Controlling an External LED

In this project, you'll learn how to connect and control an external LED.

Before you do this project, you'll first need to know how a LED works, and how to use a breadboard.

Parts needed: Arduino      LED      Breadboard      150 ohm resistor
How do you turn on a LED?  Connect it to a power source. (If you don't know how to do it then read this first.)

How do you turn off a LED?  Disconnect it from the power source.

How do you make a LED blink once?   Connect and then disconnect the LED from the power source.

How do you make a LED blink continuously?   Keep connecting and disconnecting the LED from the power source.

     This is very tiring and boring!

To automatically turn on and off a LED, we need to get the Arduino to control it by connecting one leg of the LED to a digital I/O pin on the Arduino board.

The pins labeled 2 to 13 on the Arduino board are the digital I/O pins.
Arduino digital I/O pins

1 Making the connections
  • Connect the positive end (long leg) of the LED to pin 3 on the Arduino board.
  • Connect the negative end (short leg) of the LED to one end of the 150 Ω resistor.
  • Connect the other end of the resistor to GND on the Arduino board.
External LED connections
2 Create a new Bare Minimum program by selecting File from the menu
  • then select Examples
  • then select Basics
  • then select BareMinimum
You will see this Bare Minimum template.
BareMinimum template
3 Type in this program.

The pinMode command tells the Arduino that you will be controlling pin 3 for OUTPUT since you connected the LED to pin 3.

The digitalWrite command sends a HIGH or LOW signal to pin 3.

The delay command makes the Arduino wait a bit. The number specified in the delay command is the number of milliseconds to wait.

1000 ms = 1 sec
External LED program
3 Upload and run the program. You should see the external LED blink on for 1 second and then off for another second.

How (not) to blow up a LED. If you have not read the document on how a LED works then you should read it before going any further, otherwise you'll end up with a lot of blown up LEDs.