Hit-and-Run Detection Camera Group #25: Nick Prozorovsky, Eric Stiles, and Wilson Wang

Introduction  Hit-and-run incidents are common and frustrating  This camera provides proof of the incident  Mounted in rear window of car  Automatically detects accidents  Decreases storage requirement

Features  Automatic detection of an accident using accelerometer  Microcontroller interaction with all hardware  Low car battery detection and product shutdown  User interface with LED’s and buttons  Voltage regulation from car battery to microcontroller

System Overview  Hardware:  Accelerometer  Microcontroller (Raspberry Pi)  Camera  Voltage Regulator  Voltage Comparator  Buttons/LED interface  Software:  Main python script  Accelerometer polling python script  Startup bash script

3. Camera 7. Button/LED Interface 6. Voltage Comparator (PCB) 1. Accelerometer 2. Microcontroller (Raspberry Pi) 4. Voltage Regulator Components

= Signal = Power Block Diagram Data Collection A. Execution B. Accelerometer 1. Microcontroller 2. Camera v Car Battery 5. Voltage Regulator (*v->5v) 4. Voltage Comparator (PCB) 6. Buttons/LED interface 7. = Power = Signal

Accelerometer  Inputs: 3.3V, GND  Outputs: SDA and SCL Data Lines  ADXL 326  ADC  ADXL 345  ± 16 g  2,4,8,16  3.3 V

Microcontroller  Inputs: Power, accelerometer data lines, camera data, buttons, PCB shutdown  Outputs: Accelerometer power, camera data/power, LEDs  Raspberry Pi Model B+  512MB SDRAM  Micro SD GPIO Pins Accelerometer data 5V Input Pin

Camera  Inputs: 3.3v, data control  Outputs: Video data  Continuously running  Up to 1080p30

Voltage Regulator  Inputs: Car Battery  Outputs: 5V  12.6 V to 5 V  V  Original circuit  Voltage Regulator – LM 7805A TO-220  5 mA to 1 A, up to 15W  Rpi draws around.5 A, averaging 2.5W

Car Battery  Inputs: None  Outputs: Approximately 12.6 V DC  Actual amount will vary  Uncontrollable variable  Should not drop below 12 V

Voltage Comparator LM339N Comparator Chip Output Resistor divider circuit regulates output to 3.3V when V+ is above V- LM339N Chip grounds its output when V+ drops below V- Diode holds V- at a constant 6.8V Resistor divider circuit drops 12 V down to 6.8V IN4736A Zener Diode

V- = 6.67 Volts V+ = Vin [R2/(R1+R2)] V+ = 12 [10/(8+10)] = 6.67 Examples: Vin = 13  V+ = 7.22 > 6.67 Vin = 11.9  V+ = 6.61 < 6.67 Vin V+ V- Voltage Comparator Calculations

Conditions: Vin = 11 V V+ = 6.11 V V- = 6.67 V Output should have been grounded, but wasn’t Vin = 7.2 V V+ = 4 V V- = 6.67 Output became grounded Vin V+ V- Voltage Comparator Issue

Voltage Comparator Issue (Cont.) Breadboard circuit conditions: Vin = 12 V V+ = 6.68 V- = 6.67 Output was not grounded Vin = V V+ = 6.66 V V- = 6.67 V Output was grounded Deduction: LM339 Chip on PCB was faulty

PCB Design Voltage Regulator Output V+ V-

Button/LED Interface Volt connection from Raspberry Pi 2.GPIO Output connection 3.GPIO Input connection 4.Ground connection

Button/LED Interface Volt power from Raspberry Pi 2.GPIO output connection 3.Push button 4.GPIO input connection Output Voltage: 5*[9.92/( )] = 3.2 Volts

Software Function Overview (hitNrun.py) def log(string)  Inputs: String to log to USB.  Outputs: None.  Purpose: Log strings to USB for debugging and event timestamps.  Description:  Helper function for debugging.  Logs events to USB.  Helpful when no monitor is attached to Raspberry Pi.

Software Function Overview (hitNrun.py) def moveFiles()  Inputs: None.  Outputs: None.  Purpose: Save files in a folder so they cannot be overwritten.  Description:  Creates new directory with timestamp.  Moves all video files to new directory.  Attempts to copy entire folder to USB.

Software Function Overview (hitNrun.py) def deleteFiles(clipsToKeep)  Inputs: Integer representing the number of looping clips to keep.  Outputs: None.  Purpose: Deletes oldest clips to save storage space.  Description:  Ensures less than ‘clipsToKeep’ total video clips.  If more, deletes oldest video clip.

Software Function Overview (hitNrun.py) def deleteDirectories(direcsToKeep)  Inputs: Integer representing the number of saved directories to keep.  Outputs: None.  Purpose: Deletes oldest saved directories to save storage space.  Description:  Ensures less than ‘direcsToKeep’ total saved directories.  If more, deletes oldest saved directory.  Reduces false-positive saves.

Software Function Overview (hitNrun.py) def check_accel()  Inputs: None.  Outputs: Character in the signal text file.  0 – Accelerometer is not triggered.  1 – Accelerometer has been triggered.  2 – Accelerometer is disconnected.  Purpose: Communicates with accelerometer script to determine when to save files.  Description:  Reads from signal file to determine accelerometer status.  Returns code to main function to determine appropriate action.

Software Function Overview (hitNrun.py) def check_buttons()  Inputs: None.  Outputs: Whether or not files need to be moved.  0 – No buttons are pressed.  1 – Manual save button pressed.  Shutdown – Reset button pressed or input voltage too low, shuts down Raspberry Pi immediately.  Purpose: Interfaces with buttons and PCB directly to receive user-inputs.  Description:  Buttons have to be held down for >3 seconds so buttons are not accidentally pressed.  If manual save button held, return 1 to main file to indicate file save.  If PCB outputs voltage high or reset button held, powers down Raspberry Pi.

Software Function Overview (hitNrun.py) def powerdown(option=0)  Inputs: Optional integer value to indicate power down or restart  Outputs: None  Purpose: Helper function to power down the Raspberry Pi.  Description:  Shuts down Raspberry Pi by default.  If ‘option’ specified, attempt to restart Raspberry Pi.

Software Function Overview (hitNrun.py) def main()  Inputs: None.  Outputs: None.  Purpose: Initializes variables, starts camera recording, calls all helper functions and takes appropriate actions.  Description:  Initializes variables, turns red LED on to indicate power.  Camera started, constantly checks accelerometer and buttons.  If accelerometer triggered or manual save button, sleep for ‘clipLength’ time and save all video files.  If accelerometer error, save video files and blink red LED, wait for reset.  Call deleteFiles and deleteDirectories functions to clean up old files.

Software Function Overview (accel.py) def writeToFile(option)  Inputs: Character to write to signal file.  Outputs: None.  Purpose: Writes signal character to signal file to communicate with main script.  Description:  Opens up signal file.  Writes accelerometer status to file.  Closes file pointer.

Software Function Overview (accel.py) def main()  Inputs: None.  Outputs: None.  Purpose: Reads accelerometer axes to determine if threshold is exceeded or if an error is present.  Description:  Infinite loop to get data from accelerometer, writes data to USB file for graphing.  If accelerometer values exceed threshold, alert main script.  If accelerometer error, alert main script.  If trigger or error, wait for 5 seconds so main script has time to acknowledge.

Software Function Overview (start.sh) None  Inputs: None.  Outputs: None.  Purpose: Bash script to launch on startup and start both python scripts.  Description:  Starts both python scripts in background.  Attempts to copy new USB scripts to update scripts for next bootup.

Software Flowchart

Accelerometer Verification -Rotation of device on all three axes -Shows 1g on each axis when rotated -1g = 9.8 m/s 2  Accelerometer is functioning properly

Accelerometer Data Product run-through in Car 1. Slamming car door (.5g) 2. Slamming car trunk (.8g) 3. Hitting a pothole (.65g) 4. Slamming on brakes while traveling 30mph (1.25g) Results: Normal activity will not cause false positives if tripping value is 2g’s

Accelerometer Data (Cont.) -Data collected from shaking device -Triggers at magnitude of 3g’s -Offset of 1g due to gravity

Rear End Collision Acceleration -Acceleration from collisions are all 3g’s or greater -Set tripping value to 2g’s -False positives ignored -Accidents will be captured Table taken from “Real World and Vehicle Test Data” from the Motor Insurance Repair Research Centre Rear End Collision Data

Requirements and Verifications  Product powers on from voltage regulator  Accelerometer triggers at correct values  Footage is saved and events are logged on USB  Device shuts down with low voltage volts instead of 12)  Buttons and LED interface properly interact with software

Current Limitations/Future Work  Replace faulty comparator chip  Replace voltage regulator/heat sink with one rated for higher power  Send data to cloud storage  From lab to car:  Way to mount system down so camera and accelerometer are stable  Way to wire/power it up throughout the car  Car batteries are not all same, they won’t all be in 12.6v-12v range  Raspberry Pi still draws a very small amount of current even when powered down

Thanks!