Light Emitting Diodes

Types:

• Wide assortment of colors (wavelengths)
• Operating voltages and currents vary depending on type

Interfacing LEDs to the Arduino:

• The easiest way to control an LED is to connect it directly to a digital output pin as follows:

  int ledPin = 12;                 // LED connected to digital pin 12
  
  void setup()
  {
    pinMode(ledPin, OUTPUT);      // sets the digital pin as output
  }
  
  void loop()
  {
    digitalWrite(ledPin, HIGH);   // sets the LED on
    delay(1000);                  // waits for a second
    digitalWrite(ledPin, LOW);    // sets the LED off
    delay(1000);                  // waits for a second
  }
  

• Another option is to use pulse wave modulation (PWM) to fade an LED on and/or off. Note that only certain digital pins support PWM.

  int value = 0;                            // variable to keep the actual value
  int ledPin = 9;                           // LED connected to digital pin 9
  
  void setup() 
  {
    pinMode(ledPin, OUTPUT);      // sets the digital pin as output
  } 
  
  void loop() 
  { 
    for ( value=0; value<=255; value+=5 ) {   // fade in (from min to max)
      analogWrite( ledPin, value );           // sets the value (range from 0 to 255)
      delay( 30 );                            // waits for 30 milli seconds to see the dimming effect
    } 
    for ( value=255; value>=0; value-=5 ) {   // fade out (from max to min)
      analogWrite( ledPin, value ); 
      delay( 30 ); 
    }  
  }