Wireless Telemetry System for Solar Vehicle
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Transcript of Wireless Telemetry System for Solar Vehicle
Wireless Telemetry System for Solar Vehicle
Scott CowanElliot Hernandez
Tung Le
April 25, 2011
School of Electrical and Computer Engineering
Project OverviewWireless Data from the Solar Car to the Chase Car
Source: http://www.ece.gatech.edu/academic/courses/ece4007/10fall/ECE4007L01/ws1/files/sjt_final_presentation.ppt
Design Overview
Chase Car
Laptop
Solar Car
SBC
USB
Current
Speed
Temperature
Voltage
RS-485/RS-232
GPS
Battery Mgmt.Motor Ctrl.
MPPTHMI
Data Storage
USB
USB
SPIDIO
Transmitter
Design Problems & Solutions
Problem: Programming C code for TCP/IP protocol for file sync
Solution: Switched to C++ to use FTP protocol
Problem: Using hardware SPI for the ADC converter
Solution: Bit-bang(software based) using the SPI bus
Hardware Problems & SolutionsProblem: PCB errors discovered too late to correctSolution: Used wires to bypass incorrect traces; corrected
schematics and PCB files for future reference
Outside View of Telemetry Box
Comm. JacksInput Terminals USB Ports
Inside View of Telemetry Box
USB Hub
Flash Drive
SBC
PCB
Sensor Testing Methods
Voltage Inputs
• Telemetry box accepts 0-5 Vdc signals
• Signal conditioner used to convert high voltage signals to low voltage signals at point of origin
• Three of six voltage inputs scaled for 0-120 Vdc
• Remaining voltage inputs scaled for 0-5 Vdc
Testing High Voltage Input
• Available power supply limited to 50 V• Inputted 0-50 Vdc into signal conditioner in 5
V increments• Compared readings from SBC to Fluke 199C
Scopemeter
Testing Low Voltage Inputs
• Input 0-5 Vdc into telemetry box in 0.5 V increments
• Compared readings from SBC to Fluke 199C Scopemeter
Voltage Measurement Results
DC Input (V)SBC measured
Voltage (V) Percentage Error (%)0 0.35 N/A5 4.31 13.80
10 9.44 5.6015 14.51 3.2720 19.6 2.0025 24.7 1.2030 29.8 0.6735 34.93 0.2040 40.06 0.1545 45.13 0.2950 50.26 0.52
Percentage error decreases as DC input increases
Current Inputs
• Telemetry box accepts 10 current inputs with a range of ±140 A
• To simulate high currents, 10 loops of wire were passed through current sensor
Testing Current Inputs
• Looped wire connected in series with 12 V battery and 1 Ω, 225 W variable resistor
• Resistance varied to give various currents• Reversed wiring to give negative values• Current measured using Fluke 199C
Scopemeter with 80i-110s clamp-on ammeter• Ammeter readings multiplied by 10 and
compared to SBC readings
Current (I) Sensor Results
“Simulated” Current (A) with Loops
Measured Current (A)
Percentage Error(%)
111 109.32 1.51
140 138.7 0.93
57 56.5 0.88
-57 -55.91 1.91
-114 -112.95 0.92
Current sensor is capable of bi-directionality
Temperature Inputs
• Readings from temperature are incorrect• Error occurred after soldering to PCB• Cause of error remains unknown
GPS Output
• $GPRMC,201740.394,V,,,,,,,101110,,,N*43• $GPRMC,201741.394,V,,,,,,,101110,,,N*42
• Note: GPS is in the NMEA 0183 format, where the output is $GPAAM,A,A,CR,N,WPTNME*32
Future Testing
• RS-485 To RS-232 converter
• Speed sensor input comparison to tachometer
Remote Laptop Program
• C++ program that runs FTP protocol– Can be used on any OS
• Updates the file from the SBC to host computer every 10 seconds
• Re-establish the connection when WIFI signal is broken
• CSV file readable using text editor, Excel, Matlab, etc…
Project Costs
Inherited Components $322.95Purchases this Semester $204.51
Cost to Replicate $527.46
Future Improvements
• Add LED status sensors to enclosing• Upgrade SBC to newer hardware
– Increase in computation – lower power usage– Reduce compatibility issues
• Use hardware interrupts for RPM calculations• Correct discovered errors in PCB
Questions?