Assignment: Sensing PART II: Force sensors and photocells

Collaborators:

Part I: Programming

I modified the Puff sample code by Ira Greenberg that creates an organic-looking trail of elipses that move around. The input from the pressure sensor interrupts the motion, making it appear that the creature-puff is twitchy.

Components Used

• Arduino Board
• Red, Green, and Blue LEDs
• 3 220-ohm Resistors
• Wire
• Breadboard
• USB cable
• Laptop running Arduino
• Cotton ball, small glass for diffuser
• Force sensor
• Photocell

Arduino Code

/*
 * Resistive Sensor Input
 * Takes the input from a resistive sensor, e.g., FSR or photocell
 * Dims the LED accordingly, and sends the value (0-255) to the serial port
 */
int sensorPin = 0;  // select the input pin for the sensor
int ledPin = 11;    // select the output pin for the LED
int val = 0;        // variable to store the value coming from the sensor
void setup() {
  Serial.begin(9600);
}
void loop() {
  val = analogRead(sensorPin); // read the value from the sensor, 0-1023
  analogWrite(ledPin, val/4);  // analogWrite (dimming the LED) can be between 0-255
  Serial.println(val/4);       // writing the value to the PC via serial connection 
  delay(50);                   // rest a little...
}

Processing Code

 /*
 * Twitchy Puff. 
 * Based on Puff by Ira Greenberg. 
 * http://processing.org/learning/topics/puff.html
 * Series of ellipses simulating a multi-segmented organism, utilizing a follow 
 * the leader algorithm. Pressure sensor adds twitchiness.
 */

import processing.serial.*;
String portname = "/dev/tty.usbserial-A70061pj"; // my Mac's serial port address
Serial port;
String buf="";
int cr = 13;  // ASCII return   == 13
int lf = 10;  // ASCII linefeed == 10
int val;


// For puff head
float headX;
float headY;
float speedX = .7;
float speedY = .9;

// For puff body
int cells = 1000;
float[]px= new float[cells];
float[]py= new float[cells];
float[]radiiX = new float[cells];
float[]radiiY = new float[cells];
float[]angle = new float[cells];
float[]frequency = new float[cells];
float[]cellRadius = new float[cells];

void setup(){
  
  size(640, 360);
  
  // Begin in the center
  headX = width/2;
  headY = height/2;

  // Fill body arrays
  for (int i=0; i< cells; i++){
    radiiX[i] = random(-7, 7); 
    radiiY[i] = random(-4, 4);
    frequency[i]= random(-9, 9);
    cellRadius[i] = random(16, 30);
  }
  frameRate(30);
}

void draw(){
  background(0);
  noStroke();
  fill(255, 255, 255, 5);

  // Follow the leader
  for (int i =0; i< cells; i++){
    if (i==0){
      px[i] = headX+sin(radians(angle[i]))*radiiX[i];
      py[i] = headY+cos(radians(angle[i]))*radiiY[i];
    } 
    else{
      px[i] = px[i-1]+cos(radians(angle[i]))*radiiX[i];
      py[i] = py[i-1]+sin(radians(angle[i]))*radiiY[i];

      // Check collision of body
      if (px[i] >= width-cellRadius[i]/2 || px[i] <= cellRadius[i]/2){
        radiiX[i]*=-1;
        cellRadius[i] = random(1, 40);
        frequency[i]= random(-13, 13);
      }
      if (py[i] >= height-cellRadius[i]/2 || py[i] <= cellRadius[i]/2){
        radiiY[i]*=-1;
        cellRadius[i] = random(1, 40);
        frequency[i]= random(-9, 9);
      }
    }
    // Draw puff
    ellipse(px[i],  py[i],  cellRadius[i],  cellRadius[i]);
    // Set speed of body
    angle[i]+=frequency[i];
  }

  // Set velocity of head
  headX+=speedX;
  headY+=speedY;

  // Check boundary collision of head
  if (headX >= width-cellRadius[0]/2 || headX <=cellRadius[0]/2){
    speedX*=-1;
  }
  if (headY >= height-cellRadius[0]/2 || headY <= cellRadius[0]/2){
    speedY*=-1;
  }
}

// called whenever serial data arrives
void serialEvent(Serial p) {
  int c = port.read();
  if (c != lf && c != cr) {
    buf += char(c);
  }
  if (c == lf) {
    int val = int(buf);
    println("val="+val);
      if(val==0){
      speedX=speedX-.5;
      speedY=speedY-.5;
      }
      else{
      speedX=speedX+(val/500);
      speedY=speedY+(val/500);
 
      }
    }
  } 

Part II: Mechanical

I played with sensing the pressure on a keyboard when a person is typing. If the sensor notices that there is heavy fluctuations in typing, like the user is typing angrily, it could send a message to the user to take a break from the computer. Also, if the pressure lasts a long time, indicating that the user hasn't moved from the computer in too long, it could remind the user to stretch or have a snack.