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Personal Trip-Odometer

Personal Trip-Odometer. By Akin Adekoya & David Chung. Table of Contents. Introduction Block Diagram Part Explanation Performance Problems Improvements Conclusion. Introduction. Reasons for our project Athletic improvements Future business opportunity A portable device . Objectives

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Personal Trip-Odometer

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  1. Personal Trip-Odometer By Akin Adekoya & David Chung

  2. Table of Contents • Introduction • Block Diagram • Part Explanation • Performance • Problems • Improvements • Conclusion

  3. Introduction Reasons for our project • Athletic improvements • Future business opportunity • A portable device

  4. Objectives • Accurate conversion of accel. to distance • Reliable transmission and receiving • Keeping track of both the time and distance traveled by the user • Displaying the time and distance • Overall small and light

  5. Block Diagram Accelerometer Display User input Acceleration Data PIC PIC Transmitter Receiver Calculated Values Calculated Values Main Device Receiver/Display

  6. Polarity and over voltage protection + μ P – (+) (–) Zener diode + μ P – (+) 1N5822 or 1N5817 Schottky diode (–) Polarity Protection Fuse (eg. 1A) 1N5339 (eg. 5.6V) Parts shop: 1N4734 Over-voltage Protection

  7. Vdd 8 ST 7 XFILT 1 Cx1 T2 2 6 YFILT ADXL202 0.1u 5 COM 3 XOUT 4 Rset1 125k YOUT Accelerometer(ADXL202) • Single axis • 312mV/g • +-2g sensing • 125kOhm = 1000sample/s • 0.1uF = 50Hz BW 1.8mg rms Noise Analog output

  8. PIC I (16F877) • Voltage Divider • 20MHz Oscillator • Sample at 60Hz • Convert accel. to dist. • Output calculated dist. to transmitter

  9. Main equations • Vf = Vi + a*t • X = Vi*t + 0.5*a*t^2 where t = 1/60s a = acceleration from accelerometer Vi = Initial velocity Vf = Final velocity X = distance traveled

  10. Transmitter/Receiver (HP2) • Operating frequency = 903.37MHz • Operating temp. = 0~70 oC

  11. PIC II (16F877) • Input at 60Hz • 20MHz Oscillator • Reset Switch • Display Switch • Adds distance • Output to LCD

  12. LCD (Shelly)

  13. Final Device

  14. Performance • Accelerometer provided accurate values • First PIC converted analog acceleration accurately to digital distance • Transmitter/Receiver operated successfully • Second PIC was able to toggle between displaying time and distance

  15. Accelerometer at 0g

  16. Accelerometer at 1g (gravity)

  17. Accelerometer at 2g

  18. Calculation • (2.977V - 2.352V)/2 = 0.3125V/g • Value from data sheet = 0.312V/g

  19. Input and output of transmitter/receiver

  20. Challenges • Learning the PIC functions • Making the PIC work in synchronous with the entire circuit • Calibrating the Accelerometer • Accuracy decreases using a PIC (overflow) • Final product was functional but inaccurate

  21. Example (accelerometer reference differs each time) • Our zero g Bias was between 2.35~2.48 about 80% of the time.

  22. Improvements • Initial calibration as user turns on device • Use an op amp to improve the sensitivity • Make measurements in smaller standards to improve accuracy • Use microcontroller with more capability • Make the overall circuit smaller in size

  23. Conclusion • We have learned to work as a team to work on a real engineering project • We learned to use sensors, process the output data with a PIC, transmitting and receiving the data, and reprocessing to display our data

  24. Questions??

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