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Posture Watcher

Posture Watcher . By: Bradley Thompson and Christopher Wolf. Presentation Outline. Introduction/Features Objective Original Design Project Build Functional Tests Software Successes/Challenges Ethics Closing. Introduction.

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Posture Watcher

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  1. Posture Watcher By: Bradley Thompson and Christopher Wolf

  2. Presentation Outline • Introduction/Features • Objective • Original Design • Project Build • Functional Tests • Software • Successes/Challenges • Ethics • Closing

  3. Introduction • Mission “a modern-day ergonomic solution for you!” - improve productivity - prevent long-term physical discomfort - build good posture habits

  4. Features -Pressure Sensing/Proximity Sensing -Calibrate user’s “good posture” -Ability to store an individual’s unique posture -LCD Text Screen/Buzzer/LED to give feedback onposture

  5. Objective • Strategically place sensors to best understand user's current posture • Develop control for the system which will tell when a user’s back is out of line with the calibrated correct posture, and when weight is unevenly distributed compared to the calibrated posture. • Provide accurate feedback to the user • Package a compact design

  6. Concept Realization

  7. Overall Block Diagram

  8. Pressure Sensors Voltage (V) VOUT = -VT(RF/RS) This case: Vt=-5V, RF=1kΩ Resistance (RS) (kΩ)

  9. Excitation Circuit VOUT = -VT(RF/RS)

  10. Ultrasonic Sensors

  11. Power Supply

  12. Power Supply 9V DC and 2V AC Supply Voltage (V) Regulated Output Time 9V DC and 4V AC Supply Voltage (V) Regulated Output Time

  13. LCD

  14. Project Build

  15. BOARD

  16. Functional Tests (Pressure Sensors) Actual No Load > 5MΩ Ohms Law (5V/120k Ω) =.0417mA<2.5mA  On wooden table Resistance Rs (Ω) Weight (lbs) Actual (zoomed in) VOUT = -VT(RF/RS) For Desired Sensitivity: Chose: Rf=120kΩ Resistance Rs (Ω) Weight (lbs)

  17. Functional Tests (Ultrasonic Sensors) TOP Angle (degrees) Distance (cm) SIDE Resolution < 3-4 cm  Sensors mounted at 90⁰  Operates in the range of 3 cm to 4 m  Angle (degrees) Distance (cm)

  18. Ultrasonic Sensor Waveform Trigger Voltage (5V/div) Echo Time

  19. Functional Tests (Power Supply) 6.625V Supply: 6V DC and 2V AC Voltage (2V/div) Regulated Output Time Both currents supplied are less than 100 mA  Typically: +9 draws 21 mA -9 draws 6 mA

  20. Battery Discharge Performance • Our current draw is usually around 25mA or less for each battery • We are using Advanced Lithium 9V Batteries. • 1 hour of life after low battery LEDs light up

  21. Software • Start up • Debug (Ultrasonic; Pressure; Battery voltage; Second Timer; Buzzer/LEDs/LCD) • User Choice - New User - Returning User • Calibration • Memory Store / Recall • Hour Timer - User detection • Posture Algorithm - LCD feedback

  22. Calibration • Stores your correct posture in memory • Sensor criterion: - Pressure Sensors 50-1000. +-100 Stability range - Ultrasonic Sensors 3-200. +-2 Stability range • Periodic samples for 2 stable seconds - Time weighted average over sampling time

  23. Successes • Sensors gave realistic data • Useful Debug mode • Calibrate/Recall multiple users posture • Gave Feedback to User (Lean Forward… etc.) • Getting out of chair/1hr stretch • Product is user-friendly • Developed a compact and sleek design

  24. Challenges/Problems • Software: - Building code - ROM filled • Calibration -Top Ultrasonic Sensor on sweatshirt/hair • Circuit - Excitation Circuit Op Amp Supply Voltage - Fried a PIC - LCD voltage divider resistors got too hot

  25. Ethics • Ultrasonic/skin – Max SPL is 110dB for 40kHz • Safety/liability waiver • We need to consider the safety of a person using the posture watcher when they are sitting in a chair. Rule 1. Make sure sensors and housing cannot harm user. • Accounting for different weights and heights of people. This relates to Rule 8 of the IEEE code. Want Posture Watcher to work for all different people.

  26. Summary • We accomplished all hardware design and implementation - monitored persons posture through sensor data - could store and recall that data - compact design - gave feedback to user through LED and Buzzer from their current posture • Passed all verification tests • Future software work can improve functionality

  27. Credits • Justine Fortier • Jim Kolodziej • Jane Tu • Machine Shop - Skee Aldrich • Parts Shop - Mark Smart • Professor Jonathan Makela

  28. Thank You

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