How to Use Your Raspberry Pi as a Powerful Controller for Home Automation Projects

Learn how to connect a relay to your Raspberry Pi and control it using Python. …

Updated September 10, 2023

Learn how to connect a relay to your Raspberry Pi and control it using Python.

Raspberry Pi is an affordable, credit card-sized computer that can run Linux and has become popular in recent years due to its versatility and expandability. One of the many things you can do with a Raspberry Pi is use it for home automation projects where you can automate your daily tasks such as controlling lights or other devices at home using internet-connected devices like smartphones, tablets, or computers. In this article, we will explain how to connect a relay to your Raspberry Pi and control it using Python code.

Materials Needed

Raspberry Pi (any model)
Relay Module
Breadboard
Jumper Wires
Power Supply (5V or 12V, depending on the relay module you have)
Soldering Iron and Solder (optional but recommended)

Step 1: Connect the Relay to the Raspberry Pi

To connect the relay to your Raspberry Pi, follow these steps:

Identify the pins on your relay module. The relay module should have at least five pins - VCC (power), GND (ground), IN (input signal), COM (common), and NO (normally open) or NC (normally closed).
Connect the VCC and GND pins to the 5V or 12V power supply depending on your relay module’s specifications. If you don’t have a separate power supply, you can use the Raspberry Pi’s GPIO pins for power as well.
Connect the IN pin to any of the Raspberry Pi’s GPIO pins (e.g., GPIO 4) using jumper wires or soldering it directly onto the breadboard.
Connect the COM and NO/NC pins to two separate output devices you want to control with your relay (e.g., a light bulb and a fan).

Step 2: Install the necessary libraries

Before writing the Python code, you need to install the necessary libraries for GPIO pin manipulation. Open the terminal on your Raspberry Pi and type the following command:

sudo apt-get update && sudo apt-get upgrade

After updating the system, run this command to install the required libraries:

sudo apt-get install python3-rpi.gpio

Step 3: Write the Python code

Create a new Python file named relay.py and add the following code:

import RPi.GPIO as GPIO
import time

# Set up the GPIO pin numbering mode
GPIO.setmode(GPIO.BCM)

# Define the GPIO pin connected to the IN pin of the relay module
relay_pin = 4

# Set the GPIO pin as an output
GPIO.setup(relay_pin, GPIO.OUT)

try:
    while True:
        # Turn on the relay
        print("Relay ON")
        GPIO.output(relay_pin, GPIO.HIGH)
        time.sleep(5)

        # Turn off the relay
        print("Relay OFF")
        GPIO.output(relay_pin, GPIO.LOW)
        time.sleep(5)

except KeyboardInterrupt:
    # Clean up the GPIO pins and reset them to their default states
    GPIO.cleanup()

This code will turn on and off the relay every 5 seconds. You can adjust the time.sleep() values to control the duration of the ON and OFF periods.

Step 4: Run the Python script

Open the terminal again and navigate to the directory where you saved the relay.py file. Then, run the following command:

python3 relay.py

You should see “Relay ON” and “Relay OFF” messages printed in the terminal every 5 seconds as the relay turns on and off. You can also observe the devices connected to the COM and NO/NC pins switching on and off.