Enhanced Security Rotary Pattern Recognition Lock

Transcription

1 Enhanced Security Rotary Pattern Recognition Lock Group #11 Design Review TA: John Capozzo Group Members: Taiming Zhang Jingjing Li Oct 9 th,

2 Table of Contents 1. Introduction Statement of Purpose Objectives Goals & Benefits Functions & Features Design Specification Block Diagram Block Description including Schematics, Calculations, and Simulations Pattern Recognition (Rotary Encoder and Potentiometer) a Rotary Encoder & LED circle b Potentiometer Force Sensing Resistor UVLO and Low Power Indicator circuit a UVLO b Low Power Indicator circuit Bolt Control with Motor Microcontroller Requirement and Verification Requirement and Verifications Table Tolerance Analysis Tolerance Analysis for Potentiometer Cost and Schedule Labor Cost & Part Cost Total Cost Schedule Safety and Ethics Safety Statement Ethic Citations

3 1. Introduction 1.1 Statement of Purpose The gym is the place where we can see various kinds of locks, but each kind of locks has its disadvantages. For example, people find it inconvenient to bring keys during workout, so they commonly use combinational padlock instead. However, such locks are way too easy to decipher. It will only take less than one hour to try all possible combinations even in the worst scenario. Additionally, highly secure biometric locks such as fingerprint locks are not practical to be designed in a portable manner and they often consume too much energy, making it impossible for the battery to supply. As a result, portable locks with more passcode combinations are needed. 1.2 Objectives Goals & Benefits Goals Our lock will focus on short-time storage in lockers such as gyms and supermarkets. Inspired by the existing directional combination padlock [1] which allows the user to define their unique pattern by pushing a knob into four different directions (up, down, left, and right), we would like to improve the complexity of passcode so that the user could create an even more secure pattern. The lock that we design will provide the user with an intuitive way of inputting their passcodes. Specifically, we propose to design an electrical rotary pattern recognition lock that takes initial position, angle of rotation, and direction of rotation as passcode inputs. Users are allowed to store at most three rotary patterns as their passcodes (Each rotary pattern should not exceed 360º). The number of combination in our lock is amazingly large. For user-friendly purpose, we will divide the circle into 36 states of positions with each corresponding to 10º. For each rotary pattern, users have 36 different positions to starts with; the remaining 35 positions can be used as the ending position, and they also have options to rotate clockwise or counterclockwise. If a user creates three such rotary patterns, the number of combinations can be derived 3

4 as (36*35*2) 3 = 1.6*10 10, which is about times more than traditional padlocks. Benefits No key required for entry. Less expensive than biometric locks such as fingerprint locks. More passcode combinations than keypad lock Functions & Features Similar to the knob in the game controller of PS4, a rotary knob with arm will be used for the users to first push and hold the knob at a certain position, rotate the knob by certain angles, and finally release and bounce back to its neutral position. Such processes can be repeated at most 3 times to form unique patterns of users. Low power indicator light will notify users when battery power runs low, and voltage lockout function will be integrated to prevent the lock from heavily discharging the battery. The alarming system will sound when the lock is pulled by brute force for notification purpose. 2. Design Specification 2.1 Block Diagram Figure 1: Top-Level Block Diagram 4

5 Figure 2: Full project schematic 2.2 Block Description with schematic, calculation, and simulation Pattern Recognition (Rotary Encoder, LED Circle and Potentiometer) a Rotary Encoder & LED Circle The rotary encoder enables the main functionality of our design. It takes inputs from the patterns entered by the user and returns outputs, the angle of rotation, as digital signals. The input of this block is connected to a rotary knob, which could be rotated freely by the user, and the output is connected to the microcontroller for passcode comparison and storage. We will use a 2-bit quadrature rotary encoder (25LB10-Q) that, in every cycle, contains 36 states of positions with each corresponding 10 degrees. It is a mechanical rotary encoder that requires no power supply. The encoder outputs a 2-bit (A and B) string and repeats itself every four states. A set of LEDs (36 in our case) will be placed around the knob to indicate the starting/ending location as well as the path the knob rotates. It takes input from the microcontroller and powers with 5V power supply. Due to repeating binary strings in one cycle, one cannot distinguish the initial position from only the rotary encoder. Therefore, a self-made potentiometer is used to facilitate the 5

6 determination of its initial and final position. When the user pushes the knob outward, the knob touches the circle-shape potentiometer; analog output voltage produces and is used as the input of microcontroller, according to which we can determine the starting point. For the rotary encoder, each of the position is assigned to two-bit binary code in our design, so there are in total 4 outputs: 00, 01, 10 and 11. However, when we are rotating from the forth position to the fifth position, ie. from 11 to 00, both bits will change. (clearly shown below in Table 1) This will result in some errors if the switches inside the rotary encoder are not ideal. When both bits are changing, the output will read some spurious positions. Which is why we need to use the gray code. The gray code is designed so that each of adjacent position code is differ by only one symbol [2]. In our case, 00, 10, 11, 01is the optimal gray code. Note that the rotary encoder we are using (25LB10-Q) has a built in gray code so that we do not have to worry about implementing it, but we do want to make sure that the gray code is taken care of in our design. Position Number Encoder Value (with gray code) Encoder Value (without gray code) Table 1: Encoder value comparison (gray code vs no gray code) 6

7 Rotary encoder Figure 3: schematic of rotary encoder Input: Patterns entered by users. Output: 2-bit binary string from rotary encoder. Power: 5V DC Calculation In order to determine whether the knob is going clockwise or counterclockwise, we need to draw the k-map of the logic. Note that A 1 B 1 is the first two-bit output from the rotary encoder and A 2 B 2 is the next two-bit output. A 1 B x 1 x 0 A 2 B x 1 x 11 x 0 x x 0 x Table 2: K-map for determining clockwise or counterclockwise 7

8 For the output of Table 2, 1 stands for clockwise, 0 stands for counterclockwise and x stands for do not care. We could simplify the logic to a simple equation: B 1 A 2 +B 1 A 2. Thus we could determine which direction the knob is rotating by inputting the first two 2-bit outputs from the rotary encoder and deriving the direction with the above equation. Angle of rotation Due to the fact that the outputs of rotary encoder repeat itself every four positions (9 repetitions in one cycle), we cannot directly find the angle of rotation by subtracting the outputs of initial position from the outputs of final positions. Here, we introduce a simple algorithm that runs in the microcontroller to determine the angle of rotation. Figure 4: Algorithm for getting the angle of rotation b Potentiometer We will use a self-made potentiometer to determine the position of the rotary knob. The circuit schematic we built is shown below in Figure 5&6. When the knob contacts with the potentiometer, the circuit starts to work. We apply 5 V to the potentiometer and the pull-down resistor and the voltage output will be mapped to the position. Different positions on the potentiometer will be corresponding to different resistances (we divided the potentiometer into 8 resistors, 9 regions, each corresponding to 40 degrees) and thus different voltages. We will use both the output from the potentiometer circuit and the output from the rotary encoder to determine the initial position of the knob. 8

9 5V Vout Figure 5: Schematic of Potentiometer Block Figure 6: Sketch of pattern recognition configuration 9

10 Input: Patterns entered by the user. Output: Analog voltage at V out. Power: 5V DC. Calculation To determine the resistance of both the potentiometer and the pull-down resistor, we have two constraints to satisfy. Note that we will use x as the value of pull-down resistance and y as the value of each of the potentiometer s resistance. First, we have the constraint from the resolution. The microcontroller only has limited bits in ADC (Analog to Digital Converter), so the resolution is limited as well. So we can derive the equation below: The left side of the equation (1) is the minimum voltage difference that could happen in our design and the right side of the equation is the resolution of the voltage. Note that n stands for the number of bits in ADC. Then we need to take power consumption into consideration because the resistor will burn out if it exceeds maximum power. For pull-down resistor, we have: (1) (2) For Potentiometer, we have: (3) By solving Equation (1), (2), and (3), we get the theoretical value of x=10kω and y=10kω Next, we can calculate the mapping between the voltage output and the position. Note that we will use k as the position number (from 0-8). 10

11 After plugging in x and y, we solve for k and round it to the nearest integer to get the position number, Force Sensing Resistor ( ) The force-sensing resistor is used to detect if anyone is trying to open the lock with brute force. When a brute force is trying to lift the shackle, the shackle will apply great force to the force-sensing resistor causing it to bend and thus change the resistance of it. The force-sensing resistor is applied to a 5V voltage source and is in series with a pull-down resistor. The voltage in the midpoint between two resistors is output to the microcontroller for further calculation. If the calculation result is positive, then the microcontroller will output a signal and cause the buzzer ( LC) to sound. The buzzer has an input of 5V and outputs around 2kHz and 60dB audio signals. V out 10k Figure 7: Schematic of FSR circuit Input: Force applied on FSR. Output: Analog voltage at V out. Power: 5V DC. V out is then connected to a digital input pin of microcontroller. If V out is above a threshold voltage, the microcontroller will then send a signal to the 2-1 MUX where 5V V cc and 11

12 GND are connected as its inputs and the output is connect to a buzzer. Figure8 shows a simple MUX schematic made by logic gates. If the microcontroller inputs a digital HIGH to the MUX, the buzzer will be connected to 5V and produce sound; if the microcontroller inputs a digital LOW to the MUX, the buzzer will be connected to ground and remain silence. buzzer Figure 8: MUX schematic made by logic gates Calculation From the datasheet [2] we know that when the force-sensing resistor is flat, the resistance is as high as When the FSR is not triggered, so that (shown below in Figure 9). V out > 1V When the FSR is triggered, so that (shown below in Figure 9). Power Consumption When the FSR is not triggered (at steady state), the power consumption is When the FSR is triggered (at alarm state), the power consumption is 12

13 As we can see, even if the circuit is always working, the power consumption, in either case, is significant low such that the general power consumption of our design remains low. Simulation Force applied No force applied Figure 9: Parameter Sweep Resistance VS Voltage Figure 10: Force VS Resistance [3] 13

14 2.2.3 Under voltage lockout circuit and low power indicator circuit We would like to avoid over-consuming of battery, because over discharging lithium-ion battery would cause side effects such as capacity degradation and internal short circuit [4]. Therefore, an under voltage lockout circuit is needed for safety purpose. Meanwhile, the low power indicator circuit also alerts the users when the battery power runs low to avoid device function abnormally. We will introduce each circuit as well as the calculation in the following section a Under voltage lockout circuit ( Enable pin circuit design) The under voltage lockout circuit cuts off the current through the device when the voltage is below a threshold voltage and prevents the lithium-ion battery from over consumption. Because we use a 9V (8.4V in reality when the battery is fully charged) rechargeable battery as power supply and the required voltage for most of the components in our project is 5V, we need a step-down voltage regulator. Here, we choose TPS7A6150-Q1 automotive 300-mA 40V low-dropout regulator where an enable pin is provided to shut down the output voltage of the regulator when the input voltage is below a threshold voltage. The enable pin reads voltage below 1.6V as LOW and reads voltage above 2.2V as HIGH. Hence, we would like to design a circuit that could produce a voltage below 1.6V to shut down the output voltage when the battery is below 7.4V. Figure 11 shows the circuit schematic that is connected to enable pin. 9V Figure 11: Circuit schematic of UVLO enable circuit 14

15 Calculation R 1, R 2, & zener diode We need to set the values for three resistors and a zener diode in the above circuit. When the voltage of the battery is right at 7.4V and we assume the zener diode is in breakdown region (denoting breakdown voltage as V z ), we will first arbitrarily choose a zener diode whose break down voltage V z =6V. The npn transistor is ON and V BE,ON =V R2 =0.7V, and the voltage across R 1 is V R2 =0.7V & V R1 = V battery V R1 V z =7.4V 0.7V 6V =0.7V For BJT transistor at the edge of ON and OFF region, there is no current flowing through the base. The currents through R 1 and R 2 are the same, then we have R 1 =R 2. We might need to pick a large resistance to get a smaller power consumption as R 1 and R 2 here are only used for voltage divider purpose. We thus pick R 1 =R 2 =10kΩ. R 3 We first need to understand three transistor regions with corresponding battery voltage. 1. When V BE is less than 0.5V which corresponds to a battery voltage less than 7V, the transistor is in cut-off region; there will be no current flowing through R 3 and V c =V battery. 2. When V battery is between 7V and 7.4V, the transistor is in forward active region. V c is determined by the current, I c, that flows through R When V battery is above 7.4V, the transistor is in saturation region. V c is the saturation voltage, V CEsat = 0.2V. Given these three situations, we need to add an inverter before connecting our circuit to the enable pin. We can also see that the transistor will experience the forward active region between cur-off and saturation region. In order to avoid ambiguity of the voltage read by enable pin, we might want to transit the forward active region as fast as possible. For transistor in forward active region, we have V CE = V battery I b R 3 (4) At node 1 in Figure 11, we apply a Kirchhoff current law and derive equation (5) V VEon R 2 + i b = V battery V z V R1 R 1 (5) 15

16 where V BEon =V R1 =0.7V, R 1 =R 2 =10kΩ, and V z =6V. Combining and simplifying Equation (4) and (5), we get Equation (6) V CE = V battery (1 R 3 10k )+7.4V R 3 10k (6) If we take the derivative of Equation (6) with respect of V battery, we can get the following dv CE dv battery =1 R 3 10k Since we prefer the rate of change in V CE with respect of battery voltage as fast as possible, we can easily see that we need a large R 3 and we thus pick R 3 to be 30kΩ. Simulation Figure 12: Simulation of V CE (Red) and V out (Green) in DC sweep From Figure 12, we simulated a DC voltage sweep from 6.0V to 8.5V and measure the voltage of V CE and V out. We can see that the V out produces a 3.5V(greater than 2.5V read by the enable pin as HIGH) voltage when the battery voltage is above 7.4V; V out is 16

17 nearly 0V(less than 0.8V read by the enable pin as LOW) when the battery voltage is below 7.0V. After we have design the UVLO circuit that connects to the enable pin in the voltage regulator, we can refer to the application section in datasheet [5] to connect the voltage regulator to the battery b Battery life indicator light The battery life indicator light is used to indicate whether the battery is running out of power so that the user can replace the battery before the UVLO circuit shuts down the power. An LED will light up when the battery voltage is below 7.7V, approximately at 36% battery life [6]. We are using two NPN transistor, one zener diode, four resistors and an LED to build the circuit. The circuit schematic is shown below in figure 13. Figure 13: Schematic of low power indicator circuit Calculation Before we make any calculation, we first need to clarify the states of the transistors with different battery voltage. When the battery voltage is less than 7.5V, the left transistor will be in saturation region and the right one will be off. When the battery voltage is 17

18 greater than 7.6V, the left transistor will be off and the right one will be in saturation region. Between 7.5V and 7.6V, both transistors are in forward active region. For VBattery > 7.6V, we have VCE1 = 0.2V = VBE2 < 0.7V, so the right transistor is verified at off region. So no current is going through R4, the LED will be off. For VBattery < 7.6v, we have VBE1 < 0.7V, so the left transistor is verified at off region. Then Ib2 will equal to the current going through R3 and the right transistor will be on. So Ic2 will go through R4 so that the LED will be on. R1 & R2 We need to set the values for three resistors and a zener diode in the above circuit. When the voltage of the battery is right at 7.4V and we assume the zener diode is in breakdown region (denoting breakdown voltage as Vz), we will first arbitrarily choose a zener diode whose break down voltage Vz=6V. The npn transistor is ON and VBE,ON=VR2=0.7V, and the voltage across R1 is For BJT transistor at the edge of ON and OFF region, there is no current flowing through the base. The currents through R1 and R2 are the same, then we have R1:R2 = 2:7. We might need to pick a large resistance to get smaller power consumption as R1 and R2 here are only used for voltage divider purpose. We thus pick R1=4kΩ, R2=14kΩ. R3 & R4 The choice for R3 and R4 is rather arbitrary since we do not have a strict restriction for them. But we do want to make sure the power consumption is as low as possible, so big values for R3 and R4 is preferred. We also want to make the forward active region as small as possible. With the same derivation shown in the UVLO circuit, we can easily get So we want R4/R3 to be small in this case, the derivative is positive. So we arbitrarily choose R3 = 20kΩ and R4 = 1kΩ. 18

19 Simulation Figure 14: Voltage drop across LED in DC voltage sweep of battery In Figure 14, we simulated a battery voltage DC sweep from 0V to 10V and measure the voltage across the LED (difference between red and green line). As we can see, when the battery voltage is less than 7.7V, the voltage drop across LED is approximately 0.7V, which turns the LED on Bolt Control with Motor This bolt control block takes output from microcontroller as input. When the microcontroller gives the signal that the lock is ready to be unlocked, the bolt control will enable the motor to pull the bolt as well as the force-sensing resistor in to unlock the lock. When the button on the bottom of the shackle is pressed (the user is trying to lock), the bolt control will enable the motor to rotate in the other direction to push the bolt and the force sensing resistor back the locked position. The microcontroller communicates the servomotors through PWN signal (Pulse-width modulation) [7]. The main use of this technique is to control the power supplied to the 19

20 electrical device. The average value of voltage fed into the load is controlled by turning the switch between load and supply on and off; the longer the switch is on, the more power is supplied to the load. Calculation We need to calculate the time it takes for the servo arm motor to lock/unlock the lock. By referring to datasheet [8], we know that its angular speed is 60º/0.11sec. Flow Chart Flow Chart 1: Bolt Control 20

21 2.2.5 Microcontroller (ATmega328P) The microcontroller in this project is ATmega328P that performs logic operations including comparison and store the pattern entered by the user. It has 28pins, including 6 analog inputs and 17 digital I/O pins. It is powered by 5V and contains built-in 10-bit ADC. It generates output signal to the servo arms when passcode matches and it controls the buzzer if the FSR detects anyone trying to break the lock. The logic flow chart of the software runs on the microcontroller is shown below in flow chart 2 and 3. And the pin connection configuration is shown in Figure 15. Figure 15: Microcontroller pin configuration 21

22 Flow Chart Flow Chart 2: Software overview. 22

23 Flow Chart 3: Detailed description of a particular step in Flow Chart 2 Inputs: Analog voltage inputs from both FSR and Potentiometer module, 2-bit digital string from rotary encoder, two buttons from both bolt control and interface module. Outputs: 1-bit digital signal to buzzer, 2-bit digital signal to servo arm. Power: 5V DC. 3. Requirements and Verifications 3.1 Requirements and Verifications Table Module Requirement Verification Points Out of 50 Microcontroller 1. The microcontroller can

24 (10 points) distinguish the minimal voltage difference between two consecutive positions on potentiometer when its ADC has more than 7 bits (a) Use a microcontroller with an 8-bit ADC (b) Connect the output of microcontroller to an oscilloscope. (c) Use the analog voltage output of potentiometer as the input of microcontroller. (d) Make sure the two consecutive positions produce different digital outputs. (e) Discard two bits on the LSB side to make the ADC 6-bit. (f) Repeats procedure (b)-(d) to see if it still can produce different digital outputs. (The answer should be NO) points 2. The microcontroller is still able to read the stored binary strings in EEPROM even after the powered was disconnected once. 2. (a) Connect the microcontroller with 5V power supply. (b) Store an arbitrary binary string into EEPROM using Arduino IDE. (c) Disconnect the microcontroller from the power supply. (d) Wait for 3 minutes and reconnect the microcontroller to the power supply. 5 points 24

25 (e) Read the binary string from EEPROM in the microcontroller and check it the string is the same as that we stored. Alarming System (10 points) Force Sensing Resistor (FSR): 1. When applied a 5kg force, the output voltage of the FSR block is read as HIGH by microcontroller. 1. (a) Connect a 5V power supply to the FSR block. (b) Connect the output of FSR block to the microcontroller as its input. (c) When 5kg weights is hung on FSR, read digital value from Arduino IDE. (d) Make sure the value is 1. 5 points 2. When FSR is flat, the output voltage of the FSR block is read as LOW by microcontroller 2. (a) Connect a 5V power supply to FSR block. (b) Connect the output of FSR block to the microcontroller as its input. (c) Keep the FSR flat and read digital value from Arduino IDE. (d) Make sure the value is 0. 5 points 25

26 Bolt Control 1. The motor is able to push 1. 5 (5 points) and pull (lock and unlock) (a) Connect the microcontroller points the bolt within 0.5 seconds to a 4.8V voltage source. when the motor is powered (b) Connect the motor to the by ±4.8V. microcontroller. (c) Program the motor to continuously rotate between lock and unlock position for ten times. (d) Use stopwatch to record the times it takes, and divide the time by 20. (e) Compare the time (after divided by 20) with 0.5 seconds to see if it satisfies the requirement. Pattern Rotary Encoder: Recording 1. The microcontroller is 1. 5 (10 points) able to tell the angle of (a) Connect the microcontroller points rotation from the rotary with a 5V power supply. encoder. (b) Connect the output of the rotary encoder to the digital I/O of the microcontroller. (c) Rotate the rotary encoder by a certain degree. (d) Use the algorithm in Figure 4 to determine the angle of rotation and read the value from Arduino IDE. (e) Make sure the value from 26

27 Arduino IDE is the same as the angle we rotated. 2. The microcontroller is able to tell the direction of rotation from the rotary encoder. 2. (a) Connect the microcontroller with a 5V power supply. (b) Connect the output of the rotary encoder to the digital I/O of the microcontroller. (c) Rotate the rotary encoder to an arbitrary direction. (d) Use logic equation derived from Table 2 to determine the direction of rotation and connect a LED to the output of the microcontroller. (e) Make sure the LED is on when it is rotated clockwise and off when it is rotated counterclockwise 5 points Potentiometer: 1. The microcontroller is able to distinguish two consecutive positions from potentiometer when the potentiometer supply 1. (a) Connect the analog voltage output to the microcontroller. (b) Connect a 4.3V voltage supply to the potentiometer. (c) Make sure the digital outputs of microcontroller are 5 points 27

28 Power System (10 points) voltage is above 4.3V(derived in the tolerance analysis section) Low power indicator circuit: 1. The indicator LED is on when the battery voltage is below 7.6V. different between 8 th position and 9 th position (extreme case). (d) Connect a 4.2V voltage supply to the potentiometer. (e) Make sure the digital outputs of microcontroller are same between 8 th position and 9 th position (extreme case). 1. (a) Connect the indicator circuit to a DC power supply. (b) Set the DC power supply to be 7.5V. (c) Make sure the LED is ON. (d) Set the DC power supply to 7.8V. (e) Make sure the LED is OFF. 5 points Under voltage lockout circuit: 1.The circuit will shut down the regulator when the battery voltage is below 7.0V. 1. (a) Connect the UVLO circuit to a DC power supply. (b) Connect the UVLO circuit output to Enable pin in 5V voltage regulator. (c) Set the power supply to be 6.9V. 5 points 28

29 (d) Measure the voltage across the output of the voltage regulator with a multimeter. (e) Make sure the multimeter reads the value below 0.5V. 3.2 Tolerance Analysis The tolerance analysis of our lock design will specifically focus on minimal and maximal limits of parameters such as voltage, resistance, and capacitance, in order for the device to function properly. For wireless charging module, we have to guarantee the output voltage that connects to the battery is a constant 10V; for pattern recording module, the microcontroller needs to distinguish two consecutive positions of the analog inputs from potentiometer. This analysis takes some parameters that could possibly change during the usage into account so that each module can always function correctly Tolerance Analysis for potentiometer Since we are using battery as our voltage source, it is very likely to be the case where the voltage will not be constant at 5V when the battery is running low. We are interested in investigating the lowest possible voltage that still maintains the full functionality of our lock. So tolerance analysis needs to be introduced to ensure that the mapping between the voltage and the position still gives the correct result. In other words, we need to calculate the lowest voltage that does not affect the correctness of mapping. We denote x as the value of pull-down resistance, y as the value of each resistor in potentiometer, and k as the region number (from 0 to 8). Then we get the voltage output to be: Plugging back into the equation: 29

30 Then we solve for the low voltage: which means the potentiometer block can output the correct position when input voltage is above 4.29V. This is low enough because we expect the battery to keep working when voltage is above 4.29V. We will use a 9V battery and add a 5V regulator to keep the voltage constant at 5V. 4. Cost and Schedule 4.1 Labor Cost & Part Cost Labor Cost Name Hourly Total Hours Total = Hourly Rate *2.5*Total Rate Invested Hours Invested Jingjing Li $ $15000 Taiming Zhang $ $15000 Total 400 $30000 Parts Cost Part Part Number Unit Cost Quantity Total LED s HLMP3401 $ $13.86 Buttons MS $ $

31 Microcontroller ATmega328P $23 1 $23 FSR $ $10.97 Buzzer LC $ $4.49 Battery ELB 840 9V Li-ion Battery $ $15 Capacitor 33µF 50V $ $0.9 Resistor 10kΩ 0.5W $ $ Ω 1W $ $ kΩ 1W $ $0.25 Rotary Encoder 25LB10Q $ $18.23 Zener Diode 1N5235 $ $3.48 1N5233 $ $2.49 MUX 74C157 $ $1.05 5V Regulator TPS7A6150-Q1 $1.2 1 $1.2 BJT Q2N3904 $ $0.45 Servo arm DSP75 $ $15.99 Total $

32 4.2 Total Cost Cost Labor $30000 Parts $113.9 Total $ Schedule Week 9/19 Week 9/26 Week 10/3 Week 10/10 Week 10/17 Week 10/24 Jingjing Li Mock Design Review preparation, eagle assignment Design Review preparation Design the lock model, Design Review Start designing buzzer and force sensing resistor circuit and the LED circle and the indicator light/button, Soldering assignment Test the Pattern Recording Block and the buzzer and force sensing circuit, Design PCB on eagle Programming the microcontroller (Alarming system), Individual progress report Taiming Zhang Mock Design Review preparation, eagle assignment Design Review preparation Design potentiometer rings and solder resistor onto the rings, Design Review Test potentiometer block under different supply voltages, Design Bolt Control Block, Soldering assignment Test bolt control, Adjust servo arms to meet the desired moving speed and position Design PCB on eagle Programming the microcontroller (Bolt control), Submit PCB design, Individual progress report 32

33 Week 10/31 Week 11/7 Week 11/14 Week 11/21 Week 11/28 Week 12/5 Programming the microcontroller (Main function including pattern storage and pattern comparison), Test the pattern recording module in microcontroller Assemble the lock, Building the UVLO circuit and the low power indicator circuit submit final PCB design Test the UVLO circuit and the low power indicator circuit, Mock Demo Solder components onto PCB, Demo Registration Demo Prepare for final documentation Presentation, Final paper write up Sign-out lab equipment Assemble the lock, Test the alarming system and the buzzer. Test the pattern recording module. Programming the microcontroller (Debugging), Test the bolt control module in microcontroller Assemble the lock, Test the voltage regulator circuit, Mock Demo Test the full circuit, debug each block and check each block with R&V table, Assemble the lock, Demo Registration Demo Prepare for final documentation Presentation, Final paper write up Sign-out lab equipment 5. Safety and ethics 5.1 Safety Statement Our goal is to design a safety device so we want to make sure the product itself is safe. This product contains high voltage component so it is necessary for us to take safety precautions. 33

34 Here is a list of safety guidelines to follow when dealing with the lock either in lab or somewhere else: 1. Do not modify any part of the circuit when the power supply is not cut off 2. Keep all components working at designed environment (Temperature, pressure, voltage, current, etc.) 3. Do not put the product close to any liquid 4. Do not overcharge the battery 5. Always double-check the voltage to prevent any breakthrough 6. Unplug the wall plug immediately if something is not functioning properly 7. Always have at least two people working in lab Normally, our product is safe to use. 5.2 Ethics The IEEE Code of Ethics [9] will be our guide while accomplishing our final goal in this project. We will strictly follow them throughout the semester. The following are the statements apply directly to our project, we agree: -to accept responsibility in making decisions consistent with the safety, health, and welfare of the public, and to disclose promptly factors that might endanger the public or the environment; Since our project involves a 120VAC input, there is a potential risk of electrical shock which may cause severe consequences. We will follow the guideline listed in the safety statement and always look out for potential risks. We will make sure that there are no exposed conductors when someone else is playing with it. In addition, we ensure that we will use environmentally friendly materials. -to be honest and realistic in stating claims or estimates based on available data; 34

35 We will only make reasonable assumptions and claims based on data from simulation, experiment, or credible references. And after we made the estimates or claims, we will always go back and double-check the reliability of them. -to seek, accept, and offer honest criticism of technical work, to acknowledge and correct errors, and to credit properly the contributions of others; We will always be more than happy to seek and accept honest criticism of our work throughout the semester. We can both provide and accept criticism when we are doing peer reviews. Also, we will include all references in the reports and make sure to credit the contributions of others properly. -to assist colleagues and co-workers in their professional development and to support them in following this code of ethics. We will help each other throughout the project. We always remember that we are a team and support each other with everything we get. 6. Citation [1] 2-1/8-inch (54mm) Wide Speed DialTM Set Your Own Combination Directional Padlock. The Master Lock Company, 2016, Accessed Sep. 19, [2] Gray Code. Wikipedia, Accessed Oct 14, [3] FSR 400 Series Datasheet. Interlink Electronics. Accessed Oct 1,

36 [4] Mechanism of the entire overdischarge process and overdischarge induced internal short circuit in lithium-ion batteries. National Center for Biotechnology Information. Accessed Oct 14, [5] TPS7A6xxx-Q1 300-mA, 40-V Low-Dropout Regulator With 25-µA Quiescent Current Datasheet. Texas Instrument. Accessed Oct 14, [6] How does capacity correlate with charge voltage for lithium ion batteries. Power Stream. Accessed Oct 14, [7] Pulse-width Modulation. Wikipedia. Accessed Oct 14, [8] 7.5 Gram Super Sub-Micro Digital Prog Servo, DSP75. E-flite. Accessed Oct 1,2016. [9] IEEE Code of Ethics. IEEE org, Accessed Oct 1,