Relay Module with ESP32 DOIT Kit v1

Introduction

A relay module is an electrically operated switch that allows your ESP32 to control high-voltage or high-current devices like lights, fans, motors, and other home appliances. Since the ESP32 operates at 3.3V logic and can’t directly handle high power loads, the relay acts as a bridge between low-power control (ESP32) and high-power devices (AC/DC).

Relay modules typically have:

• VCC (5V or 3.3V depending on module)
• GND (Ground)
• IN (signal input, connected to ESP32 GPIO pin)
• COM, NO, NC (output terminals for load control)

In this tutorial, we’ll connect a single-channel relay to ESP32 (GPIO 23) and control it using Arduino IDE.

⚡ Safety Note: If you’re working with AC mains, take proper precautions. Beginners should test with small DC loads (like a 5V LED bulb) first.

Components Required

• ESP32 DOIT DevKit v1
• Single Channel Relay Module
• Breadboard and jumper wires
• USB cable
• Small DC load (like 5V LED bulb or motor)

Circuit Diagram

• Relay VCC → ESP32 3.3V (some modules may require 5V, check your relay specs)
• Relay GND → ESP32 GND
• Relay IN → ESP32 GPIO 23
• Relay COM → One wire of the load power supply
• Relay NO (Normally Open) → Load device (e.g., bulb, fan)
• Other load wire → Power supply directly

Arduino Code

// Relay Module with ESP32 DOIT DevKit v1
// Relay IN pin connected to GPIO 23

int relayPin = 23;  // Relay connected to GPIO 23

void setup() {
  Serial.begin(115200);
  pinMode(relayPin, OUTPUT);  // Set relay pin as output
}

void loop() {
  Serial.println("Relay ON");
  digitalWrite(relayPin, HIGH); // Turn relay ON
  delay(2000); // 2 seconds delay

  Serial.println("Relay OFF");
  digitalWrite(relayPin, LOW); // Turn relay OFF
  delay(2000); // 2 seconds delay
}

Step-by-Step Code Explanation

Define Relay Pin

int relayPin = 23;

Relay is connected to GPIO 23.

Setup Function

pinMode(relayPin, OUTPUT);

Sets relay pin as output.

Loop Function

digitalWrite(relayPin, HIGH);
delay(2000);
digitalWrite(relayPin, LOW);
delay(2000);

Turns relay ON for 2 seconds, then OFF for 2 seconds repeatedly.

Real-Life Applications of Relay with ESP32

• 🏠 Home Automation – Turn on/off lights, fans, and appliances.
• 🌱 Smart Agriculture – Control water pumps and irrigation systems.
• 🏭 Industrial Automation – Operate heavy motors and machinery.
• 🔒 Security Systems – Control sirens, alarms, or door locks.
• ⚡ Energy Management – Schedule loads for efficient power use.

Troubleshooting