Connect a relay board to your Raspberry Pi

August 25, 2014 / trafex / 5 Comments

If you want to switch things like lights with your Raspberry Pi, you need a relay board.
A relay is an electronic switch that can be switched with a low-voltage signal.
Exactly what the Raspberry Pi offers as GPIO pins.

The relay board I’ve found is ideal for the Raspberry Pi.
It has 8 relays and every relay can separately be switched with the Raspberry Pi because it has 8 GPIO pins.
Also, the voltage needed to switch the relays is 5V, this can be taken directly from the RPi.
This is why you don’t need any additional electronics.

Hardware

You need the following things.
I’ve bought these on banggood.com, but they’re widely available.

• 5V 8 channel relay board (or Sainsmart 5V 8 channel relay board)
• Female to female jumper cables
• Raspberry Pi

Pin scheme

WiringPi uses its own pin numbering system.
The scheme below connects relay 1 to WiringPi number 0, relay 2 to number 1, etc.
See this page to find the right pins on the Raspberry Pi.

(This scheme is based on a revision 2 Raspberry Pi)

Software

I’m using WiringPi as library to control the connected relay board.
WiringPi is widely supported for popular languages like NodeJS, PHP, Python, etc.

1. Install WiringPi
2. Set every pin on OUT mode

   gpio mode 0 out
   gpio mode 1 out
   gpio mode 2 out
   gpio mode 3 out
   gpio mode 4 out
   gpio mode 5 out
   gpio mode 6 out
   gpio mode 7 out
   

3. Write 0/1 to the ‘WiringPi number’ from the pin scheme to test the relays

   gpio write 0 0 
   gpio write 0 1 
   gpio write 1 0 
   gpio write 1 1 
   

Now startup your IDE and build something awesome to control the electronics connected to the relay board!

#electronics#gpio#light#Raspberry PI#relay#switch#tutorial#WiringPi