With a simple modification of the breadboard, we could attach the LED to an output  pin of the Arduino. Move the red jumper wire from the Arduino 5V connector to D13, as shown below:

Now load the 'Blink' example sketch from Lesson 1. You will notice that both the built-in 'L' LED and the external LED should now blink.

  Turns on an LED on for one second, then off for one second, repeatedly.
  This example code is in the public domain.
// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;

// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT);     

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);               // wait for a second
  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);               // wait for a second

Lets try using a different pin of the Arduino – say D7. Move the red jumper lead from pin D13 to pin D7 and modify the following line near the top of the sketch:

int led = 13;
so that it reads:
int led = 7;
Upload the modified sketch to your Arduino board and the LED should still be blinking, but this time using pin D7.

In the next lesson, we will be using LEDs again, this time, the Arduino will be controlling the LED.
About the Author

Simon Monk is author of a number of books relating to Open Source Hardware. The following books written by Simon are available from Adafruit: Programming Arduino30 Arduino Projects for the Evil Genius and Programming the Raspberry Pi.

This guide was first published on Nov 29, 2012. It was last updated on Nov 29, 2012.

This page (Blinking the LED) was last updated on Oct 09, 2012.

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