Wireless Telemetry System for Solar Vehicle

Scott CowanElliot Hernandez

Tung Le

March 14, 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

Prior Work from Fall 2010

• GPS receiver• Wi-Fi link• Data storage• Data acquisition

– Voltage– Current– Temperature– Speed

Shortcomings of Fall 2010 Design

• Current sensors– Low sensitivity– Unipolar sensing

• Speed sensor– Fragile design

• Interface board– Proto-board

Transition Problems

• Programming– Serial Peripheral Interface (SPI) bus not working

• Hardware dismantled– All sensors lost

• Parts list incomplete– Part numbers missing

Spring 2011 Remedies

• Current sensors– Lower range = higher sensitivity– Bipolar = bidirectional sensing

• Speed sensor– Industrial sensor = robustness

• Interface board– Printed circuit board (PCB) = permanence

Additional Features

• Take advantage of SPI bus• Enclose PCB and SBC for protection• Read data from other subsystems on the

RS-485 network

Current Status• Completed tasks

– Preliminary schematic design– Component selection– Linux driver installation– Cross-compiler setup

• Present tasks– Finalizing schematic and PCB designs– Soldering components– Coding program

• Auto-sync • Transmit data

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

Current Measurement

• Bi-polar Hall-effect sensor – Sensing range: ± 140 A– Maximum cable size: 1/2″ OD– 10 available inputs

Speed Measurement

• Industrial Hall-effect sensor – Senses magnet attached to wheel– Sends pulse to SBC– Computes Δt between pulses

Wheel

Temperature Measurement

• Diode-connected transistor – Two available inputs for remote sensors– On-chip ADC– Accuracy of ±1 degree C

Voltage Measurement

• Simple voltage divider network – Total of six 0-5 Vdc inputs– Three remote signal conditioners for voltages up to 120 Vdc

Interface Board

• Custom PCB– Interconnection between Inputs/Outputs (I/O) and SBC – Signal buffering– Analog to Digital conversions

Single Board Computer

• TS-7250– Heart of telemetry system– Linux operating system– C language programming

Vehicle Location

• GlobalSat BU-353 GPS receiver – NMEA 0183 protocol– Waterproof– Five foot USB cable

Data from Other Subsystems

• Other subsystems communicate on RS-485 network – Telemetry “listens” through RS-485 to RS-232 converter– Relevant data captured and stored– Requested data sent to HMI

Battery Mgmt.Motor Ctrl.

MPPTHMI

Data Storage

• 2GB USB flash drive– FAT16 file system– One record set per second– CSV file format

Data Transmission to Chase Car

• ASUS WL-167g Wi-Fi transmitter– IEEE 802.11g standard– Supported by SBC drivers– Range of up to 150 m

Enclosure

• Lightweight ABS plastic– Approximately 7 x 8 x 2.5 inches (W x L x H)– IP 54 rating

General Challenges

• Slow delivery of parts has delayed testing– Current sensors– QSOP to DIP adapters

• Identification of major components has delayed SBC programming– TS-7250 SBC– 2 GB USB memory stick

Interface Board Challenges

• DesignSpark learning curve– Design and Library Creation tutorials helpful

• Printed Circuit Board size limit– ECE machine limited to 7 x 8 inch PCBs

• Component specification– Connector selection

Programming Challenges

• TS-7250 SBC learning curve– Tyler Mann has assisted

• Linux compatible drivers– GPS, Wi-Fi, and memory devices

• Serial Peripheral Interface (SPI) Bus– Needs to work before PCB design is finalized

Future Testing• Speed sensor• Current sensors• Temperature sensors• Voltage signal conditioners• SPI bus• RS-485 to RS-232 converter• Communication to HMI

Project Schedule

March 23, 2011 SBC sensing all sensors

March 30, 2011 Wi-Fi transmission of data

April 6, 2011 Complete printed circuit board

April 13, 2011 Display data on remote laptop

April 20, 2011 Final demonstration

Future Costs for Solar Jackets

Description Quantity UOI Unit Price Extended CostCurrent sensors 6 ea $10.00 $60.00

Signal wiring 1 lot $100.00 $100.00Misc connectors 1 lot $100.00 $100.00

Total $260.00

Questions?