Use an Arduino to Control a Relay
Learn to turn high power devices on and off
Written By: Madeleine Schappi


Difficulty
Easy

Steps
10
Introduction
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 an LED on and off. In this guide, a Little Bird Uno R3 board, the 5V 1-Channel relay board module is used. 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

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Connect an Arduino Ground Pin to the Ground Pin of your relay.
Step 2 Connect Relay to 5V

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Connect the Arduino 5V pin to the Relay's middle pin.
Step 3 Connect Pin 13 to the Relay

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Connect Pin 13 to the Relay's Signal pin.
Step 4 Insert LED into Breadboard

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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

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Insert a 220 Ohm Relay so that one pin is in line with the LED's Anode (longer leg)
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The 220 Ohm Relay has the bands: Red, Red, Black, Black, Brown.
Step 6 Connect LED to Ground

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Connect the Cathode to a Ground pin on the Arduino.
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The Cathode is the negative (shorter) leg of the LED.
Step 7 Connect the 3.3V Arduino Pin to the Relay

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Connect the 3.3V Arduino Pin to the Relay.
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The 3.3V jumper should go to the NC side of the screw socket.
Step 8 Connect the Relay to the Resistor

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Connect COM on the relay to the other side of 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 }
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Grab the code and upload it to your board.
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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.
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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!
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This is what a working relay looks (and sounds) like!