Controlling a 5V Relay Using Arduino to cotrol AC or DC load like bulb or motor

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Controlling a 5V Relay Using Arduino to cotrol AC or DC load like bulb or motor

This tutorial demonstrates how to use a 5V relay module with Arduino to control high-voltage devices such as lights, fans, or other appliances. The relay used in this lesson is high-trigger, meaning it activates when the signal pin receives a high-level voltage (5V).

Relay modules are essential in home automation and industrial control systems, allowing you to safely interface microcontrollers with AC-powered devices.

The Arduino code and wiring diagram are available below this article.

What is a High-Trigger Relay?

A relay is an electromechanical switch controlled electrically. The high-trigger version activates when the input signal pin is brought HIGH (typically 5V). It contains:

An electromagnetic coil for switching
A normally open (NO) and normally closed (NC) contact
Signal, VCC, and GND pins

This module allows Arduino to control devices that operate at a higher voltage than the board can handle directly.

Wiring the Relay Module

Arduino wiring for AC bulb with HIGH-level trigger relay

To safely use the relay with Arduino, wire it as follows:

VCC (middle pin) -5V on Arduino
GND -GND on Arduino
IN (Signal pin) -Digital Pin 2 on Arduino
Relay Output terminals -Connect one of the terminals in series with a light bulb, fan, or any other AC/DC load.

Code Overview

Hereâ€™s the basic Arduino code used in this lesson:

cppCopyEditvoid setup() {
  pinMode(2, OUTPUT);     // Set pin 2 as output
}

void loop() {
  digitalWrite(2, HIGH);  // Turn relay ON
  delay(1000);            // Wait 1 second
  digitalWrite(2, LOW);   // Turn relay OFF
  delay(1000);            // Wait 1 second
}