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Active Monitoring and Alerting for Hypotonia of the Jaw

Active Monitoring and Alerting for Hypotonia of the Jaw. Shabab Mustafa and Jason Strack Group 31. Outline. Problem & Solution List of parts Design Testing Future work. Problem. Solution. Create a device to monitor the jaw position Alert the user when needed

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Active Monitoring and Alerting for Hypotonia of the Jaw

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  1. Active Monitoring and Alerting for Hypotonia of the Jaw Shabab Mustafa and Jason Strack Group 31

  2. Outline • Problem & Solution • List of parts • Design • Testing • Future work

  3. Problem Solution Create a device to monitor the jaw position Alert the user when needed Close the jaw automatically • Jaw open for extended periods of time • Who suffers? • Stroke victims • Downs’ syndrome • Effects • Drooling • Embarrassing

  4. Our Device Accelerometer placement Base device placement

  5. Circuit Block Diagram

  6. Circuit Diagram (Eagle)

  7. Batteries Two LiFePO4 • 2.4Wh each • 3.2V • 750mAh • Rechargeable • Fairly safe • Non-toxic • Virtually incombustible • No memory effect • Expect 3 days of continued use

  8. Accelerometers Two MMA7341Ls • Comes with circuit board • Three axes • Only using two axes each • 2.2–3.6V operating voltage • We operate at 3.53V • 1.65mW power consumption • Sensitive to ± 3 or ± 11g • We use ± 3g • Better sensitivity • Mounts to jaw and temple • One is stationary reference • One moves with jaw • Added silicone rubber

  9. Microcontroller MSP430G2231 • 1.8-3.6V operating voltage • Operating at 3.56V • 0.66mW power consumption • 8 ADC inputs • Using 4 from accelerometer signals • Emits 0.5 second output

  10. Regulators 7805 UA78M33KC VIN = 5.3V to 25V VOUT = 3.3V IOUT = 500mA • VIN = 5.5V to 20V • VOUT = 5V • IOUT = 1A

  11. Transistor as a Switch 2N2222A • NPN • 400mW • VCE,max = 10V • BVEB0,max = 6V • Microcontroller to Timer

  12. 555-timer and Op-Amps LM555 LF347 Better than LM374 Quad op-amp 570mW VCC = ±18V Noise-cancelling and clipping • Timer IC • 5V Operation • Pmax = 1180mW • Signals for both audio and electric stimulation

  13. Output and Casing • Board-mounted 3.5-mm jack and 3.5-mm headphones (32Ω Imp.) • Electrodes • Black box • Discrete • Hip-mounted • Easily accessible front-panel

  14. Building an Oscillator • Initially built an AC oscillator • Periodic charging/discharging of capacitors • Needed DC, square wave • TENS Unit • Chose 555-timer

  15. AC Oscillator Output

  16. 555 Monostable Timer (1)

  17. 555 Monostable Timer (2) 1s interval 5s interval

  18. 555 Astable Timer (Stage 1)

  19. 555 Astable Timer (Stage 2)

  20. 555 Astable Timer (Stage 3)

  21. 555 Astable Timer (Stage 4)

  22. Programming

  23. Determining Jaw Open • ADC converts 0V to max voltage (3.53V) to values from 0-1023 • Accelerometer range is only 238 • Change in angle must be calculated • init_accel[i] and accel[i] get digital acceleration readings • diff[i] = init_accel[i] – accel[i] • i = 0 is accelerometer 1’s x-axis, 1 is Y1 axis, 2 is X2 axis, 3 is Y2 axis • angle = arcsin( ((diff[3]/((1-diff[2])/119)) – (diff[1] /((1-diff[0])/119)) )/119 ) • Microcontroller lacks necessary flash memory for math.h • However arcsin(x) can be approximated as x + x3/6 + 3x5/40 + 5x7/112 • Only accept ±60̊ change in x1-axis • if( (diff[0] > 103) || (diff[0] < -103) ) declare jaw closed • if( angle > 0.524 || angle < -0.524) angle > ±30̊ jaw is open

  24. Timing Microcontroller Signal • Track time, reset if jaw closed time = wdtCounter / (float)WDT_FREQUENCY/1000; while ((wdtCounter – time) < 3000){ if( jawOpen() = 0 ) time = wdtCounter; } • If closed for 3 seconds send signal • Signal lasts one half second • After this resumes checking jaw

  25. Accelerometer Testing • Measured x and y axes • Rotated both axes in circles • X-axis voltage 1.15-1.97V • Y-axis voltage 1.18-2.00V • Accelerometer 2 not working • Was working before demo • Started acting up around demo • Not working now, do not have picture

  26. Microcontroller Testing • Insert angle values in code • Check with LED to test microcontroller • Next use actual accelerometers • Again use LEDs to test • Move accelerometers in various positions

  27. Future Work • Reserve one channel of 3.5mm jack for electrodes • Mount jacks on side panel for easier part replacement • Headphones • Accelerometers • Sealing • Battery holder • Adjustable frequency • Separate timers • Use/manipulate a timer such that low when inactive • Circuit protection for electrodes • Thinner wire • 30 – 40 AWG

  28. Future Work • Could add two 3-axis magnetic sensors • Would measure jaw for all head positions • Would add cost and complexity • Could use optical distance sensor instead • More simple, but also larger and more power consumption • Test electrical stimulation • Control output wave shape with microcontroller • Will reduce needed circuitry, reduce power, give cleaner output • Package everything to fit on ear • Easier to attach and remove device • Considerable improvement in being discreet

  29. Questions?

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