(Reference) RGB LEDs

RGB LEDs

Pins

RGB LED

  • RGB LEDs have four pins
  • Three pins to each of R, G, B (shorter pins)
  • One pin serves as either common anode or common cathode (longer pin)

Wiring (Common Cathode)

common cathode wiring

  • R, G, B pins are anode (positive)
  • Connect cathode (longer pin) to Ground (negative)

  • These are physically the opposite of regular LEDs

    • Regular LED: anode is longer pin
    • Common cathode RGB LED: cathode is longer pin

Operation

Digital Write

  • Each LED color is either on or off
  • Output HIGH to anode turns that LED color on
  • Output LOW to anode turns that LED color off

Analog Write

  • Use pulse width modulation
  • Each LED color can have a brightness level that varies from 0 to 255
  • You can blend LEDs to create many different colors
  • Only certain pins support PWM
    • D1 (SCL or A4)
    • A2
    • A5
    • MISO (D16)
    • MOSI (D15)

Color Mixing

color mixing

Code

const int PIN_RED = D1;
const int PIN_GREEN = MISO;
const int PIN_BLUE = MOSI;

void setup() {
  pinMode(PIN_RED, OUTPUT);
  pinMode(PIN_BLUE, OUTPUT);
  pinMode(PIN_GREEN, OUTPUT);
}

void loop() {
  //digital write - White (R + G + B)
  digitalWrite(PIN_RED, HIGH);
  digitalWrite(PIN_GREEN, HIGH);
  digitalWrite(PIN_BLUE, HIGH);
  delay(1000);
    
  //digital write - Magenta (R + B)
  digitalWrite(PIN_RED, HIGH);
  digitalWrite(PIN_GREEN, LOW);
  digitalWrite(PIN_BLUE, HIGH);
  delay(1000);

  //analog write - White (R 255 + G 255 + B 255)
  analogWrite(PIN_RED, 255);
  analogWrite(PIN_GREEN, 255);
  analogWrite(PIN_BLUE, 255);
  delay(1000);

  //analog write - Orange (R 255 + G 165 + B 0)
  analogWrite(PIN_RED, 255);
  analogWrite(PIN_GREEN, 165);
  analogWrite(PIN_BLUE, 0);
  delay(1000);
}

Credit

Updated: