Blink and No Blink


For this lab, I used 2 LEDs and wrote up my sketch such that one would blink and one would always be on.


  • 1 Arduino
  • 2 LEDs
  • 1 Resistor (220Ω)
  • 1 Breadboard


Turns on an LED on for one second, then off for one second, repeatedly.

Most Arduinos have an on-board LED you can control. On the Uno and
Leonardo, it is attached to digital pin 13. If you’re unsure what
pin the on-board LED is connected to on your Arduino model, check
the documentation at

This example code is in the public domain.

modified 8 May 2014
by Scott Fitzgerald
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin 12 and 13 as an output.
pinMode(13, OUTPUT);
pinMode(12, OUTPUT);

// the loop function runs over and over again forever
void loop() {
digitalWrite(12, HIGH); // turn the LED on pin 12 on
digitalWrite(13, HIGH); // turn the LED on pin 13 on (HIGH is the voltage level)
delay(100); // wait for a second
digitalWrite(13, LOW); // turn the LED on pin 13 off by making the voltage LOW
delay(100); // wait for a second

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