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