XYGStudy Raspberry Pi Expansion Board Power Relay Module for Raspberry Pi 4 3 2 Model B B+ A+

Between the images printed on the circuit board (showing which terminals were normally open vs normally closed) and the top reviews here (for basic code to turn it off/on), it was super straightforward to get this working. The metal standoffs included are really nice, and I love how this just sits cleanly on top of the raspberry pi. It includes an extra screw, at least the tiny ones. It worked immediately without any trouble. The wire connections are nice too.I did have to pull up some updated code for controlling the GPIO pins - no fault of the product, I'm just going off of the other amazon reviews b/c I don't want to wait for the seller to send over example code. Here's what I used to make it turn off and on (other comments have the GPIO pin numbers correct):echo 20 > /sys/class/gpio/exportecho out > /sys/class/gpio/gpio20/directionecho 0 > /sys/class/gpio/gpio20/value # onecho 1 > /sys/class/gpio/gpio20/value # offecho 20 > /sys/class/gpio/unexport # cleanup

I needed exactly 3 relays to use with my Pi, so this was a perfect design. The only real problem is their absurd labeling that does not match the Pi's pin numbers or GPIO numbers. The P25, P28, and P29 are labeled on the 40-pin header of the HAT, but do not line up Pi pins 25, 28, 29, nor GPIO 25, and there is no GPIO 28 & 29 on the Pi. For anyone wanting to use this, here's what the pins actually are:P25 = GPIO26, Pin 37P28 = GPIO20, Pin 38P29 = GPIO21, Pin 40

Really nice board! A little more expensive than some stand-alone relay boards, but for Raspberry Pi, this is the best!The board is very high quality, well made, not junk like some others.I'm using it with OctoPrint to control camera lights and cooling fans for my 3D printer. Works really well!

This board is made by Waveshare. Check their website for the schematic & sample code.The information below is for a Raspberry Pi v2:Relay 1 - Pin 37 (labeled P25 on board) Piv2 GPIO25Relay 2 - Pin 38 (labeled P28 on board) Piv2 GPIO28Relay 3 - Pin 40 (labeled P29 on board) Piv2 GPIO29* The labels on the PCB correspond to the WiringPi code* All the terminals are low active. 1=OFF 0=ON (LED also ON)At boot, GPIO pins are setup via /etc/init.d/gpio_start which is called by /etc/rc.localgpio_start:#!/bin/sh -e## Set all three GPIO pins to the OFF value/usr/bin/gpio write 25 1/usr/bin/gpio write 28 1/usr/bin/gpio write 29 1# Set all three GPIO pins to output mode/usr/bin/gpio mode 25 out/usr/bin/gpio mode 28 out/usr/bin/gpio mode 29 outMy Pi2 is now reading the battery voltage from a solar charge controller. If the weather has been cloudy for a few days and the battery voltage gets too low, a relay turns on a battery charger. Magic :)

Worked perfectly out of the package.Wish it was a bit cheaper, but not too bad.

Great little board. In a manner of minutes I had it working with python. You don't need any special libraries.It is as simple as : import RPi.GPIO as GPIOGPIO.output(yourPin,GPIO.HIGH)GPIO.output(yourPin,GPIO.LOW)

its been a few weeks since i received my pi relay and i am yet to get it working, no fault of my own but more so because i received a board with the relays that don't work. All the lights work but the relays do absolutely NOTHING. I am still waiting on a replacement and still Nothing.

This product worked after I spent some time fiddling (thanks Jon H for giving the GPIO numbers). Out of the box the GPIO pins need to be pulled LOW to get the relays to turn on and HIGH to turn them off. I used the RPi.GPIO library w/Python w/o any issues. I could argue that there should have been some documentation BUT since there are various ways to use the Raspberry Pi (Python, Java, etc...) I can see why nothing was included as they vary, just to reiterate Jon H's review:Relay 1 - Use GPIO26 in Python (labeled P25 on board)Relay 2 - Use GPIO20 in Python (labeled P28 on board)Relay 3 - Use GPIO21 in Python (labeled P29 on board)