Light Emitting Diode (LED)

LED (two wire / single color)

The longer lead goes to positive, the flat spot points toward the cathode (negative).   The current goes from the anode (positive) to the cathode (negative).

 

RGB LED

RGB CA (common anode) LED

Connect the longer pin (common anode) to +5V, and the red, green, and blue each go to microcontroller PWM digital output through a resistor.   Use a slightly higher value resistor (220 to 330 ohm) for the red than for the green and blue (100 to 220 ohm).  

Adafruit product #159

/*

  Single RGB LED (common anode or common cathode)
  
*/

/////////////////////////////////////////////////////////////////////////
//  RGB LED (assign PWM digital output or analog output pins)
const byte pinRed = 11;
const byte pinGreen = 10;
const byte pinBlue = 9;
const boolean IsCommonAnode = true;
const unsigned int iDelay = 1000;

void setup () {
  pinMode(pinRed, OUTPUT);
  pinMode(pinGreen, OUTPUT);
  pinMode(pinBlue, OUTPUT);
  
} // setup()


void loop() {
  
  SetRGBcolor(255, 0, 0);  // red
  delay(iDelay);
  
  SetRGBcolor(0, 255, 0);  // green
  delay(iDelay);
  
  SetRGBcolor(0, 0, 255);  // blue
  delay(iDelay);
  SetRGBcolor(0, 255, 255);  // cyan / aqua
  delay(iDelay);
  
  SetRGBcolor(255, 255, 0);  // yellow
  delay(iDelay);  
  
  SetRGBcolor(80, 0, 80);  // purple
  delay(iDelay);
  SetRGBcolor(255, 0, 255);  // magenta
  delay(iDelay);

  SetRGBcolor(255, 255, 255);  // white
  delay(iDelay);
  
  SetRGBcolor(0, 0, 0);  // off
  delay(iDelay);
  
} // loop()


////////////////////////////////////////////////////////////////

void SetRGBcolor(byte red, byte green, byte blue) {
  if (IsCommonAnode == true) {
    // invert the color value
    red = 255 - red;
    green = 255 - green;
    blue = 255 - blue;
  }
  analogWrite(pinRed, red);
  analogWrite(pinGreen, green);
  analogWrite(pinBlue, blue);
} // SetRGBcolor()

 

RGB CC (common cathode) LED

Connect the longer pin (common cathode) of the RGB (common cathode) to ground (of microcontroller), and the red, green, and blue pins each through a resistor to the microcontroller digital output PWM pins.   Use a slightly higher value resistor (220 to 330 ohm) for the red than for the green and blue (100 to 220 ohm).  

 

 

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