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Lesson 30: Relay Module

In this lesson, you’ll learn how to use an ESP32 Development Board to control a one-channel relay module. We’ll cover turning the relay on and off in a loop, with a 3-second delay between each state change. This project provides hands-on experience with digital output operations in embedded systems, making it ideal for beginners entering the realm of ESP32 and relay modules.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
ESP32 & Development Board (ESP32 Board)	BUY
Breadboard	BUY
5V Relay Module	-
RGB LED Module	-

Wiring

Code

Code Analysis

Setting up the relay pin:
- The relay module is connected to pin 25 of the ESP32 Development Board. This pin is defined as relayPin for ease of reference in the code.
```
const int relayPin = 25;
```
Configuring the relay pin as an output:
- In the setup() function, the relay pin is set as an OUTPUT using the pinMode() function. This means the Arduino will send signals (either HIGH or LOW) to this pin.
```
void setup() {
  pinMode(relayPin, OUTPUT);
}
```
Toggling the relay ON and OFF:
- In the loop() function, the relay is first set to the OFF state using digitalWrite(relayPin, LOW). It remains in this state for 3 seconds (delay(3000)).
- Then, the relay is set to the ON state using digitalWrite(relayPin, HIGH). Again, it remains in this state for 3 seconds.
- This cycle repeats indefinitely.
```
void loop() {
  digitalWrite(relayPin, LOW);
  delay(3000);

  digitalWrite(relayPin, HIGH);
  delay(3000);
}
```