EE+413+Final+Project

=EE 413 Final Project= Project wiki URL: http://ee413s09-02.wikispaces.com/ Group 2 - Chiweng Kam (ckam at calpoly.edu) and Dan Strengier (dstrengi at calpoly.edu)

The objective of the final project is to apply the __design process__ and __cooperative teamwork__ to design a robust electronics system design and automated electronics test module using LabVIEW.

Final Project Requirement: 1. Design and prototype a system to foster sustainability. 2. Design an automated test suit to assist an engineer to evaluate the system's sustainability.

[|EE 413 Course Link] - The course website for EE 413. [|EE 413 Final Project]  - This webpage contains the details and the requirements for the project.

=Project Title - FridgeAlert=

According to the 2001 Residential Energy Consumption Survey by the Energy Information Administration (EIA), refrigeration consumes 13.7% of the total electricity consumption in U.S. Housing Units. The electricity consumption of the refrigerator ranges second among all the household appliances, next to the 16% for air-conditioning [1]. As a result, a lot of resources were devoted to minimize the electricity consumption of refrigerator in order to reduce the overall electricity consumption of a household. Appliance energy efficiency plays a key role in creating a sustainable household. One method to increase the energy efficiency of the refrigerator is to ensure the end user will not waste energy. When refrigerators are left open for extended periods of time, energy is wasted due to cold air seeping out of the refrigerator, which requires increased energy consumption to lower the internal temperature back to an optimal temperature. Our Fridge Alert system addresses this issue by producing an alarming (and annoying) buzz when the fridge door is open for more than 15 seconds, which alerts the users to close the door. This system fits well with the scheme of fostering sustainability.

The idea for this project came from Babu, T.A's design idea presented in EDN in March 2009, in which he proposes to alert the user after the refrigerator door is open for 20 seconds [10]. The design requires interfacing with the refrigerator's internal circuitry. This solution is not ideal for non-technical consumers to implement. There are significant inherent safety issues with utilizing the refrigerator's 120V circuitry. Also, the design requires too much power consumption from the inefficient power transfer from 120V to 6.8V through a bridge rectifier.

__Project Goal__
This project aims to create a safe, low cost, and low power device that can be easily installed on refrigerator door to alert users when their refrigerator door is open too long.

__Project Requirements:__
> 1. Alert users when the refrigerator door remains open for more than 15 seconds. > 2. No interface with the refrigerator 120V circuit - low Voltage DC operation. > 3. Use less power than the original design - create a circuit with low power dissipation (foster sustainability). > 4. Create a product that is safe and easy to use, also small in size (user-friendly).
 * Note:** This represents the final version of the project requirements. Different revisions were created. See Design Process Page.

__Specification and Constraints:__
> 1. Audible alarm sounds when the refrigerator door remains open for a duration of 15 seconds. > 2. DC battery operation, utilizing common battery standards (AAA, AA, or 9V). > 3. Low power consumption, below 1W. (Original design used about 2W). > 4. Minimum space requirement (3 X 5 X 1'') > 5. Prototype cost below $4.00.
 * Note:** This represents the final version of the specifications. Different revisions were created. See Design Process Page.

__Circuit Design Consideration:__
When evaluating possible design implementations, the following design criteria are considered and weighted with decreasing importance: user safety, power dissipation, cost, ease of use and size. User safety is of paramount concern, and is addressed by using two AAAs to power the circuit which requires no connection to high voltage outlet. Since the prototype is not completely enclosed, there are dangers inherent with exposed circuitry, but the circuit only drives 1mA at 3V. Its low power design reduces any significant threats of electric shock occurring to users.

The main challenge of this project is to create an ultra low power dissipation device that rarely requires replacing batteries. To achieve this, we chose not to use active components that require a constant supply voltage to operate. To make FridgeAlert a viable business opportunity, we designed a simple and low cost circuit that could be mass-made and cheaply sold. To increase customer appreciation, the FridgeAlert has to be easy to use. Finally, a small device, approximately the size of a fridge magnet, is ideal for market penetration.

__Design Methodology:__
The FridgeAlert circuit addresses the problem of wasted energy from refrigerator doors remaining open for too long.

The ultimate solution to this problem is to close the door after it is open for too long, through user assistance or a mechanical solution. However, implementing a device that manually closes the door seems impractical. A product of this nature introduces issues of complexity, dangers of closing the door during usage, and the unlikeness of implementing it into the existing refrigerator doors. A product that automatically closes the door would need to be integrated into the original design of a refrigerator instead of a stand alone 3rd-party product that could attach to the refridgerator.

Simply alerting refrigerator users to close the door appears to be a better approach than designing a product that closes the fridge door. Once users are informed that the door has been open for too long, they can provide the mechanical means of closing the door.

The aims of the project is to design a system that can be easily and safely installed on existing refrigerator doors. Sustainable design is stressed by designing a circuit with low power dissipation

Brainstorming sessions indicated that there are three fundamental components of the design: a means of sensing when the door is open (sensor), a circuit that is able to time for 15 seconds (timer) and an alerting device. Lighting and aural means were considered to alert the user, but an audible buzz seemed be the most effective approach. Unfortunately, deaf users are not considered in this version of FridgeAlert. Future versions could incorporate a flashing LED array to alert deaf users.

The following options were generated for each component (sensor, timer, buzzer) in our brainstorming sessions. __**Possible options for Sensor:**__ > 1. Mechanical switch (button) - the circuit is activated when the button is released; place the button on the edge of refrigerator door. > 2. Optical switch (IR emitter and sensor) - an IR emitter and detector are inside a fridge magnet. The magnets are placed on a refrigerator door and freezer door. With proper alignment, the circuit can detect the light. > 3. Magnetic switch. > 4. Proximity sensor. > 5. Light Detector (using Phototransistor or Photodiodes)

__**Possible options for Timer:**__ > 1. 555 Timer > 2. 4060B Timer/Counter IC, as used in the original design idea. > 3. Microcontroller

__**Possible options for alerting user:**__ > 1. Flashing light > 2. Buzzer > DC Buzzer - requires DC voltage. Produces a frequency of 1 tone > AC buzzer -requires AC waveform around resonant frequency, approximately 2KHz. Allows tones of different frequencies

There were two design reviews during class. (See [|Design Review I Power Point] and [|Design Review II Power Point]). The information and comments generated from the two Design Reviews helped us evaluate our options and deal with the complications we encountered in our design. Table 1-3 summarize the evaluation for each main component. Table 4 summarize the comments from the Design Reviews and our responses.

emitter and detector circuit. ||
 * Table 1 - Component Evaluation for the Sensor**
 * = **Switch Selection** ||= **Pro** ||= **Con** ||
 * Mechanical Switch (button) || * Similar to the built-in switch of the refrigerator door and light bulb.
 * Possibly use existing fridge switch || * Fridge shapes aren't universal. Difficult to create a universal switch to operate on all fridges
 * Require long length of wire connection from the switch to the main circuit.
 * Require two separate switches for freezer and refrigerator. ||
 * Optical Switch (IR emitter and sensor) || * Can be placed in between the freezer and refrigerator door;
 * Potentially, one switch for both freezer and refrigerator;
 * Inexpensive || * If placed between freezer and refrigerator door, circuit fails when opened together;
 * IR emitter constantly draws current.
 * Require long length wire connection from the switch to the main circuit or require batteries for
 * Magnetic Switch || * Can work similarly as mechanical switch. || * Calibration will be critical.
 * Require long length wire connection from the switch to the main circuit. ||
 * Proximity Sensor || * Similar to mechanical switch; || * Calibration will be critical.
 * Also require long length wire connection from the switch to the main circuit. ||
 * Light Detector (Phototransistor and Resistor) || * Can be placed next to the refrigerator door light bulb.
 * Potentially, no long length wire required; || * More complicated circuit configuration.
 * Encounter problem if refrigerator or freezer has no light. ||


 * Table 2 - Component Evaluation for the Timer**
 * = **Timer Selection** ||= **Pro** ||= **Con** ||
 * 555 Timer Chip || * Team is familiar with its operation.
 * Circuit requires less components.
 * Runs on 2V || * Possibly limited by length of pulse and accuracy ||
 * 4060B IC Timer || * Component used (and recommended) by the original design;
 * It can provide a separate pulse to drive the AC Piezo-Buzzer;
 * More Accurate Timing. || * Higher Power Dissipation compare to 555 Timer Chip; ||
 * MicroController || * Can provide a lot of different functionality; || * Might require more time to learn and develop the circuit. ||


 * Table 3 - Component Evaluation for the Alerting Devices**
 * = **Buzzer Selection** ||= **Pro** ||= **Con** ||
 * Piezoelectric Buzzer (Self Drive) || * Requires DC voltage
 * Easy to interface with DC circuit, doesn't require timing component || * Can only work in one frequency.
 * Increased Cost ||
 * Piezoelectric Buzzer (AC) || * The tone can be varied based on driving frequency.
 * Cheaper than DC buzzer || * Requires driving circuit
 * Sound strength varies with frequency ||

Design Review I (Number 1-7); Design Review II (Number 8-13) ||= **Response** ||
 * Table 4 - Suggestion from Design Review and Responses**
 * = **Design Review Suggestions**
 * # Try to use existing fixture for the sensor;
 * 1) Keep Buzzer away from the refrigerator;
 * 2) Create variation in the sound output. i.e. the sound is getting louder as the time gets longer;
 * 3) Consider about deaf user;
 * 4) Position sensor
 * 5) Send an e-mail to the user if the refrigerator remained open for TOO LONG!
 * 6) More detail financial analysis
 * 7) Implement an outer LCD interface for the user.
 * 8) Use Schmitt Trigger to block out ambient light in order to solve the false beeps on slow illumination.
 * 9) Will the circuit work in cold temperature?
 * 10) Use FET instead of BJT to solve the false beeps on slow illumination problem.
 * 11) Louder Buzzer Sound.
 * 12) Not constantly buzz, stop for a period and buzz for a period, such that it is more pleasant for the users. || # This requires interfacing with the 120V AC circuit (as in the original design).
 * 13) It might require extra wire length and might not make such a big difference; we can adjust the sound level instead;
 * 14) Great idea, but requires more complicated circuitry and higher cost; might be easier to implement with microcontroller;
 * 15) Also great point, the question is how to implement it. We can add extra LED indicator, but it might not achieve any significant effect.
 * 16) More complex.
 * 17) Great Idea also, but will increase the cost of the circuit and might not be very practical for such an small application.
 * 18) Will do when time permits
 * 19) This is a practical idea if we aim to design a more functional device, such as a device that can monitor the energy use and temperature inside the refrigerator.
 * 20) If the issue with false beeps on slow illumination is solved, ambient light is actually desire to activate the circuit, especially with refrigerator with no light.
 * 21) We will verify that by testing the circuit inside the refrigerator.
 * 22) It will provide faster switching.
 * 23) The level of the buzzer sounds can be adjusted by using higher voltage source. From cost and power dissipation point of view, it is better to have low voltage operation.
 * 24) It is in the original design idea; we decided to keep the constant buzz because we believe that it is more effective as alarm. ||

__**Final Circuit Component Selection**__ After considering all of the options and availability of the different circuit components, we selected the final components for our design, shown in Table 5. Table 5 also lists the reasons why the components were selected for our design.


 * Table 5 - Final Circuit Component Selection**
 * = **Circuit Component** ||= **Selection** ||= **Reason** ||
 * = Sensor ||= Light Detector with Phototransistor || * Small in size and easy to implement into the circuit. Cheap and simple.
 * This allows the user to easily install the product into most refrigerators. ||
 * = Timer ||= 555 Timer || * Cheaper than other alternatives, uses a simple counting mechanism, widely available. ||
 * = Alert Device ||= Piezoelectric Buzzer (DC/ Self-Drive) || * Small in size and provides effective audible alert ;
 * Main circuit does not have to produce a AC waveform at resonant frequency to drive the buzzer, decreases complexity of circuit ||

__System Design and Implementation__
 Figure 1 shows the final circut schematic. The photodetector transistor is biased such that that it nearly saturates with ambient light. When the transistor detects light, most of the battery voltage is seen at the its emitter and is then dropped over a 67K resistor. This voltage is applied to the input of a CMOS inverter, which inputs into another CMOS inverter. The CMOS inverters used in series act as a voltage comparator, producing a binary output voltage that does not follow small variations in detected light. The 67K allows the stored charge in the gate of the CMOS gate to be dissipated when light is no longer detected.
 * __Circuit Operation__**

The double CMOS inverters are a clever way to implement a voltage comparator without large current draw. Comparators were considered in early design stages but were then neglected due to their constant current consumption. The CMOS double-inverting configuration draws current only when the inverters are switching, i.e. when the input threshold voltage is reached. David Braun is credited for the double-inverter idea.

When the voltage at the emitter of the photodiode exceeds the threshold voltage of the inverter, approximately 1.8V when powered by 2 AAA batteries, the double-inverter outputs a rail voltage to the base of the NPN transistor. Originally, the BJT was used for current gain to drive the rest of the circuit because the phototransistor was unable to produce sufficient current. Due to the late implementation of the CMOS inverters, the BJT had been already soldered into the circuit despite the ability to use the CMOS inverters as current drivers. Future design revisions should investigate the feasibility of using the CMOS inverters to supply current to the circuit, eliminating the need for the NPN transistor.



Current flows only when ambient light is detected by the circuit. Figure 2 illustates the sensor portion of the circuit. When there is not sufficient light present, the phototransistor is in cut-off mode and provides 0V to the input of the CMOS inverters. The current-boosting BJT is also in cutoff mode so the timing and buzzing components do not have a connection to the battery. This proved difficult to implement, but we felt it was important to design the circuit so that it would not draw power when the refrigerator door is closed.

Figure 3 illustrates the timing portion of the circuit. The timing circuit consists of a 555 monostable circuit, and is powered directly through the emitter of the BJT. When the BJT is on, the 555 timer is powered by approximately 2.3V. Upon being powered on, the reset pin on the 555 is connected to ground, which activates its reset functionality. The reset capacitor then charges to 2.3V at a time constant of 5.1 milliseconds, which deactivates the reset. When the reset is on, the 555 connects the output to ground. Similarly, upon power-on the trigger input is at ground and begins to charge at a time constant of .5 seconds. This allows the reset to discharge the timing capacitor upon startup, eliminating glitches occurring when the refrigerator door is open and closed quickly. The 555 output is pulled high in its unstable mode. If the door is still open after 15 seconds, the 555 switches into its stable mode and the output is pulled low, which drives the buzzer stage.



The buzzer circuitry is also connected to the emitter of the BJT so that it does not receive power when light is not present. The buzzer portion of the circuit is shown in Figure 4. A PNP transistor allows current to flow when its base voltage is pulled low by the output of the 555. A resistor connected in-between the base and the 555 output is used to limit current flow to reduce the volume of the buzzer, and to provide to increase the charge time of the buzzer capacitor. This capacitor holds the output voltage high for a brief period to eliminate annoying buzzing that occurs when the circuit is initialized. It has a time constant of .5 seconds. This adds to 15 second timing counter from the 555, for a total timing of 15.5 seconds.

555 monostable period: 1.1*R_time*C_time = 1.1(128K)(106uf) = 15s T_trig = R_trig*C_trig = (500K)(1uf) = 0.5s T_reset = R_res*C_res = (5.1k)(1uF) = 5.1ms T_buzz = R_buzz*C_buzz = (5k)(100uF) = 0.5s
 * __Time Constant Calculations:__**

__**Final Circuit Picture and PCB layout**__ Figure 5 shows the picture of the final prototype circuit. The color wires are used for easy interface with the LabVIEW test suit. The user can connect the color-coded terminal with associated instrument for the test suit to operate properly. Refer to the User Manual for the for the detail connections to different instruments.

Figure 6 illustrates the PCB layout for the prototype circuit and is representative of its actual size. The layout was created using PCB express and is designed for a single-sided PCB, minimizing manufacturing costs.


 * __Bill of materials:__**
 * = Model ||= Price ||= Layout ||= Datasheet ||= Seller ||
 * = U1ICM7555 ||= $0.36 ||= DIP-8 ||= [] ||= Mouser 771- ICM7555ID/01-T ||
 * = U2MC14007UBCPG ||= $0.41 ||= PDIP-14 ||= http://www.datasheetcatalog.org/datasheets/270/397423_DS.pdf ||= 863-MC14007UBCPG ||
 * = Q1SFH 310-2/3 ||= $0.42 ||= T1 ||= []; ||= Mouser720-SFH310-23 ||
 * = Q2PN2907ATF ||= $0.06 ||= T1 ||= http://www.fairchildsemi.com/ds/PN/PN2907A.pdf ||= Mouser 512-PN2907ATF ||
 * = Q3PN2222AG ||= $0.14 ||= TO-92 ||= http://www.onsemi.com/pub/Collateral/PN2222-D.PDF ||= Mouser 863-PN2222AG ||
 * = C1 1uf ||= $0.07 ||= N/A ||= http://www.mouser.com/catalog/specsheets/XC-600144.pdf ||= Mouser 140-50N5-1R0D-RC ||
 * = C2 1uf ||= $0.07 ||= N/A ||= http://www.mouser.com/catalog/specsheets/XC-600144.pdf ||= Mouser 140-50N5-1R0D-RC ||
 * = C3 100uF ||= $0.67 ||= N/A ||= http://products.nichicon.co.jp/en/pdf/XJA043/e-vz.pdf ||= Mouser 647-UVZ1J101MPD ||
 * = C_time 100uF ||= $0.41 ||= N/A ||= http://products.nichicon.co.jp/en/pdf/XJA043/e-vz.pdf ||= Mouser 647-UVZ2C220MPD ||
 * = R1 5k, R2 500K, R3 68K, R4 5K, Re 780, R_time 148K ||= $0.09 each ||= N/A ||= http://www.mouser.com ||= Mouser.com ||
 * = AAA Battery Holder ||= $0.99 ||= N/A ||= http://www.radioshack.com/product/index.jsp?productId=2062246 ||= Radio Shack 270-398 ||
 * = Buzzer MSR516N-VP ||= $0.99 ||= N/A ||= [] ||= Jameco 335564 ||
 * = **Total Cost** ||= **$4.27** ||=  ||=   ||=   ||

Original implementations of the circuit used 2.3V rails to power the 555 timer, turned either on or off to simulate light being sensed. It worked properly in this configuration due to the supplied voltage being either 0 or 3V. When the light sensor was implemented, the 555 timer functioned poorly, causing immediate buzzing when light was sensed. This was due to the transient voltage that appeared on the 555 supply rail due to the supply rail voltage following variations in sensed light. The 555 was supplied voltages between 0-1.8V when the circuit went from a dark to light environment. Since the 555 IC does not function properly below 1.8V, the circuit did not operate correctly.Attempts to hold the trigger and reset inputs low for a duration much longer than the supply voltage transient times were not effective.
 * __Troubleshooting and Addressing Prototype Failures__**

Increasing the time constants of the reset and trigger pins did not alleviate the problem. A zener diode used as a voltage regulator was considered, but was disregarded because it would also provide an unregulated voltage below 1.8V until its knee current was achieved.

Dr.David Braun suggested using a double CMOS inverter stage to mimic a voltage comparator. This ultimately proved successful, and is implemented in the final design. Detailed analysis on its functionality can be read in Circuit Operation section. It essentially forces the 555 supply rail to be either 2.3V or 0V, which fixed the problem.



Click the following to download the LabVIEW test suit: [|FridgeAlert Test Suit].
The objective of the test suit is to assist the engineer to evaluate the operation and the sustainable aspect of the prototype. The LabVIEW test suite was designed to address these two issues.
 * 1) The LabVIEW test suit tests the timing mechanism of the circuit to ensure glitches do occur through everyday opening and closing of the refrigerator.
 * 2) Because the circuit was designed to consume minimal power possible, the test suite also examines its power dissipation. We need to consider the test waveform carefully because there is no 'standard' fridge door opening. Users may frequently open and close the door at small intervals, or perhaps have it open for a long period of time, close it, and then open it again. The power dissipation is displayed through each of these stages and the average power consumption is displayed for the entire cycle.

The FridgeAlert Test Suite front panel is shown in figure 7.1. In order to test the timing mechanism of the circuit, a sequence of test pulses are used to simulate the fridge door opening and closing. With the Elapsed Time module in LabVIEW as the time counts, the custom pulses can be generated with the Agilent Function Generator. The subVI InitFG.vi initializes the Function Generator at the pulses edge and subVI ReadFG.vi read the voltage readings; then, the readings are displayed on the front panel in real time, labeled as the test pulse. Figure 7.2 shows the test pulse sequence. Test pulses are applied to the input of the inverter, the same location where the phototransistor delivers voltage to the circuit. For the first pulse of a 20 second period, the buzzer does not activate because the pulse is only high for 10 seconds. The two pulses with 20 seconds high (40 seconds period) activate the buzzer for about 5 seconds.. The two short pulses (6 seconds and 4 seconds) are implemented to test the resetting functionality of the timer. Through the entier sequence of 6 test pulses, the buzzer should only buzz twice, each with 5 seconds duration.

To determine if the buzzer is on through labview, the voltage across the PNP is measured. When the circuit is buzzing, the voltage across the base-emittor junction is 0.7V, and is 0V when it is not buzzing. The Agilent Digital Multimeter was used to measure the turn on voltage of the PNP and the voltage waveform is displayed in real-time at the front panel, labeled as output waveform. SubVI ReadAMM.vi is used to read voltage data from the Agilent Multimeter.

Finally, the power dissipation is measured from the battery voltage and supplied current. The Keithley Sourcemeter is used for battery voltage measurements and the Fluke Multimeter for the current measurements. SubVI SetKeithl.vi initializes the Keithley as a current source with output current of 0A. Then, subVI ReadKeithl.vi read the voltage data. SubVI, ReadFMM.vi initializes the Fluke Multimeter to take current readings. The product of the source voltage and source current is then display in the front panel, labeled as Power Measurment in real-time. Meanwhile, the average power is calculated and displayed in the front panel. SubVI ProcPlot.vi contains the organization of all the input devices readings. Figure 8 displays the wiring diagram of the test suite and Figure 9 displays its hierarchy.









**__Final Design Evaluation__**
remains open for a duration of 15 seconds. || Circuit is glitch free and only beeps after light is sensed for 15.5 seconds ||  =__User Manual:__= __**How it Works:**__ The FridgeAlert circuit utlizes light sensitive components to detect the presence of light. When placed in a refridgerator, it determines if the refridgerator door is open by detecting the surrounding light conditions. The detection of light activates a timer that turns on a buzzer after 15 seconds. For a detailed explanation of its operation, refer to the **Circuit Operation** section.
 * = **Design Goal** ||= **Final Performance** ||
 * Audible alarm sounds when the refrigerator door
 * DC battery operation, utilizing common battery standards (AAA, AA, or 9V). || Two AAA batteries power the circuit ||
 * Consume less power than the original design idea presnted in ED (2W) || Average power disspation is 5.5mW with a peak power dissipation of 12 mW occuring during buzzing. ||
 * Minimum space requirement (3 X 5 X 1'') || The final protoype measures 2.5" X 3.5" X 1/2" ||
 * Prototype cost below $4.00. || Protoype costs $4.27 per unit. Ordering parts by the bulk would dramatically decrease this cost. ||

__**Requirements:**__ Proper FridgeAlert operation requires an internal light in the refrigerator. The product might work without an internal light source, but operation cannot be guaranteed. Please see the troubleshooting section for recommendations on using FridgeAlert in refrigerators without internal lights.

Place two AAA batteries in the battery compartment. Upon insertion, the circuit will be active and will emit a tone after 15 seconds. To turn off the alarm, place FridgeAlert in a dark environment or briefly put your hand over the light sensor. The light sensor is the clear component next to the buzzer.
 * __Operation__:**

__**Placement:**__ FridgeAlert can be placed anywhere within the refridgerator as long as there is ambient light in its proximity.

Refer to the following figure for clarification on proper connections between the instrument used in the FridgeAlert test suit. All connections are made on the exposed ends of wires on the circuit board. Orientation references (left, right, above, below) are relative to the layout shown in Figure 10.
 * __Connecting to FridgeAlert Test Suite:__**

Recommended connector: Bannana to grabber Positive terminal - Either red wires. Negative terminal - black wire || __Agilent 3401A Digital Multimeter:__ Recommended connector: Bannana to grabber Positive terminal: Purple wire Negative terminal: Yellow/orange Wire || Recomended connector: Bannana to grabber Positive terminal: Left red wire Negative terminal: Right red wire || __Agilent 33120A Function Generator__ Recommended connector: BNC to grabber Positive terminal: Green wire Negative terminal: Black wire ||
 * __Keithley 2400-LV Source Meter :__
 * __Fluke XXX Digital Multimeter:__



__Troubleshooting of the Circuit:__
Replace AAA batteries Get better ears
 * Alarm volume is very low:**

Insert AAA batteries Ensure proper placement of FridgeAlert. FridgeAlert needs to be exposed to the refrigerator's light source. Replace refrigerator light bulb if it is burnt out. The red wire coming out of the battery module must connect to the red wire next to it. It is left unconnected to allow measurement of total current draw through the Test Suite. Ensure that this wire is connected.
 * Alarm does not sound after 15 seconds:**

The light sensor on FridgeAlert is sensitive enough to sense ambient light from outside the refrigerator. Placement is crucial with refrigerators without lights. Place FridgeAlert in a position that can optimally pick up ambient light. It is recommended to put it on the inside of the refrigerator door on a shelf so that it will be directly exposed to outside light when the door is open. It is not recommended to put it in the far back of the refrigerator or in a drawer where little outside light will reach it.
 * Refrigerator Door does not have internal light:**

__Troubleshooting of LabVIEW Suit.__
Ensure that the FridgeAlert circuit is properly connected to the test instruments. To properly connect the circuit, refer to the connections sections. Ensure that there are two AAA batteries placed in the battery holder. Ensure that all GPIB instruments are turned on. Ensure that all GPIB instruments are connected to the computer.
 * Data stays at 0 in the output waveform and power dissipation graphs: **

Ensure that all connectors have the correct polarity applied to the test instrument terminals and the circuit connections.
 * Power dissipation is negative: **

Ensure that the period pulses allow enough time for the timer to activate. Use the default values in the advanced functionality window for a standard FridgeAlert. Replace the two AAA batteries.
 * Circuit does not buzz during test cycle: **

__Teamwork Evaluation__
The team collaberatively decided on labview test suit functionality and general circuit operationg. We then focused our work on designing the circuit and labview test suit. Dan was in charge of circuit assembly, design, and prototyping. Chi designed the labview test suite.

It is difficult for two people to work on labview at a time since only one user can use the mouse at a time. Its also similarly difficult for more than one person to solder and test small circuits. We decided to each focus on different portions of the project to increase our efficiency in completing the task.

While each of the team members focused on their projcut, frequent collaberation and discussion occurred to assist in each other's problems and issues.

__Sustainability Analysis__
According to United State Department of Energy, the United States has an increasing trend in per capita energy consumption (kWh/person), while California' per capita energy consumption has not change since the 1970s [2]. This is the result of the electricity efficiency movement in California in the 1970s. Under the state energy standard regulation, improvements in refrigerator’s energy efficiency have played an important role in this movement. Refrigerators made before 1976 use about 1800kWh energy per year whereas refrigerators made after 2001 use only 425kWh per year [3]. Having 150 million refrigerators with 2001 efficiency rate would save 200 billion kWh of electricity per year, which reduces 194 million tons of CO2 emission from Coal Power Plant (assuming carbon density of coal as 25.8 gC/MJ and the efficiency of the coal power plant as 35%) [4]. This further emphasizes the importance of energy efficiency improvement in refrigerators. All these data also demonstrates that improving energy efficiency did make an impact in sustainability, which leads directly to the sustainability analysis of the design idea.

The FridgeAlert increases the energy efficiency of refrigerators by reducing the loss of excess energy due to refrigerator doors remaining open for too long. Also, its becoming increasingly common for many households to have multiple refrigerators. Using FridgeAlert is a great step for sustainable households.

Economically, this circuit involves the costs of several diodes, resistors, capacitors, an IC (7555), three transistors and a piezoelectric buzzer, for a total cost of $4.27. Each kWh of energy saved not only saves $0.14 of electricity cost, but also reduces 970g of CO2 emission from coal power plant. It only takes about 24kWh energy saved to breakeven with the cost of the circuit. More importantly, it reduces 23.28kg of CO2 emission, which creates a positive environmental impact. In order for this calculation to be fair, the carbon footprint of producing each electronic components and its associated waste need to be considered. Also, we need to account for the energy it takes to power the circuits.

According to the article Natural Capitalism, making a semiconductor chip generates waste that is 1000 times of its own weight [5], which includes the IC chip used in the FridgeAlert. The energy and carbon emission associated with the transportation and process of these wastes is considerable. The good news is that semiconductor manufacturer is creating method to recycle and reuse the waste. For example, IBM Corp has developed a way to recycles scrap silicon for use in making solar PV panel [6]. This provides a win-win situation in which the waste goes into the promotion of renewable energy.

This design idea includes two capacitors. It is important to realize that this tiny electronic component has caused a civil war in Congo due to terrritorial wars in extracting the raw material called Coltan [7]. As described in Hardin’s paper titled The Tragedy of the Commons, the competition to extract earth’s resource eventually drives resources to extinction, especially for non-renewable resources [8]. This kind of competition not only drives the resource to extinction, but can also create social and political unrest, the civil war in Congo being one of them. The Colten War broke out because both the Ugandans and Rwandans wanted to take control of the Colten-rich eastern Congo. This is something we have to think about when we decide to use a capacitor.

The objective of this design idea is to reduce energy consumption. In order to achieve this goal, we have to ensure that the power consumed by the alarm systems will not excess the amount of energy that will potentially save. We hence need to examine the power consumption of each component in this design and try to reduce the power consumption if possible.

__References__
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