1. Wireless Telemetry System for Solar Vehicle
School of Electrical and Computer Engineering
Wireless Telemetry System for Solar Vehicle
Scott Cowan
Elliot Hernandez
Tung Le
April 25, 2011

2. Project Overview What is telemetry? Why are we doing this project?
Throughout the solar car race, two escort vehicles accompany the one-man solar-powered vehicle to monitor its safety and performance. The Solar Jackets Telemetry System is an automatic, remote monitoring device that collects and transmits crucial instrumental data from low-power sensors and controllers inside the solar car to its chase car through a radio frequency (RF) transmission.
The Solar Jacket’s telemetry system allows a user to view and store real-time data from the solar powered car. The data will be viewable remotely through a computer program that will be installed on a laptop computer. The main purpose of this system is to provide the individuals in a chase car with real time data that will help monitor performance of the solar car.
Source:

3. Design Overview Solar Car Chase Car SBC Current Speed Temperature
Laptop
Solar Car
SBC
USB
Current
Speed
Temperature
Voltage
RS-485/RS-232
GPS
Battery Mgmt.
Motor Ctrl.
MPPT
HMI
Data Storage
SPI
DIO
Transmitter
Made changes: font size, LCD to Driver

4. 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

5. Hardware Problems & Solutions
Problem: PCB errors discovered too late to correct
Solution: Used wires to bypass incorrect traces; corrected schematics and PCB files for future reference

6. Outside View of Telemetry Box
Comm. Jacks
Input Terminals
USB Ports

7. Inside View of Telemetry Box
Flash Drive
PCB
SBC
USB Hub

8. Sensor Testing Methods

9. 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 Vdc
Remaining voltage inputs scaled for 0-5 Vdc

10. 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

11. Testing Low Voltage Inputs
Input 0-5 Vdc into telemetry box in 0.5 V increments
Compared readings from SBC to Fluke 199C Scopemeter

12. Voltage Measurement Results
DC Input (V)
SBC measured Voltage (V)
Percentage Error (%)
0.35
N/A 5
4.31
13.80 10
9.44
5.60 15
14.51
3.27 20
19.6
2.00 25
24.7
1.20 30
29.8
0.67 35
34.93
0.20 40
40.06
0.15 45
45.13
0.29 50
50.26
0.52
Percentage error decreases as DC input increases

13. 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

14. 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

15. 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
0.92
Current sensor is capable of bi-directionality

16. Temperature Inputs Readings from temperature are incorrect
Error occurred after soldering to PCB
Cause of error remains unknown

17. GPS Output
$GPRMC, ,V,,,,,,,101110,,,N*43
$GPRMC, ,V,,,,,,,101110,,,N*42
Note: GPS is in the NMEA 0183 format, where the output is $GPAAM,A,A,CR,N,WPTNME*32
The NMEA 0183 standard uses a simple ASCII, serial communications protocol that defines how data is transmitted in a "sentence" from one "talker" to multiple "listeners" at a time.

18. Future Testing RS-485 To RS-232 converter
Speed sensor input comparison to tachometer

19. 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…

20. Project Costs

21. 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

22. Questions?