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Hands Free Calculator

Hands Free Calculator. ECE 345 Senior Design Project Tim Bruns, Caroline Harvey Project #11. Outline. Introduction Hardware Software Results Conclusions. Overview. Design a system that allows user to operate simple calculator, needing only movements of eyes and clenching of jaw

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Hands Free Calculator

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  1. Hands Free Calculator ECE 345 Senior Design Project Tim Bruns, Caroline Harvey Project #11

  2. Outline • Introduction • Hardware • Software • Results • Conclusions

  3. Overview • Design a system that allows user to operate simple calculator, needing only movements of eyes and clenching of jaw • Small electrodes acquire signals from face • Biopotential amplifiers make signals viewable • NI-DAQ software sends signals to computer • LabVIEW software implements calculator

  4. Block Diagram EMG Amplifier from Jaw Rectifier Low Pass Filter (LabVIEW) Comparator Number/ Function Select Vertical EOG Amplifier 7 0 8 ^ 9 . Calculator LabVIEW Position Select 4 * 5 C 6  Horizontal EOG Amplifier  Output 1 + 2 - 3 

  5. Electrodes • Used pediatric size Ag/AgCl electrodes • Allow measurement of biopotentials • Serve as a transducer to change ionic current from skin into an electric current

  6. Placement of Electrodes

  7. EOG Background • Electro-oculogram • Signal detected from movement of eye • Steady corneal-retinal potential modeled as a dipole • Signal parameters: • Range: 0.05 - 3.5 mV • Frequency response: dc - 10 Hz

  8. EOG Circuit • Gain: 10,800 • Bandpass region: 0.08 - 4.3 Hz

  9. EMG Background • Electromyogram • Muscle composed of many single motor units • contraction generates action potential • sum of AP’s leads to an ac signal (EMG) • Signal parameters: • Range: 0.1 - 1 mV • Frequency response: 100 - 3000 Hz • Rectifier - Low Pass Filter addition

  10. EMG Circuit • Gain: 3460 • Bandpass region: 75 - 1850 Hz

  11. Design Verification PSPICE Simulation Vs. Measured Output

  12. Design Verification

  13. Data Acquisition • NI-DAQ (National Instruments Data Acquisition) • Provides connection between hardware & LabVIEW computer software • LabVIEW • Graphical programming language • Used to implement a simple calculator and comparator for output voltages of EOG/EMG

  14. Software Flowchart Start Get EOG & EMG Signals Check EMG Input (0,Function,or C) Check EOG V & EOG H Low Range? No Function Selected? Yes No Yes Send X & Y to Calculator Input Digit (1-9) EOG in Range? No Yes Store Number in X Display Result High Range? Return to Start Light up Corresponding Keypads Yes Store Number in Y No

  15. LabVIEW Software

  16. User Interface

  17. Results • Able to control keypad selection through eye movement • Need time to calibrate eye movements based on position of electrodes • Jaw clench challenging to separate between hard and soft clicks

  18. Costs • Electrodes: donated • Circuit parts: free through parts shop • LabVIEW manual, software: $50 • Labor: 2 people x 100 hours x 2.5 (overhead) x $20/hour = $10,000 • Total: $10,050

  19. Uses • Assist handicapped • Could be expanded to include entire keyboard • Implementation of military guidance system

  20. Improvements • Automatic calibration • Shielding • Better electrodes • Increased sensitivity to eye and jaw movements • Synchronize LabVIEW timing of EOG and EMG signals

  21. Finished! • Worked • Can be improved in ways • Possibility for marketable product • Any questions?

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