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Wireless Telemetry for Solar Powered Car

Wireless Telemetry for Solar Powered Car. Heather Chang Farhan Farooqui William Mann December 13, 2010. School of Electrical and Computer Engineering. Project Overview. Objectives. Real-time processing of vital information: Measure vehicle speed Measure battery pack voltage and current

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Wireless Telemetry for Solar Powered Car

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  1. Wireless Telemetry for Solar Powered Car Heather Chang FarhanFarooqui William Mann December 13, 2010 School of Electrical and Computer Engineering

  2. Project Overview

  3. Objectives • Real-time processing of vital information: • Measure vehicle speed • Measure battery pack voltage and current • Measure motor controller voltages andcurrents • Measure outdoor andcabin ambient temperature • Receive vehicle location (GPS) • Receive motor controller status (on/off) • Receive currents, voltages, temperature readings from solar panels • Wireless link with solar car (at least 100 ft) • GUI displaying data on LCD to driver and on laptop in chase car • Storage of data in solar car

  4. Design Overview

  5. Data Acquisition: Vehicle Speed • Two part system • Hall effect sensor • Temperature-stable • Stress-resistant • Supply voltages of 3 to 24 V • Magnet

  6. Vehicle Speed Process • Vout switches from 2.8V to -0.022V as a south pole comes in close proximity (ca. 25mm) to the sensor • SBC keeps track of ‘LOWS’ to return a RPM measurement

  7. Vehicle Speed Test Results

  8. Data Acquisition: Current (I) Sensor • HASS 200-S Sensor: • Nominal current: 200 A • Measurement range: ± 600 A • Low power consumption (5V, 22 mA)

  9. Current (I) Sensor Process Vout (Analog) = Vref ± (0.625·Ip/Ipn) where Vref = 2.487V Ip = measured current Ipn = 200 (HASS 200 model)

  10. Current (I) Sensor Problem and Potential Solution • Problem • Change in Vout of current (I) sensor too small • Δi of 10A leads to ΔVout of 0.03125V • ADC can’t recognize change • Potential Solutions • Amplify signal (differential amplifier) • LEM HASS-50 (measuring range ± 150) • Δi of 10A leads to ΔVout of 0.125V

  11. Current (I) Sensor Potential Solution • Differential Amplifier Circuit

  12. Current (I) Sensor Results

  13. Data Acquisition: AC Voltage Schematic of AC Voltage divider circuit:

  14. DC Voltage Schematic of DC voltage divider circuit:

  15. Voltage Process

  16. Voltage Measurement Motor Controller Results • Max voltage Reading on SBC: 96 V • Max Voltage Reading on Oscilloscope: 94 V

  17. Voltage Measurement Battery Pack Results

  18. Data Acquisition: Temperature • Temperature sensor outputs a binary value • SBC sees binary value as an integer • Divide integer value by 8 to get Kelvin scale • Convert Kelvin scale to Fahrenheit scale

  19. Temperature Results

  20. Data Acquisition: GPS • GPS Tracking • Plugs into the SBC’s USB port • Outputs longitude, latitude and altitude data as ASCII text • Data captured by the SBC and forwarded to a laptop • Has a 5 ft long wire

  21. GPS Output • $GPRMC,201740.394,V,,,,,,,101110,,,N*43$GPRMC,201741.394,V,,,,,,,101110,,,N*42$GPRMC,201742.407,V,,,,,,,101110,,,N*4C$GPRMC,201743.394,V,,,,,,,101110,,,N*40$GPRMC,201744.394,V,,,,,,,101110,,,N*47

  22. Single-Board Computer (SBC) • Running Linux at 200 Mhz • Programmed using C • Allows for multi-process scheduling • Full socket connection available via network. • Start-up script to load drivers for hardware when powered on.

  23. Asus Wireless-G USB Module • Easier to interface with SBC than previous ZigBee module. • Allows full network connection • Built in encryption/checksum • Socket programming • Remote debugging (Telnet/FTP) • Outdoor range up to 1085 ft • Compatible with standard Wi-Fi equipment

  24. SBC Program Routine Constant loop • Receive data from ADC via SPI bus. • Convert voltages received to appropriate measurements • Receive data from temperature sensor via SPI bus • Receive new string from GPS receiver • Monitor RPM sensor over 5 second period • Create string containing all new data • Broadcast string via datagram socket over network 2.75,2.94,2.67,38.33,0.08,0.07,76.2,78.8,0.0,$GPRMC,183411.675,V,,,,,,,081110,,,N*4E

  25. Remote Laptop Program • Runs on Linux • Listen for any packets being sent through socket on specified port • Format and display received strings in console • Save received string to CSV file on laptop • CSV file readable using text editor, Excel, Matlab, etc…

  26. Data Storage • USB thumb drive attached to SBC • Saves to FAT16 formatted drive • Saves every string broadcasted out in CSV file • 200 byte strings saved every second • ~700kB/hour • Remote laptop storage • Listening program on remote laptop saves every string received

  27. Code: Suggestions For Improvement • Increased compatibility: Listener program could be easily ported to Windows API’s. • Enhanced GUI or addition of threshold warnings for some measurements could be added to listener program. • Multiple listeners: Additional addresses could be added to broadcast to more than one laptop.

  28. Problems • Temperature Sensor • Driver • SPI • Zigbee Module for Wireless Data Transfer • Compatability • Range • Power Consumption

  29. Future Work • Current Sensor • RS-232 Data Reception • LCD • Range • Power Consumption • Printed Circuit Board

  30. Cost

  31. Questions?

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