Transcript Solar Jackets: Wireless Telemetry Senior Design Group

School of Electrical and
Computer Engineering
Wireless Telemetry System for
Solar Vehicle
Scott Cowan
Elliot Hernandez
Tung Le
March 14, 2011
Project Overview
Wireless
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
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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
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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
Solar Car
Chase Car
Transmitter
Data Storage
USB
USB
Current
Speed
SBC
SPI
DIO
Temperature
Laptop
USB
GPS
RS-485/RS-232
Battery Mgmt.
Motor Ctrl.
MPPT
HMI
Voltage
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
Battery Mgmt.
Motor Ctrl.
MPPT
HMI
• 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
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
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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
Current sensors
6
ea
Signal wiring
1
lot
Misc connectors
1
lot
Unit Price Extended Cost
$10.00
$60.00
$100.00
$100.00
$100.00
$100.00
Total
$260.00
Questions?