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ECE445 Final Presentation. Group 1 - Ski Computer Brian Vaughn Chris Gerth. Overview. Project Description Design & Construction Issues Addressed Summary of Verifications Manufacturability & Future Work Conclusion. Project Overview.
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ECE445 Final Presentation Group 1 - Ski Computer Brian Vaughn Chris Gerth
Overview • Project Description • Design & Construction • Issues Addressed • Summary of Verifications • Manufacturability & Future Work • Conclusion
Project Overview • Datalogging device similar to bike computer or run tracker, but for skiing, skateboarding, etc. • Challenge - no large rotating wheel or recurring acceleration pattern for velocity measurement. • Solution - Doppler Radar sensor detects velocity. • Amplifier, Simple A/D conversion, wireless transmission to processor. Image Credit: http://www.pgl.co.uk/NR/rdonlyres/B9D9D613-B4B3-4FD1-9137-92AB6A24AA4E/0/1.jpg
Features Overview • Semi-permanent data logging in EEPROM of speed, acceleration, altitude, temperature, time. • Real-time display of parameters • Data can be downloaded to computer, saved, and viewed in graph format
Lower Unit Wireless Upper Unit Design Mounted near the ground Attached to user’s forearm • Two units: Lower Unit and Upper Unit Lower Unit: • Radar Speed Sensor • Speed Sensor Signal Amplification • Wireless Transmission Upper Unit • Wireless Reception • Data Gathering, Processing, and Logging • User Display and Interface Image Credit: http://www.bbc.co.uk/ouch/images/flush_286/mike_may_skiing_tuck.jpg
Sensor Output Amplifier Output Comparator Output Freq. Div. Output
Design - Upper Unit I2C Bus User Display All units driven by 3.3V supply. Accelerometer Temp/Pres Sen. XBEE Radio RX EEPROM Micro- controller 1xGPIO RTC USB FTDI To external PC Serial 4xGPIO 3.0V Battery Backup User Buttons
Design - Upper Unit Software • Purpose: Gather, Display, and Log Data • Structure: • Main Execution Loop • 1 Hz Task Loop • Interrupt Service Routines
Start Initialize Unit Main Loop Tasks 1Hz Flag True 1Hz Tasks False
INIT Default End Record Record_ended flag == true Standby Menu Exited Menu User Button Menu Pressed Record_ended flag == false User Button Start/Stop Record Pressed User Button Start/Stop Record Pressed Default User Interacting with menu PC Cmd = $S Recording PC Cmd = $E Start Record PC Connect Record_ready flag == true Default Record_ready flag == false
Issues Addressed • Amplifier gain at high frequencies • XBEE Transmission Bandwidth • Lower Unit Current Draw
Verifications Summary • Amplifier Performance: At least 100x Gain at 0-2000Hz • Comparator Performance: Reject up to 2mV of input noise at all frequencies • XBEE Performance: Transmit up to 5 ft and through a human body • Software Performance: Read all data, record datapoints at 1 s intervals • Battery Life: 6 hours of continuous operation, 1 hour of continuous recording.
Manufacturing & Future Work • V2.0 Improvements: • Lower-power radio solution (TI CC85xx series?) • Single-PCB designs • Non-Arduino microprocessor • Smaller, more robust physical units • Estimated Cost after improvements ~ $200 • Cheapest equivalent on the market is $250 and has fewer features