Vehicle Detector for Cyclists Nathaniel Liu Parth Narielwala Ian Simon

Introduction Radar detects vehicles up to 30m Camera provides mirrored rearview on LCD –Alerts user when radar detects

Purpose/Motivation To help deaf and hear-impaired cyclists Promote safer riding 1: 1 2: 2

Block Diagram

FMCW Radar FMCW: Frequency- Modulated Continuous- Wave – Signal constantly changes in frequency around fixed reference Change is usually linear – Used to detect stationary objects Unlike Dopplar Radar Red: transmitted signal Green: received signal

Radar Block Diagram

Signal Power Transfer

Sawtooth Wave Generator Beagle Board couldn’t create a sawtooth wave –Needed to build with analog components Analog * Figure from

Sawtooth Wave Generator

VCO: 1.7V  GHz 3.2V  GHz

Microstrip Design VCO –Wilkinson Power Divider –Microstrip Impedance High Frequency Amplifier –Microstrip Impedance

Microstrip Design

Microstrip Design * From Microwave Engineering, By: David M. Pozar

Microstrip Design

Microstrip Design: VCO

Microstrip Design: Amplifier

Microstrip Design: Amplifier

VCO: Voltage-Controlled Oscillator

Post-Mixer Signal Output No reflective metal:

Post-Mixer Signal Output Reflective Surface ~1m:

Problems with Finding Δf Mismatched impedances –Reflection dominates return signal Resonant frequencies from sawtooth –Reasoning for 230 Hz differences

Signal Detector BeagleBoard couldn’t do Digital Signal Processing Created circuit to detect incoming signals of a certain level by thresholding Alerts BeagleBoard via GPIO

Signal Detector

GPIO Input voltage – 1.8V “high” 0V “low” First reads samples signal Second called by code –High is default

MicroController BeagleBoard-Xm (BeagleBoard.org) Archlinux OS (archlinux.org) Features essential to project: –S-video(TV out) –RS232 Serial Port –Ethernet Port –USB Ports –GPIO Ports

BeagleBoard Functions This microcontroller needs to take in an image from a webcam, flip it, and then display that on a 3.5” LCD module Upon a received signal from the FMCW sensor, the microcontroller needs to output a caution image in the upper left hand corner of the display, overlaying the video feed. The display must also show the battery level(Either full, half charge, or low battery)

Rearview Camera

Difficulties/Bugs Could not find a proper linux-based operating system that would work on the BeagleBoard. –Came across issues with obtaining proper boot files Displaying a the desktop GUI on the LCD module through the s-video was not working –Had to do with xorg.conf files in the system files of archlinux All problems were solved content/uploads/2011/04/xfce_logo.png

Power Overview Battery Duration Calculations Power Supply Circuit Battery Level Detecting Circuit –Battery voltage drop

Battery Capacity Battery Capacity: 5000mAh Initially chosen to maintain at least 3 hours of operation Initial calculations done with worst case scenarios –Beagle board dissipating power at its maximum rating –Sensor unit dissipating high amount of power

Power Dissipation (measured)

Battery Duration

Power Supply Circuit Supplies different levels of voltage for Sensor and Microcontroller Units Uses Voltage regulators to generate stable voltage output Voltage regulators are chosen to supply sufficient power (current)

Power Supply Circuit

Battery level Detection Voltage for battery drops as power is drawn Model relation between voltage and battery level Detect battery level via detecting voltage Send Beagle Board signals when voltage drops under certain level

Voltage vs. Battery level Estimated state of charge (%)open circuit voltage (V) 100 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Battery level Detection Circuit

Divides Battery voltage by 3 to get voltage available for comparators

Battery level Detection Circuit 4.92V 4.81V 4.70V 4.65V Goes low when Vbattery < 14.76V Goes low when Vbattery < 13.95V

Ethics Any guarantees regarding safety will have to be well tested before they are made to a consumer. We need to make sure that there are clear directions regarding the use of this device, for if used incorrectly, it could cause more danger than if it weren’t installed in the first place FCC regulations on frequency

Improvements Impedance matching –Especially for antenna Better parts (circulator, mixer) –Reduce leakage Decrease resolution –Increases fps (more reactive image)

Special Thanks To Serge Minin Professor Steven Franke Professor Jennifer Bernhard Professor Jont Allen Skot Wiedmann Mark Smart Nihar Gandhi Wally Smith