THE LIE DETECTORTHE LIE DETECTOR

Tim FleckTim Fleck

Mike GruenerMike Gruener

Brian HalaburkaBrian Halaburka

Chris MoskaitesChris Moskaites

OBJECTIVESOBJECTIVES

To create a sensing device modeled after To create a sensing device modeled after a polygraph testa polygraph test

Test would incorporate results from Test would incorporate results from several physiological sensorsseveral physiological sensors

Create a Labview program to gather and Create a Labview program to gather and analyze subject dataanalyze subject data

POLYGRAPH THEORYPOLYGRAPH THEORY

Polygraphs measure:Polygraphs measure: Heart rateHeart rate Respiratory rateRespiratory rate Blood pressureBlood pressure Arm and leg motionArm and leg motion Electrodermal activityElectrodermal activity

INITIAL IDEASINITIAL IDEAS

Use real world polygraphs as design Use real world polygraphs as design modelsmodels

Assemble a polygraph which monitors Assemble a polygraph which monitors heart rate, breathing rate and heart rate, breathing rate and electrodermal activityelectrodermal activity

Create a Labview program which would Create a Labview program which would self-analyze data and “detect” deceptive self-analyze data and “detect” deceptive behaviorbehavior

FINAL LIE DETECTORFINAL LIE DETECTOR

Incorporates two physiological sensors Incorporates two physiological sensors detecting two phenomenondetecting two phenomenon

1)electrodermal activity1)electrodermal activity

2)motion2)motion

Self analyzes received dataSelf analyzes received data

DETECTOR LOGICDETECTOR LOGIC

Subject

Electrodermal Sensor/Motion Sensor

DAQ New Data

LABVIEW/CPU

Display Results

SENSORSSENSORS

Electrocardiogram or EKGElectrocardiogram or EKG

Galvanic Skin Response SensorGalvanic Skin Response Sensor

ELECTROCARDIOGRAMELECTROCARDIOGRAM

Measures the Measures the electrical activity of electrical activity of the heartthe heart

Determines hearts Determines hearts rate and rhythmrate and rhythm

Our project used it to Our project used it to measure motionmeasure motion

GALVANIC SKIN GALVANIC SKIN RESPONSE SENSORRESPONSE SENSOR

Senses moisture Senses moisture Stand-alone unitStand-alone unit Produces noiseProduces noise Frequency was too Frequency was too

fast for the DAQ fast for the DAQ

CREATED SKIN SENSORCREATED SKIN SENSOR

Based off the idea that Based off the idea that skin resistance skin resistance decreases with moisturedecreases with moisture

Used a voltage Used a voltage difference circuitdifference circuit

Amplified the voltage Amplified the voltage difference to obtain difference to obtain obvious resultsobvious results

LABVIEW LOGIC (EKG)LABVIEW LOGIC (EKG)

Take initial readings visually from the Take initial readings visually from the waveform graphwaveform graph

Calibrate the high and low end of the Calibrate the high and low end of the threshold based on the initial readingsthreshold based on the initial readings

Every question after will be compared to Every question after will be compared to the thresholdthe threshold

If a person’s motions go above the If a person’s motions go above the threshold, a LED goes on, indicating a liethreshold, a LED goes on, indicating a lie

LABVIEW LOGIC (GSR)LABVIEW LOGIC (GSR)

Takes voltage readings of subject’s fingers Takes voltage readings of subject’s fingers until button is pusheduntil button is pushed

Then it computes and displays and average Then it computes and displays and average voltage for the given time periodvoltage for the given time period

Displays a waveform chart showing how much Displays a waveform chart showing how much the subject’s voltage is increasing from the the subject’s voltage is increasing from the average as resistance decreasesaverage as resistance decreases

If the in average increase goes above a certain If the in average increase goes above a certain predetermined value, a light goes on, indicating predetermined value, a light goes on, indicating a lie a lie

DATADATA

Thresholds were determined by Thresholds were determined by analyzing results gathered from group analyzing results gathered from group testingtesting

Normalized against predetermined Normalized against predetermined valuesvalues

DATA ANALYSIS AND DATA ANALYSIS AND RESULTSRESULTS

Galvanic Sensor:Galvanic Sensor: Computes voltage Computes voltage

averageaverage Determines a lie if Determines a lie if

the subject’s voltage the subject’s voltage goes above a goes above a thresholdthreshold

DATA ANALYSIS AND DATA ANALYSIS AND RESULTSRESULTS

EKG:EKG: Displays the electrical impulses generated by a Displays the electrical impulses generated by a

human bodyhuman body When a certain level of voltage is generated in When a certain level of voltage is generated in

the body it rises above a predetermined value the body it rises above a predetermined value indicating irregular behaviorindicating irregular behavior

Detects movements from bodily extremities, Detects movements from bodily extremities, specifically the arms and legsspecifically the arms and legs

NORMAL EKG WAVEFORMNORMAL EKG WAVEFORM

DECEPTIVE WAVEFORMDECEPTIVE WAVEFORM

SOURCES OF ERRORSOURCES OF ERROR

Nervousness of test subjectNervousness of test subject Calibration errorsCalibration errors

DifficultiesDifficulties

Heart Rate MonitorHeart Rate Monitor

Galvanic Skin ResponseGalvanic Skin Response

LABVIEWLABVIEW

Lab SetupLab Setup

CONCLUSIONSCONCLUSIONS

““Simple” circuitry increases in complexity Simple” circuitry increases in complexity once work beginsonce work begins

Check and recheck components before Check and recheck components before and after assemblyand after assembly

Start earlyStart early Be flexible and constantly improveBe flexible and constantly improve