Use a potentiometer to show scroll through the visible spectrum

Step 1: Parts

Arduino uno
1x long blue jumper cable
1x long red jumper cable
2x short black jumper cable
1x of each RGB jumper cables
Tri color led
Potentiometer

All can be gotten in sidekick kit

Step 2: Schematics

Wire as shown in picture. if led has common cathode rather than anode connect to ground, not 5v.

Step 3: Code

Copy and paste. If common cathode as RGB values to 0 instead of subtracting.

int rPin = 11;
int gPin = 10; int bPin = 9; float rPinBrightness; float gPinBrightness; float bPinBrightness; float value; float mval; float Red; float Green; float Blue; float factor; void setup() { // put your setup code here, to run once:

}

void color() { mval = analogRead(A1); value = map(mval, 0, 1023, 380, 650);

if((value >= 380) && (value<440)){ Red = -(value - 440) / (440 - 380); Green = 0.0; Blue = 1.0; }else if((value >= 440) && (value<490)){ Red = 0.0; Green = (value - 440) / (490 - 440); Blue = 1.0; }else if((value >= 490) && (value<510)){ Red = 0.0; Green = 1.0; Blue = -(value - 510) / (510 - 490); }else if((value >= 510) && (value<580)){ Red = (value - 510) / (580 - 510); Green = 1.0; Blue = 0.0; }else if((value >= 580) && (value<645)){ Red = 1.0; Green = -(value - 645) / (645 - 580); Blue = 0.0; }else if((value >= 645) && (value<781)){ Red = 1.0; Green = 0.0; Blue = 0.0; }else{ Red = 0.0; Green = 0.0; Blue = 0.0; }; if((value >= 380) && (value<420)){ factor = 0.3 + 0.7*(value - 380) / (420 - 380); }else if((value >= 420) && (value<701)){ factor = 1.0; }else if((value >= 701) && (value<781)){ factor = 0.3 + 0.7*(780 - value) / (780 - 700); }else{ factor = 0.0; };

}

void loop() { // put your main code here, to run repeatedly: color(); analogWrite(rPin, 255 - Red*100*factor); analogWrite(gPin, 255 - Green*100*factor); analogWrite(bPin, 255 - Blue*100*factor); delay(10); }