RGB LED Transition (Arduino)




Introduction: RGB LED Transition (Arduino)

About: Hey YOU! Yeah, I'm talking to you who is reading this. Send me ideas for instructables, like things that you are wondering how to make or build, or really anything electronically related, and I'll get back t...

Hello Guys, in this instructable I will give you a code for transtioning an LED. My group, Newton Labs, has spent quite a bit of time on this. Transitioning isn't as easy as it seems for a nice smooth transition.

Submitted by Newton Labs for the Instructables Sponsorship Program

Step 1: The Circuit

In this circuit, you will need to use 3 Pulse Width Modulation pins, PWM for short. Pins that are not specified as PWM pins are digital pins, which can only turn on and off. PWM pins can go from lets say 3.3 volts to five volts to 1.1 volts.

In my program  Red = pin 3, Blue = pin 5, and Green = pin 6.

Step 2: The Code

int prevR = 0, prevG = 0, prevB = 0; // all of the previous RGB values
int const Red = 3; //pin 3 
int const Blue = 5; // pin 4
int const Green = 6; // pin 5

void setup(){} // sets up the program
void loop() { //main loop of the program
  RGB(255, 255, 255); // this calls the RGB function
  delay(1000); //stays on white for one second
  RGB(0, 0, 255); 
    RGB(0, 255, 0);
    RGB(255, 0, 255);

void RGB(int R, int G, int B) {
for (int i = 0; i <= 255; i++)
if (i >=  prevR - R && prevR < R) {
  analogWrite(Red, prevR + i);
if (i >= prevG - G && prevG < G) {
  analogWrite(Green, prevG + i);
if (i >= prevB - B && prevB < B) {
  analogWrite(Blue, prevB + i);
//for (int i = 0; i <= 255; i++)
if (i >= R - prevR && prevR > R) {
  analogWrite(Red, prevR - i);
if (i >= G - prevG && prevG > G) {
  analogWrite(Green, prevG - i);
if (i >= B - prevB && prevB > B) {
  analogWrite(Blue, prevB - i);
analogWrite(Red, R);
analogWrite(Green, G);
analogWrite(Blue, B);
prevR = R;
prevG = G;
prevB = B;

Step 3: Hooray!

You are done and you should have Revision 3 of my RGB LED transitioning program! 



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13 Discussions

i've been trying to make my own but i've had no luck,your one is awesome!

1 reply

I've programmed two other ways to transition this, and working on a 3rd that takes into account how LED's are observed by the human eye, but for the time being for a simpler to understand program (as I feel programming should be just as much about getting the job done as it should be about clairty) you can try looking through this.

This is the simplest one I have so far.

int const Red=3, /* Pin 3 */ Blue=5, /* Pin 5 */ Green=6; /* Pin 6 */
void RGB(int R,int G,int B){

void setup(){}
void loop(){

int r =255, g =0, b =0;

for(int i =0; i <=255;++i){




r =255; g =255;b =0;

for(int i =255; i >=0;--i){




r =0;g =255;b =0;

for(int i =0; i <=255;++i){



r =0;g =255;b =255;

for(int i =255; i >=0;--i){




r =0;g =0;b =255;

for(int i =0; i <=255;++i){




r =255;g =0;b =255;

for(int i =255; i >=0;--i){





how did you make this awesome code,man!?

I've had relatively good luck dimensioning rgb into arrays, then using an array I use a for loop to increment the values based on the next array value and splitting the difference between then and dividing it by 16 where I have 15 analogWrite instances each adding or decreasing 1/16 rgb value . (In my arrays each jump is 32 rgb values +/-) I need to amend the code to deal with the values above 255, but where the values are below 255 the transition is as smooth as butter. Oh and the delay is 100ms between each.

This was a very useful tutorial and program to help me get started in using the Arduino, thank you!

Because of the way the "i" counter works, this program will fail if you start using RGB values that are different than 255 or 0. I had many problems with the software counting too far.

I modified the software and created two completely different ways of processing the data (with slightly different results). If you or anyone is interested, get in touch with me :-) it allows you to custom set the RGB values without affecting the quality of the transition from one colour to the other.

Similar instructable here:

Also I uploaded code to continuously change from one random color to another here (just change the color pins to your pin numbers):
int red = 11; //this sets the red led pin
int green = 10; //this sets the green led pin
int blue = 9; //this sets the blue led pin

int redNow;
int blueNow;
int greenNow;
int redNew;
int blueNew;
int greenNew;

void setup()
{ //this sets the output pins
pinMode(red, OUTPUT);
pinMode(green, OUTPUT);
pinMode(blue, OUTPUT);
redNow = random(255);
blueNow = random(255);
greenNow = random(255);
redNew = redNow;
blueNew = blueNow;
greenNew = greenNow;

#define fade(x,y) if (x>y) x--; else if (x<y) x++;

void loop()
analogWrite(blue, blueNow);
analogWrite(red, redNow);
analogWrite(green, greenNow);
redNew = random(255);
blueNew = random(255);
greenNew = random(255);
// fade to new colors
while ((redNow != redNew) ||
  (blueNow != blueNew) ||
  (greenNow != greenNew))
  analogWrite(blue, blueNow);
  analogWrite(red, redNow);
  analogWrite(green, greenNow);

1 reply

Well, I know that my group was the only one who was trying to do this, but its nice to know that we aren't the only ones trying to do this.