Fading Arduino RGB LED from one color to the other?

Question

I\'ve currently managed to get my LED to cycle through eight colors that I\'ve selected. Everything is working correctly, except that I want to go for a more natural feel, and w

Answer 1

This is probably what you are looking for. Whenever we want to shift color over the spectrum and trasition the colors in a circular and smooth motion, what we are really doing is shifting light using HUE in the HSI/HSV (Hue, Saturation, Intensity/Value) color space.

Take if you will this figure:

We will attach a value from 0-360 for hue because hue has 360 degrees of color. A value of 0.00 - 1.00 for saturation, and a value of 0.00 -1.00 for intensity/value

Here is my circuit on the MEGA 2560:

Here is video of this code running:

So lets build a function that we can pass the hue value and a for loop inside our loop function to call that value 360 times to shift over the full rainbow of color.

//Define the pins we will use with our rgb led
int redPin = 9;
int greenPin = 10;
int bluePin = 11;

//define that we are using common anode leds
#define COMMON_ANODE

void setup()
{
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
}

int rgb[3];
//Arduino has no prebuilt function for hsi to rgb so we make one:
void hsi_to_rgb(float H, float S, float I) {
  int r, g, b;
  if (H > 360) {
    H = H - 360;
  }
  // Serial.println("H: "+String(H));
  H = fmod(H, 360); // cycle H around to 0-360 degrees
  H = 3.14159 * H / (float)180; // Convert to radians.
  S = S > 0 ? (S < 1 ? S : 1) : 0; // clamp S and I to interval [0,1]
  I = I > 0 ? (I < 1 ? I : 1) : 0;
  if (H < 2.09439) {
    r = 255 * I / 3 * (1 + S * cos(H) / cos(1.047196667 - H));
    g = 255 * I / 3 * (1 + S * (1 - cos(H) / cos(1.047196667 - H)));
    b = 255 * I / 3 * (1 - S);
  } else if (H < 4.188787) {
    H = H - 2.09439;
    g = 255 * I / 3 * (1 + S * cos(H) / cos(1.047196667 - H));
    b = 255 * I / 3 * (1 + S * (1 - cos(H) / cos(1.047196667 - H)));
    r = 255 * I / 3 * (1 - S);
  } else {
    H = H - 4.188787;
    b = 255 * I / 3 * (1 + S * cos(H) / cos(1.047196667 - H));
    r = 255 * I / 3 * (1 + S * (1 - cos(H) / cos(1.047196667 - H)));
    g = 255 * I / 3 * (1 - S);
  }
  rgb[0] = r;
  rgb[1] = g;
  rgb[2] = b;

}
void setColor(int red, int green, int blue)
{
  #ifdef COMMON_ANODE
    red = 255 - red;
    green = 255 - green;
    blue = 255 - blue;
  #endif
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);
}


///here we have our main loop and the for loop to shift color
void loop()
{
//the for loop counts to 360 and because its in our control loop it will run forever
// We will use int i to increment the actual desired color 
for (int i=0; i<=360;i++){
  hsi_to_rgb(i,1,1);
  setColor(rgb[0],rgb[1],rgb[2]);
  //Changing the delay() value in milliseconds will change how fast the
  //the light moves over the hue values 
  delay(5);
  }


}