Laboratory in Engineering Fundamentals
Contents
1. How Toilets Work http www cln or Welcome to the Community Learning Network WWW home page CLN is designed to help K 12 teachers integrate technology into their classrooms We have over 265 menu pages with more than 5 800 annotated links to free resources on educational WWW sites all organized within an intuitive structure http www cln org searching_ home html Search Engines and Subject Directories http webhome idirect com jadams electronics Welcome This website allows you to browse the subject of ELECTRONICS If you are just starting the journey of learning electronics I hope you ll make use of the simple nature and graphical content of this site Feel free to look around Don t worry there are no tests at the end of the day http www cln org themes electronics html Electronics Circuitry Theme Page ELEC 199 Useful References and Internet Resources 6 2 Below are the CLN Theme Pages which support the study of electricity and electronics CLN s theme pages are collections of useful Internet educational resources within a narrow curricular topic and contain links to two types of information Students and teachers will find curricular resources information content to help them learn about this topic In addition there are links to instructional materials lesson plans which will help teachers provide instruction in this theme http ourworld compuserve com homepages Bill_ Bowden A small collection of elec2. A voltage divider using a potentiometer is shown symbolically in Figure 3 7 ELEC 199 Electronic Fundamentals 3 6 5V Sliding electrode Rt R a V0 R2 Ground Figure 3 7 Potentiometer The total resistance of the potentiometer is R R R A potentiometer usually has the form of a round drum with a central rotating shaft that controls the position of the wiper as shown in Figure 3 8 Sliding electrode Schematic Symbol Sliding electrode Figure 3 8 Potentiometer Current and Voltage laws A circuit node is a point where two or more wires are electrically connected together Any closed path along a circuit is called a loop All voltages directed in clockwise directions from negative sign to positive sign are considered positive and all voltages opposing that direction are negative Current Law The sum of all currents flowing into a node must be equal to the sum of all currents leaving this node This law is quite obvious if you think of a node as a point where flowing rivers wires meet All the water leaving such a junction must equal the water supplied The Voltage law The sum of all voltages with proper sign along a closed loop is equal to zero ELEC 199 Electronic Fundamentals 3 7 This law is obvious if you think of voltage as an elevation Walking along the closed loop will always bring you to the starting point with no gain in altitude Both current and voltage laws are
3. EE EE ka SSTAMP BS2 Identifies processor type FLAG var bit Comparator output high or low TOTAL var word Count of lows to highs LEE E E E E E E E E E E E E E E E E E Initialize Constants akaaka aka aka aka aka akaaka aka aka akaaka aka akaaka aka kaakaa N9600 con 4054 Set baudrate to 9600 ELEC 199 Projects 5 13 I con 254 Instruction prefix value CLR con 1 LCD clear screen instruction L2_C4 con 195 Line 2 character 4 code L2_C10 con 202 Line 2 character 10 code INIT Start of program pause 100 Small delay serout 0 N9600 I CLR Clear the display pause 1 Small delay serout 0 N9600 THREE MUSKETEERS Insert your names here serout 0 N9600 I L2_C4 Count Dislay Count FLAG 0 Set FLAG to 0 TOTAL 0 Set the counter to 0 RO SE SE Oo SE fo SE AE AE SE AE AE SE AE SE Of AE AE E SFe Main Program OO OO Oe SE AE SFe SE AE SFe SE AE SE SFe SE SE Of AE oe ob oe MAIN pause 100 Small delay for debouncing if in15 0 then OFF If P15 is low go to OFF if in15 1 then ON If P15 is high go to ON goto main Loop to MAIN forever OFF FLAG 0 Set FLAG to 0 goto MAIN and return to MAIN ON if FLAG 1 then MAIN If flag was already 1 go to MAIN TOTAL TOTAL 1 else increment the counter serout 0 n9600 I L2_C10 On line 2 character 10 serout 0 n9600 dec TOTAL display the counted decimals FLAG 1 Reset the flag to 1 goto MAIN and return to main ELEC 199 Pr
4. Sensing Resistor FSR will be used for various experiments The sensor shown in Figure 5 1 has a sensing element made of a conductive material Two electrodes deposited on a plastic sheet are in contact with the material Applying a force F to the sensing element decreases the resistance R between the electrodes This forces the electrodes into more intimate contact with the conducting layer It takes a certain time before this resistance settles Repeated measurements with the same applied force yields different values of resistance This is due to a certain randomness of the process Calculating the standard deviation will determine the accuracy one can expect from this sensor approximately 10 in our case The maximum error can also be used as a measure of accuracy The FSR characteristics R f F is nonlinear and can be approximated by a suitable function such as R a b F aand bare suitable constants 5 1 ELEC 199 Projects 5 2 For forces F in the range of 1 N to 10 N the resistance R will vary between several hundred kohms to a few kohms The FSR shows different characteristics depending on whether the applied force is increasing or decreasing This phenomenon is called hysteresis and is an attribute of most sensors In order to minimize the effects of hysteresis a force must be applied in a consistent manner that is in a specified direction if at all possible i Scale construction Platform Figure 5 2 Beam scale In ord
5. a switch to the I O pin 14 as illustrated in Figure 4 6 Leave the circuit of exercise 1 connected Write and run the program of Figure 4 7 This program is a modification of exercise 1 It will turn the blinking LED on when the switch is closed and turn the blinking LED off when the switch is open 5V R S 10k Port pin 14 Switch Figure 4 6 Switch input circuit Example program to read the state of I O pin 14 and switch a blinking LED on off loop if in14 0 then blink Is switch on Read I O pin 14 Goto loop Switch is off do nothing blink High 15 Turn on LED connected to I O pin 15 Pause 500 Delay for 5 seconds Low 15 Turn off LED connected to I O pin 15 Pause 500 Delay for 5 seconds Goto loop Go back to loop and blink LED forever End Figure 4 7 Program will switch on off a blinking LED ELEC 199 Projects 5 1 5 Projects Students must complete demonstrate and document two projects described in Sections 5 1 and 5 2 These projects can be implemented using simple parts and procedures described in this manual However students are encouraged to incorporate their own ideas and solutions Students can also propose a new project but must first seek approval from the course instructor 5 1 Project 1 Force Sensor Measurements 5 1 1 Beam Construction Electrodes Sensing Element 42 Figure 5 1 Force Sensing Resistor Interlink Electronics Force Sensing Resistor FSR A Force
6. gravity force F applied at distance l from the support a This distance is called an arm The force applied times its arm is called a moment of force The force F applied to the beam generates an opposing force F at the support b This force has moment F 1 Moments of force law In equilibrium sum of all moments with proper sign must be equal to zero In our case F L F l 0 2 6 ELEC 199 Mechanical Fundamentals 2 4 Torque Figure 2 3 Rotating body Moment of force applied to a rotating body is called a torque Torque applied to a wrench shown in Figure 2 3 is given by d x F 2 2 Exercises The exercises must cover all the material in Section 2 and be useful for designs described in Sections 5 1 and 5 2 Exercise 1 Compare pressures exercised by the foot of an elephant with that of a person on high heels Assume reasonable parameters Exercise 2 Exercise 3 Exercise 4 Exercise 5 ELEC 199 Electronic Fundamentals 3 1 3 Electronic Fundamentals 3 1 Basic ideas and components Current Electrons are negatively charged particles The movement of electrons constitutes the flow of electric current The movement of a negative charge in one direction can be thought of as the movement of a positive charge in the opposite direction The direction of the positive charge is the direction of current flow You can think of an electric charge as water and of an electric current as water flowing in a river or a pipe T
7. symbols designated for battery and resistors Rseries gt E a oo I E Ri R2 gt E T Rparallel b Figure 3 5 a Series and b parallel connections ELEC 199 Electronic Fundamentals 3 5 The equivalent resistors will draw the same current I from the battery Their value can be calculated as R series R R 3 3 R parallel R R 1 1 R 1 R 3 4 Voltage Divider Shown in Figure 3 6 a is a simple circuit called voltage divider E Implied Ri connected Ri to ground lt a b Figure 3 6 Voltage Divider The current flowing through both series resistors is given by I E R R This current following Ohm s law will cause a voltage drop across the resistor R This voltage drop is given as V I R E R R R E 1 R R 3 5 By selecting a proper ratio of R R we can obtain any voltage V between zero and E Figure 3 6 b shows a simplified way of drawing the circuit shown in Figure 3 6 a Here we use the symbol ground to indicate common connection or common node Any voltage indicated without additional reference information is taken with respect to the ground Potentiometer A voltage divider can be conveniently built using a variable resistor called a potentiometer or pot for short A potentiometer has a sliding electrode a wiper the position of which can be manually adjusted at a desired location resulting in a variable resistance
8. vo t a b Figure 3 12 Charging a capacitor Assuming that the switch S is turned on at time t 0 the voltage on the capacitor is given by t RC V t E 1 e 3 6 ELEC 199 Electronic Fundamentals 3 9 The value of RC is called the time constant for this circuit Symbols and codes for capacitors are shown in Figure 3 13 Ceramic disc Polyester Schematic Symbol Value Multiplier Tolerance Non polarized i I IT Tantalum Electrolytic Schematic Symbol Polarized Multiplier in pF Tolerance 10 rt l 1 10 7 2 102 3 104 g 104 5 Lt 10 20 6 Figure 3 13 Symbols and values for capacitors ELEC 199 Electronic Fundamentals 3 10 Comparator A comparator is an electronic subsystem that compares two voltages applied to its inputs as illustrated in Figure 3 14 Comparator o 4 L Figure 3 14 Comparator The function implemented by a comparator is mathematically described as For V V gt 0 we got V High typically 5 volts 3 7 For V V lt 0 we got V Low typically zero volts Figure 3 14 shows an example of a circuit with a comparator using two pots and an LED The LED is on whenever V gt V and is off otherwise Figure 3 15 Comparator with LED indicator ELEC 199 Electronic Fundamentals 3 11 Oscillator An oscillator is a circuit which can generate a waveform at a certain frequency expressed in cycles per second or Hertz Hz The frequency rang
9. 9V battery or by the 9V power adaptor When the power is properly connected the Power LED will illuminate The power supply voltage is reduced from 9V to 5V by a 5V regulator 5V supply will be used for circuits on the Prototype Board Note You must connect the 5V wires to V and connect your ground to V NEVER connect any wires to V To understand how the prototype board makes internal connections read the Board of Education Manual You can do this by loading the CD choosing Documentation selecting a topic choosing View ELEC 199 Projects 5 10 5 2 4 Interfacing with the Microprocessor 9V Battery Power 6 30V Wall 5V Regulator LED adapter External power pins Serial port cane Board of Education chip Prototype Reset switch Port pins board Figure 5 11 Board of Education with Prototype board Connect and program the BASIC Stamp II computer to count the number of repetitions of the hand gripper and connect the display that count on the LCD Liquid Crystal Display module Figure 5 12 shows how to connect the Basic STAMP II to the output of the comparator and to the LCD module The output of the comparator connects to P15 of the BASIC Stamp II which you will program to continuously poll P15 for a high voltage When the LED turns on P15 goes high and the computer will increment the count on the LCD module For LCD pin connections see Figure 4 3 CAUTION Always check the connections to V4 V and to the display be
10. LABORATORY MANUAL ELEC 199 Laboratory in Engineering Fundamentals This manual was prepared by Adam Zielinski Adam Zielinski November 2001 Contents Acknowledgement 1 Introduction 1 1 Justification and Motivation 1 2 Calendar Description 1 3 Course Implementation 2 Mechanical Fundamentals 2 1 Basic ideas 2 2 Exercises 3 Electronic Fundamentals 3 1 Basic ideas and components 3 2 Exercises 4 Microcontroller Fundamentals 4 1 Basic ideas 4 2 STAMP microcontroller 4 3 Interfacing to the LCD 4 4 Exercises 5 Projects 5 1 Project 1 Force Sensor Measurements 5 1 1 Beam construction 5 1 2 Force Measurement Principle 5 1 3 Experiments a FSR Characteristics b Hysteresis of the FSR c Mass measurements 5 2 Project 2 Hand gripper exerciser 5 2 1 Principle of Operation 5 2 2 Mechanical Design 5 2 3 Electrical Design 5 2 4 Interfacing with the Microprocessor 5 2 5 Software 5 2 6 Parts 6 Useful references and Internet resources ELEC 199 Introduction 1 1 Acknowledgement Funding from UVic Innovative Teaching grant Cinkant Endowment Fund Summer Career Placement Program and the Department of Electrical and Computer Engineering was received in support of the development of this course Thanks are due to Susumu Kirimura Mr Dwayne McLean and Paul Fedrigo for their involvement Several other personnel from ECE and Mechanical Departments were also helpful in the preparation of this course 1 I
11. Modules ELEC 199 Microcontroller Fundamentals 4 4 Pin Symbol Level Function 1 5V 5V Positive power pin Vdd 2 GND OV Negative power pin Vss 3 SER Pulses Serial data pin 4 GND OV Duplicate negative power pin Vss 5 5V 5V Duplicate positive power pin Vdd Figure 4 3 Pin connection for the BPI 216 serial LCD module 4 4 Exercises Here are a couple of simple BASIC programs that will introduce you to some programming rules as well as the BASIC Stamp computer Exercise 1 Connect the power adapter cable and serial cable to the Board of Education as per page 26 of the Basic Stamp Manual on your CD You may need a DB9 to DB25 adapter and may have to remove the 2 screws on your serial cable to plug it into your serial port Connect the circuit of Figure 4 4 for this first exercise This circuit can be connected on the Stamp II prototype board Write and run the program of Figure 4 5 This program will turn the LED on and off every half second R Port gt NNA pin 15 2 2k LED Figure 4 4 LED output circuit Example program to blink an LED connected to I O pin 15 loop High 15 Turn on LED connected to I O pin 15 Pause 500 Delay for 5 seconds Low 15 Turn off LED connected to I O pin 15 Pause 500 Delay for 5 seconds Goto loop Go back to loop and blink LED forever End Figure 4 5 Program will blink an LED ELEC 199 Microcontroller Fundamentals 4 5 Exercise 2 Connect
12. ctronic Fundamentals 3 2 fsx RE a Supply Battery Ground Typical Batteries Schematic Symbols Figure 3 1 Batteries and ground Resistance Some materials like metals are good conductors of current while some are not Electrical connecting wires are made from good conductors usually copper The degree in which a material resists the flow of electric current is called resistance and is measured in ohms An electronic component called a resistor has a specific and constant value of its resistance An instrument called an ohmmeter measures the resistance placed in its path as illustrated in Figure 3 2 i R Figure 3 2 Measure of resistance using an ohmmeter The symbol and value codes used for resistors are shown in Figure 3 3 ELEC 199 Electronic Fundamentals 3 3 Color Value Multiplier Black 0 Brown Red Value x10 Orange Value x1 ae x MI ultiplier Blue Violet Tolerance Gray White Schematic Symbol Color Tolerance Gold Fo Silver 10 Wo Color 20 Figure 3 3 Symbol and code used for the resistors A multi meter or tester is an instrument that combines the functions of a voltmeter an ammeter and an ohmmeter Ohm s Law If you connect a battery rated E volts to a resistor R using a wire as shown in Figure 3 4 a current I will flow through the resistor in the direction as indicated The voltage across battery terminals can be measured by voltmeter V while the current I through re
13. ding metal screws When the gripper is squeezed the grip angle decreases Decreasing this angle will either increase or decrease the resistance of the potentiometer depending on which way the potentiometer is mounted or which two of three terminals are used You can use the 50kQ potentiometer from your kit instead of the gripper while building your circuit then replace it with the gripper for your final testing ELEC 199 Projects 5 9 5 2 3 Electrical Design 5V 5V Comparator LM393 Vsensor 3 3 3k Hand gripper Ri with potentiometer 50k Vout Figure 5 10 Comparator circuit for the hand grip exerciser Squeezing the hand gripper changes the sensor voltage V ensor at the input of the comparator of Figure 5 10 Resistor R represents the potentiometer of the hand gripper The comparator outputs a high at V pu when V sensor reaches the reference voltage Ve This will turn on the LED indicating that the hand gripper has been squeezed to a certain degree Adjusting R can change the amount of force needed to light the LED Comparators usually have what is called an open collector output and require a pull up resistor R When the output is high approximately 2V is dropped across R This leaves V 3V Resistor R will limit the maximum current that can pass through the LED Build the circuit on Figure 5 10 on your prototype board located on your Board of Education see Figure 5 11 The Stamp Board is powered by a
14. e FSR resistance against force for n 8 measurements Average Maximum 1 m EIN Rtkohea error 0 000 1 99 5 45 2 69 0 100 3 41 4 45 1 88 0 200 4 83 3 78 0 86 0 300 6 25 3 43 1 31 0 400 7 68 3 18 0 51 no reference mass applied force is due to mass of platform e Resistance m Error Resistance R kohm Maximum Error 0 0 2 0 4 0 6 0 8 0 10 0 Force F N Figure 5 6 FSR resistance vs force n 8 b Hysteresis of the FSR Put a weight on the platform at the end close to the hinge and read the FSR resistance Gently slide the weight without lifting it and read the corresponding resistances Take measurements every 50mm until the end of the platform is reached Plot your results R vs F A sample result is presented in Figure 5 7 for n 3 repeated measurements ELEC 199 Projects 5 6 increasing force m decreasing force Resistance R kohra 0 0 2 0 4 0 6 0 8 0 10 0 Force F N Figure 5 7 Hysteresis of FSR n 3 c Mass Measurement You will use the scale to make a measurement of an unknown weight mass predict the error of such a measurement and verify your finding by using another high precision scale say at your friendly grocery store The unknown weight should be such that FSR resistance is in the measurable range Three methods can be used Method 1 Using ratio of positions Put an object with an unknown weight but with a symme
15. e from approximately 50 Hz to 20 000 Hz 20 kHz is called an audible frequency range This is because a signal with such a frequency if applied to a speaker will generate an audible tone The frequency of an oscillator can be changed controlled by an external voltage applied to it Such a circuit is called Voltage Controlled Oscillator VCO It is also possible to change the frequency of the oscillator by varying the value of a resistor that is part of the oscillating circuit Oscillators are often built using a comparator and a capacitor charged discharged through a suitable resistor Sensors Converters A sensor is an electronic device that typically converts a non electrical quantity such as angular or linear displacement force light intensity and others into an electrical quantity such as resistance capacitance voltage or current An example of an angular sensor is a rotary potentiometer that changes its resistance as a function of the angular position of its control shaft This resistance can in turn be used to change the frequency of an oscillator One can call such a circuit an angle to frequency converter Used in a voltage divider configuration as shown in Figure 3 7 a potentiometer can be used to build a simple angle to voltage converter If changing the pot s shaft angle requires overcoming a certain restoring force say generated by a spring we then have a force to frequency or force to voltage converter Using a thin co
16. e some hardware We ll be using a pre assembled Printed Circuit Board PCB that contains several parts Refer to Figure 4 1 for the block layout of the Stamp Board This board was created to simplify connecting real world stuff to the BASIC Stamp Connectors are provided for the power supply wall adaptor or 9 volt battery the programming cable serial port and the Input Output pins of the BASIC Stamp There is also a prototyping area or breadboard the white board with all the holes in it You will be using an additional prototype board to build your circuits on Serial Memory Port EEPROM BASIC Stamp II Microcontroller Input Output Pins Figure 4 1 Block diagram of Stamp board Prototype Board We also require a language to program the microcontroller One of the most popular languages is called BASIC that stands for Beginner s All purpose Symbolic Instruction Code The Stamp stores the software program on EEPROM ELEC 199 Microcontroller Fundamentals 4 3 To understand how a BASIC program is written let us look at the program in Figure 4 2 Anywhere you see the tick mark the text that follows it to the end of the line is a comment The computer ignores comments they provide an explanation of the program The first line in the program that is not a comment is the label loop Labels serve two purposes in a BASIC program e Like comments they can provide a hint to the readers about the purpose
17. e without friction The force F needed to speed up an object having a mass m with acceleration a is given by Newton s Law F ma 2 1 Force is a vector and therefore it has magnitude and direction The unit of force is called Newton N One Newton 1N is the force required to accelerate a mass of 1 kg to 1 m s Gravity Objects attract pull each other with a certain force On a planet this attraction demonstrates itself as a gravitational force that pulls down an object with a force proportional to its mass F gm 2 2 ELEC 199 Mechanical Fundamentals 2 2 The proportionality constant on Earth g 9 81 m s The constant g for other planets is different Mass can be measured by measuring the force of gravity also called a weight An instrument to measure weight is called a scale Not recommended but a convenient measure of force is a force by which a mass of 1 kg is pulled by the gravitational force on Earth This unit of force is called a kilogram force kgf Using eq 2 2 we note that 1 kgf 9 81 N The gravity force is distributed over all volume of the object however for many situations it is sufficient to model this force as one vector attached at the center of gravity of the object Pressure Force F applied over a certain area S exercises a pressure P given by P F S 2 3 Pressure is measured in Pascals One Pascal is the pressure exercised by one Newton of force applied to a surface of 1m Not a recommended m
18. easure of pressure is one atmosphere atm that is 1 kgf applied over 1 cm area Spring Springs or springing members are made from an elastic material that can be reversibly deformed under the force applied This deformation if within a certain limit is proportional to the force applied with the proportionality constant k spring constant When deformed by amount d a spring exercises a restoring force F equal to that of the applied force and opposing that force This force can be found by using Hook s Law F kd 2 4 As illustrated in Figure 2 1 gt 0 0 W i a b Figure 2 1 Spring and Force Shown in Figure 2 1 a is a spring with a platform attached to it The position of the platform is set to zero Suppose now that an object with a mass m is placed ELEC 199 Mechanical Fundamentals 2 3 on the platform The gravitational force exercised on the object will displace the platform by a certain amount d At the equilibrium these forces must be equal therefore Equation 2 5 allows us to calculate the mass m if the other three variables g k and d are known This arrangement is the basis for a scale Moment of force E ES MXXXKKKKKKKKKKXKKKK KKK XK Support a Support b Figure 2 2 Beam Consider an ideal weightless beam supported by support a and support b as illustrated in Figure 2 2 Suppose that a weight with mass m is suspended at a certain point of the beam This mass is exercising
19. er to investigate the properties of the FSR sensor you need a suitable mechanism to apply a force to it You will build a beam scale as shown in Figure 5 2 You can use two wooden boards as beams and connect them with a low friction hinge The beam on the bottom is the base while the other is the platform where test weights are placed Include a suitable scale on the platform mm resolution so you can determine the position of the weight The beams can be metal or plastic however the platform must be stiff enough to support an applied weight without bending The platform should not be too heavy as this will reduce the force sensing range Place the FSR on the base securing it with Scotch tape The FSR is pressed by the platform through a suitable round plunger that covers the face of the sensing element The material for the plunger should be elastic so that it will return to its original shape shortly after the force is released The material should not be so soft that the applied force deforms it A sheet of rubber plastic foam vinyl leather or cork may be suitable Make sure that the plunger pushes the FSR uniformly During series of measurements keep FSR under constant pressure of the platform to obtain consistent measurements Spacers between the two beams are added in order to make enough space for the platform to bend slightly under the applied weight It also allows for variation of the FSR position by sliding it on the base ELEC 199 Pr
20. fore turning on the power so that you don t damage the display or the computer On the CD select Board of Education and read the Board of Education Manual pages 24 32 Under the Basic Stamp heading read the Basic Stamp Manual pages 25 38 which describe how to connect the serial cable between the Board of Education and your serial port and how to install the Stampw exe file onto your computer The serial cable is used in the downloading of the BASIC program to the BASIC Stamp chip When the reset switch is pressed it will restart the execution of the downloaded program ELEC 199 Projects 5 11 5V Comparator LM 393 Vsensor toPC Serial port Figure 5 12 Complete hand grip exerciser schematic ELEC 199 Projects 5 12 Figure 5 13 Implementation of hand gripper The photo of Project 2 is shown in Figure 5 13 5 2 5 Software The program shown in Table 5 2 can be copied from the computers on the laboratory or it can be typed into a Windows or Mac computer as directed in the manual on the CD This software program is then to be downloaded into the Basic STAMP II via the 9 pin serial cable This program will count the number of times that the comparator goes from a low voltage to a high voltage and display that count on the LCD module Table 5 2 Software to operate STAMP as a counter VO 2h EE bE aE EO ab a bb ee Basic Stamp Project DEE EEE EE ee bE EE NOE ta aka EE bE EE ab a bE Declare Variables DEE EEE EE OE EE
21. gure 5 8 The force applied to the gripper will change the angular position of its handles This angle can be monitored using a potentiometer suitably attached to the gripper Sucha potentiometer serves as an angle to voltage converter that generates voltage V proportional to the angle The voltage V increases with the applied force In order to complete the exercise cycle the force must exceed a certain predetermined level A comparator with an adjustable threshold voltage V can detect this event The output of the comparator goes high for V gt V and turns on an LED to indicate this event The signal from the comparator will be used by the microprocessor to count and to display the number of exercises completed see Sections 5 2 4 and 5 2 5 for details ELEC 199 Projects 5 8 5 2 2 Mechanical Design Potentiometer Shaft Plates Grip angle Figure 5 9 Hand gripper mounted with potentiometer The hand grippers shown in Figure 5 9 will be located in the Project Lab If you prefer you can build your own gripper potentiometer Grippers can be purchased at most sporting goods stores i e Canadian Tire Wal Mart etc For this project the gripper is assembled with a 50k potentiometer The potentiometer is fitted with two plastic pieces on either side of the hand gripper The plastic can be purchased at hardware store They can be suitably cut using a knife The plastic pieces are fixed to the gripper with small self threa
22. he water flows in a certain direction from the higher ground to the lower ground The measure of current is ampere A An instrument called ammeter is used to measure the current that must pass through it Battery and Voltage You can think of an electric battery as a generator of a positive charge Once an electric load is connected to the battery the current flows from its positive terminal to its negative terminal through the connecting wires and the load The batteries come with different voltage ratings expressed in volts V For instance a car battery is a 12 volt battery The higher the voltage the more current will flow from the battery when you connect an electric load to it You can think of a battery as a pump which pumps the water from the lower ground usually referenced as zero to a higher ground You can think of a battery s voltage as the height of the elevated water level The battery is often called a voltage source Voltages are measured by an instrument called a voltmeter To measure the voltage the voltmeter must be connected between two points where there is a certain voltage difference like between the and the terminals of the battery The reference point used to measure voltages is called ground For example one of the terminals of the car battery is connected to the car s body and is considered an electric ground Drawings of batteries and associated symbols are shown in Figure 3 1 ELEC 199 Ele
23. illustrated in Figure 3 9 VR1 I b Ri B E R2 VR2 k e LB h k E VR1 VR 0 a b Figure 3 9 Current and Voltage Laws Diodes A diode is an electrical valve that conducts current only in one direction from Anode to Cathode as shown in Figure 3 10 A special diode called Light Emitting Diode LED emits light whenever there is current flowing through it An LED is often used as an indicator of the voltage presence LED is on or absence LED is off Anode Cathode Anode Cathode p Schematic Symbol Diode RR Anode Cathode Schematic Symbol LED Light Emitting Diode Figure 3 10 Diodes ELEC 199 Electronic Fundamentals 3 8 A simple circuit with LED is shown in Figure 3 11 1k I 5mA 5V wW LED Figure 3 11 LED in action Capacitor A capacitor is an electronic device capable of storing the electric charge This capacity is measured in units called Farads F or wFarads 1uF 10 F Once a capacitor is charged it will have a certain voltage present between its terminals You can think of a capacitor as a water reservoir and the voltage across it as the water height When a discharged capacitor zero voltage across its terminals is connected to a voltage source through a resistor as shown in Figure 3 12 a it will gradually be charged The voltage across the capacitor will increase in time and will eventually reach the voltage supplied to it as illustrated in Figure 3 12 b
24. ing programs and quietly doing calculations not interacting with humans at all These computers are in your car on the airplane in your kid brother s toy and maybe even inside your hairdryer We call these devices microcontrollers Micro because they are small and controller because they control machines gadgets whatever Microcontrollers are designed to be connected to machines rather than to people They are handy because you can build a machine or device write programs to control it and then let it work for you automatically In this course we will use the BASIC Stamp II microcontroller Port A port is a physical connection that allows devices such as a keyboard mouse monitor printer etc to connect to and communicate with a computer A computer has serial and parallel ports that differ in their number of pins and the rules associated for communication A microcontroller also has ports These are often referred to as I O Input Output pins An I O pin has two usable known states a high state or a low state and it can also be floating A high state in the digital circuits represents voltage of approximately 5V and a low state is approximately OV ground The BASIC Stamp II has 16 I O pins that can be used to directly connect interface to devices such as switches LED s displays potentiometers etc LCD The acronym LCD stands for Liquid Crystal Display This device if connected to a microcontroller can display number
25. nductive film one can produce a force sensor that changes its resistance with the applied force or pressure Such sensors are called Force Sensing Resistors FSR s and are available commercially The resistance of such a sensor decreases nonlinearly with the applied force and eventually levels off saturates at a certain force The accuracy of such a sensor is relatively low in 10 range An FSR can be used to control the frequency of an oscillator or to produce variable voltage using a suitable voltage divider Multi meter A multi meter is a measuring instrument that combines the functions of an ammeter a voltmeter and an ohmmeter When using the multi meter make sure that it is set for the proper function For example you can damage it if you try to measure a voltage when the device is set for ohmmeter function 3 2 Exercises These exercises must cover all the material in Section 3 and be useful in designs from Sections 5 1 and 5 2 Exercise 1 Exercise 2 Exercise 3 Exercise 4 Exercise 5 ELEC 199 Microcontroller Fundamentals 4 1 4 Microcontroller Fundamentals 4 1 Basic ideas and components Microcontroller Most of us know what a computer looks like It usually has a keyboard a monitor a Central Processing Unit CPU a printer and a mouse These types of computers like the Mac or PC are primarily designed to communicate or interface with humans But did you know that there are computers all around us runn
26. ntroduction 1 1 Justification and Motivation Students enrolled in the Bachelor of Engineering Programs Electrical Computer and Mechanical Engineering come into contact with engineering courses late in their programs This situation has undesirable effects a students who are potentially interested in engineering may get discouraged a some students who are not inclined to engineering discover it too late and a Students are not given the opportunity to sample different engineering disciplines before making their decision on which program to choose In the past the Faculty considered a new general engineering course for the First Year students However it was not implemented primarily because of the lack of resources and a suitable textbook ELEC 199 intends to address this need Its introduction is expected to enhance our programs add to the engineering design science components as defined by the accreditation requirements and increase CO OP employability of our junior students The advances in electronics materials and computer technology make it possible to accomplish breathtaking tasks such as sending men to the moon launching space shuttles and sending unmanned robots to ocean depths or to other planets Modern technology is being used in computer games musical instruments automobiles house appliances and in numerous other applications The typical key components of systems used in such applications are sensors micro
27. of a section of code e They serve as markers for instructions that change the order in which the program is carried out The command Goto tells the program to go back to the beginning of the program and do some more work The command End tells the computer that there are no further instructions Access PIC16C7x A D loop ADCONDOD 45 Start Conversion Pause 1 Wait Ims for conversion Serout SO N2400 ADRES 10 Send variable to serial out Goto loop End Figure 4 2 Example of BASIC programming To program the BASIC Stamp II you plug it into the Board of Education connect it to a Windows or Mac computer and run the editor software to create and download your program via a serial cable The BASIC Stamp Manual Version 2 0 describes the BASIC command set and can be found on your CD in the Board of Education folder Additional information and software is available at http www stampsinclass com 4 3 Interfacing to the LCD For this course a serial display is used It is a 2 line by 8 character Liquid Crystal Display LCD module This unit accepts data transmitted by the Stamp s Serout instruction The serial LCD allows you to display text numbers and symbols using simple Serout instructions The display is connected through the RS233 3 pin connector These pins are connected as illustrated in Figure 4 3 For further information refer to the Serial LCD User Manual BPI 216 Serial LCD
28. ojects 5 14 5 3 Parts ELEC 199 Project Course Parts Parts assembled as a kit approximate cost 300 Basic Stamp II Education Kit LCD display 2 X 16 Characters Digital Multi meter 50k Potentiometer 100k Potentiometer Comparator Red LED 1k Resistor 5 7k Resistor Long nose pliers Wire stripper Tool Box DB 9M to DB 25F adapter Beam scale with force sensor FSR 400 by Interlink Electronics Additional subsystem is supplied by the ECE Department e Hand grip with mounted 50k potentiometer Table 5 3 Component Specifications Hand grip Comparator IC LM383N LED 5mm Red Battery 9V LCD Module www stampsinclass com BASIC Stamp II www stampsinclas com Potentiometers 50kQ amp 100kQ Resistors Variety Capacitors Variety Force Sensor FSR Inter Electronics Multimeter Range M830 BUZ Hinge 1 wide Wooden Plates 20x3 2x1 2 ELEC 199 Useful References and Internet Resources 6 1 6 Useful References and Internet Recourses Books 1 Scott Edwards Programming and Customizing the Basic Stamp Computer McGraw Hill 1998 USD34 95 2 Basic Stamp Manual Version 1 9 by Parallax www parallaxinc com Internet Sources http www howstuffworks com How Car Engines Work How Web Pages Work How Cell Phones Work How CDs Work How Jet Engines Work How Telephones Work How Web Servers Work How Diesel Engines Work How Television Works
29. ojects 5 3 BU ji l N HERTENS ie OL yy I Mass of the latform 90 0 Hinge Plunger Platform P 8 WO S T Spacer Spacer movable 450 Figure 5 3 Sample dimensions of a beam scale The suggested dimensions of the beam scale in millimeters are shown in Figure 5 3 Figure 5 4 The actual beam scale The photograph of an actual design is shown in Figure 5 4 5 1 2 Force Measurement Principle lw Sensor lb Figure 5 5 A model for beam scale ELEC 199 Projects 5 4 The beam scale constructed earlier can be idealized as shown in Figure 5 5 By placing a known mass m and by varying its position on the platform we can vary the force applied to the FSR Measure the resulting resistance using an Ohmmeter The force applied to the sensor can be calculated using the principle of balance of moments There are three forces at the beam The applied weight and the weight of the beam itself will push down the platform The sensor pushes up the beam to keep the balance As all moments must be balanced the following equation applies F 1 m g1l m g1 0 5 2 where F force on sensor unknown 1 distance to center of FSR measured known 1 distance to center of weight measured known l distance to center of beam mass measured known m mass of platform measured known m mass of weight known or unknown g gravity constant known g 9 81 m s All distances are measured from the hinge 5 1 3 Ex
30. periments a FSR characteristics Apply a known weight mass at a certain location on the platform Using eq 5 2 calculate the force applied on the sensor Any object with simple geometry can serve this purpose since the center of its mass is easily determined A cylindrical pile of one dollar coins may be used one loonie is about 7g Coins can be packed into a plastic film container 6g Make sure the coins are kept aligned Considering the sensor range it is recommended that you use 20 loonies as a known reference weight m 146 g they can be put to good use after the course is over Place a reference mass at several locations 1 on the platform and use your multi meter to read the FSR resistances R corresponding to a given distance Measurements must be done several times for the same applied force To avoid hysteresis errors remove the weight before each measurement and place it again Convert your data to the applied force F F Construct a conversion table and indicate any errors standard deviation and or maximum errors Plot the relation between the force F and the average resistance R Comment on your results and observations A sample results table using a Microsoft Excel spreadsheet is presented in Table 5 1 Calibration Table and plotted in Figure 5 6 The vertical bars in Figure 5 6 indicate maximum absolute errors encountered based on n repeated measurements ELEC 199 Projects 5 5 Table 5 1 Calibration Tabl
31. processors and actuators A sensor senses a physical variable such as force pressure temperature or light intensity and converts it into an electrical quantity such as current or voltage The latter is called a signal The signal is then processed by electronic circuits and often converted into digital form to be manipulated by a microprocessor or computer After the processing is done a suitable electric signal is used to control actuators such as motors power amplifiers lights car breaks and others In this course you the student will walk along a similar path You will start by getting familiar with basic mechanical electrical and computer concepts as well as electrical components and subsystems You will explore simple sensors that convert non electrical quantity such as position or force to electrical quantity such as resistance or voltage You will build and test a simple force to frequency ELEC 199 Introduction 1 2 converter and a force to voltage converter to be interfaced with a micro processor By suitable programming of such a microprocessor diverse tasks can be accomplished You will see your design working and find out numerous new applications for them We hope that this course will be a fun learning experience for you 1 2 Calendar Description 2001 02 Calendar ELEC 199 Units 1 S 0 1 5 1 Laboratory in Engineering Fundamentals The objective of this course is to introduce students to concepts in electrical compute
32. r and mechanical engineering through a practical project to be undertaken by teams of students The project will involve mechanical construction sensing of mechanical quantity by electrical means as well as interfacing to and programming of a simple microcontroller Students will be required to acquire suitable components demonstrate their designs and write a report documenting their efforts Grading COM N or F 1 3 Course Implementation One faculty member will coordinate the course with the help of several teaching assistants A laboratory space with several PC stations to test and to program the microprocessor will be provided and a suitable technical staff will be assigned to look after this space Before the second week of classes students are to form groups of threes and acquire the required components and tools Before starting the project on the fourth week students must complete all the required exercises and pass a multiple choice test A test failed is to be repeated within one week Before the tenth week each group must demonstrate the completed project The final report documenting designs and findings must be submitted before the end of classes The students should select the specific topic and research should be done using the Internet and other resources The report should contain independent research on a suitable sensor converter or transducer to sense a non electrical quantity using electrical means It should also include
33. s characters graphs etc Examples of LCD s are the screen on your notebook computer calculator digital watch etc Software Program A software program is a list of precise instructions for the microcontroller to follow A typical program looks at the inputs processes them and uses the information to decide what the states of the outputs should be ELEC 199 Microcontroller Fundamentals 4 2 Programming Language A programming language is a set of words and rules for combining those words like the vocabulary and grammar of a human language A programming language is either understood by a microcontroller or readily converted to a form that the microcontroller understands High level programming languages are available to program such a device In this course you will use Stamp Microcontroller which uses BASIC programming language to implement diverse operations Memory A software program is stored in memory The microcontroller reads from or writes into this memory Some computers store the software program on an Electrically Erased Programmable Read Only Memory or EEPROM This type of memory can be programmed many times The microcontroller fetches one instruction at a time from memory and performs the appropriate operation on the input output pins or internal structures within the microcontroller 4 2 STAMP The BASIC Stamp II is one very popular microcontroller In order for our microcontroller to function we need to assembl
34. sistor R can be measured by ammeter A Voltmeter Connecting wires Battery E Figure 3 4 Battery connected to a resistor ELEC 199 Electronic Fundamentals 3 4 The value of current I can be found using a simple relation called Ohm s Law that is I E R 3 1 For instance if you connect a car cigarette lighter which has R 0 5 ohm resistance to the car battery rated E 12 volts the resulting current I will be I 12 0 5 24 A The current needed for a starter motor can reach several hundreds of Amps A current I that flows through a resistor R will develop a voltage drop Vp across it with its direction opposing the flow of current as shown in Figure 3 4 The opposing direction occurs when sign is facing the current flow arrowhead This voltage can be found using Ohm s Law Va l R 3 2 In electronic circuits we usually use resistors in the range of 10 ohm 1 kohm 1k and current is usually expressed in milliamps 1 mA 10 A Because current through a resistor is proportional to the voltage applied we call such a resistor a linear resistor There are also nonlinear resistors elements where dependence between current and voltage applied is a nonlinear function An example of such a nonlinear element is a diode that will be described later Series Parallel Connections Resistors can be connected by conducting wires or paths in series or in parallel as shown in Figure 3 5 a and b In Figure 3 5 we use the
35. suggestions for interesting future projects The guidelines on report format can be found at http www coop engr uvic ca engrweb WTR HTML ch33 Summary of the tasks is shown in the Table below TASKS When weeks in the term Form a group of 3 students 2 Pass the test 4 Demonstrate the Designs 10 Submit the Final Report End of classes The course will be graded based on the test demonstration and the final report as COM Completed N not Completed or F Failed ELEC 199 Mechanical Fundamentals 2 1 2 Mechanical Fundamentals 2 1 Basic Ideas Distance The distance between two points is measured in meters m or kilometers km Motion An object can move with a velocity speed measured in meters per second m s A car s speed is usually measured in kilometers per hour km h Acceleration Acceleration is the measure of the increase in velocity in time and is measured in meters per second over a period of one second or in m s A car that can accelerate to 60km h in 6 seconds has an average acceleration of 10 km s or 6000m s Mass Mass is an inherent property of all material objects It is measured in kilograms kg or grams g Force Force is a basic mechanical quantity encountered in everyday life If you want to move a car you have to push it with a certain force The same applies to an object of a certain mass on the smooth ice surface where ideally the object can mov
36. tric shape on the platform and find the position that yields the same resistance as that obtained in your calibration Table 5 1 Measure this position and calculate the unknown mass of the object using eq 5 2 Method 2 Using linear interpolation Put an object on the platform at a known distance and read the corresponding FSR resistance R Apply linear interpolation between two adjacent reference points from your calibration Table 5 1 to find the corresponding force F applied to the sensor Based on this result and knowing the distance of your weight you can calculate the mass of the object ELEC 199 Projects 5 7 Method 3 Global Interpolation Using equation 5 1 and your calibration Table 5 1 you can find suitable coefficients a and b Use this information to link any measured R at a known distance with applied force F and therefore with the mass of an object Try all three methods on 2 3 objects Discuss the results and comment on your findings 5 2 Project 2 Hand Gripper Exerciser 5 2 1 Principle of Operation Design task Using a commercially available handgrip spring exerciser design a suitable exercise monitoring system The microprocessor should display a number of hand contractions that exceed a predetermined force level Force Angle to Gripper Voltage Comparator Convertor Micro Processor Threshold V2 Figure 5 8 Block diagram of hand gripper exerciser The block diagram of the system is shown in Fi
37. tronic circuits for the hobbyist or student Site includes 93 circuit diagrams links to related sites commercial kits and projects newsgroups and educational areas Most circuits shown here can be built with common components available from Radio Shack or salvaged from scrap electronic equipment Almost all of the circuits have been built and tested and are believed to perform as described However possible mistakes may be found New items are shown in red color
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