Arduino lie detector - How to make a simple and easy lie detector with Arduino

Yesterday we studied how to detect Galvanic Skin Response GSR with Arduino.

Today we are going to see how we can use this knowledge to build a simple Arduino based Lie detector.

I found two projects that made sense about the subject.

Actually I have a certain criteria for choosing what projects to post.

First:

There must be scientific and practical credibility for the project.

I mean that it must be real, well written and well researched.

Second:

It must be easy to build and to realize.

Easy doesn't mean with no effort. But easy means that it can be built by following the steps as stated in the project.

That's what I found in those two projects here.


First Project

This project makes the GSR analysis with Arduino and then gives the result on one of two LEDs. Green or RED.

Circuit

Code

void setup()
{
 Serial.begin(9600);
 pinMode(2, OUTPUT);
 pinMode(3, OUTPUT);
 pinMode(4, OUTPUT);
 digitalWrite(2, HIGH);
 delay(500);
 digitalWrite(3, HIGH);
 delay(500);
 digitalWrite(4, HIGH);
 delay(500);
}

void loop()
{
 if (analogRead(A0) > 60)
 {
  digitalWrite(4, HIGH);
 }
 else
 {
  digitalWrite(4, LOW);
 }
 if (analogRead(A0) > 20)
 {
  digitalWrite(2, HIGH);
 }
 else
 {
  digitalWrite(2, LOW);
 }
 if (analogRead(A0) > 45)
 {
  digitalWrite(3, HIGH);
 }
 else
 {
  digitalWrite(3, LOW);
 }

 Serial.println(analogRead(A0));
 delay(20);
}

Second Project

This project uses temperature sensor to measure skin temperature as one of important parameters of biofeedback.

The project displays the result on an LCD and can also display results of GSR analysis on Processing code just as in yesterday project.

Circuit

Code

You can find all software for Arduino and Processing here.



Sources: Arduino Website , instructables

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How to make Galvanic Response Sensor with Arduino?

Today I found a Mind controlled quadcopter that is fully controlled by the power of thoughts with the NeuroSky headset and Arduino MKR1000 Board.

The project is very cool and thrilling.
It's definitely for quadcopter or Arduino haters. It actually needs a lot of work, patience and understanding.

Above all, it needs that you have the NeuroSky MindWave Headset(~$75) and MKR1000 Board(~$60) from Microsoft.

I've been searching all night about a way to make a simple and easy way to read mind signals (EKG Sensor) but without any result.

All circuits and sensors are complicated and very expensive.

Then I just stumpled upon the GSR (Galvanic Skin Response) which is typically the skin resistance variation in different times due to stress or fear.


I found that this sensor is faily simple and easy to make.

It is actually made of two simple electrodes to measure the skin resistance without the need for any amplifiers or filters as in any other biometric signal measurement.

With one lead sends current while the other measures the difference.

Arduino is used to measure the resistance at a 50 milliseconds intervals.

The results are sent to processing code to be displayed.

That's what I call an easy project.

So I've decided to include it here on my blog.

Code

Arduino Code:

void setup(){
  Serial.begin(9600); 
}

void loop(){
  int a=analogRead(0);
  if (Serial.available() > 0) {

    byte inbyte=Serial.read();
    if(inbyte=='a'){
      Serial.print(a,BYTE);


    }
  }
}

Processing Code:

import processing.serial.*;
Serial myPort;  

int hPosition = 1;     // the horizontal position on the graph
float currentReading;
float lastReading;
int count=0;
int zeroLinePos=0;

float gsrAverage,prevGsrAverage;
float baseLine=0;
long lastFlatLine=0;
color graphColor=color(255,255,255);
int baselineTimer=10000;
int gsrValue;
int gsrZeroCount=0;
float gsrRange=0;
int downhillCount=0;
int uphillCount=0;
boolean downhill;
boolean peaked=false;
float peak, valley;

void setup () {
  size(900, 450);
  // List all the available serial ports
  //println(Serial.list());

  myPort = new Serial(this, Serial.list()[0], 9600);
  currentReading=0;
  lastReading=0;
  gsrAverage=0;
  background(0);

  smooth();
}

void draw () {
  //best delay setting for gsr readings
  delay(50);
  //image(myMovie, 0, 0);

  if (gsrValue<15 amp="" gsrvalue="">-15){
    if( gsrZeroCount>10){
      currentReading=0;//flatline
      gsrAverage=0;
      baseLine=0;
      lastFlatLine=millis();
      gsrZeroCount=0;
      // println("reset");

    }
    gsrZeroCount++;
  }
  else{
    currentReading=gsrValue-baseLine;
    gsrZeroCount=0;
  }

  if(millis()-lastFlatLine>baselineTimer){
    baseLine=gsrAverage;
  }

  //graph colors
  if(gsrAverage>0 && gsrAverageheight/2.0*.25 && gsrAverageheight/2.0*.5 && gsrAverageheight/2.0*.75) graphColor=color(255,100,0);

  gsrRange=peak-valley;

  // at the edge of the screen, go back to the beginning:
  if (hPosition >= width) {
    hPosition = 0;

    //cover last drawing
    fill(0,200);
    noStroke();
    rect(0,0,width,height);
  }
  else {
    hPosition+=1;
  }

  gsrAverage=smooth(currentReading,.97,gsrAverage);

  //draw stuff

  //spike
  noStroke();
  if(gsrRange>200){
    fill(255);
    ellipse(10,10,20,20); 
  }
  else{
    fill(0);
    ellipse(10,10,20,20); 
  }

  //graph
  strokeWeight(.5);
  stroke(graphColor);
  line(hPosition-1, height/2.0-lastReading, hPosition, height/2.0-currentReading);
  stroke(255,0,100);
  line(hPosition-1,height/2.0-prevGsrAverage,hPosition,height/2.0-gsrAverage);

  //draw peaks
  int thres=7;

  noFill();
  stroke(255,0,0);
  strokeWeight(2);

  if (currentReading-thres>lastReading&& peaked==true){
    downhill=false;
    //println(downhillCount);
    uphillCount++;  
    downhillCount=0;
    point(hPosition-1, height/2.0-lastReading);
    valley=lastReading;
    peaked=false;

  }
  if(currentReading+thres 1){      // check to make sure param's are within range
    filterVal = .99;
  }
  else if (filterVal <= 0){
    filterVal = 0;
  }
  smoothedVal = (data * (1 - filterVal)) + (smoothedVal  *  filterVal);
  return (int)smoothedVal;
} 

   

Source: Makezine , Autho

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