(Most Awesome Backpack - Ever)
Contents
1. 56 Appendices Appendix A BC547 Transistor Data Sheet 6 6 6 6 6 58 Appendix B BC557 Transistor Data Sheet 6 6 6 59 Appendix C CSD16321Q5 Transistor Data Sheet 60 Appendix D IRF510 NMOSFET Transistor Data Sheet 6 61 Appendix E SCR Rectifier Data Sheet 62 Appendix F Zener Diode Data Sheet 6 63 Requirements Specification Solar Powered Backpack Refrigeration Unit Adrian Villalobos Eric Locke Natalie Nill Simon Reinhardt Overview Vaccines have been one of the most beneficial healthcare discoveries of the past couple centuries Unfortunately many people are unable to receive vaccines because among other reasons health services are unable to reach them while keeping the vaccines cool enough According to the PATH organization transporting vaccines in Africa can be extremely challenging because regulating the temperatures of vaccines while transporting them to rural areas is difficult and especially challenging in areas without constant power sources In 2002 over 84 000 people died from Hepatitis B a vaccine that requires cooling alone Some of these deaths are due to the inability of health organizations to transport vaccines to every place they are needed M2. 23 be used Only capacitors with new values need to be ordered The modified circuits are shown next C 1 TPS40192 2 2uF VOUT GND Figure 14 New circuit design of DC to DC converter for the microprocessor V 5 8V V 6 2V V 3 30V I 0 05A VIN c9 Ul 540192 VOUT GND Figure 15 New circuit design of DC to DC converter for temperature sensor V 5 8V V 6 2V V 3 00V I 0 01A Before the last modifications were made we started working with the printed circuit board But a problem we have been facing is that the footprints for the integrated circuits have not been found These ICs manufactured by Texas Instruments are so small the circuit board needs to be precisely made in order to have a successful soldering We have been trying to contact this company in order to get the footprints of the TPS40192 buck converter and CSD16321Q5 NFET transistor Since these footprints are unavailable we are currently drawing them using software given the size specifications We have considered that these printed circuit boards should be professionally made due to the high precision it 1s required I ses TOP AND BOT TOM 0 20 REF amp D 0 08 sn em m 27 PLANE 000 m YSED THERMAL PAD __ A DPTIONAL EXPOSED METALLIZED FEATURE Example Board Layout Example Stencil Design Note E 8
3. Set port EU high foricounter 1 counter 2 100000 counter delay FORTEbhbitz REU OQ Set port EU low foricounter 1 counter 2 100000 counter delay i return close function This line is never reached Figure 38 The test code used by the microprocessor 6 P This code turns an LED on and off by sending a voltage high and low continuously while delaying to allow the user to see the light turn on and off This code confirms the ability to control digital input and output to the microcontroller and to access and utilize the commands that are specific to the PIC24FJ256GB 106 microcontroller M UR T A iy ay gt 2 re id i ne pe eee eee BENNNNNHMNEEEZA MEVYL YEY X C X X x cd 14 Bir m m 4 n mu 8 8 s 1 NEBNWENMNNNNNEMNENENWMMKLEWLLILXLL WENMNNNENNENNNNENENMNMENNMENMHMMMMWMHMWMHY HRUSNNNN N x x x N x x x x x it li x s x il k TT TT k v EREKLKEUUUURUNMU vk iy kn k MOM x x MON k kl MN WR PREPRESS RRP RRP RR uzi xi x kin k x x x CE 2 1329 LL e 2 2 A HERE te bin n n Ex On a s o 9 LU 0 01 121 121 2121 1221112121011 111111 nunuuuuuuunuuuunuumu m m un nu s BM LESS S27 1101117212721 uw x x i a 2 26 27 ee s Figure 39 Circuit for the microprocessor and user interface f 4 Jh User Interface All of the components
4. 0 5 8x0 5 J OL KL H 1 138 we 4x0 26 4x z j 20 2 WP 0 5 um Se yt 1 Ts 15 3 75 7 5 O PN a u funy NC Am N 0x0 8 10x0 2 23 u 240 72 solder coverage on center pad Non Solder Mask Exposed Pad Geometry Defined Pad SRE H 7 z 4206987 2 F 06 10 Figure 16 TPS40192 IC size specifications and shape s Jl Figure 17 Several footprints have been tested in order to see which one is the best match to the integrated circuit Power Control The power control has been designed built in a breadboard and tested The circuit has an N channel power MOSFET transistor IRF510 that works as a switch The gate pin of the transistor will be connected to one of the outputs of the microprocessor and this will send a digital signal 0 or 5V The source pin of the transistor is connected to the circuit ground The negative side of the load fan cooler and TEC is connected to the drain of the transistor and the positive side 1s connected to the positive terminal of the external power supply 12V lead acid battery Now whether the transistor is on or off will depend on whether the gate is at OV or 5V When the gate is at V the transistor stays off so no current can flow keeping the cooling system off But when the gate is at 5V the transistor turns on and it starts acting as a very low r
5. Lows MISC 776 o Termal Paste Amazon com MISC 695 S erevvs VVashers 7 Lows MISC 255 7 2 Miscellaneous includes DC poem ECS ES Money Budget aM uNMTEN 1 000 704 59 1 06 295 41 The budget is almost the same from last semester only two minor changes have been made First instead of buying DC to DC converters we are now making them Because of this we put the cost of the converters into our miscellaneous fund And secondly we bought several new pieces of insulation because we discovered that the ones we had bought earlier were the wrong type Miscellaneous funds have been used to purchase electrical components thermal paste and hardware components To date these amount to approximately 160 Sufficient miscellaneous funds are still available to use for any unforeseen changes or emergencies that may occur 5 Schedule Analysis 16 8w 16 8w mw t ian 2017 Fab 2011 Mar 2011 Apr 2011 May 2017 Duration 4 11 2011 2 21 2011 148 2011 148 2011 Documentation A2 0 E ET E E 8 0 Project Finalization Figure 47 Spring schedule Figure 39 above is the schedule that was set up last semester for this semester On the mechanical side we are slightly behind schedule on the cooling chamber and full frame assembly Currently the insulation section 1s being built and attached to the inner chamber We
6. The circuit is a half way rectifier so it only charges the battery on every half cycle The plug pack does not like this as it leaves residual flux in the core of the transformer and causes it to get warm But that is the only disadvantage of the circuit f oj The SCR turns on during each half cycle and current flows into the battery A voltage is developed across three 3 9 Y resistors in parallel and this voltage is fed into the 47uF capacitor It charges and turns on the BC547 transistor located in the Maximum Current block The transistor robs the SCR of gate voltage and the SCR turns off The energy in the 47uF capacitor feeds into the transistor but after a short time it cannot keep the transistor turned on The transistor turns off and the SCR switches on and delivers another pulse of current to the battery As the battery charges its voltage increases and this is monitored by the Voltage Monitor block Figure 22 Functional blocks of the battery charger circuit 1 The circuit is very complex and one way to look at the operation is to consider the top rail as a fixed rail and as the battery voltage increases the rail connected to the negative terminal of the battery is pushed down This lets you see how the Turn On transistor is activated and how the Voltage Monitor block components create voltage drops across each of them The Voltage Monitor block components consist of a transistor and zener diode as well as an 8 2 K
7. and the board was etched z2 P zl 2A 4 8 i y ER I m ar Figure 23 Footprint of the battery charger circuit in Ultiboard ad Figure 24 3D view of the battery charger circuit L T er u Figure 25 Footprint used for the zener diode The components were soldered into the board as shown in Figure 26 All the components were mounted on one side of the board except for the zener diode which was surface mounted on the other side LP 2 nn mn n me Figure 26 The soldered circuit of the battery charger l Once the circuit was complete it was hooked to the power plug and to the 12V battery and the circuit was tested The LED turned on and the current going into the battery was measured The battery was being charged with a current of 20mA when it was supposed to be of about 200mA This current was very small that the voltage of the battery was kept constant with a value of 12 45V during the testing period of 15 minutes as shown in Figure 27 The circuit was carefully analyzed until the problem was found The output of the power plug was providing 12V and 500 mA but the current was DC instead of AC It must be an AC supply as we do not want any electrolytics substance that disassociates into ions and can transmit electric current through positively and negatively charged 10ns to be present o
8. Cold Chain PATH A Catalyst for Global Health May 2010 Web 13 Sept 2010 lt http www path org projects cold chain php gt Statistics about Hepatitis B WrongDiagnosis com Wrong Diagnosis Aug 2010 Web 20 Sept 2010 http www wrongdiagnosis com h hepatitis b stats htm 2 1 External Power The pack can be cooled by using external power from any outlet that has an output standard to the US or African power grid 2 Cooling Packs The backpack can be cooled by placing cold packs such as those used to keep non electric vaccine shipping boxes cool inside the chamber 3 Refrigerator The backpack can be cooled by placing the chamber inside a larger refrigerator or freezer until the target temperature is reached 4 Solar Power The backpack can be cooled beforehand using solar power This method may require time to charge the packs batteries and cool the chamber Also the batteries must be charged before the vaccines are transported any distance This can be accomplished by either using an external power source and or using solar power to charge the batteries For a faster charge time the batteries can be charged while the cooling system is off to send all power from the solar panels or external source to the batteries The user will be able to select the allowable temperature range via the user interface First select the mode for temperature selection then type in the lowest allowable temperature and then the h
9. EEE EEE RR RU RR RU GR GR RUN EEL 20 0 FCCC CEE EEE EEE EEE EEE EEE EEE EEE EEE EEE EEE EEE ELE 15 0 10 0 u Series1 2 0 RE ISS ER H See ee eee ee ee ee TEES ER EE ER B Series2 Temperature E 0 0 IMEEEEEEEEEEEEEEEEEEEEEE 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Time min Figure 7 Graph of temperature vs time for cooling system tests U Because the voltage is constant it can be concluded that the resistance of the TEC decreases with a decrease in temperature When the cooling system is initially turned on the current spikes but quickly decreases and eventually levels out around 3 A Both the fan and the pump took a current of 0 11 A each which means that the TEC took the rest of the current which was 2 78 A which is a value very close to the expected value of 2 82 A The design assumed the cooling system to reach the operating temperature range of 22 to 82 instantaneously This test shows that this range is not reached until approximately five minutes after the cooling system is turned on This
10. and because our load was purely resistive and now power was being drawn towards the devices as will be the case in the backpack This test does prove that the solar panel can output the necessary current that corresponds to the voltage being created across it in these tests Also it should be noted that the more voltage that is created across the solar panel the faster the power will change as a result in changes in the voltage value This can be seen by the non linear data trends in figure 31 4 Jh Microcontroller The microcontroller was originally planned to be coded all through the spring semester Due to the absence of the correct socket however it has not been possible to connect the microprocessor to the computer This has restricted us from testing the microprocessor and building peripheral circuitry that connects the user interface and analog inputs from the temperature sensor and batteries The socket however has been received and tested for the ability to put code on it The code that was placed on the microcontroller can be seen in Figure 32 below Due to this fact the microcontroller programming is behind schedule Code has been created to configure the A D converter inside the chip to execute the needed sequence of sampling This function is at the heart of our software for this project since the microprocessorG primary duty is to control the backpack based on the current temperature of the chamber The user interface cir
11. could potentially cause an imbalance to the power management However both fans and the pump of the liquid cooler use less current than expected see Table 3 One way to conserve energy would be to not turn on the cold side fan until the operating temperature range is reached which would save an additional 0 24 A for that time Table 3 Expected vs actual current draw for components of cooling system Expected Current A Actual Current A Cold Side Fan On average the cooling system used 37 W of power If the cold side fan was used the power would increase to a value of 40 W Cooling Chamber There are three main parts that make up the cooling chamber 1 the inner chamber 2 insulation and 3 the outer chamber The plan is to build outwards This avoids several problems and ensures it all fits together well Figure 8 below shows how the three parts will fit together Inner Chamber Total depth 47cm Outer Chamber Insulation gt Total width 2 57cm Figure 8 Top view of cooling chamber The inner chamber has been completed the lid is not attached since it will be attached to the outer chamber lid and can be seen in Figure 10 The wall material used is the tempered hardboard that was chosen last semester and the screws are countersink screws The inner chamber is very sturdy No specific test was performed because it 1s not very important for the inner chamber to be sturdy since it will be sur
12. currently being tested on a breadboard The constructed circuit can be seen in Figure 35 on the next page The power to the temperature sensor circuit will come from the DC to DC Converter with a value of 3 V The sensor circuit was made using the Multisim schematic below Figure 42 Temperature sensor voltage division and amplification circuit The temperature sensor is connected in a voltage division circuit with the resistor marked RI in the circuit above The high RI resistance was chosen to limit the current to limit the current through the temperature sensor to less than 100 uA to keep internal heating from affecting the sensor The op amps in this circuit comprise the amplification necessary to create an output from the sensor circuit that moves across the full range of the microcontroller amp A D converter system The first op amp is a follower to prevent the amplification circuit from affecting the voltage division circuit The second op amp is a summer that will subtract the minimum voltage value coming from the divider circuit This is done to make the smallest voltage going into the microprocessor zero volts The last op amp on the right amplifies the relatively small voltage change to span from OV to 3 3V This 1s the full range of voltage on the A D system This circuit has been significantly simplified from last semester due to the decision to make the microprocessor user interface temperature sensor and battery life circuits all
13. for the user interface have been obtained including the LCD screen the keypad the keypad encoder and the LED indicators The Screen and the Keypad and encoder have been integrated into the same board as the microcontroller This can be seen in figure 34 These sample circuit for the keypad and encoder can be seen below in Figure 35 EDE1144 130 Onm 4 x 4 Keypad XMIT Bep Haud Valid 5y OSCI 5V OSC GND H R1 Re R3 DO LSB D D2 D3 Parallel Outputs Figure 40 Keypad encoder chip and keypad Lines DO D3 go to I O pins of the microcontroller The four lines DO 1 D3 are the only required input to the microcontroller to identify which button has been pressed The LED indicators will be connected to the transistor and resistor circuit shown in Figure 32 The small resistor R2 is included to limit the current through the LED The large resistor in between the microcontroller and the transistor restricts current to the transistor to keep it from affecting the output of the transistor voltage This has not been prioritized in construction due to the simplicity of the design The circuits will be constructed once the more complicated parts of the user interface are operational Figure 41 LED indicator circuit 5V source will be provided by the microcontroller while VCC will be from the battery y Temperature Sensor The temperature sensor circuit has been constructed and is
14. operate at 6V relative to the batteryG ground This decision is discussed in more detail in the DC to DC Converter section of this report The temperature sensor acted as expected when it was connected to the circuit The voltage drop across the sensor was the anticipated amount and the voltage coming out of the sensor dropped when the environmental temperature increased s Jh A roadblock that was encountered when testing the circuit was the fact that the op amps were not providing values between about 3V and 3V Upon further investigation it was found that this separation between data points was due to the variable power supplies inability to change their voltage output less than 0 1 V Since the amplification is designed for voltage changes around 0 01 V the data points are very far apart To confirm that each op amp stage 1s working correctly the inputs and outputs were recorded and entered into excel for differing points The results from this test can be seen in Tables 7 through 9 below v nm cvs nL o Pe m 2 aaa ununu WARE maWERE VENER o uu us v m 2 Ges i Q0 73 3323272232222 22222222222222 inunununn nini m Figure 43 Constructed Temperature Sensor Circuit Table 7 Temperature sensor circuit test 1 Temperature Sensor Circuit Test 1 Op amp 1 Voltage Follower input V output V Difference V In this test the voltage follower was tested across the input range th
15. placed properly within the refrigerator or freezer in which proper temperatures are maintained 4 temperature logs are reviewed for completeness and any deviations from recommended temperature ranges 5 any out of range temperatures prompt immediate action to fix the problem with results of these actions documented 6 any vaccines exposed to out of range temperatures are marked do not use and isolated physically 7 when a problem is discovered the exposed vaccine is maintained at proper temperatures while state or local health departments or the vaccine manufacturers are contacted for guidance and 8 written emergency retrieval and storage procedures are in place in case of equipment failures or power outages Around the clock monitoring systems might be considered to alert staff to after hours emergencies particularly if large vaccine inventories are maintained Additional information on vaccine storage and handling is available from the Immunization Action Coalition at http www immunize org izpractices index htm Links to state and local health departments are available at http www cdc gov other htm Especially detailed guidelines from the Commonwealth of Australia on vaccine storage and handling vaccine storage units temperature monitoring and stability of vaccines at different temperatures 6 are available at http Ammunise health gov au cool pdf References 1 CDC General recommendations on immunization recommendations of
16. plan on completing the unit and running tests on it the week we get back from spring break Once we finish this testing we can complete the full frame assembly On the electrical side we are behind schedule on the battery battery charger DC to DC converter power control circuit A s and programming the microcontroller The battery battery charger and DC to DC converter are both behind schedule because they require a surface mount soldering technique for assembly and Adrian is still in the process of learning how to do it The programming of the microcontroller is behind schedule because the correct socket was not received until mid February The plan for catching up on the programming can be found in the microcontroller section of this report We plan on having almost our individual systems running and tested by the beginning of April This will give us a month to work on any unforeseen problems that arise and complete the system integration Appendix A BC547 Transistor Data Sheet Appendix B BC557 Transistor Data Sheet Appendix C CSD16321Q5 Transistor Data Sheet Appendix D IRF510 NMOSFET Transistor Data Sheet Appendix E SCR Rectifier Data Sheet Appendix F Zener Diode Data Sheet
17. results in loss of the adjuvant effect and vaccine potency 4 Physical changes are not always apparent after exposure to freezing temperatures and visible signs of freezing are not necessary to result in a decrease in vaccine potency Although the potency of the majority of vaccines can be affected adversely by storage temperatures that are too warm these effects are usually more gradual predictable and smaller in magnitude than losses from temperatures that are too cold In contrast varicella vaccine and LAIV are required to be stored in continuously frozen states and lose potency when stored above the recommended temperature range 5 Vaccine Storage Requirements Vaccine storage units must be selected carefully and used properly A combination refrigerator freezer unit sold for home use is acceptable for vaccine storage if the refrigerator and freezer compartments each have a separate door However vaccines should not be stored near the cold air outlet from the freezer to the refrigerator Many combination units cool the refrigerator compartment by using air from the freezer compartment In these units the freezer thermostat controls freezer temperature while the refrigerator thermostat controls the volume of freezer temperature air entering the refrigerator This can result in different temperature zones within the refrigerator Refrigerators without freezers and stand alone freezers usually perform better at maintaining the p
18. was confirmed that both the radiator and the cold sink were needed several test runs at two ambient temperatures were performed to ensure functioning of the cooling system Because the cold sink was surrounded by warm air the cold side fan was not turned on in these test runs Conduction from the ambient air to the cold sink would have prohibited accurate results because it would have prevented the cold sink from cooling below freezing if warm air was blown across its fins The temperature of the cold sink was measured with an infrared temperature gauge All components were supplied with 12 V DC and both the current and temperature were recorded with respect to time Table 2 on the following page shows the cold sink temperature at ambient temperatures of 22 52 and 29 42 and the associated current draw The temperature of the reservoir of the liquid cooler never got higher than 52 above the ambient temperature Figure 7 gives a better understanding of the time frame at which the cooling took place f s Table 2 Data from cooling system tests Test 22 52 Series 1 Test 29 42 Series 2 ni A 2 ME 2 193 315 243 319 41 s 310 132 34 44 30 72 831 6 06 30 15 308 0751710 9 30 7060 30 8 041 30 26 30 9 53 304 48 30 10 68 304 62 304 14 796 30 91 30 30 0 25 0 BEING ENG B GG UU DR GU RR EU UR RR D E EU RR RU RR
19. A performance test will be conducted The backpack will be taken on a mile hike then will immediately be put into a ventilation chamber for a 48 hour period It will be tested at temperatures between 22 C and 30 C x 72 F and 86 F The solar panels will be exposed to two cycles of simulated sunlight for 12 hours then darkness for 12 hours The maximum and minimum temperatures will be recorded over that period This test will be executed three times Temperature gauge will be tested to insure accurate within 1 C temperature readings inside the chamber Backpack will be weighed to ensure it does not exceed the maximum weight Attachments The following attachments come from the site Centers for Disease Control and Prevention d Web 13 Sept 2010 Guidelines for Maintaining and Managing the Vaccine Cold Chain In February 2002 the Advisory Committee on Immunization Practices ACIP and American Academy of Family Physicians AAFP released their revised General Recommendations on Immunization 7 which included recommendations on the storage and handling of immunobiologics Because of increased concern over the potential for errors with the vaccine cold chain 1 e maintaining proper vaccine temperatures during storage and handling to preserve potency this notice advises vaccine providers of the importance of proper cold chain management practices This report describes proper storage units and storage temperatures outlines appropriate te
20. Harding University MAB E Most Awesome Backpack Ever Midterm Status Report March 8 201 1 Eric Locke Natalie Nill Simon Reinhardt Adrian Villalobos Table of Contents Requirements Specification 6 2 Project Overview and latun A baa el 9 Sub Systems Cooling System l0 Cooling Chamber 8 6 6 8 6 6 8 6 a a 6 6 a 19 DC to DC Converter 6 6 6 6 6 6 6 6 6 6 6 8 6 23 Power Control 6 6 8 6 6 8 8 6 8 6 6 6 6 6 6 6 6 6 6 6 6 27 Battery Charger 6 6 8 6 eae 6 6 8 6 dd 6666 30 Solar Panels 6 6 6 6 6 38 Microcontroller 6 6 45 User Interface 6 47 Temperature Sensor 6 6 6 6 6 6 8 6 48 Batterise 52 Full Frame Assembly 6 6 6 8 6 6 6 6 6 8 6 6 6 6 6 6 6 6 6 6 54 System Integration 6 6 6 8 6 6 6 6 6 8 6 6 6 6 6 6 6 6 6 54 Budget Analysis 6 8 6 6 6 8 8 6 8 8 d dd dd dddd dd dldd 55 Schedule
21. V A W 0 7 7072 096 865 0 0854 0 739 1272 1 24 Tet3 l0 J D Light Intensity Voltage mW nr V A W Tet4 78 0 1712 mW m V A W 067 696 0 0688 0479 Figure 30 compares the results of the tests made It displays the voltage generated by the solar panels at different angle positions and at different percent output from the light source Voltage Across Solar Panels vs Percent Output from Source at Differing Angle Positions 1 Voltage V MN N 40 30 60 70 80 30 100 110 Percent Output from a 140V source Figure 36 Comparison of the results of the tests f 78 90 ur 8 10 Power W 2 5 1 5 0 5 Power W at different angles Power W at 78 degrees gt Power W at 90 degrees Z 2 Power W at 98 I degrees Power W at 110 degrees 0 100 110 m from d N 40 5 Figure 37 Comparison of power and percent output voltage In these four test runs the current on each data point reflects the fact that the circuit load was 100Y The current was approximately equal to the voltage amount divided by 100 within plus or minus 10 mA This affirms that the power calculated from the voltage and current are accurate in this case The power that was produced is significantly lower than the solar panelG maximum power rating of 40 W This 1s due to the size of our load
22. Y resistor a KY potentiometer or trim pot a 1 5 KY resistor a 150 Y resistor and a signal diode The signal diode is actually part of the flasher circuit As the voltage across the battery increases to 13 75 volts each resistor in the voltage detecting block will have a voltage drop across it that corresponds to the resistance of the resistor The diode has a constant 0 7V across it The voltage on the wiper of the pot will be about 3 25v and the voltage across the zener will be 10V This leaves 0 6V between the base and emitter of the Voltage Monitor transistor This voltage is sufficient to turn the transistor ON When the Voltage Monitor transistor turns ON it robs the Turn On transistor of base emitter voltage and the circuit turns off The SCR has only two states ON and OFF During the half cycle when it is turned on the battery gets a high pulse of current and the current is only limited by the capability of the plug pack There is not enough energy to allow very high pulses of current to be delivered and this is fortunate as the SCR is only a 0 8 A device but will endure surges of 10A for half a cycle Whenever the SCR is triggered into conduction during the half cycle of its operation it remains in conduction until the voltage delivered by the plug pack falls to zero This is when the SCR turns off When the plug pack delivers a negative voltage to the top rail and a positive voltage to the lowest rail the SCR is not triggered i
23. any of these organizations are working to raise awareness about this issue and find ways to reach more people If more people could be reached thousands of lives could be saved There are multiple ways of using alternate power to refrigerate vaccines currently being used The most predominant include nonelectric uncontrolled cold packs kerosene powered refrigeration and solar power The cold packs have limited use because they have a maximum cooling time of 48 hours The kerosene refrigeration is impractical because it requires continuous refueling and is potentially dangerous Therefore our team has decided to use solar power because it is a portable reliable and an efficient way to solve this problem Problem Statement There is a need for a better method for transferring vaccines into rural areas of developing nations where power is not easily accessible for refrigeration There is no developed method that involves continuous refrigeration from a portable consistent and environmentally friendly power source By having a refrigeration system that can be powered during transportation the ability to distribute vaccines will be greatly increased and the chances of ruining vaccines will be diminished Operational Description Before Transportation Before using the refrigeration backpack to transport vaccines any distance the target temperature must be met inside the refrigeration chamber This can be achieved by one of four ways t PATH
24. at 1s possible in the backpack The difference between the input and output of this stage is supposed to be OV It can be seen in the table that the difference between the input and output never goes higher than 0 002V across the entire range This confirms that the op amp stage is working within error Table 8 Temperature sensor circuit test 2 Temperature Sensor Circuit Test 2 Op amp 2 Voltage summer l _ Expected Actual input 1 V input 2 V Output V Output V 3 0181 3 022 0 002 0 008 3117 3 022 0 097 0097 3217 3 022 0 1977 0 0 006 Difference Between Sum and Output 0 3 318 0 298 3 417 3 516 The second test was conducted with the Voltage summer of the circuit The output is supposed to be the negated sum of the input voltages The theoretical output of this equation can be seen in the expected output column of the table The difference between the expected and actual outputs was calculated grew fairly linearly as the difference between input 1 and input 2 changed The difference between these two inputs 1s not expected to grow above 0 5 volts Table 9 Temperature sensor circuit test 3 Temperature Sensor Circuit Test 3 Opampl Amplifier input V Gain V V 0 11 62 91 0 2176 13 014 59 81 The third test involved the amplifier stage of the circuit This stage requires very small intervals in input voltage to obtain data from the output that is within the range of am
25. at a faster rate in the first 3 hours of testing while in the next hours the voltage increase rate was smaller but was kept constant 27 hours is a long period of time to charge the battery 1 5V but considering that it is I2AH battery being charged with a 200mA current small current that is safe for the battery if kept unattended makes it a reasonable time The current that charged the battery was constantly varying When the circuit started to charge the battery a current of 194mA was being supplied to the battery then in the next hour it drop to about 182mA and in the rest of the test of test the current was varying constantly between 173mA and 177mA Figure 28 Charging the battery at 5 5hrs after the test was initiated The voltage in the battery has increased 0 95V The LED is on and the current flowing to battery is 173 mA Battery Voltage V 10 8 0 5 10 15 20 25 Time hours Figure 29 Voltage of the battery as it is being charged over a period of 27 hours 30 Solar Panels The solar panels have been ordered and received A series of experiments were made in order to show that the solar panels are functioning properly The outputs of the solar panels were soldered with long wires and connected to a 96Y load For the circuit it was considered that we would have a voltage output of 18V which is 0 7V above the maximum expected voltage This was done so the power dissipated through the resistors would be less than the max
26. ccines can block the fanG airflow and prevent an evenly distributed temperature within the inner chamber a mesh like material will be installed to separate the cooling system from the vaccines J1 Figure 2 Inplementation of the cooling system into the inner chamber In order to verify that the cold sink and fan are indeed needed multiple tests were performed on the TEC with different parts missing in each test First the TEC by itself was powered and the temperature of the cold side was measured No data was collected during this experiment because the temperature on the cold side spiked up to 322 within the first few seconds and kept climbing This verified that the TEC could not be used alone This result was expected the TEC can only generate a temperature differential if the heat is removed from its hot side Next the TEC was attached to the water block of the liquid cooler and only the fan but not the pump was powered Figure 3 below shows the results of this test As can be seen the temperature cooled slightly but then started climbing until the test was stopped This indicates that more heat dissipation is needed 45 0 40 0 35 0 30 0 25 0 20 0 Temperature E 10 0 5 0 0 0 0 0 5 1 1 5 2 2 5 3 Time min Figure 3 Graph of temperature vs time for the TEC and radiator fan on only After this the TEC was left attached to the radiator while only the pump of the liquid cooler was powered Figure 4 s
27. connecting the circuit that more resistance 1s required to safely test the batteries A second 47Y resistor as well as an additional 1Y resistor was added to each line to double the resistance in each parallel path It was also decided to test one battery at a time to allow the testing period to remain at 12 hours This 1s due to the fact that the battery will J discharge half as fast with double the resistance therefore only using one battery instead of two will cause that battery to discharge in the same amount of time as previously determined The new test circuit that was constructed can be seen in figure 38 below The calculations conducted on the previous circuit was correct in the power dissipation conclusions however the resistors were still not safe to use under the conditions of the circuit to the right When the new circuit was hooked up to the battery the resistors were much slower in heating up and did not reach the same high temperatures that they did previously However they were still hot enough to hurt if touched for any significant amount of time Therefore it was decided to place a fan blowing across the resistors while the battery is being discharged to allow the heat produced to be dissipated faster This test is not necessary to stay on schedule with the project until the user interface is made and the A D code has been written It will be conducted at this point Figure 46 New test circu
28. cuitry has been constructed and the necessary code will be created to send text and variable values to the LCD screen and receive interrupts from the keypad The circuitry layout can be seen in figure 30 Only one interrupt will be needed to allow the user to input the minimum and maximum temperature values It is anticipated that the user interface will be fully functional before the time of the stage gate After the user interface is operational the transistor circuits will be built to be able to control the backpack mode with the microcontroller This will be done by connecting simple transistor switches to the microprocessorG I O pins and causing the switch to close connect if a digital high signal is sent to the transistor and cause it to open disconnect if a digital low is sent to it These transistors will be tested on a breadboard with LEDG confirming if the transistor is providing the voltage from the power source or if it is disconnected Finally code will be written to record time stamped temperature values every minute and be able to output them to the LCD screen when the user specifies to see the output These programs compose all of the functionality of the backpack Zinclude lt p24FJ2566GBl06 h gt include header file CONFIGI FHDTEH OFF turn off Watchdog timer int main void long counter initialise delay count variable TEISE Ox configure port E for output vhilefl infinite loop PORTEbite REO 1
29. d the box in a puzzle fit as illustrated in Figure 12 not to scale This allows for a close fit that minimizes air pockets which increase heat loss The cooling system has been integrated into the insulation and has been built so that it can be removed in case any unforeseen complications occur Inner chamber Side view top Side view bottom Bird s eye view Figure 12 Insulation placement The outer chamber has not been built yet and will not be built until the insulation has been built around the inner chamber and has all the components integrated into it The outer chamber is a simple build and will not take long It will be tested as is described in the requirements specification DC to DC Converter The DC to DC converter circuits were modified since it was decided to change the inputs from 12V to 6V This modification has to be done because we found easier to use op amps The op amps comprise the amplification necessary to create an output from the sensor circuit that moves across the full range of the microcontroller amp A D converter system The cooling system will be powered with 12V being supplied from the batteries and op amps will be used to derive the steady 6V needed for the microprocessor temperature sensor and user interface These 6V coming from the voltage regulator will power the DC to DC converters The same buck converter integrated circuits TPS40192 are still going to be used for the DC to DC converters of t
30. ed polio vaccine IPV Measles mumps and rubella vaccine MMR in the lyophilized freeze dried statet Meningoccoccal polysaccharide vaccine Pneumococcal conjugate vaccine PVC Pneumococcal polysaccharide vaccine PPV Trivalent inactivated inflenza vaccine TIV lt 5 F 15 C Instructions Vaccine Live attenuated Maintain in continuosly influenza vaccine frozen state with no freeze LAIV thaw cycles Contact state or local health department or manufacturer for guidance on vaccines exposed to temperatures above the recommended range ActHIB Aventis Pasteur Lyon France in the lyophilized state is not expected to be affected detrimentally by freezing temperatures although nodata are available TMMR in the lyophilized state is not affected detrimentally by freezing temperatures TABLE 2 Comparison of thermometers used to monitor avccine temperatures Thermometer type Standard fluid filled Min max Continuous chart recorder Advantages Inexpensive and simple to use Thermometers encased in biosafe liquids can reflect vaccine temperatures more accurately inexpensive Monitors temperature range Most accurate Continuous 24 hour readings of temperature range and duration Can be recalibrated at regular intervals Disadvantages Less accurate 1 C No information on duration of out of specification exposure No information on min max tempe
31. ensor itself will be etched on a separate board from the sensor circuit to allow it to be placed on the inside of the backpack chamber while the circuitry will be located with the other circuits at the bottom of the backpack AII circuits will be etched and placed inside the backpackG electrical box at the bottom of the backpack once fully tested on breadboards All of these circuits are expected to be etched by the end of March to be able to be tested with the backpack The solar panel will be tested for its ability to charge the batteries and supply power to the electronics before being integrated into the backpack frame The wall and car power circuits will be tested for output consistency with design values before being tested on the actual circuitry Once the power supply devices have been tested in both areas they will be permanently connected to the backpackG circuitry and integrated into the backpack frame Budget Analysis Table 10 Current budget Item Description Vendor nouas Cost Difference Cost Cost Casing Insulation 1 53 00 52 51 0 49 Angle Irons 15 00 14 62 0 38 Electronics Cireuit Board UC o 4000 o o Electric components 17 Digikey 6027 07 Transformer GatecomUSA MISC 1996 Transistors and power supply Jameco 2707 0 00 Serevrs VVashers Loves MISC 305 7 0 27 Loves MISC 3804 Wood Glue amp Caulking
32. er temperature monitoring Different types of thermometers can be used including standard fluid filled min max and continuous chart recorder thermometers Table 2 Standard fluid filled thermometers are the simplest and least expensive products but some models might perform poorly Product temperature thermometers 1 e those encased in biosafe liquids might reflect vaccine temperature more accurately Min max thermometers monitor the temperature range Continuous chart recorder thermometers monitor temperature range and duration and can be recalibrated at specified intervals All thermometers used for monitoring vaccine storage temperatures should be calibrated and certified by an appropriate agency e g National Institute of Standards and Technology In addition temperature indicators e g Freeze Watch 3M St Paul Minnesota or ColdMark Cold Ice Inc Oakland California can be considered as a backup monitoring system 5 however such indicators should not be used as a substitute for twice daily temperature readings and documentation 6 J1 All medical care providers who administer vaccines should evaluate their cold chain maintenance and management to ensure that 1 designated personnel and backup personnel have written duties and are trained in vaccine storage and handling 2 accurate thermometers are placed properly in all vaccine storage units and any limitations of the storage system are fully known 3 vaccines are
33. esistance current path so current can flow The current will flow from the battery to the load into the drain of the transistor and then out from the source of the transistor into ground So when the transistor is on the cooling system will turn on too Figure 18 shows the circuit built in the breadboard using an LED to test its functionality When gate is connected to 5V the LED turns on and remains on until it is connected to ground OV Figure 18 Power control circuit Figure 19 Testing the power control circuit with an LED The LED turns on and off depending on whether the gate of the transistor is at 5V or OV The circuit was tested with an LED to show its right functioning and later it was connected to the cooling system But before the power control circuit was connected the cooling system was connected to the 12V power supply and it draw a current of 2 095A when it was expected to draw about 3 5A The cooling system was working and cooling but it seemed there might had been a problem with the power supply or the TEC which is the component that draws most of the current The power control circuit was then connected to the cooling system as shown in Figure 20 and tested When the gate pin of the transformer was connected to ground simulating the OV digital signal the cooling system was off When the pin was connected to a 5V the cooling system would turn on and remain on until it was connected again to ground The transistor i
34. he microprocessor and temperature sensor which operate with 3 3V and 3 0 respectively A DC to DC converter circuit for the user interface cannot be created with the IC TPS40192 because in order to provide an output of 5V the buck converter would require a duty cycle greater than 8596 which cannot be operated by the IC TPS40192 In order to power the user interface a regular 5V voltage regulator will be used Although regular voltage regulators are usually not recommended because of their inefficiencies we have decided to use one in this case because the drop out voltage is going to be very small 1V and it will not produce that much heat Figure 13 shows how the DC to DC converters will power the microprocessor temperature sensor and user interface while the cooling system will be directly powered from the batteries Microprocessor Cooling Temperature System TEC User Interface Pump Figure 13 The DC to DC converters have been modified so that their input is 6V instead of 12V The good thing about the structure of the circuits that use the integrated circuit TPS40192 is that in order to modify the output voltage only the values of the capacitors and resistors change The new to DC converters operate with V 5 8VandV 6 2V The electric components in order to build the previous designs were already ordered and received Although modifications have been made the same buck converters and buck transistors are going to still
35. hin the insulated chamber and decides whether it needs to be cooled The device will weigh less than 37 kg 82 lbs and will not exceed a size of 60 cm x 100 cm x 60 cm The major accomplishments that have been reached this semester include constructing the inner chamber of the backpack conducting performance tests on the cooling system solar panels and batteries integrating the cooling system into the insulation and inner chamber building the insulation around the inner chamber constructing the temperature sensor circuit assembling the user interface circuit and making a detailed circuit image to be sent to a professional company to be etched Though we have reached many of our goals on time we are still slightly behind schedule in coding the microprocessor and constructing peripheral circuitry and building the cooling chamber Over the next few weeks we plan to complete tests on the solar panels and batteries to obtain detailed measurements on the output of each under different operating conditions We will also develop code to use the analog to digital system of the microcontroller finish testing the cooling system and insert it into the chamber and begin constructing and soldering the DC to DC converter Cooling System The cooling system removes heat from the inner chamber It has had no change in design and consists of a thermoelectric cooler TEC a self contained liquid cooler with radiator and fan to dissipate heat to the en
36. hows the results of this test As can be seen the temperature decreased but then slowly increased until the test was stopped This indicates that more heat dissipation is needed Temperature E Time min Figure 4 Graph of temperature vs time for the TEC and radiator pump on only Next the TEC was left attached to the water block and the entire liquid cooler with its pump and fan were powered Figure 5 shows the results of this test at two different ambient temperatures of 22 52 Series 1 and 29 42 Series 2 As can be seen the temperature decreased to an average of 52 and 8271 respectively but this is not low enough for our requirement specification Thus more heat dissipation is needed 14 0 1 1L T FT 7 4 1 T TT 7 t Series1 12 0 oa oe oo ot B Series2 Temperature E Time min Figure 5 Graph of temperature vs time for the TEC and liquid cooler A test was run with the TEC just connected to the cold sink in order to see if liquid cooler was needed with the cold sink Figure 6 shows the results from this test As can be seen the TEC did not cool down at all since no heat was being dissipated This verifies that the liquid cooler is needed with the cold sink 24 0 23 0 22 0 21 0 20 0 19 0 18 0 17 0 16 0 15 0 14 0 Temperature 2 B N O 0 0 5 1 1 5 2 2 5 3 3 5 4 4 5 5 Time min Figure 6 Graph of temperature vs time for the TEC and cold sink Once it
37. ighest allowable temperature in that order when prompted on the screen During Transportation IMPORTANT Avoid opening the refrigerator door until the destination has been reached as this will compromise the environment of the vaccines and might deplete the backpacks energy supply prematurely The user will be able to monitor the current temperature inside the refrigerator via the indicator mounted on the outside of the refrigeration chamber They will also be able to read the approximate battery life reading that will inform them as to the amount of energy currently in the pack in the same screen The user should make sure that the solar panels are clear of anything that may block them from the sun when possible After Transportation When the destination 1s reached the user should transfer the vaccines to a secure environment to be used as needed The backpack should remain in the refrigeration mode until vaccines are no longer stored in the chamber Technical Requirements unit will cool a chamber within the backpack and maintain it at a temperature range between 27 and 827 3521 and 462 for a minimum of 48 hours at an average ambient temperature up to 30 C 86 F while stationary e The temperature inside the refrigeration chamber will be read and relayed so it can be displayed on the outside of the unit The temperature sensor will have a maximum resolution range of 121 and will cover a temperature range of at lea
38. imum amount R 96Y V 18V 19Y 2 1875A R 96Y P VI 18V 1875A 3 375W In order to have a load of 96Y 4 resistors 47Y 47Y 1Y and 1Y were connected in series The solar panels were exposed to two different fluorescent lights and the voltage and current were measured Moving the solar panels toward the source of light increased the readings in voltage and current Using fluorescent lights there were readings of up to 3 4V and 0 037A Figure 30 Soldered outputs of solar panel Figure 32 Exposure of solar panels to a fluorescent light source In order to test the solar panels more accurately light measuring equipment and a tungsten lamp were borrowed from Dr Wilson to simulate and measure sunlight Now that we were able to measure the light intensity with a digital light meter we measured the output voltages and currents coming from the solar panels The solar panels were tested under a 100Y load and measurements were made with the solar panel tilted and vertical with respect to ground The tilted position can be seen on the left in figure 24 while the vertical position can be seen on the right Tables 4 and 5 show the results of these experiments J Figure 33 Solar panels being exposed to a light emitter with a light intensity of 2 705 mW m Solar Panel Output vs Light Intensity Table 4 Test 1 panel tilted results Table 5 Test 2 panel vertical results as so
39. it for battery f 5 J Full Frame Assembly Because the backpack is being assembled from the inside out the frame which gives the whole structure stability will be added last Once the cooling system is attached to the inner chamber and the insulation is added part of the frame can be built The top part of the frame that surrounds the inner chamber will be constructed from aluminum L beams The four side parts of the frame will be attached and then this partial frame can be put over the rest of the backpack Once all the other hardware such as circuit boards radiator batteries and user interface 1s attached the rectangular bottom frame piece can be added to make the frame complete System Integration System integration has started and will continue through early April A large step that has been completed is that the cooling system was integrated into the insulation The next main thing will be to build the temperature sensor into the chamber The user interface will be attached to the outer chamber once it is completed The electronics will be constructed on a breadboard to be tested until the DC to DC converter has been tested and constructed This includes the microcontroller the user interface the temperature sensor the battery life circuit and the CMOS switches that will turn each subsystem on and off The user interface will be constructed within the next week to prepare to integrate it into the backpack frame The temperature s
40. mperature monitoring practices and recommends steps for evaluating a temperature monitoring program The success of efforts against vaccine preventable diseases 1s attributable in part to proper storage and handling of vaccines Exposure of vaccines to temperatures outside the recommended ranges can affect potency adversely thereby reducing protection from vaccine preventable diseases 7 Good practices to maintain proper vaccine storage and handling can ensure that the full benefit of immunization is realized Recommended Storage Temperatures The majority of commonly recommended vaccines require storage temperatures of 35 F 46 F 2 C 8 C and must not be exposed to freezing temperatures Introduction of varicella vaccine in 1995 and of live attenuated influenza vaccine LAIV more recently increased the complexity of vaccine storage Both varicella vaccine and LAIV must be stored in a continuously frozen state 5 F 15 C with no freeze thaw cycles Table 1 In recent years instances of improper vaccine storage have been reported An estimated 17 37 of providers expose vaccines to improper storage temperatures and refrigerator temperatures are more commonly kept too cold than too warm 2 3 Freezing temperatures can irreversibly reduce the potency of vaccines required to be stored at 35 F 46 F 2 C 8 C Certain freeze sensitive vaccines contain an aluminum adjuvant that precipitates when exposed to freezing temperatures This
41. n the power rail as this will allow a very high charge current to flow and possibly damage the SCR A DC supply will not allow the SCR to turn off as it turns off when the current through it falls to zero It was decided to keep the DC power plug as it will be useful for powering the cooling system when a wall outlet is available as specified in the requirement specifications Figure 27 Testing the circuit LED is on current flowing to the battery is 18 mA and voltage across the battery 12 45V remains constant The correct power plug was ordered and the circuit was tested The current charging the battery was of 195mA The initial voltage of the battery was 12 45V and in five minutes the voltage increased to 12 50V This showed that the circuit was actually charging the battery but it was considered that another test was required by charging a battery that was almost fully discharged So the 12V lead acid battery was discharged by connecting it to the load shown in Figure 46 for 12 periods of an hour each to prevent overheat in the resistors until the voltage across the battery was dropped to 10 7V The battery was then connected to the battery charger circuit for 27 hours and the voltage and current were measured constantly Figure 29 shows a 3 graph with the voltage of the battery as it 1s being charged during the test period From this figure it can be observed that the voltage of the battery increased
42. ncreased in temperature when it was on so a heat sink had to be added The current draw from the power supply was kept to 2 095A the same as when the cooling system was tested directly with the power source These results showed that the power control was working correctly and the microprocessor will be able to turn the cooling system on and off Figure 20 Testing the power control circuit with the cooling system A 5V voltage at the gate of the transistor turns the cooling system on Battery Charger After looking at different options for circuit designs it was decided to use a circuit that uses a 12V transformer The circuit 1s shown in Figure 21 The circuit was originally taken from the website talkingelectronics com but some modifications were made on our design Figure 21 Battery charger circuit The circuit does not turn on until a battery 1s connected across the terminals as shown in the diagram This action turns on the PNP transistor in the Turn ON block shown in Figure 22 The resistance between the collector emitter terminals decreases and the indicator LED comes on The path to the bottom rail of the circuit goes through a signal diode the gate cathode junction of the SCR Silicon Controlled Rectifier and through three 3 9 Y resistors in parallel This is why the LED illuminates The circuit works on an AC plug pack A DC supply will not allow the SCR to turn off as it turns off when the current through it falls to zero
43. nly rated in CFM of airflow However the parameter used to calculate the impact of forced air on a sink rating is LFM which can be calculated by dividing the CFM rating by the area of the fan Table 1 Cold sink adjustment factor as a function of airflow of the fan LFM 200 300 400 500 600 700 800 900 The cold side fan has an LFM rating of 476 To account for backpressure which limits the net airflow this value was multiplied by the recommended correction factor of 0 8 In order to find the factor of improvement that the fan has on the thermal resistance of the cold sink Table 1 was interpolated between the values of 300 and 400 which gives a correction factor of 0 3896 for the cold sink Dividing the cold sinkG thermal resistance requirement by this correction factor shows that the fan significantly decreases the thermal resistance which in turn er 2 means that the cold sinkG thermal resistance can have a much higher value of 2 35 Because weight is a big design factor a compact light weight extruded aluminum sink with a thermal resistance of 2 0 was chosen The fan also helps to distribute the cold air to and circulate it through the inner chamber The cooling system will be attached to the bottom of the inner chamber as shown in Figure 2 The cold sink and the fan are going to be inside the inner chamber and the water block and pump of the liquid cooler will be attached below it To ensure that no va
44. nto conduction and none of the components in the circuit deliver current to the battery The SCR delivers current for a few half cycles and then it is turned off for a few cycles This 1s how the average current delivered to the battery 1s controlled The circuit 1s designed to deliver about 180 220 mA average charge current The actual value 1s determined by the three 3 9 Y resistors in parallel When the battery is fully charged the indicator LED begins to flash The flashing is produced by the 2 2 KY resistor and 47uF capacitor connected to the voltage monitor section When the battery is charging the capacitor is charged via the diode connected to the BC557 transistor and through the 150 Y and signal diode to the negative of the battery When the battery is fully charged the Voltage Monitor section turns ON and turns off the Turn ON section This removes the voltage on the positive side of the 47Uf capacitor and the positive side 1s brought to the negative rail via the 2 2K Y resistor This brings down the negative side of the capacitor and the 150 Y resistor is allowed to drop below the negative rail due to the presence of the diode as the diode becomes reverse biased This holds the circuit in the off condition as the voltage monitor section sees an extra voltage across it and thinks the battery it is over charged The electric components for this circuit have been ordered and received The footprint has already been design using Ultiboard
45. plification of the op amps The gain is expected to be approximately 62 5 It can be seen that the first data point is very close to this value The second gain found is low because it is approaching the limit of the op ampG amplification range Batteries Both batteries have been obtained and successfully charged As of right now LABVIEW code is being tested to be able to test the batteries voltage while being discharged over a 12 hour time period To do this the voltage from the batteries will be sent into the NI ELVIS board and loaded into LABVIEW via a DAQ Assistant This DAQ assistant will read the voltage periodically and load the information into a spreadsheet in the computer The code that will be used in LABVIEW can be seen below Time Figure 44 Battery test code in LabVIEW The DAQ Assistant will output the batteries voltage constantly while the elapsed time module will cause the case structure to send the DAQG output to the spreadsheet every minute All of this code is inside a while loop that will continually run until the user presses the off button on the front panel The load circuit that the batteries will be hooked up to while being tested has been constructed and tested on a breadboard The design used for this circuit can be seen in Figure 37 below Upon being connected to the batteries in the initial test the 47Y resistors became hot enough to burn and began to smell in less than one minute It was decided after dis
46. r s 8 SW EE Test 2 Panel Vertical 16 14 12 10 Voltage V O0 O 0 2 0 4 a 0 8 1 1 2 1 4 1 6 Light Intensity mW m 2 Figure 34 Voltage and light intensity relation for solar panels Test 2 Panel Vertical 180 160 140 9 mol x go x so 40 20 Current mA o Ui 1 1 5 2 2 5 3 Light Intensity mW m 2 Figure 35 Current and light intensity relation for solar panels This test confirmed the solar panelG ability to output a sufficient amount of voltage to charge the batteries and to power the system Furthermore the voltage and current are shown to move in a linear fashion with respect to light intensity 4 J1 Further tests were made to compare the voltage across the solar panels at different angle positions having the base of the solar panels 0 5 meters away from the source light The results of these tests are shown in Table 6 These results show that having a lower angle inclination towards or away from the light source significantly affects output voltage of the solar panels Having an inclination of 78 the solar panels were able to provide 16 93V which is close to the maximum power voltage 17 3V mentioned in the data sheet of the solar panels Table 6 Results of testing the solar panels at different angle positions 100Y load Tet1 900 2 Light Intensity Power mVV m V A W Tet208 0802 22 Light Intensity Power mVV m
47. ratures Cannot be recalibrated Inexpensive models might perform poorly Less accurate 1 C No information on duration of out of specification exposure Cannot be recalibrated Most expensive Requires most training and maintenance P L Project Overview and Status There is a need for a better method for transferring vaccines into rural areas of developing nations where power is not easily accessible for refrigeration There is no developed method that involves continuous refrigeration from a portable consistent and environmentally friendly power source By having a refrigeration system that can be powered during transportation the ability to distribute vaccines will be greatly increased and the chances of ruining vaccines will be diminished Our goal is to create a means of transporting vaccines to remote areas in rural parts of developing countries The design is a solar powered backpack refrigerator The device will be driven by a battery which can be recharged by either plugging it into a 110 V AC power outlet or 12 V DC car jack when available or by a solar panel that is attached to the backpack when on foot A user interface will allow the user to set the temperature within the insulated chamber and will inform him of the current temperature It will also warn the user if the temperature ever gets too high so that the ruining of vaccines can be prevented A microcontroller continuously checks the temperature wit
48. recise temperatures required for vaccine storage and such single purpose units sold for home use are less expensive alternatives to medical specialty equipment Any refrigerator or freezer used for vaccine storage must maintain the required temperature range year round be large enough to hold the year s largest inventory and be dedicated to storage of biologics 1 e food or beverages should not be stored in vaccine storage units In addition vaccines should be stored centrally in the refrigerator or freezer not in the door or on the bottom of the storage unit and sufficiently away from walls to allow air to circulate Temperature Monitoring Proper temperature monitoring is key to proper cold chain management Thermometers should be placed in a central location in the storage unit adjacent to the vaccine Temperatures should be read and documented twice each day once when the office or clinic opens and once at the end of the day Temperature logs should be kept on file for gt 3 years unless state statutes or rules require a longer period Immediate action must be taken to correct storage temperatures that are outside the recommended ranges Mishandled vaccines should not be administered One person should be assigned primary responsibility for maintaining temperature logs along with one backup person Temperature logs should be reviewed by the backup person at least weekly All staff members working with vaccines should be familiar with prop
49. rounded by rigid insulation and an outer chamber But once completed it was shaken and shown to be rigid and unmoving The cooling system has been attached to the bottom of the inner chamber as mentioned in the previous section and illustrated in Figure 2 To seal the inner chamber and prevent moisture from seeping into the insulation the inner corners and the bottom of the cold sink were sealed with white caulking shown in Figure 9 Figure 9 Inside view of the inner chamber after caulking Figure 10 Inner chamber Width 57cm Depth 47cm Height 75cm 3s Rigid Styrofoam insulation will be used to significantly decrease the rate at which heat enters the inner chamber of the backpack A total of five layers of the 2 54 cm 1 inch thick insulation will surround each side of the chamber With a box cutter the insulation was cut to the correct dimensions In order to increase the stiffness the first layer of the insulation was pressed onto the screws of the brackets that hold the inner chamber together shown in Figure 11 Figure 11 Insulation shell built on top of inner chamber The next layers were attached to the first layer using wood glue Clamps were used to press the layers together while the glue was drying Four layers of the insulation have been completed The rest of the build will be completed by the end of the first week after spring break This can be seen in Figure 11 The insulation is being built aroun
50. st 0 C to 30 C 32 F to 86 F JF The entire unit will weigh less than 37 kg 82 Ibs The backpack will not exceed a size of 60 cm x 100 cm x 60 cm The refrigeration system will be controlled to within the specified temperature range The unit will be able to measure the temperature inside the chamber to within 12 The unit will be able to control the temperature inside the chamber to withint 32 There will be a user interface used to control the refrigeration system It will include an on off switch a digital temperature display a temperature control interface and battery status indicators The unit will have a frame that can perform while being transported on foot and by vehicle All systems will operate in a safe manner that will pose no threat of harm to the users Temperatures will not go above 50 C or below 30 C voltages will not exceed 30 V DC and moving parts will be protected by a grill Deliverables QO 129 R D User Manual Technical Drawings and Analysis of Hardware Schematic of Circuit with Simulation Results Code and Flowcharts Report of Testing Parts List with Budget Final Technical Report Solar Powered Refrigeration Backpack Preliminary Test Plan Four healthy individuals with a minimum height of 1 6 m 63 inches and weight of 54 kg x 120 Ibs will be able to pick up put on and take off the backpack with the assistance of one other individual
51. the Advisory Committee on Immunization Practices ACIP and the American Academy of Family Physicians AAFP MMWR 2002 51 No RR 2 2 Gazmararian JA Oster NV Green DC et al Vaccine storage practices in primary care physician offices Am J Prev Med 2002 23 246 53 3 Bell KN Hogue CJ Manning C Kendal AP Risk factors for improper vaccine storage and handling in private provider offices Pediatrics 2001 107 E100 4 World Health Organization Thermostability of vaccines Geneva Switzerland World Health Organization 1998 publication no WHO GPV 98 07 Available at http www who int vaccines documents DocsPDF www9661 pdf 5 World Health Organization Temperature monitors for vaccines and the cold chain Geneva Switzerland World Health Organization 1999 publication no VVHO V amp B 99 15 Available at http www who int vaccines documents DocsPDF www9804 pdf 6 Commonwealth Department of Health and Aged Care Keep it cool the vaccine cold chain Guidelines for immunisation providers on maintaining the cold chain 2nd ed Canberra Australia Commonwealth of Australia 2001 TABLE 1 Vaccine storage temperature requirements 35 F 46 F 2 C 8 C Instructions Vaccine Instructions Diphteria tetanus or pertussis containning Do not freeze or expose the freezing temperatures vaccines DT DTaP Td Haemophilus conjugate vaccine Hib Hepatitis A HepA and hepatitis B HepB vaccines Inactivat
52. vironment and a cold sink with fan to distribute the cold air within the insulated chamber The individual components were assembled with round steel bolts and are shown below in Figure 1 Figure 1 Assembled cooling system Thermoelectric cooling utilizes the Peltier effect to create a temperature differential across the junction of two dissimilar metals In a TEC electric power is used to generate a temperature difference between the two sides of the device Connecting the TEC to a direct current causes one side to get hot and the other side to get cold With a small flat scrap piece of plywood thermal paste was thinly but evenly distributed over both sides of the TEC which then was sandwiched between the liquid cooler and the cold sink Thermal paste fills small voids and crevices that are present due to the imperfectly flat and smooth surfaces of the components which helps heat flow and lowers the thermal resistance o Jh The lower the thermal resistance a heat sink has the more it allows the flow of heat energy The ECO A L C liquid cooler unit has a very low thermal resistance 0 5 and acts as a heat sink that dissipates heat from the hot side of the TEC to the environment via a radiator and fan For the cold sink an extruded aluminum sink was used In order to reduce the thermal resistance and satisfy the requirement of 0 916 the cold sink was combined with a low profile fan Fans are commo
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