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THE LIE DETECTOR

THE LIE DETECTOR. Tim Fleck Mike Gruener Brian Halaburka Chris Moskaites. OBJECTIVES.

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THE LIE DETECTOR

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  1. THE LIE DETECTOR Tim Fleck Mike Gruener Brian Halaburka Chris Moskaites

  2. OBJECTIVES • To create a sensing device modeled after a polygraph test • Test would incorporate results from several physiological sensors • Create a Labview program to gather and analyze subject data

  3. POLYGRAPH THEORY • Polygraphs measure: • Heart rate • Respiratory rate • Blood pressure • Arm and leg motion • Electrodermal activity

  4. INITIAL IDEAS • Use real world polygraphs as design models • Assemble a polygraph which monitors heart rate, breathing rate and electrodermal activity • Create a Labview program which would self-analyze data and “detect” deceptive behavior

  5. FINAL LIE DETECTOR • Incorporates two physiological sensors detecting two phenomenon 1)electrodermal activity 2)motion • Self analyzes received data

  6. DETECTOR LOGIC Subject Electrodermal Sensor/Motion Sensor DAQ New Data LABVIEW/CPU Display Results

  7. SENSORS • Electrocardiogram or EKG • Galvanic Skin Response Sensor

  8. ELECTROCARDIOGRAM • Measures the electrical activity of the heart • Determines hearts rate and rhythm • Our project used it to measure motion

  9. GALVANIC SKIN RESPONSE SENSOR • Senses moisture • Stand-alone unit • Produces noise • Frequency was too fast for the DAQ

  10. CREATED SKIN SENSOR • Based off the idea that skin resistance decreases with moisture • Used a voltage difference circuit • Amplified the voltage difference to obtain obvious results

  11. LABVIEW LOGIC (EKG) • Take initial readings visually from the waveform graph • Calibrate the high and low end of the threshold based on the initial readings • Every question after will be compared to the threshold • If a person’s motions go above the threshold, a LED goes on, indicating a lie

  12. LABVIEW LOGIC (GSR) • Takes voltage readings of subject’s fingers until button is pushed • Then it computes and displays and average voltage for the given time period • Displays a waveform chart showing how much the subject’s voltage is increasing from the average as resistance decreases • If the in average increase goes above a certain predetermined value, a light goes on, indicating a lie

  13. DATA • Thresholds were determined by analyzing results gathered from group testing • Normalized against predetermined values

  14. DATA ANALYSIS AND RESULTS Galvanic Sensor: • Computes voltage average • Determines a lie if the subject’s voltage goes above a threshold

  15. DATA ANALYSIS AND RESULTS EKG: • Displays the electrical impulses generated by a human body • When a certain level of voltage is generated in the body it rises above a predetermined value indicating irregular behavior • Detects movements from bodily extremities, specifically the arms and legs

  16. NORMAL EKG WAVEFORM

  17. DECEPTIVE WAVEFORM

  18. SOURCES OF ERROR • Nervousness of test subject • Calibration errors

  19. Difficulties • Heart Rate Monitor • Galvanic Skin Response • LABVIEW • Lab Setup

  20. CONCLUSIONS • “Simple” circuitry increases in complexity once work begins • Check and recheck components before and after assembly • Start early • Be flexible and constantly improve

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