you just installed you use a standard high Z video monitor SP A FIG 7 TO CONNECT THE COMPUTER to a video monitor simply plug a shielded or coaxial cable into the new video jack on the righi side of the computer 4 FIG 8 MOST VIDEO MONITORS have both 75 ohm and a high impedance nominally 1 Megohm inputs a selector switch determines the input impedance For the ZX 81 and Timex computers use the HIGH Z input FIG 9 Here s the modified Sinclair Timex Computer in terconnected computer buffs like to use interface with a video monitor void of an RF front end Picture clarity is razor sharp and is void of all the noise and interference when using a TV modulator 86 YHAWWNS SPECIAL PROJ
170. o the board making sure of JUST SITTING THERE doing nothing makes the circuit board section of this project seem Simple Nevertheless it would be wise to resort to a printed circuit board for construction instead of using point to point wiring proper orientation of the IC sockets and capacitors Make sure that all wire jumpers are installed Due to the wide variety of component sizes available the power supply 1s mounted on a terminal strip as shown in Fig 5 Capacitor C6 is not a critical value the bigger the better Any value from 3 000 to 10 000 uF at 35 volts will do the job If other than the specified transformer and bridge recti tier are used make sure they can handle the current If the value of C6 is above 5 000 uF then the bridge should be rated at least 5 amperes Otherwise the high inrush of current during power up could cause early failure of the rectifier The 78H05 regulator IC7 must be mounted on a finned heat sink as it will be dissipating around 25 watts at 3 FIG 3 HERE IS THE ART for the foil side of the printed circuit board The use of the PC board is the only sure way to go WIRING SIDE oe i ede i Jell DNISIW some amperes output Use heat sink compound when mounting the regulator to the heat sink If the heat sink is mounted inside the chassis then adequate ventilation must be pro vided The case of the regulator is ground so it is safe to mount it to the back of the chassis wher
171. oading slot On other models it is accessible through a hole in the rear or the side of the chassis Finally re install any ash tray glove box or accessory hardware you might have had to remove to get at the radio s location If you have tapped into the cigarette lighter s wiring make certain you have re connected it to the back of the lighter assembly SP SNAP IN A CASSETTE when you tire of listening to the good sound your in dash radio is playing If you installed an AM FM unit then FM is for you when driving about town or the local countryside For long rides cassettes and AM listening is best ies J aie 861 YAWWNS NO J SPECIAL PROJECTS NM ao JOHN SMITH RICHARDSON Computer cables either stock items or custom design are very expensive Make them yourself and experience a retail savings from 50 to 75 percent IT IS SAID NOT COMPLETELY IN JEST THAT POLAROID COULD afford to give their cameras away because once you own one ycu re married to Polaroid forever Only they make the film they can charge what the traffic will bear and that s eco nemics The same can be said of computer peripheral manufactur ers There are many places to get a discount on hardware such as modems printers and the other gizmos that make per sonal computing a pleasure but in almost all instances the gear comes without cables When you ask for the cables you then find out why they can sell the peripherals at such
172. ock out conditions must be eliminated amp 86t YAWWNS SPECIAL PROJECTS gt gt 4 I i t f LI LI l ranom meu to score f i TRIGGER CIRCUITS I RELEASE IC1 a PIN 6 USEC TO SET IC1 b AND ENABLE SWEEP CIRCUITS j m PUSH ICt a PIN 5USEO TO SET 1C1 b ANO ENABLE SWEEP CIRCUITS lt a o m oo IC1 b PIN 9 a w w IC1 b PIN 8 SCOPE TRISGEE alii toy RAE ease SCOPE SWEEP GATE l t l A te aaa SCOPE RAMP i t i SWEEP ENDS KGLD OFF STARTS I j t o o ren MANUAL RESET i l t SWEEP TRIGGERS FIG 3 TIMING DIAGRAM for the circuit action on Fig 2 Time advances are from left to right And the circuit must be relatively insensitive to ramp or gate repetition rates Overview Fig 4 is the circuit of the basic Single Sweeper One It accomplishes all the above by debouncing the reset or sweep command signal from ICI a It stores the command in IC 1 b when the RESET switch SI is released or an external pulsed reset command ts applied to IC1 b s set input IC2 b syncs up the reset command and the leading edge of sweep gate or 47K MANUAL RESET St H 4 AIM 1C3 a gt t A ro ACTIVE HIGH SWEEP GATE INPUT SWEEP Z AXIS tN OuT or ON sare RESET in cy SINGLE SWEEPER O ao THIS VARIATION of the Single Sweeper One uses a built in 5 volt regulator supply Raw DC voltage is supplied from a plug in modular 12 volt DC s
173. od until July 31 1983 Mee ee es ec a aj PI OS 9 Nr ee ee ee It s full of fun sun barefeet amp bikinis It s runnin with the wind to small tropical islands and unique ports o call for those with itchy feet and adventure in their soul We re not the Love Boat but we ll take on anybody when it comes to beach combing sailing amp exploring the exotic Carib bean It s our backyard and we know all the great places in paradise And 6 day cruises start from 425 So send for the rest of the booklet It s free Look us over amp sea it our way 7O n Windiamm arefoot Cruises io Box 120 Dept 1642 Miami Beach FL 33119 0120 or call TOLL FREE and tell us you need the rest of the booklet 800 327 2600 in FL 800 432 3364 Industries Inc lorkKoen comtinued ARE Conner Steet Bronx New York 10475 U S A Tele 1 SK MYK Telex 232395 OK NY UR Phone 212 90 1 405mm 4
174. of the industrial grade cable connectors utilize crimp type connectors that require a special tool that costs between 100 to 250 Do not get talked into any kind of sockets using push in crimp terminals you ll cause unbelievable damage if you get one in the wrong connector hole and then try to get it out If you must use solder type terminal connectors on both ends of the wire your best bet is to use multi wire round cable But if one end of your cable can be a ribbon connector then use ribbon cable and wrap both sides inward where it s to enter the clamp of a solder type connector Wrap several turns of plastic tape around the ribbon wire s fold pass it through the clamp and shell and solder to the connector terminals Usually if you must use a solder type connector the wiring order will have no relationship to the order on the other end so double check each individual wire with an ohmmeter when it s installed And when you check the latest wire double check the connection that preceeds it to make certain there s no unseen shor circuit As a rule of thumb if IF YOU FOLLOWED instructions very carefully used all your basic skills and proceeded with care your computer cables assembled from the instructions in this article should have a pro type look your cable has a ribbon connector on one end and a solder connector on the other install the wires at the solder con nector in the orde
175. ok knowl edge is important but it s just as important to know how to apply your book learning in practical situations From basic circuitry in CIE s Personal Training Laboratory in several Career Courses through the Microprocessor Training Laboratory in the Associate Degree program CIE helps chan nel your desire to make things work into skills you can sell IN A CLASS BY YOURSELF One of the great benefits of home study is the independence it gives you You study where and when you want to You move as fast as you can handle it There s no class room to go to because with CIE the classroom comes to you But you re never alone When you request help the CIE electronics expert best qualified will personaily respond in writing SET YOUR OWN GOALS CIE s wide selection of courses gives you many options You start with a Career Course that suits your talents Then since more than half of CIE s courses include a series of optional lessons to prepare you to pass the government administered FCC License exam you can get an FCC License a requirement for some electronics jobs and a credential for all electronics jobs You may then go on and earn an Associate in Applied Science Degree in Electronics Engineering Technology It s all up to you START MAKING m THINGS WORK FOR YOU Send today for the CIE school catalog and complete package of career information It s all FREE and it will h
176. on the printed circuit board illustrated in Fig 9 The location of parts and jumpers are illustrated in Fig 10 The Single Sweeper One is a designer s dream project If you use your oscilloscope a great deal this project 1s one that may be what the Z axis ordered SP FIG 10 PARTS LOCATION DIA GRAM indicates that there is ample room for circuit parts plus tie points for experimental work with the cir cuit IC4 may run slightly warm but no heat sink is necessary TO Z AXIS OUT Ba oe a LED3 SWEEP IN O 5VDC REGULATED FIG 8 POWER YOU NEED POWER YOU GET In A above you can tap right into a bench operated regulated 5 volt DC power supply but that ties you to the bench area In B below you can be powered by an AC op erated 9 to 12 volt battery eliminator and operate anywhere there s an outlet in sight Otherwise plug in a 9 to 12 volt battery pack to go portable FIG 9 FULL SIZE PRINTED CIRCUIT BOARD for the Single Sweeper One has more copper elements than needed to wire the circuit The author designed the board for the original Single Sweeper and after circuit modifications reduced the total num ber of circuit parts One section of IC3 is not used you may come up with something and the extra Soldering points may come in handy LED2 LEDI 861 YSAWWNS i gt J SPECIAL PROJECTS Bas SIMPLE VOLTMETER EVERT FRUITMAN HOW WOULD YOU LIKE TO BE ABLE TO MEASURE AGC
177. onics Special Projects publishes avallabie plans or information relating to newsworth SUMMER 1983 Hugo Gernsback 1884 1967 founder M Harvey Gernsback editor in chief Larry Steckler CET publisher Art Kleiman editorial director Julian S Martin KA2GUN managing editor Josef Bernard K2HUF technica editor Car Laron associate editor Brian C Fenton assistant editor mm Dan Rosenbloom production manager Robert A W Lowndes production associate Joan Roman Circulation director Arline R Fishman advertising coodinator Cover photo by Robert Lewis Composition and interior design by Mates Graphics BUSINESS AND EDITORIAL OFFICES Gernsback Publications Inc 200 Park Ave S New York NY 10003 President M Harvey Gernsback Vice President Larry Steckler ADVERTISING SALES Stanley Levitan Radio Electronics 200 Park Ave South New York N Y 10003 212 777 6400 PACIFIC COAST Mountain States Marvin Green Radio Electronics 413 So La Brea Ave Los Angeles Ca 90036 213 938 0166 MIDWEST Texas Arkansas Okla Ralph Bergen The Ralph Bergen Co 540 Frontage Road Suite 325 Northfield Illinois 60093 312 446 1444 products techniques and scientific and technological developments Because of possible variances In the quality and condition of materials and workmanship used by readers Radio Electronics Special Projects disclaims any responsibility for the safe and proper
178. ook Experience would suggest that the K130 alone is quite adequate for lead guitar unless you really want to slice cheese with your strings at 30 feet The horn really comes into its own with keyboards and Moog Both drivers mount from the front and it is most important that the flanges form an airtight seal against the baffle sur tace If there is the slightest doubt about that it is wise to envisage a gasket adhesive felt adhesive foam or non hardening sealing compound between the surfaces when the drivers are ultimately bolted into place Two port tubes will be needed each 5S inches long and internal diameter nomi nally 4 inches Results will not be adversely affected if the tube is Mie inch to inch oversize Individual constructors may be able to obtain suitable scraps of large diameter cardboard tubing or plastic drainage tubing or even make up their own by gluing and rolling sufficient layers of stout paper or light cardboard Alternatively rectangular port tubes could be fabricated trom scraps of plywood or masonite securely pinned and glued at the corner and then glued into matching cutouts in the baffle The length would have to be the same as for the round tubes but the internal cross sectional area would have to be manipulated to about 12 6 square inches After pinning gluing and sealing the port tubes into position the whole front of the baffle and the inside of the tubes should be painted flat black The baffle shou
179. or large auditoriums it adds up to one or more powertul bass drivers a bulky enclosure and a power amplifier with an appropriate output rating To meet that specific need JBL offers a number of special tst bass drivers of which the 140 is typical With a diameter of I5 inches it has a nominal frequency response trom 40 2500 Hz and a power rating of 200 watts RMS continuous tone or 400 watts continuous program For a bass guitarsst it could probably be used alone but for a recital orgar it would have to be supplemented by adequately rated drivers covering the mid and upper range For all other applications it is evident that the bottom octave can be compromised if not sacrificed and that has Important implications The driver cone suspension can be stiffened raising the natural system resonance to around 50 60 Hz and a more compact enclosure can be designed around those new parameters While such a system will siill produce plenty of output from low frequency drive it will tend to be less fundamental in its quality It will alse absorb a lot of punishment A driver reflecting that philosophy ts the one which forms the basis of the JBL System the JBL E130 Also a 15 inch type with a 4 inch voice coil it has a nominal frequency range of 50 6000 Hz and a power rating of 150 watts cen tinuous tone or 300 watts continuous program The fact thai fundamental output is not required below about 50 Hz Fas another important implica
180. ork You ll either snap the nuts or a shaft s or the shafts will work loose in a few days The clamps must be used If they don t easily fit in a hole try a different orientation for the clamps at some point they will drop directly into a matching hole Strap it Next locate the metal strap with the holes that was sup plied with the radio The instruction manual that came with the radio probably shows the strap hanging from some part of the dash to a screw on the back of the radio thereby support ing the radio The radio dces need support if it has a tape player because tape radios are relatively large they place a lot of strain on the dash if all that holds the thing in place are a couple of nuts on the front panel Unfortunately most mod ern cars don t have any place to which you can attach the strap as shown in the radio s manual The hanging strap might have been possible five to twenty years ago but the modern dash probably is plasic is molded and has no room USING AN INSULATED ALIGNMENT SCREWDRIVER adjust the AM trimmer for maximum sensitivity to high end AM sta tions Set the radio s dial to a weak station near 1400 kHz on the dial raise the car antenna ard tune for maximum volume j b W USE a DEEPWELL SOCKET WRENCH to tighten the nuts on the control shafts Pliers wrenches and other ill suited tools only cause damage to the control shafts which aren t all
181. out including the direction indicator in the dash penel and then only on that side It is very important that all signal lamps be checked periodically tor proper operation as well as the brake lights emergency warning lights side marker lights ete Burned out lamps should be replaced immediately Throughout North Amer ica you will receive a summons for a moving violation should you drive your car on a street or highway with im proper lights Let the local yoke chase speeders and light jumpers SP Q6 Q7 The romance of a flame whether it be a she or a candle can be heated up with this electronic taper SYNDLE RICHARD L SCHUH THI FLICKERING LIGHT OF A CANDLE FLAME HAS FASCINATED man throughout the centuries and has illuminated the dark hess in a thousand different forms However despite major advances in technology the candle has somehow managed to keep its basic form it exists virtually unchanged in today s world of VLSI and synthetic sound and will probably remain so tor some time to come The primary function has changed however and today the candle finds far greater use as a decoration than as a practical method of illumination Although it may be difficult to surpass as an interesting tablepiece the traditional candle has a few disadvantages when applied to many applications Commercially even when overlooking the potential danger of an open flame the associated insurance risks and tedious maintenanc
182. oved when installing the radio Make certain you re connect the cigarette lighter If your car has missing hardware and worn parts on the dashboard try to pick those up at the junk yard E l MMs WHAT S THIS The trimplate doesn t fit Correct The days are long past when a universal trimplate that actually fits all cars is supplied with a universal radio You will have to do considerable material fabrication to make a new trimplate fit the old gap openings showing around the trimplate or it s just plain ugly I think they train student designers on radio trim accessories Try your local junk yard for an original equipment trimplate Even if its cutout is somewhat oversize a few strips of black rubber or leather scrap from a shoe repair shop cemented to the factory trimplate will look like original equipment to all but the most thorough scrutiny If you don t have the hardware to install an original equipment trimplate use a few drops of an adhesive such as Barge it comes in a tube and is the same stuff used to cement rubber soles to shoes It will certainly hold the trim plate You re almost done Install the knobs plug in the speak er power and antenna wires tune the radio to a weak station near 1400 kHz and using an insulated alignment screwdriver adjust the AM trimmer for maximum Signal strength On cassette radios the trimmer is often reached through the cassette l
183. p such that a fixed number of turns remains in the gap even during extensive cone excursions The method provides good linear cone drive and accords with compact enclosure design but it markedly reduces sensitivity there by necessitating considerable audio drive power For that reason domestic hi fi amplifiers are more likely these days to be in the 25 to 100 watt per channel class than 5 20 watts In short sensitivity is sacrificed in the knowl edge that extra drive power in that range anyway can be secured without too much hassle Nor does a hi fi loud speaker manufacturer have to worry unduly about overload With the onset of overload distortion most hi fi listeners will react automatically and turn down the volume before damage occurs to the voice coil A specialized music loudspeaker system differs from 861 HIWWNS Le ao SPECIAL PROJECTS D D the foregoing on almost every count Consider for example the matter of frequency response A music speaker is not required to reproduce the sound of all instruments but only that of one type Needs vary with the type of instrument as the following examples should indicate Church or classical electronic organ Bass should be well sustained down to 32 Hz middles smooth upper treble tapered off to minimize risk of the instrument sounding too reedy Popular electronic organ For theater style recitals much the same as for a classical organ For group wor
184. parts are mounted on the foil side of the low voltage PC board where as both sides of the board are HIGH VOLTAGE Ms TES FIG 3 HIGH VOLTAGE cir cuit board is a bit tricky to wire because there s not much room inside the Pomo na case Some parts are mounted on the foil side and others on the reverse side Resistor are axially mounted where space demands As with most ohmmeter circuits the set points and zero adjust will depend on the battery voltage For this reason ZERO control R4 was not calibrated With an average battery drain of 20 milliamperes and useful operation down to 64 volt the life of B should be about normal shelf life As mentiuned above lower ranges could be calibrated and include a range switch but for practical purposes this does not seem necessary What is important is that hazardous and deadly current leaks in appliances electrical equipment and test instruments be detected by Meg O Dapter and not a human SP LOW VOLTAGE Dea a LER T aap SEC WIND TO st SPECIAL PROJECTS o9 used to mount parts on the high voltage PC board In the diagram both boards are shown foil up Hole A was drilled by the author to pass battery B1 leads In your con figuration in the Pamona box one or more others leads may pass through hole A so drill a Slightly larger hole to cover any contingencies Refer to Fig 1 when connecting the ex ternal leads to switch 1 Photo of hig
185. pasator IC3 has all its nan inverting inputs tied to the 2 5 valt DC tap at R8 and R9 As the squarewaves from IC2 pin 9 arrive at the invertirg inputs all lied together the quad sections switch or and off swiftly controlling four sets of 2N3306 2N3055 high current switching circuits paralleled at the cutput terminal for the maximum Switching capacity thal is required far automobiles with trailer hookups are connected to resistors 10 11 12 and 13 respectively Those resistors limit the base current to transistor Ql Q2 Q3 and Q4 Transistors Q through Q4 combined with QS should have 4 in spade plugs on the ends That will allow you to install the project in your car by simply plugging it in to the car s flasher socket no cutting or splicing to your car s through Q8 respectively forming tour Darlington pairs The emitters of transistors Q5 through Q8 are connected together to increase the current handling capability of the Electronic Flasher and form the output of the Electronic Flasher which is used to drive the turn signal lamps of the car Gcnstruction and operation The circuit can be constructed on a protetype grid board pertboard using point to point wiring Plan to keep the units size small since the space behind most dashbeards is very cramped The circuit layout is not critical Transistors Q5 Q6 Q7 and QS should be mounted on heat sinks because most cars turn signals draw a lot of current The Vin
186. peculiar connections they won t be in the cable but rather in IF YOU MUST use a solder type connector make the con nections short circuit proof The wires insulation should extend right up to the terminal and a little bit into the terminal if you can manage it It takes practice The trick is to have only about 1 8 inch of tinned wire protrud ing beyond the insulation Here is where practice makes per fect and patience is a virtue RIBBON connections are sim ultaneously secured by squeez ing the connector with the rib bon wire in position between the jaws of a vise Use only as much pressure as necessary to seat the ribbon completely against the connector there must be no daylight between the ribbon and the connecior the equipment For example if you re connecting serial O input output equipment the ground TX transmit and RX receive connections are standard or TX and RX will be reversed for a modem but after that anything goes and usually does On some RS 232 modem cables the RTS and CTS connections must be reversed for a modem or com pletely disabled or the 20 terminal polarity must be re versed through an outboard integrated circuit serving as an inverter All those things are your problems But once they re resolved it s on to assembling the cables Ribbons are easiest Quite possibly the cables for the most of the Radio Shack computers and printers Heath Zenith
187. r used at the solder connector starting with the lowest number terminal 1 or 2 etc Forget about the other end You re more likely to get tangled up in the order if you try to follow the order of the ribbon connector when installing soldered wires If you re making an RS 232 gender reverser cable make certain the 1 terminal on each connector is correct If you have it right one end will have the 1 to 13 terminals at the top and when you turn the reverser end to end the other connector will have the 1 to 13 terminals on the bottom Hard to get connectors As a general rule Radio Shack stores stock an excellent assortment of ribbon connectors at reasonable prices However there are many common connector types they don t have such as a ribbon or solder Centronics connector and the 9 pin cable type connector Unfortunately many local electronics parts stores charge up to 50 above ist for the special connectors One of the lowest cost sources for unusual connectors Is a data supply accessories distributor MISCO Inc Box 399 SP Helmdel NJ 07733 Write for their catalog They have such items as Centronics con nectors 9 25 and even 50 pin D connectors and they stock the D connector hood large encugh to accommodate an in ternal miniature switch for only 1 85 SP ELIMINATE THE TEDIOUS JOB OF RINGING OUT MULTI conductor ribbon or flat cables with the Ribbon Cable Tes ter This easy to assemble unit
188. re used measuring 12 inch X 23 inch with all low voltage components on one board and all high voltage components mounted on a second board Transfor mer T1 and bettery B1 are both mounted on the bottom cover in jacks are used for the vom output J3 and J4 and banana jacks J1 and J2 used for the inputs and were mounted near the top of the top cover Power on off switch S1 and ZERO control R4 were mounted on the top cover between the low voltage board and T1 Due to the close tolerance of the above components care should be used in their location The low voltage PC board Fig 2 can be completed and the voltage doubler with the bleed resistors installed on the high voltage PC board Fig 3 Connect a micro amp meter in place of the test jumper See Fig 4 Press power on and turn ZERO control R4 to maximum Output current should range from 30 to 35 microamperes which would equal 900 to 1050 volts DC open circuit For calibration a 30 to 50 Megohm resistive source should be used The exact value is not important for meter scale selection but accuracy will depend on the values selected For example 3 or 4 ten Megohm resistors may be series connected but they should be 1 rated The VOM to be used can now be connected to the circuit in the 50 to 100 volt DC range Values for resistors R10 R11 R12 must be selected These values will vary depending on the meter used Begin with R10 at 4 7 Megohms R11 at 2 2 Megohms and R12 at 1 Connec
189. recommended because of its low cost and availability Upon powering up the chip must be reset by holding pin 4 low at least 50 milliseconds That is accomplished by adding a uF capacitor C3 from pin 4 to ground An internal 200K resistor will charge capacitor C3 to a high level and allow the chip to run Now you can learn the differences between the Dahs and the Dits and pick up required code speed to get your Amateur Radio ticket amp e861 HSAWWNS Selecting a particular practice group is done by first plac ing switch S1 in either an open TABLE A or closed position TABLE B position The microprocessor C1 tests that switch first to determine which table to look at A particular practice sub group 1s selected by pulling any one of the pins 28 34 of the CPP to ground through SELECT switch S2 By not pulling any pin to ground one selects an additional sub group If that is done with switch S1 open and switch S3 is set to F 40 X1 02 22pF 3 57 MHz 3 22pF 4 127 sy 2 4 1 E R12 15K 39 5V s3 START STOP gt R2 15K O inim o loim Pp Kx m lt m x hy 8 R3 15K amp 37 5V o R4 15K 38 DASH J1 26 40 20 INPUT C7 100 O 5V FIG 1 SCHEMATIC dia gram for the CPP1 Code Practice Oscillator cent ers about the CPP1 inte grated circuit chip co ett SPEED potentiometer R7 s
190. rest of the wiring is done with No 22 insulated hook up wire Be sure to us short direct wiring on the circuit boards and on the crystal switch S1 The main circuit board is mounted in the box with two 4 inch 4 40 screws with two nuts serving as standoffs The high pass filter board is mounted in the same way using one screw and a ground lug in the center of the board Coil winding Transformer T1 is close wound with No 22 magnet wire on a coil form made from a 12 inch long piece of 2 inch inside diameter PVC hot cold water pipe The pipe actually Pull in the hottest three shortwave bands with this all FET tunable converter designed to work with an auto radio 86 YHAWWNS J SPECIAL PROJECTS oe T1 R3 11 16 R2 R4 13 19 PRI R1 Q1 C8 11 16 21 R6 Q2 R7 C12 R9 27 32 37 41 45 c9 C10 C11 R8 C7 25 29 38 39 43 The circuit board is cut te fit the inside of the chassis box used by the author See Parts List The board has 48 rows of 11 holes The numbers in parentheses indicate which row from the left a component part is mounted Resistor R3 which is mounted horizontally on the board has two numbers for the two different rows to which its leads are secured The rows given for the field effect transistors FET indicate the center position on the board about which the leads are terminated A printed circuit board for this project is unnecessary
191. ringly over the surface Another problem with spray enamel paints is that some reject transfer type pane markings Many of the better spray enamels have such high gloss surfaces when they dry that most of the usual materials used by hobbyists to letter panels won t stick Again I ve had best results with real cheap private brand spray paints If you like the colors of better paints and insist on their use you can try applying an over coat of clear matte or preparation paint that s sold in art supply stores The product is made to provide a tooth on slick surfaces Ask your local art supply dealer he knows of products we electronic hobbyists rarely get to see On the left of photo 4 is DaTAkoaT matte protective spray which is used to protect the lettering etc that will be applied to the cabinet This is a clear paint that merges the lettering which we ll cover later into the base coat and it also protects the finish The stuff is not the easiest thing to locate and you might have to substitute a product similar to the one shown on the right of photo 4 a standard artist s protective nen glossy spray sold in art supply houses The stuff smells to the heavens when used but it protects the panel markings I prefer DatakoatT but if you can t get it use whatever is suggested by your local art supply store Spraying To avoid spraying everything in sight make yourself a spr
192. s Light emitting diodes LED1 through LED10 indicate current supplied to an external connected project in steps of 300 milliamperes Clock outputs offer six frequencies from 170 kHz to 10 Hz at high setting of FREQ ADJ potentiometer R24 at maximum and 1560 to 01 Hz approximately 5 7 pulses per minute at the minimum setting Two independent and separate pulse probe circuits are provided with suitable high and low state indicaters with pulse memory Of course there s the 5 volt regulated power supply terminals and POWER on oFF Switch 1 the brutish but ever so essential purpose of the Digital Prototyping System FIG 2 THE LOGIC AND CLOCK PORTION of the Digital Prototyping System could be separate projects by themselves The clock section offers six time related clock signals for intervals listed in Table 1 The logic probe section actually consists of two identical probes The diagram lists symbol and pin designations for one logic probe and another set of designations in parentheses for the second probe 5V 5V HIGH gy if oS 02 LED il IN A B N 5V 15 3 LED 12 501 16 15 14 FREQ oq eS OUTPUT Jo PULSE 03 03 _ Q1 M oy R7 Q2 i 33K B i RIA i a LED 15 r Aa 1K 14 LED 18 q lt i S C2 6 15 11 14 k 9 8 C3 i 47 F 2N3906 16 4 1C1 1C6 CLOCK GENERATOR l 4 a R21 z i 3 R22 Heed A 2709 01 04 a CABLE3 R9 R10 Naa R17 4 33K A uns 12 lt an z 27082 02 14 5 kd 2N39
193. s avail able from Micro Power Systems RFD 2 Rt 4 A Enfield NH 03748 Price is 11 50 and includes ship ping and handling charges Please note All boards shipped UPS unless otherwise specified Visa and MasterCard accepted Be sure to give all informa tion on card VENTED gt S W ES G EPR CIRCUIT h 4 5 i pA BOARD om ta a a r i jo am a S be CABINET PRINTED DROP THE FRONT PANEL and the interior looks like a well designed project with good construction prac tice Ribbon cables are used to in terconnect components on the front 3 panel with the printed circuit board RIBBON Thus in the event that faulty wiring wl CABLES occurs in construction it can be ba quickly traced by using the cable s color code The printed circuit board o is held in place by holders specially designed for that purpose However you may want to go the less ex A FRONT pensive route by using low cost e PANEL standoff posts which do the same in the same manner and can only be used for TTL and positive CMOS circuits The clock frequency is adjusted by potentiometer R24 By selecting a range tap and changing the setting of R24 any desired frequency can be obtained within the range selected The outputs B through F are CMOS outputs with a 5 volt swing External buffering may be necessary for some cir cuits The 4060 CMOS divider chip IC6 has a fan out of 2 TALS loads and cannot drive 7400 TTL devices direc
194. s best on stranded wire Solid wire gets nicked and breaks easily If you need to tap the vehicle s wiring for radio power use the original power wire for the factory radio or the wire meant for the cigarette lighter It often can be pulled directly off the back of the lighter assembly and since it usually gets turned off by the ignition lock it s a good power source for the radio How to do it Before starting the actual installation of the radio adjust the spacing of the contro shafts Measure the separation of the shaft or control holes on your dash then loosen the nuts GET AN ORIGINAL EQUIPMENT trimplate from your local junk yard and cement it to the dash if necessary Fill in any open spaces in the new trimplate with strips of scrap rubber or new shoe leather Cement these strips to the trimplate x i i A Y Ma 3 i gern N ee THE PERFORATED STRAP supplied with the radio provides both rear support and the ground cnnection for the radio Bend it to the required shape before you install the radio If possible alsa get one end secured before the new radio is slid into position on the shafts enough so their locking clamps can be slipped out of their holes set the shafts to the correct spacing and then rotate the clamps so they easily fall into a hole drilled in the chassis around the shaft Then tighten the shaft nuts Do not discard the clamps and try to hold the shafts in place with just the nuts it won t w
195. sioral 4 function oS LCD digital multimeter you keep to use later in your work Then you use the lab and meter to actually access the in terior of your computer build special circuits and write programs to control them You see your computer at work and demonstrate its power Same Training Available With Color Computer NRI offers you the opportunity to train with the TRS 80 Color Computer as an alternative to the Model III The same technique for getting inside is enhanced by using the new NRI developed Computer Access Card Only NRI offers you a choice to fit your specific training needs Become the Complete Computer Person In addition to training in BASIC and advanced machine language you gain hands on experience in the operation and application of the latest computers microcomputers fom mere ake money for both business and personal jobs You re trained to be come the fully rounded new breed of technician who can interface with the operational programming and service facets of all of todays computers You re ready to take your place in the new electronic age Other Opportunities NRI has been giving ambitious people new elec tronic skills since 1914 Todays offerings also include TV Audio Video Systems servicing with training on our exclusive Heath Zenith computer programmable 25 diag onal color TV Industrial Electronics Design Technol ogy and other state of the art courses Free Cat
196. supply power to the 5 voit DC regulator chip IC7 Resistor R26 senses the current used at the output and displays that miniscule voltage drop across the bar dot display driver C2 With jumper JU1 installed a bar display will indicate current in 300 mA steps very much like a rising thermometer SPECIAL PROJECTS _ output current Two ohm 10 watt resistors were used ir parallel to form R26 The internal current used by the 78H05 regulator IC7 is small enough to be ignored That pro portional voltage across terminal points Ry and R is fed into Cl a LM324 unity gain op amp that ground references the signal so that any voltage drop on the unregulated side of the power supply will not affect the current reading IC2 is a LM3914 bar dot display driver The input divider is cali brated to read 300 mA per LED by resistors R5 and R6 Pin on C2 selects either a bar or dot display Connecting pin 9 to 5 volts DC will select the bar mode The regulator IC7 can put out slightly more than amperes tor short lengths of time Prolonged use above amperes will cause early failure of the transformer or bridge rectifier unless they are rated well over 3 amperes The regulator IC7 is internally protected against short circuits that draw more than 5 amperes Staying within those limits should insure long life of the power supply la pd Double logic The two logic probes are identical and are shown in Fig 2 Half of 1C3 and IC4 make
197. t a pilot light wasn t used because of the current it consumes Even a light emitting diode LED with a current limiting resistor Fig represents a moderate drain on the battery when compared to the circuit s normal battery load Cheer up The Extra Low Power Pilot Light does just what its name implies It draws very little power from a battery and its periodic flicker serves as a reminder for the user to turn off the portable equipment Its wide range of operating voltage 5 30 DC and small size make it ver satile enough to be added to almost any project that might require its use Of course it could be added to new equip ment too There is or was a LED chip on the market made to do almost the same thing I ran into three little problems with it It has a limited voltage range it was expensive and it wasn t always available The first problem was solved witha Zener diode in series with the power supply line The last problem was solved with the circuit shown in Fig 2 The CURRENT LIMITING LED be RESISTOR o _ _ D O AN 0 FIG 1 HERE S A TYPICAL light emitting diode LED circuit that usually draws approximately 20 milliAmperes The LED light is on continuously when power is supplied causing a severe battery drain when left running over night Often the pilot light consumes more power than the equipment itself would when left on after being used What a way for a battery to go middle problem remained th
198. t noise actually decreases with increasing collector current 1 f or flicker noise is a Significant source of noise at low frequencies because as its name suggests it has 1 f spectral characteristic and thus noise voltage increases as the inverse of the frequency The best known source of noise 1s probably the thermal or Johnson noise generated in a resistor That also has a white noise distribution We can minimize that source of noise by minimizing the input resistance and that has the added benefit of reducing input noise voltage due to base noise current Referring to Fig we can see that the input resistance consists of the source resistance and the base spreading resistance of the input transistor The source resistance Rs is the resistance of the moving coil cartridge while the base spreading Rbb resistance is an inherent feature of the transistor GUTS EYE VIEW of the MoCo preamplifier illustrates how neat and clean this project can be assembled Batteries take up the bulk of the volume in the cabinet Should you prefer a 12 volt regulated supply the outside case can be greatly reduced Use shielded cables for input and output leads to and from the printed circuit board Use a wall plug battery supply to feed the regulator circuit Clearly we can significantly reduce thermal noise by choosing a transistor with a very low Rbb or base spreading resistance Most audio transistors have an Rbk of around 100
199. t precision resistors to the input and adjust ZERO control R4 for the exact reading on the meter scale On some models this reading can read directly in Megohms On one model VOM the readings were in PARTS LIST FOR MEG O DAPTER SEMICONDUCTORS D1 D2 1000 PIV silicon diode rectifier axial leads SK3081 125 1N4007 or equivalent 121 7555 CMOS timer Q1 2N1711 NPN silicon transistor Q2 2N3439 NPN silicon transistor RESISTORS All fixed resistors are Y watt 10 composition types unless otherwise noted R1 R3 R6 1000 ohms R2 56 000 ohms F4 10 000 ohms watt carbon potentiometer R5 10 000 ohms R7 R8 R9 10 Megohms 5 R10 R11 R12 Selected values see text R1i3 1 Megohm multiple turn trimmer potentiometer PC mount R14 1000 ohms 1 watt CAPACITORS C1 1 uF 10 Mylar C2 01 yF 10 Mylar WYDC C3 1 F 50 WVDC electrolytic C4 100 F 25 V VDC electrolytic C5 C6 01 yF 000 WVDC disc ceramic ADDITIONAL PARTS AND MATERIALS Bi 9 volt transistor battery J1 J2 Banana plug jack one black one red J3 J4 Pin plug jack one red one black S1 DPDT spring return pushbutton or toggle switch T1 Stancor P8380 117 12 VAC 150 mA secondary wind ing power transformer Pomona 3301 aluminum case knob PC board materials battery clamp 8 pin DIP socket haraware wire solder etc 86 YAWAWNS N FIG 2 LOW VOLTAGE cir cuit board shown here hoids
200. t to the dash visor clip instructions and a one year warranty The price is 239 00 Bearfinder Co Inc 324 North Dixie Drive Vandalia OH 45377 POWER SUPPLIES the QPS Series are in a low profile design featuring two flush mounting surfaces for easy installation in OEM applications QPS models have an input of 115 volts AC 10 47 400Hz Voltage current ratings are 5 to 24 volts at 3 amperes Some fea tures of the QPS series include infinite resclu tion acjustments adjustable foldback current CIRCLE 819 ON FREE INFORMATION CARD limit no overshoots on turn on turn off or power failure and lowest output deratings with temperature Computer grade com ponents are used exclusively Transformers use the UL recognized Class B insulaiion system Atl models in the series are UL478 recognized and are 100 tested before ship ment All carry a 3 year transferable warran ty and each of the single output linear power supply units is priced at 19 95 Deltron Inc PO Box 1369 Wissahickon Ave NorthWales PA 19454 STEREO PROCESSOR model 6740 takes audio sub carrier signals from a satellite re ceiver and decodes them for use with an ordinary home stereo receiver system It will also allow monaural audio sub carriers to be heard through hi fi speakers for added enjoy ment df satellite video programming Decoding of separate multiplex or matrix sterec is accomplished via front panel push button selectors
201. tentiometer R7 with a rotary switch and fix resistors To determine a specific dot time use the following formula DOT 1 1 R6 R7 C8 Knowing the dot time speed can be determined by the follow ing additional formula SPEED dots min 2 5 The electronic keyer feature is another useful aspect of the CPP1 When switch S1 is open TABLE A and position h of switch S2 KEYER is selected the software goes to the keyer mode when S3 is set at START In that mode whenever pin 37 is pulled to ground a series of evenly timed dots are sent When pin 38 is pulled to ground a evenly timed series of dashes are sent Finally if both pins 37 and 38 are pulled to ground a series of evenly timed dots and alternating dashes are sent Those features are generally found only in high priced electronic keyers The speed of the dots and dashes are determined by the dot 117 VAC FIG 5 A TYPICAL 5 VOLT DC REGULATED power Supply is given here for readers who like to include a power source with the project The parts indentified in the circuit are not listed in the Parts List This is an optional circuit that appeared in previous issues in almost identical form JUMPER FIG 4 YOU SHOULD EXPERI ENCE almost no trouble drop ping component parts into the correct connection holes on the PC board More than enough room is supplied should your electrolytic capa citors be larger than usual for the parts values specified ac 2 aH
202. tery s shelf lite single cell from a flashlight across the input terminals Turn it on use the polarity reversing switch S1 if needed amd adjust R7 Fig 4 for the same reading as the shop voltmeter So much for the high range calibration Accurate calibration of the low range is a bit more difficult unless you have access to a calibrated millivolt source The low range calibration for the SSSV setup is shown in Fig 6 It uses parts that you are likely to have around the shop The wiper moving contact and the ends of a 500 ohm potentiometer are connected to the input terminals of SSSV An ordinary ohmmeter is paralleled across that potentiometer Set the ohmmeter for R X 10 orR x 100 That makes it a crude current source Set S2 on SSSV to 2 volts Adjust the 500 ohm potentiometer for a meter reading of about 42 volt Move range switch S2 down to the 0 5 volt position Adjust the potentiometer for as close to 0 05 velts as you can That will be the first major meter division Meve S3 Fig 4 to the low range position and adjust R9 for full scale deflection Disconnect the ohmmeter and the extra potentiometer That s it You are ready to measure trom a few millivolts to 2 volts DC with at least 500 000 ohms Input resistance The Super Sensitive Simple Voltmeter will give you that extra measure of resolution that vou always wanted on those low voltage readings SP SSSV OHMMETER SET AT RX100 J
203. the TRS 80 In this article I will discuss such an interface circuit how it works how to use it and how to build your Soundbox 80 BC2 BC1 FUNCTION The circuit Programmable sound generator PSG chip IC1 the AY 3 8910 by General Instruments is designed to send and receive data over the eight data lines That data is transmitted between the chip s set of 16 registers which are used to select the desired sound and the computer s bidirectional data bus The circuit of Fig 1 includes a 74LS245 octal tri state bus transceiver integrated circuit IC2 which serves that purpose The majority of the Soundbox 80 circuit in Fig 1 is used for address decoding and chip enable logic For the tri state buffer IC2 there are two controls enable IN pin 19 and direction DIR pin 1 The enable control signal must pulse low during any transaction between the computer and the sound circuit otherwise the outputs are tri stated in both directions The direction control signal pin 1 simply de cides whether the data will be shipped from Soundbox amp 0 to the computer or vice versa The enable logic for the AY 3 8910 IC1 must also be carefully planned The requirements 5V J1 IC6 a 12 eae 35 ofl So 11 AS 6 38 t fey A5 5 350 g IC3 31 A4 4 D 340A 3 40 ofA lat 1 2 Oe 55 LAD GND 80 oy E D 12 12 olaa H 1905 harer zo RESET ll BDIR BCI IC1 PROG
204. the supply voltage and inhibiting IC3 when the battery voltage drops below a pre set value forestalling the complete discharge of B1 Zener diode D4 provides a stable reference voltage for the comparators non inverting input while a portion of the battery voltage is applied to the inverting input via trimmer potentiometer R14 SYNDOLE es RLS 1982 allowing the trip point to be set at the knee of the NiCd battery s discharge curve When the supply voltage drops below a preset point IC4 s output goes high driving the threshold comparator of IC3 high via RIO and causing the output to go low extinguishing I and reducing current demand to a few mA Hysteresis provided by R19 prevents l1 from cycling on and off as the supply voltage fluctuates slightly with current demand Diode D5 isolates the output of IC4 from the timing network of IC3 when the supply voltage is normal and the output of the comparator is low Optional NiCd battery B1 see Fig 1 is slow charged via D and R16 at approximately 10 of its normal discharge rate and will recharge completely within 10 to 14 hours During recharging current flowing through D2 and R10 drives IC3 s threshold comparator high extinguishing I1 preventing un necessary current drain and decreasing the charging time An optional power switch S1 can be included if it is desired to store Syndle for a period of time Current drain averages less than 100 mA when the device is operati
205. til the adhesive dries Potentiometer P2 controls the tone frequency and the pulsation rate of the LED Potentiometer P1 controls the spin rate of the display and speaker s associated clicking sounds as the display spins A relatively slow rate pro duces very few winners A moderate rate gives a winner cn an average of every five to seven tries A fast rate improves the winning odds and will hit an average of one out of every two or three tries The adjustment range of the pot is narrow sO it takes a careful adjustment to set the winning odds you would like to have Because the power supply voltage affects the spin oscillator if you use a battery power source the winning odds will change as the battery voltage runs down SP THE PENCIL POINTS TO the speaker which can be installed face down on one corner of the PC board It is installed right over one of the jumpers which should be connected first THIS IS HOW the finished unit will look be fore you figure out what to do with the speaker Everything except the battery eli minator jack at the lower right pencil points to jack is supplied in a kit You must obtain locally the jack that matches the battery eliminator you plan to use If you don t use the eliminator you connect the batteries to the battery snaps coming out of the right side of the circuit board LAWRENCE M WALDEN WITH THE TIGHT ECONOMY MANY OF U
206. tion Cone travel will be less the voice coil can be shorter hence more of it in the magnetic gap and efficiency can be improved With its high sensitivity and power rating the JBL E130 driver can place enormous stresses on an enclosure when operating at full power Everything needs to be solicly cleated glued and screwed with front to back braces for good measure Anything less firmly constructed may rot withstand the stresses of being trucked and manhandled off stage by roadies and violently pumped on stage Many groups have experienced their loudspeaker cabinets literally coming apart at the seams with the rear panel being particularly vulnerable Nature of drive The 300 watt program rating for the E130 assumes clean drive Consider one of the hazards for stage loudspeakers amplifiers which are inadequate for the job in hand and which ure operated into overload by overenthusiastic musicians If the peaks are squashed into squarewaves and the softer passages exaggerated the heat load on the voice coil can reach destructive limits In effect the use of a 300 watt amplifier does not give automatic protection for a 300 watt loudspeaker If the amplifier is abused and overloaded so also will be the loudspeaker While the natural response of the E130 is quite reasonable for a high power driver nominally to 6000 Hz it needs reinforcement at the top end for a deliberately bright sound The problem is that no ordin
207. tional collector biasing in that there is no loading effect RIGHT CHANNEL 1 OUTPUT J2 LEFT CHANNEL 2 C OUTPUT J2 Collector load of Q4 is a 220 ohm resistor R9 which forms part of a voltage divider feedback circuit with the 10 ohm emitter resistor R3 of Q1 Q2 The voltage divider ratio sets the closed loop gain at 23 or about 27 dB which is the gain required to bring moving coil cartridge output levels up to normal phono input levels Output from the MoCo Preamplifier is AC coupled via a l0 uF tantalum capacitor C3 and a 100 ohm resistor R10 with a 10 000 ohm pulldown resistor R11 after the capaci tor to remove any DC voltage on the output The purpese of the 100 ohm resistor is to isolate the feedback loop from any loading effects of the following amplifier or shielded cable If that is not done any capacitive loading will introduce an additional phase lag which could make the MoCo Preampli fier unstable The computed equivalent input noise voltage is 98 nV That gives a S N ratio of 64 dB with respect toa 150 uV input RIGHT CHANNEL 1 _ INPUT Jt TO B1 9VOC ace LEFT CHANNEL 2 T gt INPUT Jt FIG 4 PARTS LOCATION DIAGRAM for MoCo Preamplifier shows how simple the project really is Note that there are many parts designations that are repeated because both audio circuits use the same parts symbol designation technique Those parts not duplicated on the printed circuit board
208. tly The Digital Prototyping System should give you every thing you need to easily design many more projects in the future Debugging is also a snap due to the elimination of all the extra leads and wires that normally clutter up a bread board SP WITH THE FRONT PANEL com pletely removed and the printed circuit board slid out of its hold ers the project looks very much like a simple power supply which it really is The add on cir cuits make the unit extremely val uable to the circuit designer and protctyper who must monitor Vec current and have knowledge of the switching action in the externally powered circuit job at a fration of the cost Bae Cc Qc 2N3055 E BOTTOM VIEW Gi FIG 6 HERE S A SIMPLE CALIBRATION LOAD for the Digital Prototyping System Make brief current tests of 15 seconds or less otherwise the transistor will overheat Even a brief test will raise the transistor case temperature sufficient to burn flesh 86 YAWWNAS Sa SPECIAL PROJECTS ak o ee b aus test ececesucies te bu Tuning i wordiwide Sid Steveny sten TVE pign Send today for your 52 page 8 2 x 11 booklet containing complete re prints of all eleven articles in the Build Your Own Robot series by Jim Gupton This all inclusive reprint gives you all the data you need to build your own Robot E TELLS EVERYTHING YOU NEED TO KNOW to build the Unicorn 1 Robot without the need for a
209. tment could be used The circuit could be plugged in when needed if the sweep gate was made an external output or added internally with suitable switching Further you might give some thought to butfering the sweep ramp and gate bringing them to the back panel as outputs In the case of scopes like Heathkit s 10 4510 with TTL active high and active low sweep gate IC 404 pin 9 and IC404 pin 8 respectively the blanking circuit in Fig 4 for the Single Sweeper One again requires no input pre conditioning However there s no Z axis Input you can te into so you Il have to use the blanking control circuits In that and similar applications where TTL level signals con 5V 0 E Q2 IC3 e 2N2907 1 6 7404 HIGH LEVEL SWEEP 2N3906 in OR GATE INPUT derstand the logic of action for each point fee RESET IC2 a Sin the circuit in relation to the other points yje RESET C20 1C3 t 6 1 6 7404 R9 fA b PIN 8 1247022 T Dom No LED 3 UNBLANK NORMALLY OFF Ol 25 a m wog gt z LED 2 NEW SWEEP COMMAND NORMALLY ON Ol IC 1 PI MANUAL RESET NORMALLY ON FIG 6 LED INDICATORS clue you to ihe action taking place in single Sweeper One You may want to add a few more LED s especially when the unit will be used with extremely slow sweep ing circuits Under that condition the LED s operate slowly enough for the eye to follow Is it necessary No
210. umbo red Q1 NP2907A PNP silicon transistor Q2 Q12 NP2222A NPN sili con transistor 1C4 IC6 4017 decide by 10 counter with 1 of 10 outputs 9VDC integrated circuit RESISTORS Resistors can be 1 2 or watt 5 or 10 composition units unless otherwise noted Ri R3 R9 R11 R13 R18 R20 R22 1300 ohm R2 220 ohm R4 470 000 ohm R5 680 000 ohm R6 1 5 Megohm R7 30 000 ohm R8 10 000 ohm R12 100 ohm R19 2200 ohm R23 R26 R29 560 ohm R24 R25 R27 R28 R30 R31 150 ohm ee o i pyre DI 15K 1N4454 GNE P1 P2 15 000 ohm subminiature trimmer potenti ometer P3 1000 0ohm trimmer potentiometer CAPACITORS Capacitors are rated at 15 WVDC or higher C1 22 uF electrolytic MAN 74 DISP1 MAN 74 Le i C Y 1 ic3 NP2907A E 3 4023 a B D oo SOS NP2222A 3 Pa R7 30K e SPEAKER P iT C2 C8 01 uF disc C3 C5 5 6 uF electrolytic C6 1 pF electrolytic C7 1 uF disc ADDITIONAL PARTS AND SUPPLIES PB N o miniature pushbutton switch Miniature speaker battery connector 9 volt battery wire sol der printed circuit material hardware 4 rubber feet etc Note an optional jack and battery eliminator can be sub Stituted for the battery connector end battery see text A complete set of parts for the ba tery powered version which also includes a drilled printed circuit board is available from Chaney Electronics
211. up each probe The operation of only one probe will be described here The other probe works the same way and is totally independent of the first Tne numbers shown in parenthesis are symbol and pin de signations for the second probe NPN transistors 2N3904 QI and Q3 along with two sections of hex inverter 74LS04 make up the state detector tor the logic probe Transistor Q3 turns on during low pulses causing IC4 b to go high and turning on the Low LED indicator LED13 When the input of Q3 is high or floating the input of IC4 b is pulled high by resistor R13 and holding the Low LED off The high detection circuit is much the same The input of IC4 a is held low through resistor R11 whenever the base of Q is low or floating When a high is applied to the probe s input QI turns on pulling up the input of 1C4 a and turning on HIGH LED LED11 Short pulse detection and memory are provided by C3 a a 74LS123 one shot chip C3 a is triggered by a high to law transition of IC4 b or a low to high transition of IC4 a The Q output remains low for a time determined by resistor R19 and capacitor C2 past the last trigger pulse The pulse time is approximately 250 msec with the values given for R49 and C2 Pulse memory is accomplished by closing PULSE switch S2 The low pulse from the Q is brought to the junction of C2 LED 11 LED 1 LED10 E1 CLOCK OUTPUTS THE DIGITAL PROTOTYPING SYSTEM is as rich looking as its name sound
212. upply borrowed from an old cassette pot able Select jack to match plug on supply s cable end similarly derived pulse indicating the start of a scope s sweep cycle unblanking the scope s CRT IC2 a resets the single sweep blanking control flip flop IC2 b blanking the scope s CRT again on the trailing edge of sweep gate which indicates that one sweep cycle has been completed When IC2 b unblanks the scope s CRT it simultaneously resets IC1 b in which the reset command was stored and when IC2 b begins to blank the CRT again it simultaneously resets IC2 a the tlip flop that reset it Therefore at the completion of the above cycle of events the scope s CRT will remain blanked until either the RESET button S1 is depressed arid released or a pulsed reset command Signal initiates another cycle Operation Now that was a little quick let s do it again bv the numbers this time See Fig 4 When the momentary RESET switch S is pushed and released ICl a sets and resets providing a debounced pulse output at Q pin 6 On the positive going edge at pin 6 which coincides with the release of Si IC1 b will be set by its clock input pin 11 going high with its D input pin 12 tied high IC1 b stores or holds the O 5V OUTPUTS USED FOR SINGLE SWEEP BLANKING CONTROL TO Z AXIS OR VOLTAGE TRANSLA TION CIRCUITS FIG 4 PUT IT ALL TOGETHER it spells Single Sweeper One the timing heert of the unit PARTS LI
213. upply to avoid the replacement of D cells from time to time The suggested technique is to use an external 9 volt DC plug pack a 12 volt unit will do and then regulate the voltage to 9 volts It can be done because the plug packs produce voltage as high as 20 volts DC with no load or very little load as is the case with the MoCo Preamplifier Use whatever regulated power supply you wish The LM317 IC chip can do the job Do not mount the plug pack inside the preamplifier case or keep it close to the case because the internal transformer will introduce considerable AC hum With the batteries and holders removed there is more than enough room in the chassis box Regulated power supply circuits are easy to come by yjust flip the pages of this issue Construction Construction of the unit is straightforward Most of the components are mounted on a single printed circuit board Fig 3 and 4 The author s unit was built into a standard metal case measuring 7 4 X 2 X 6 inches D X H x W The unit comes with a U shaped steel cover and an aluminum base and because the case is not all steel trouble with hum fields from nearby power transformers may be experienced in some instances Our solution was to mount the MoCo Preamp board inside a separate small galvanised more commonly referred to as galvanised iron steel box That gives excellent results and because it is inside the main case does not detract from the appearance of th
214. upted by the necessity of rewinding to the beginning of that practice section in order to Start over Also tapes and records never seem to have the right speeds for practicing They are either too fast or too slow The advent of the microprocessor however has taken a lot of potential pain out of learning Morse code A particular code practice group can be selected and it will repeat auto matically until the student feels comfortable while learning the code But not everyone has the hardware and software knowledge to justify obtaining a personal computer to teach code and the high cost may be another consideration Now there is a simple low cost dedicated microcomputer HARRY LATTERMAN for learning Morse code the CPP1 Code Practice Processor The CPP1 is a single chip microcomputer containing copy righted software specifically tailored to teach Morse code In addition the CPP1 doubles as an electronic keyer for added versatility Circuit description The Code Practice Processor is based around a single chip 8 bit microcomputer called the CPP hence the name of the project That chip contains RAM 2K of ROM I O ports with specific defined functions an internal clock and a reset circuit Refer to Figs and 2 To get ICI to function requires a crystal X1 and two capacitors Cl and C2 connected to pins 2 and 3 of the CPP1 Any series resonant crystal between to 6 MHz may be used A 3 57 MHz color burst crystal 1s
215. ur instructor that you can pass the test and hang on to the license because later that may very well make the difference between your getting a job or not Prove to yourself that you can motivate and drive yourself to higher goals SP ADVERTISING INDEX SPECIAL PROJECTS does not assume any re sponsibility for errors that may appear in the index below Free Information Number Page 801 A P Products Incorporated Cover Cleveland Institute of Electronics CIE SS O Electronics Technology Today Ing 00 NRI Schools n 802 OK Inddustries Inc Cover 4 Windjammer Barefoot Cruises Ltd Cover 3 REMEMBER THE LAST CIRCUIT THAT YOU BUILT ON A SOLDER less breadboard The wires were running Off the block every where and were connected to a makeshift power supply A quick wist of the wires insulated by precisely angled bends is all that was needed so that the bare conductors never touched but somehow did Once the power supply is deemed reliable it is a simple matter of juggling a logic probe around in a manner as to be most effective for debugging All the while keep in mind that power cord movement must be kept to a minimum thus preventing excessive testing and repair ing of the power supply The Digital Prototyping System described here provides a 5 VDC 3 ampere regulated power supply with an LED current monitor Two digital logic probes with memory are
216. ur old but still serviceable oscilloscope D E PATRICK thar and similar circuits which have appeared in the litera ture works when the scope s ramp generator is being trig gered only occasionally otherwise the asynchronous man ual reset causes partial display and lock out problems That design and similar ones cannot be used with free running synzed scopes it is sensitive to ramp or gate rates and generally isn t worth the time to build Qn the other hand single sweep disable circuits built into a scope as in Fig 2 operate on the principle of disabling trigger Or sweep Circuits as opposed to blanking the CRT They also cannot be used with free running untriggered scopes and since the trigger and sweep circuits of every oscilloscope are quite different trying to build a general purpose circuit would be next to impossible Further on some scopes where major modifications to existing circuits would be necessary the implementation of such a circuit would be too advanced a job for a neophyte In any case in Fig 2 when the momentary manual RESET switch SI is pushed and released IC1 a sets and resets providing a debounced pulse output at Q pin 6 and Q pin 5 where either may be used as the clock input to ICI b at pin 11 The former case assures that the manual RESET switch S1 must be pressed and released for the action to take place In the latter case IC1 b gets set as soon as the manual RESET switch is presse
217. urate If you split the graticule lines with the trace you will actually be calibrating to 4 8 or 4 9 volts depending on the particular transistors used f you want a precise 5 volts from the center of the trace substitute two series connected Zener diodes totalling 5 3 volts for the specified diode D1 see Fig 2 Construction The project shown is built primarily on a printed circuit board measuring 2 2 X 4 inches which just fits nicely R2 33K T 33K Q2 Y y P1 a7 v x B cf 01 02 23 2N3391 a ge Dt FIG 2 THE THREE TRANSISTOR CIRCUIT for the Scope Calibrator consists of a free running multivibrator stage Q1 Q2 and a buffer stage Q3 R8 R9 and R10 are specified as 5 resistors which are sufficient for this circuit inside a3 x 2 X 5 Y inch aluminum LMB cabinet If the printed circuit board is larger than the template edges it will interfere with the installation of the cabinet s cover The Scope Calibrator s test voltage outputs are wired tc binding posts J1 J4 see Fig 2 Since you re only going to touch the scope s test probe to the calibration voltage use the least expensive parts whatever you have lying around Feel free to substitute pin jacks banana jacks or whatever Power transformer T is rated 12 6 volts at any current the mini transformer shown in the photos is rated for 0 1 ampere Bridge rectifier BR 1 can be anything rated 25 PIV or higher Th
218. ving coil cartridges be cause they require very low ni noise preamplifiers Don t because we have a Super low noise Circuit that uses matched quality transistors that provides the gain you need without hum RETROFITTING THE SINCLAIR TIMEX COMPUTER FOR A STANDARD VIDEO OUTPUT When the title of a story says as much as this title does what more can be said than Turn to page 54 for all the facts ELECTRONIC FLASHER Here s an opportunity to re move that clicking stone age thermo mechanical turn signal flasher from your car and add a beeping solid state device whose flash frequency is not dependent on engine speed ELECTRONIC MEG O DAPTER SLOT If you are getting intc insulation testing then this project will re MACHINE place the expensive Megohm Here s a gaming project that meters called Meggers at a frac lets you keep the winnings as tionn of the cost You can test re player or builder because you f sistance at DC levels as high as own the slot machine Its a 1000 volts at safe current levels of fun project to build Only 50 to 60 microamperes 87 PRO CABINETS JBL SYSTEM This project is more to the liking of a Carpenter but with our complete construction details you can assemble a loudspeaker system especially designed for pro fessional musicians This 300 watt project is suitable for use with lead guitars vocal
219. while for some UHF transistors it can be as low as 4 In fact some designs for moving coil preamps de use UHF transistors We can also achieve low Rbb however by simply connecting a large number of transistors in parallel thus dividing Rbb by the number of transistors used The approach we eventually took was to use an LM394 super matched transistor pair Each of those transistors actually consists of a large number of individual transistors connected in parallel giving each device an Rbb of 40 or 20 when the two are connected together Those transistors also have very high Hfe of 500 and due to the large number of transistors statistical variations are considerably reduced thus 1 f noise is very low What has emerged so far is that we can minimize noise by reducing the input resistance but so far we have not cansid ered how to minimize the effect of base current noise and emitter base voltage noise Since one increases with col lector current while the other decreases there is an optimum collector current at which the overall noise is at a minimum To work that out we have to sum all the noise sources into an equivalent input noise voltage Since the various sources are Statistically unrelated we do not simply add the voltages together but take the square root of the sum of the squares Differentiating that equation with repsect to collector current reveals that the minimum noise can be calculated and suggest suitable design consider
220. wire hardware solder etc Optional on board regulated 5 volt DC power supply used with 9 12 volt DC battery eliminator Optional circuit for high level sweep gates and ramps may be deleted with TTL level design and applications The following is available from E T C P O Box 29278 Denver CO 80229 Bare circuit board 10 00 A complete set of parts for the Single Sweeper One per Fig 4 40 00 Optional power supply which includes filter and bypass capacitors regulator and battery elimina tor which plugs directly into the wall supplying 9 to 12 volts of unregulated DC to unit 15 00 signals is not advised Also the user should avoid loading scope circuits or signals Some applications Where a scope has buffered ramp and or gate outputs and Z axis or intensity modulation inputs like some Philips Tektronix Dumont et al oscilloscopes adding the single sweep blanking circuit of the Single Sweeper One Fig 4 is a simple matter A single sweeper could be built into a me en me o m m a ee a m a A INSIDE VIEW OF THE SINGLE SWEEPER ONE made by the author Printed circuit board is secured to the bottom of the plastic case with dabs of RV cement Use stranded wire to in terconnect components mounted on cover LED s are cemented in piace with some epoxy giue 86t HINNAS A an gt H MANUAL RESET IC1 a PIN 4 S MANUAL RESET OR NEW SWEEP COMMAND l IC1 a PIN 1
221. would then be 6 5 volts A non electronic note During the course of experimenting with Syndle the au thor discovered a few pertinent facts about its operation When altering component values to obtain the desired flick er look slightly away from I1 do not look at it because your peripheral vision is more sensitive to small changes in light intensity than when looking towards the light source directly That ts due to the greater number of rods light sensitive cells in that portion of the eye Surrounding the lamp with a translucent material such as frosted plexiglass paper or plastic greatly accentuates the flickering effect due mainly to the light scattering caused by the nature of these materials The Syndle can be used in a variety of applications suchas a substitute for a candle in the home or restaurant as a Christmas decoration or as a safe portable source of illumination for a Jack O Lantern As a locating beacon for your Car it is unique and easily spotted at night If left plugged into its charger continuously its slow charging rate won t overcharge B1 it will light immediately should the power fail AC powered versions which require transformer T1 may be adapted to outdoor lights or doorbell button illumi nators Other applications will undoubtedly occur to the reader just as countless uses have already been discovered for the candle SP HERE S SYNDLE before it is buttoned up Note the 1850 lamp bulb set low
222. your car radio to stereo or even to real high fidelity status Then again maybe you had a tape player in the dash that some hoodlum ripped out leaving a large gaping hole Either way you can add or retrofit one of the new hi fi or super fi AM FM stereo cassette tape radios in just a couple of hours What you save on installation can pay tor a pair of super duper multi way speakers or half the cost of the radio itself The speakers themselves are no problem Virtually every modern dash is pre moulded for miniature stereo speakers If you like something other than a thin tinny sound which is what you ll get from mini size dashboard speakers you ll find that in most instances the rear deck has been precut for larger speakers of the 5 X 7 inch or 6 x 9 inch variety or for some other size that will sound better than the itty bitty speakers generally used in the dash Usually all you have to do is fit the speakers to the existing cutouts and run the wiring to the radio location leaving a couple of feet of slack that can be folded behind the dash and taped in place The real nitty gritty of the installation will be fitting the YOU GET JUST ENOUGH hardware with a modern universal aftermarket radio to install it possibly a full length wiring har ness with the more expensive radios This harness has the speaker terminals and speaker power connector pre attached radio because so called universal radios really aren

1983 Summer - American Radio History

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