malikmal: Photoresistor

In this project, I have connected an Arduino to my computer and used a photoresistor to control an animation on the screen. Other sensors could have been used, but I chose a photoresistor because it feels like magic!!

The photoresistor responds to changes in ambient light as my hand moves up and down. The Arduino sends the reading to a Processing sketch on the computer via a Serial command (through the USB cable). The processing sketch interprets the signal from the Arduino and selects the appropriate picture to display.

I took a series of screenshots from the following YouTube video: http://www.youtube.com/watch?v=h6nE8m74kDg And after borrowing a bit of code from these sites (1,2), the project was born.
This idea is not new, nor my own. There are many people who have done this project before, but I thought to blog about how I have done it, just for fun.

The Project Movie

Components Required

Arduino Uno (and associated software), and USB cable
Photoresistor or Photocell
10K resistor
Wires to put it all together
Processing IDE from http://processing.org
Computer/laptop

The Arduino Sketch

The picture above was made using Fritzing

The Arduino Code:

You can download the Arduino IDE from this site.

/* Jumper: Using an Arduino to animate:
   Written by ScottC on 02/06/2012 */

int photoRPin = 0; 
int minLight;
int maxLight;
int lightLevel;
int adjustedLightLevel;
int oldLightLevel;

void setup() {
  Serial.begin(9600);
  
  //Setup the starting light level limits
  lightLevel=analogRead(photoRPin);
  minLight=lightLevel-10;
  maxLight=lightLevel;
  oldLightLevel=lightLevel;
}

void loop(){
   lightLevel=analogRead(photoRPin);
   delay(10);
  
  //auto-adjust the minimum and maximum limits in real time   
   if(minLight>lightLevel){
     minLight=lightLevel;
   }
   if(maxLight<lightLevel){
     maxLight=lightLevel;
   }
   
   //Map the light level to produce a result between 1 and 28.
   adjustedLightLevel = map(lightLevel, (minLight+20), (maxLight-20), 1, 28); 
   adjustedLightLevel = constrain (adjustedLightLevel, 1,28);
   
   /*Only send a new value to the Serial Port if the 
     adjustedLightLevel value changes.*/
   if(oldLightLevel==adjustedLightLevel){
     //do nothing if the old value and the new value are the same.
   }else{
     //Update the oldLightLevel value for the next round
     oldLightLevel=adjustedLightLevel;
     
     /*Send the adjusted Light level result 
       to Serial port (processing)*/
     Serial.println(adjustedLightLevel);
   } 
}

The code above was formatted using this site.

The Processing Code:

You can download the Processing IDE from this site.

/* Jumper: Using an Arduino to animate
   Written by ScottC on 02/06/2012

Source code derived from : 
  http://processing.org/learning/topics/sequential.html
  http://processing.org/discourse/beta/num_1267080062.html

Pictures captured from:
  http://www.youtube.com/watch?v=h6nE8m74kDg      
  
======================================================= */

import processing.serial.*;
Serial myPort;
String sensorReading="";

// Create the array that will hold the images
PImage[] movieImage = new PImage[29];

/* The frame variable is  used to control which 
   image is displayed */
int frame = 1;



/* Setup the size of the window. Initialise serial communication with Arduino
   and pre-load the images to be displayed later on. This is done only once.
   I am using COM6 on my computer, you may need replace this value with your
   active COM port being used by the Arduino.*/

void setup(){
  size(700,600);
  
  myPort = new Serial(this, "COM6", 9600);
  myPort.bufferUntil('\n');
  
  for(int i=0;i<28;i++){
    movieImage[i] = loadImage("Jumper" + (i+1) + ".jpg");
  }
}




// The draw function controls the animation sequence.

void draw(){
  
  //this draws the relevant image to the window  
  image(movieImage[frame-1],0,0,width,height);
}

void serialEvent (Serial myPort){
 sensorReading = myPort.readStringUntil('\n');
  if(sensorReading != null){
    sensorReading=trim(sensorReading);
    if (sensorReading.length()<2){
      frame = integerFromChar(sensorReading.charAt(0));
    }else{
      frame = integerFromChar(sensorReading.charAt(0))*10;
      frame += integerFromChar(sensorReading.charAt(1));
    }
  }
}



/* This function used to convert the character received from the
   serial port (Arduino), and converts it to a number */
   
int integerFromChar(char myChar) {
  if (myChar < '0' || myChar > '9') {
    return -1;
  }else{
  return myChar - '0';
  }
}