My first Arduino project!
I wanted an RGB LED whose colour I could control with just one potentiometer. To do this, I created this workflow:
Read potentiometer > take pot value as a Hue value in a HSB system1 > convert HSB values (with S=1 and B=1) into RGB values > Use arduino pins to PWM RGB output to my RGB LED
The hardest part was converting HSB into RGB - the equations that I worked on from wikipedia are an absolute nightmare to translate into code (at least for me at this stage). I was about to give up when I saw this link, full of ready-made colour conversion functions: http://www.easyrgb.com/math.php?MATH=M21#text21.
The hardware is sitting on a breadboard, with a bit of paper diffusing the LED lamp, so it's not too pretty-looking. Here's my code anyhow:
int potpin = 2; // Switch connected to digital pin 2
int rpin = 9;
int gpin = 10;
int bpin = 11;
float h;
int h_int;
int r=0, g=0, b=0;
int val=0;
void h2rgb(float h, int &R, int &G, int &B);
void setup() // run once, when the sketch starts
{
Serial.begin(9600); // set up Serial library at 9600 bps
}
void loop() // run over and over again
{
val=analogRead(potpin); // Read the pin and display the value
//Serial.println(val);
h = ((float)val)/1024;
h_int = (int) 360*h;
h2rgb(h,r,g,b);
Serial.print("Potentiometer value: ");
Serial.print(val);
Serial.print(" = Hue of ");
Serial.print(h_int);
Serial.print("degrees. In RGB this is: ");
Serial.print(r);
Serial.print(" ");
Serial.print(g);
Serial.print(" ");
Serial.println(b);
analogWrite(rpin, r);
analogWrite(gpin, g);
analogWrite(bpin, b);
}
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;
}
}