UPDATE! See my updated version of this code here

I was just messing around with some cheap RGB Leds I got off ebay and decided to replicate the smooth colour changing I seen on some Ikea lamp a while back… There are more complicated ways of doing this with less program “bloat”, for lack of a better word, but here is a useful example of how to;

Fade between 4 colours using an RGB LED and PWM on an Arduino Uno

Here is an example of the finished code running.

The Code I’ve commented the first bits and most of it should make sense. Let me know if/where you use it I’m always keen to see projects.

/*
  Fade RGB LED Smoothly through 4 colours
  Fades an RGB LED using PWM smoothly through 4 different colours pausing for 1.5 seconds on each colour.
  
  Connect an common Cathode RGB LED with appropriate resistors on each anode to your Arduino Uno; 
  Red to pin 11, Green to pin 10, Blue to pin 9, Cathode to GND.
  
  Developed for Arduino Uno by Joshua David - TechHelpBlog.com
   
  Please Feel Free to adapt and use this code in your projects. 

 Contact me at techhelpblog.com and let me know how you've used it!  
 */

// Assign LED Output PWM Pins
int Red = 11;
int Green = 10;
int Blue = 9;

//Set Initial Values
int RedVal = 0;
int GreenVal = 0;
int BlueVal = 0;
int fade = 10;  // Delay Time

// Colour Value 1 as each colour intensity (0-255)
int RedVal1 = 186;
int GreenVal1 = 0;
int BlueVal1 = 255;

// Colour Value 2
int RedVal2 = 9;
int GreenVal2 = 239;
int BlueVal2 = 26;

//Colour Value 3
int RedVal3 = 255;
int GreenVal3 = 120;
int BlueVal3 = 0;

//Colour Value 4
int RedVal4 = 0;
int GreenVal4 = 255;
int BlueVal4 = 78;

//Set initial mode (Colour Value Mode) to Colour Value 1
int mode = 1;

void setup()
{

 //----------------------- Assign outputs
   pinMode(Red, OUTPUT);
   pinMode(Green, OUTPUT);
   pinMode(Blue, OUTPUT);
 //----------------------- Write Initial Values of 0 to outputs
   analogWrite(Red, RedVal);
   analogWrite(Green, GreenVal);
   analogWrite(Blue, BlueVal);

}

void loop()                            // Begin Main Program Loop

{
  while(mode == 1){
    if(RedVal < RedVal1){              // If RedVal is less than desired RedVal1
      RedVal ++;                       // increment RedVal
    } else if(RedVal > RedVal1){       // If RedVal is more than desired RedVal1
      RedVal --;                       // decrement RedVal
    } else if(RedVal == RedVal1){      // If RedVal is equal to desired RedVal1
      //Do Nothing 
    }
                                       // Repeated as above for BlueVal
    if(BlueVal < BlueVal1){
      BlueVal ++;
    } else if(BlueVal > BlueVal1){
      BlueVal --;
    } else if(BlueVal == BlueVal1){
      //Do Nothing
    }
                                       // Repeated as above for GreenVal
    if(GreenVal < GreenVal1){
      GreenVal ++;
    } else if (GreenVal > GreenVal1){
      GreenVal --;
    } else if (GreenVal == GreenVal1){
      // Do Nothing
    }
                                       // Now we have a new set of values, we write them to the PWM Pins.
    analogWrite(Red, RedVal);
    analogWrite(Green, GreenVal);
    analogWrite(Blue, BlueVal);
    delay(fade);                       // Implement a bit of delay to slow the change of colour down a bit

    if(RedVal == RedVal1 && GreenVal == GreenVal1 && BlueVal == BlueVal1){ // If RedVal & GreenVal & BlueVal are all at the desired values
      delay(1500);                     // Delay to hold this colour for a little while
      mode = 2;                        // Change the mode to the next colour. Exiting this while loop and into the next one
    }
  }

  while(mode == 2){
    if(RedVal < RedVal2){
      RedVal ++;                     
    } else if(RedVal > RedVal2){
      RedVal --;                     
    } else if(RedVal == RedVal2){
      //Do Nothing 
    }

    if(BlueVal < BlueVal2){
      BlueVal ++;
    } else if(BlueVal > BlueVal2){
      BlueVal --;
    } else if(BlueVal == BlueVal2){
      //Do Nothing
    }

    if(GreenVal < GreenVal2){
      GreenVal ++;
    } else if (GreenVal > GreenVal2){
      GreenVal --;
    } else if (GreenVal == GreenVal2){
      // Do Nothing
    }

    analogWrite(Red, RedVal);
    analogWrite(Green, GreenVal);
    analogWrite(Blue, BlueVal);
    delay(fade);

    if(RedVal == RedVal2 && GreenVal == GreenVal2 && BlueVal == BlueVal2){
      delay(1500);
      mode = 3;
     //break;
    }
  }

  while(mode == 3){
    if(RedVal < RedVal3){
      RedVal ++;
    } else if(RedVal > RedVal3){
      RedVal --;
    } else if(RedVal == RedVal3){
      //Do Nothing 
    }

    if(BlueVal < BlueVal3){
      BlueVal ++;
    } else if(BlueVal > BlueVal3){
      BlueVal --;
    } else if(BlueVal == BlueVal3){
      //Do Nothing
    }

    if(GreenVal < GreenVal3){
      GreenVal ++;
    } else if (GreenVal > GreenVal3){
      GreenVal --;
    } else if (GreenVal == GreenVal3){
      // Do Nothing
    }

    analogWrite(Red, RedVal);
    analogWrite(Green, GreenVal);
    analogWrite(Blue, BlueVal);
    delay(fade);

    if(RedVal == RedVal3 && GreenVal == GreenVal3 && BlueVal == BlueVal3){
      delay(1500);
      mode = 4;
      //break;
    }
  }

  while(mode == 4){
    if(RedVal < RedVal4){
      RedVal ++;
    } else if(RedVal > RedVal4){
      RedVal --;
    } else if(RedVal == RedVal4){
      //Do Nothing 
    }

    if(BlueVal < BlueVal4){
      BlueVal ++;
    } else if(BlueVal > BlueVal4){
      BlueVal --;
    } else if(BlueVal == BlueVal4){
      //Do Nothing
    }

    if(GreenVal < GreenVal4){
      GreenVal ++;
    } else if (GreenVal > GreenVal4){
      GreenVal --;
    } else if (GreenVal == GreenVal4){
      // Do Nothing
    }

    analogWrite(Red, RedVal);
    analogWrite(Green, GreenVal);
    analogWrite(Blue, BlueVal);
    delay(fade);

    if(RedVal == RedVal4 && GreenVal == GreenVal4 && BlueVal == BlueVal4){
      delay(1500);
      mode = 1;                                 // Set mode back to 1 to return to the original colour.
      //break;
    }
  }

}