A relay is an electromagnetic switch which allows low powered devices to control highly powered circuits. There are various types of relays, but in this post, I will be focusing on a 5 pin relay.

This post is meant to help you understand how the 5 pin relay works. I am going to show you step by step procedure of using a relay to blink two leds.
One of the leds will be connected to the normally open terminal and the other to the normally closed terminal. We will give the relay a delay of 3000 microseconds to switch between the terminals.

REQUIREMENTS:
→ 2 leds (preferably of different colors)
→ 1 5v 5 pin relay
→ 1 pnp transistor (2N2222)
→ Arduino Uno (or any other of your choice)
→ 1 1N4007 diode
→ 1 1k resistor
→ 2 300ohm resistors
→ Breadboard and several jumper wires for connection

POINTS TO NOTE:

• The 1N4007 diode is connected across the electromagnetic coil of the relay and is used to prevent the fallback of high voltages when power supply is disconnected

• The transistor (2N2222) amplifies the current to drive the relay

CONNECTING THE CIRCUIT

CODE:

int relay = 8;
void setup() {
Serial.begin(9600);
pinMode(relay, OUTPUT);
}
void loop() {
digitalWrite(relay, HIGH);
Serial.println("relay pin closed; blue should be on");
delay(3000);
digitalWrite(relay, LOW);
Serial.println("relay pin open; red should be on");
delay(3000);
}