The code used to create a Spectral Radiation Cell using Arduino and RGB LED

Arduino Color Spectrum Gennerator

//set the color pins
#define RED 0
#define GREEN 1
#define BLUE 2
    

//set the pause button pins...
#define PAUSE_BUTTON 8

//MicroSeconds between each color... 
#define SPEED 3000

boolean locked;
int last_color[] = {0,0,0};
int last_btn_state;
int power_multiplier = 9;

void setup () {
    //set the color pins
  
//set the RED pin
  pinMode(RED, OUTPUT); 
//set the GREEN pin
  pinMode(GREEN, OUTPUT);
//set the BLUE pin  
  pinMode(BLUE, OUTPUT);


    //set the button...  
  //set the VOLTAGE pin  
  //set the pin of the serial INPUT
  pinMode(PAUSE_BUTTON,INPUT);
  clear_all();

  //Serial.begin(9600);
}

void clear_all(){
  digitalWrite(RED, HIGH); 
  digitalWrite(GREEN, HIGH); 
  digitalWrite(BLUE, HIGH); 
}

void light_color(int red , int green , int blue , int brightness) {
  
  if(red > 0){
    digitalWrite(RED, LOW); 
    delayMicroseconds(red * power_multiplier);
    digitalWrite(RED, HIGH);
  }
  
  if (green > 0) {
    digitalWrite(GREEN, LOW); 
    delayMicroseconds(green * power_multiplier);
    digitalWrite(GREEN, HIGH);
  }
  
  if (blue > 0){
    digitalWrite(BLUE, LOW);
    delayMicroseconds(blue * power_multiplier);
    digitalWrite(BLUE, HIGH);
    
  }
 // add white (brightness)
 if (brightness > 0) {
   digitalWrite(RED, LOW); 
  digitalWrite(GREEN, LOW); 
  digitalWrite(BLUE, LOW); 
  delayMicroseconds(brightness);
 }  
   clear_all();
}


void set_last_color(int r, int g, int b){
  last_color[0] = r;
  last_color[1] = g;
  last_color[2] = b;
}

boolean detect_pause_click(){
    int btn_state = digitalRead(PAUSE_BUTTON);
    if(btn_state == HIGH && last_btn_state != btn_state){
    locked = !locked;
    last_btn_state = btn_state;
    return true;
  }

  last_btn_state = btn_state;
  return false;
}

void loop () {
  
  if (locked){
   light_color(last_color[0],last_color[1],last_color[2],0);
   delayMicroseconds (SPEED);
   detect_pause_click();
   return;
  }
  
    // from r -> rb
  for(int i = 0;i<256;i++){
    // blue value
   light_color(255,0,i,0);
   set_last_color(255,0,i);
   if (detect_pause_click()){return;}
   delayMicroseconds (SPEED);
  }
  
  
  // from rb -> b
  for(int i = 255;i>-1;i--){
    // blue value
   light_color(i,0,255,0);
   set_last_color(i,0,255);
   if (detect_pause_click()){return;}
   delayMicroseconds (SPEED);
  }
  
  
  // from b -> bg
  for(int i = 0;i<256;i++){
    // blue value
   light_color(0,i,255,0);
   set_last_color(0,i,255);
   if (detect_pause_click()){return;}
    delayMicroseconds (SPEED);
  }
  
  // from bg -> g
  for(int i = 255;i>-1;i--){
    // blue value
   light_color(0,255,i,0);
   set_last_color(0,255,i);
   if (detect_pause_click()){return;}
    delayMicroseconds (SPEED);
  }
  
  // from g -> gr
  for(int i = 0;i<256;i++){
    // blue value
   light_color(i,255,0,0);
   set_last_color(i,255,0);
   if (detect_pause_click()){return;}
    delayMicroseconds (SPEED);
  }
  
  // from gr -> r
  for(int i = 255;i>-1;i--){
    // blue value
   light_color(255,i,0,0);
   set_last_color(255,i,0);
   if (detect_pause_click()){return;}
    delayMicroseconds (SPEED);
  }

}