3rd Inning

Introduction

Tri-color LED fading

This is the way to hook up a tri-color LED. Basically you are hooking up 3 leds that have a common ground. The average voltage that each led uses to power itself is varied using pulse width modulation. The code basically does a neato nested loop to vary the colors. This is a fun circuit to play with. Make sure to use the resistors or you may burn up your LED - The cost a couple of bucks!

Components Needed

• Freeduino or Arduino or clone
• USB cable for Freeduino
• Freeduino development software - download here!
• Solderless Breadboard
• Hookup wire 22gauge solid

• Common Cathode LED

How to

1. refer to the fritzing drawing to place the wires
2. upload the code below using cut and paste
3. Run and watch the fading of the led!

Schematic

Fritzing

Code

Cut and paste this into your Arduino code window!

int RED = 9;    // RED pin of the LED to PWM pin 9 
int GREEN = 10;  // GREEN pin of the LED to PWM pin 10
int BLUE = 11;   // BLUE pin of the LED to PWM pin 11

void setup()
{
  // nothing for setup 
}

void loop()
{
  for(int r = 0; r < 1024; r+=5) {
    for(int g = 0; g < 1024; g+=5) {
      for(int b = 0; b < 1024; b+=5) {
        analogWrite(RED, r);
        analogWrite(GREEN, g);
        analogWrite(BLUE, b);
        delay(30);
      }
    }
  }
}

or cut and paste this one... it is neater

//This code comes from...
//http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1207331496
//modified to just go through a pretty color loop!
//use tools->serial monitor to watch the values
//bpw 5/10/10


int rpin = 9;    // RED pin of the LED to PWM pin 9 
int gpin = 10;  // GREEN pin of the LED to PWM pin 10
int bpin = 11;   // BLUE pin of the LED to PWM pin 11

int r=0, g=0, b=0;
float h;


void h2rgb(float h, int &R, int &G, int &B);

void setup()                    // run once, when the sketch starts
{
   Serial.begin(9600);    
}


void loop()                     // run over and over again
{
  
  for (int val = 0; val <1024; val++) {
    h = ((float)val)/1024;

    h2rgb(h,r,g,b);
    Serial.println (val) ;
    Serial.println (h) ;
    Serial.println (r) ;
    Serial.println (g) ;
    Serial.println (b) ;
    Serial.println ("  ") ;

    analogWrite(rpin, r);
    analogWrite(gpin, g);
    analogWrite(bpin, b);
    //delay(50);
  }
}

void h2rgb(float H, int& R, int& G, int& B) {

  int var_i;
  float S=1, V=1, var_1, var_2, var_3, var_h, var_r, var_g, var_b;

  if ( S == 0 )                       //HSV values = 0 ÷ 1
  {
    R = V * 255;
    G = V * 255;
    B = V * 255;
  }
  else
  {
    var_h = H * 6;
    if ( var_h == 6 ) var_h = 0;      //H must be < 1
    var_i = int( var_h ) ;            //Or ... var_i = floor( var_h )
    var_1 = V * ( 1 - S );
    var_2 = V * ( 1 - S * ( var_h - var_i ) );
    var_3 = V * ( 1 - S * ( 1 - ( var_h - var_i ) ) );

    if      ( var_i == 0 ) {
      var_r = V     ;
      var_g = var_3 ;
      var_b = var_1 ;
    }
    else if ( var_i == 1 ) {
      var_r = var_2 ;
      var_g = V     ;
      var_b = var_1 ;
    }
    else if ( var_i == 2 ) {
      var_r = var_1 ;
      var_g = V     ;
      var_b = var_3 ;
    }
    else if ( var_i == 3 ) {
      var_r = var_1 ;
      var_g = var_2 ;
      var_b = V     ;
    }
    else if ( var_i == 4 ) {
      var_r = var_3 ;
      var_g = var_1 ;
      var_b = V     ;
    }
    else                   {
      var_r = V     ;
      var_g = var_1 ;
      var_b = var_2 ;
    }

    R = (1-var_r) * 255;                  //RGB results = 0 ÷ 255
    G = (1-var_g) * 255;
    B = (1-var_b) * 255;
  }
}
 

Troubleshooting

• is your led in correctly (the longest pin(cathode) should connect to ground)
• code for the pins on Arduino correct

Resources

Most of this example was taken from here.