Interfacing Relay Module with Arduino

Updated: Nov 28, 2020

In this topic, we are going to learn about how to control a relay module with Arduino. Here we will be controlling two devices by using them. It can be used to control the devices with a voltage 5V or less as Input. But if we want to control more than 5V or A.C devices then we need to use the relay module which can control this capacity.

List of Components:

  1. Arduino Uno

  2. Relay module

  3. LED

  4. Resistor

  5. Breadboard

Arduino Uno: It is an open-source microcontroller board. It is based on the Microchip named ATmega328P microcontroller. The circuit board is having a set of digital and analogue input/output pins. They will be interfaced with different expansion boards.

interfacing relay module with aurdino

Relay Module: It is an electrical switch in a circuit. It will on/off the circuit. Also, it can be controlled by fewer voltages like 5V from #Arduino.

interfacing relay module with aurdino
Relay module

LED: It is used to find the circuit is on/off by blinking.

Interfacing relay module with aurdino

Resistor: The #resistor plays one of the major roles in the relay module. It will protect other elements in the circuit from voltage spikes.

Circuit Diagram:

In the above diagram pin of Arduino is connected to the relay module and then further it is connected with #LED. The relay is connected with LED in open state i.e, NO pin which goes to the LED, and the common pin is connected to the breadboard. Also, the relay is receiving supply from Arduino.


void setup() {
  // put your setup code here, to run once:
  pinMode (2, OUTPUT);

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(2, HIGH);
  digitalWrite(2, LOW);

Download the code from below:

TXT • 237B


The circuit looks like below one after turning on.

If we increase the relay pin high then relay #module will be turned on.

If we decrease the relay pin it then it will off.

Video explanation of Interfacing relay module with aurdino for better understanding

See Also:

1. Interfacing Temperature sensor with Aurdino

2. Fingerprint sensor-based attendance system

3. All you need to know about sensor technology