Introduction: Stress Makes Art: Galvanic Skin Response and Visual Generation
I'm a graphic design student and built this project for a beginning electronics class. I'm interested in connecting the signals generated by one's body to the act of visual generation. This piece takes the galvanic skin response value of the user and uses it to fuel the creation of a visual on screen. Galvanic skin response is thought to be correlated to a person's stress level and is used in lie detectors. In this particular work, the GSR value affects the speed at which a black growth is visualized on screen. This represents the idea that the more stressed we are, the faster diseases and other negative consequences can spread.
The hardware part of this project is fairly straightforward and uses an Arduino Uno board and the following other materials:
- Arduino Uno w/usb connector
--Breadboard
- 2 250K resistors, in a series
- Jumper wires
- Stranded wires
- 2 ring terminals (or other metal objects to place fingers on)
- Solder + soldering iron
The more complicated part of this project was coding in the Processing environment. These instructions will be in two main steps, "Hardware" and "Code" with a brief mention in step three of the construction of the enclosure for the electronics.
Step 1: Hardware
To make the sensors, I soldered the two ring terminals to jumper wires (you can also use stranded wires) and connected the wires to the breadboard as noted in the photograph and schematic. One wire is connected to 5V and the second wire is connected to GND through two 250K resistors in a series. This second sensor's wire is also connected to the A0 terminal on the Arduino. These connections to the Arduino are all made via the breadboard.
Step 2: Code
For the coding part of this project, I referred to the two sources below. You don't need to look at these sources unless you want to understand them in their original form. If you just want to copy/paste code that works, skip to 3) My Code.
1) GSR Source Code
The first was http://cwwang.com/2008/04/13/gsr-reader/ which includes the Arduino code (for Arduino and Processing to communicate) and the Processing code to use the galvanic skin response data from the constructed sensors. Wang's code basically charts a person's galvanic skin response value in a moving line graph, which looks a little like an EKG reading visually. I wanted to have a more abstract visualization of the data so used code from another source to generate the visuals.
2) Visual Source Code
The code to create the visuals is from: http://www.generative-gestaltung.de/P_2_2_1_01
3) My Code
A) ARDUINO CODE BELOW
void setup(){
Serial.begin(9600);
}
void loop(){
int a=analogRead(0);
if (Serial.available() > 0)
{
byte inbyte=Serial.read();
if(inbyte=='a')
{
Serial.write(a);
}
}
}
---------------------------------------------
B) PROCESSING CODE BELOW
// you can copy/paste this code into a new Processing sketch
// Visual source code from: http://www.generative-gestaltung.de/P_2_2_1_01
// GSR source code from: http://cwwang.com/2008/04/13/gsr-reader/
import processing.pdf.*;
import java.util.Calendar;
boolean recordPDF = false;
import processing.serial.*;
Serial myPort;
int hPosition = 1;
float currentReading;
float lastReading;
int count=0;
int zeroLinePos=0;
float gsrAverage,prevGsrAverage;
float baseLine=0;
long lastFlatLine=0;
int baselineTimer=10000;//10 sec
int gsrValue;
int gsrZeroCount=0;
float gsrRange=0;
int downhillCount=0;
int uphillCount=0;
boolean downhill;
boolean peaked=false;
float peak, valley;
int speed ;
int NORTH = 0;
int NORTHEAST = 1;
int EAST = 2;
int SOUTHEAST = 3;
int SOUTH = 4;
int SOUTHWEST = 5;
int WEST = 6;
int NORTHWEST= 7;
float stepSize = 1;
float diameter = 1;
int direction;
float posX, posY;
int minCurrentReading = 1000;
int maxCurrentReading = 0;
void setup() {
size(800, 800);//size of window for image
background(255);
smooth();
noStroke();
posX = width/2;
posY = height/2;
println(Serial.list());
currentReading=0;
lastReading=0;
gsrAverage=0;
//find the right serial port for your computer and enter in the number inside []
myPort = new Serial(this, Serial.list()[8], 9600);
}
void serialEvent (Serial myPort) {
int inByte=myPort.read();
//0-255
gsrValue=inByte;//taking value sent from Arduino
}
void draw() {
calculateGSR();
println("currentReading = " + currentReading);
// map currentReading to speed
if (currentReading <= 50)
{
currentReading = minCurrentReading;
} else if (currentReading > 1000)
{
currentReading = maxCurrentReading;
}
else // valid zone
{
if (currentReading< minCurrentReading)
{
minCurrentReading = int( currentReading);
}
if (currentReading> maxCurrentReading)
{
maxCurrentReading = int(currentReading);
}}
println("currentReading = " + currentReading + " minCurrentReading = " + minCurrentReading + " maxCurrentReading = " + maxCurrentReading);
currentReading = map (currentReading, minCurrentReading,maxCurrentReading,10,15000);
speed = int (currentReading);
println("mapped value = "+ speed);
delay(50);//delay for stability
//applying the GSR reading to drive the speed of that the organic drawing "grows"
for (int i=0; i<=speed; i++) {
direction = (int) random(0, 8);
if (direction == NORTH) {
posY -= stepSize;
}
else if (direction == NORTHEAST) {
posX += stepSize;
posY -= stepSize;
}
else if (direction == EAST) {
posX += stepSize;
}
else if (direction == SOUTHEAST) {
posX += stepSize;
posY += stepSize;
}
else if (direction == SOUTH) {
posY += stepSize;
}
else if (direction == SOUTHWEST) {
posX -= stepSize;
posY += stepSize;
}
else if (direction == WEST) {
posX -= stepSize;
}
else if (direction == NORTHWEST) {
posX -= stepSize;
posY -= stepSize;
}
if (posX > width) posX = 0;
if (posX < 0) posX = width;
if (posY < 0) posY = height;
if (posY > height) posY = 0;
fill(0, 40);
ellipse(posX+stepSize/2, posY+stepSize/2, diameter, diameter);
//send 'a' for more bytes
}
}
void calculateGSR () {
//best delay setting for gsr readings
//println(gsrValue);
delay(50);
//image(myMovie, 0, 0);
if (gsrValue<15 &&gsrValue>-15){ // anything between -15 and +15 is considered zero
//if someone lifts fingers off for 10 seconds resulting in 10 0s, just reset
if( gsrZeroCount>10){
currentReading=0;//flatline
gsrAverage=0;
baseLine=0;
lastFlatLine=millis();
gsrZeroCount=0;
// println("reset");
}
gsrZeroCount++;
} // end of test for close to zero
else{ // ggood reading
currentReading=gsrValue-baseLine;
gsrZeroCount=0;
}
if(millis()-lastFlatLine>baselineTimer){
baseLine=gsrAverage;//if we got at least 10 seconds of reading since the last flatline
}
gsrRange=peak-valley;
gsrAverage=smooth(currentReading,.99,gsrAverage);
int thres=7;
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<lastReading && peaked==false){
//println(uphillCount);
downhill=true;
uphillCount=0;
downhillCount++;
point(hPosition-1, height/2.0-lastReading);
peak=lastReading;
peaked=true;
}
prevGsrAverage=gsrAverage;
lastReading=currentReading;
//send 'a' for more bytes
myPort.write('a');
}
int smooth(float data, float filterVal, float smoothedVal){
if (filterVal > 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;
}
Step 3: External Design/Enclosure (silver Box With Black Hand)
If you want to make a simple paper box enclosure for the electronics, you can look at this box template. I made the box with metallic cardboard and printed a hand mark on top so that people at the exhibition knew to place their hand on the box to start the experience. This is obviously optional and there are many ways to make sturdier enclosures.
