Wireless Telemetry for Solar Powered Car Heather Chang Farhan Farooqui William Mann December 13,...
-
Upload
wendy-preston -
Category
Documents
-
view
225 -
download
0
Transcript of Wireless Telemetry for Solar Powered Car Heather Chang Farhan Farooqui William Mann December 13,...
Wireless Telemetry for Solar Powered Car
Wireless Telemetry for Solar Powered Car
Heather ChangFarhan Farooqui
William Mann
December 13, 2010
Heather ChangFarhan Farooqui
William Mann
December 13, 2010
Project OverviewWireless
Data from the Solar Car to the Chase Car
Objectives• Real-time processing of vital information:
– Measure vehicle speed– Measure battery pack voltage and current– Measure motor controller voltages and currents– Measure outdoor and cabin 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
Design Overview
Data Acquisition: Vehicle Speed
• Two part system– Hall effect sensor
• Temperature-stable• Stress-resistant• Supply voltages of 3 to 24 V
– Magnet
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
Vehicle Speed Test Results
SBC (rpm)
Tachomter (rpm)
Percentage Error (%)
168.1 161.8-170 * N/A300 300.8 0.266504 505.6 0.316
* at no load, the motor was not constant
Data Acquisition: Current (I) Sensor
HASS 200-S Sensor: • Nominal current: 200 A• Measurement range: ± 600 A • Low power consumption
(5V, 22 mA)
Current (I) Sensor Process Current Sensor
Analog to Digital
Converter
Single Board
Computer
Measured Current Value
Current measured
and converted to
volatge
Voltage converted to 12 bit binary values
Binary Values converted back to Voltage, Voltage
converted to Current
Vout (Analog) = Vref ± (0.625·Ip/Ipn)where Vref = 2.487VIp = measured currentIpn = 200 (HASS 200 model)
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
Current (I) Sensor Potential Solution
• Differential Amplifier Circuit
Current (I) Sensor Results
“Simulated” Current (A) with Loops
Measured Current (A) *
Number of Loops
Parallel Resistors
Vout measured with Multimeter (V)
Vout theoretical
Percentage Error (%)
with
4.233 4.2333 1 3ohm 2.4998 2.5001 0.01
-4.217 -4.2167 1 ** 3ohm 2.474 2.47369 0.01
16.800 4.2000 4 3ohm 2.5381 2.43437 4.26
12.650 4.2167 3 3ohm 2.5255 2.44734 3.19
18.0714 18.0714 1 1, 2 ohms 2.541 2.4304 4.55* the DC ammeter has a max current of 10A; otherwise, calculated (Vbatt/Rtotal)** reversed the direction of the current sensor*** resistors have a power rating of 200W
Data Acquisition: AC Voltage
Schematic of AC Voltage divider circuit:
DC Voltage
Schematic of DC voltage divider circuit:
Voltage ProcessVoltage Divider Circuit
Analog to Digital
Converter
Single Board
Computer
Measured Voltage
Measured Voltage
scaled down
Voltage converted to 12 bit binary values
Binary Values converted and scaled back to
measured Voltage
Voltage Measurement Motor Controller Results
• Max voltage Reading on SBC: 96 V
• Max Voltage Reading on Oscilloscope: 94 V
Voltage Measurement Battery Pack Results
DC Input (V)SBC measured
Voltage (V) Percentage Error (%)10.9173 9.8 10.2320.321 19.26 5.2230.857 29.8 3.4340.358 39.6 1.8850.252 49.7 1.1059.988 59.8 0.3170.729 70.6 0.18
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
Temperature Results
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
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$GPRMC,201744.394,V,,,,,,,101110,,,N*47
Single-Board Computer (SBC)• Running Linux at 200 Mhz
– Programmed using C– Allows for multi-process
scheduling– Full socket connection
available via network.
• Start-up script to load drivers for hardware when powered on.
Asus Wireless-G USB Module• Easier to interface with SBC
than previous ZigBee module.• Allows full network
connection– Built in encryption/checksum– Socket programming– Remote debugging
(Telnet/FTP)• Outdoor range up to 1085 ft• Compatible with standard Wi-Fi equipment
SBC Program RoutineConstant loop• Receive data from ADC via SPI bus.
– Convert voltages received to appropriate measurements
• Receive data from temperature sensor via SPI bus
• Receive new string from GPS receiver• Monitor RPM sensor over 5 second period• Create string containing all new data
– Broadcast string via datagram socket over network2.75,2.94,2.67,38.33,0.08,0.07,76.2,78.8,0.0,$GPRMC,183411.675,V,,,,,,,081110,,,N*4E2.75,2.94,2.67,38.33,0.08,0.07,76.2,78.8,0.0,$GPRMC,183411.675,V,,,,,,,081110,,,N*4E
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…
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
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.
Problems
• Temperature Sensor– Driver– SPI
• Zigbee Module for Wireless Data Transfer– Compatability– Range– Power Consumption
Future Work
• Current Sensor• RS-232 Data Reception• LCD• Range• Power Consumption• Printed Circuit Board
CostDescription Quantity Cost Cost per Part- #
TS-7250 SBC 1 $149.00 $149.00
USB 802.11g wireless network interface for TS-7250 1 $35.00 $35.00
GlobalSat BU-353 Waterproof USB GPS Receiver 1 $36.95 $36.95
Hall-effect, uni-polar switch (A1120) switch 1 $1.37 $1.37
Magnet Alnico 5 (AlNiCo) 2 $1.17 $2.34
Current Sensor (HASS 200) 4 $26.00 $104.00
12-bit, 16 input channel ADC (MAX11633) ** 1 $8.13 $8.13
QSOP-24 to DIP-24 Adapter 2 $12.00 $24.00
Temperature Sensor (MAX1299) ** 1 $7.20 $7.20
SSOP-16 to DIP-16 2 $10.00 $20.00
Quad rail-to-rail op amp (LMC6484) 3 $3.61 $10.83
Voltage regulator, 5V, 3A (LD1085V50) 1 $1.63 $1.63
Voltage regulator , 3.3V, 1A, input 1 $1.13 $1.13
Total Cost $401.58
** free samples available from MAXIM
Questions?Questions?