Control a Relay with an Arduino

Difficulty
Easy
Steps
10

A relay is a device that is activated by a current in one circuit to open or close another circuit. 

In this guide, we will learn to use a relay to turn high power devices on and off. Together with a Little Bird Uno R3 board, the 5V 1-Channel relay board module used in this guide will give you control over power. Please see parts list for a complete list of components required.

After learning to use the 5V 1-Channel relay component, you can use it to turn off lamps, fans, and other appliances up to 250 VAC.

Step 1  Connect Relay to ground.

  • Connect an Arduino Ground Pin to the Ground Pin of your relay.

Step 2  Connect Relay to 5V.

  • Connect the Arduino 5V pin to the Relay's middle pin.

Step 3  Connect Pin 13 to the Relay.

  • Connect Pin 13 to the Relay's Signal pin.

Step 4  Insert LED into Breadboard.

  • Insert the LED into the bread board so that the Cathode (shorter pin) is on the left hand side.

Step 5  Insert 200 Ohm Resistor into the breadboard.

  • Insert a 220 Ohm Relay so that one pin is in line with the LED's Anode (longer leg).
  • The 220 Ohm Relay has the bands: Red, Red, Black, Black, Brown.

Step 6  Connect LED to Ground.

  • Connect the Cathode to a Ground pin on the Arduino.
  • The Cathode is the negative (shorter) leg of the LED.

Step 7  Connect the 3.3V Arduino Pin to the Relay.

  • Connect the 3.3V Arduino Pin to the Relay.
  • The 3.3V jumper should go to the NC side of the screw socket.

Step 8  Connect the Relay to the Resistor.

Step 9  Upload the code for your Relay.


              int relay = 13; // Plug the relay into Digital Pin 13 

void setup() {
  pinMode(relay, OUTPUT);
}

void loop() {
  digitalWrite(relay, HIGH); // Turn the relay on
  delay(1000); // Wait 1 second    
  digitalWrite(relay, LOW); // Turn the relay Off
  delay(1000); // Wait 1 second  
}
            
  • Grab the code and upload it to your board.
  • You should start to hear the click, click of the relay switching on and off. There is also a red light on the module to tell you when it switches.
  • The Relay can be use to control up to 250VAC but we DO NOT recommend you play with this sort of voltage / current unless you are an electrician!

Step 10  In action!

  • This is what a working relay looks (and sounds) like!