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Lesson 30: Relay Module

In this lesson, you will learn how to use a relay and an Arduino Uno to control a traffic light module. We’ll demonstrate how to turn the red light of the traffic module on and off using the relay. This project is ideal for beginners in Arduino, providing hands-on experience in controlling external modules and gaining a fundamental understanding of relay operations.

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
Arduino UNO R3 or R4	BUY
Breadboard	BUY
5V Relay Module	-
Traffic Light Module	BUY

Wiring

Code

Code Analysis

1. Setting up the relay pin:

   • The relay module is connected to pin 6 of the Arduino. This pin is defined as relayPin for ease of reference in the code.

   
   

   const int relayPin = 6;
   

2. 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);
   }
   

3. 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);
   }