Transcript PPTx
School of Electrical and Computer Engineering Wireless Telemetry System for Solar Vehicle Scott Cowan Elliot Hernandez Tung Le April 25, 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 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 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 & Solutions Problem: PCB errors discovered too late to correct Solution: Used wires to bypass incorrect traces; corrected schematics and PCB files for future reference Outside View of Telemetry Box Comm. Jacks Input Terminals USB Ports Inside View of Telemetry Box Flash Drive PCB SBC USB Hub 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 5 10 15 20 25 30 35 40 45 50 0.35 4.31 9.44 14.51 19.6 24.7 29.8 34.93 40.06 45.13 50.26 N/A 13.80 5.60 3.27 2.00 1.20 0.67 0.20 0.15 0.29 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 $322.95 Purchases 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?