WaveshareRPi Relay Board Raspberry Pi Expansion Board, Three Channel (3-CH) Power Relay Module for Raspberry Pi 4B/3B+/3B/2B/A+/B+, Loads up to 5A 250V AC or 5A 30V DC

Thoughts:~Overall, nice relay board that works once you figure out its quirks and GPIO pinout.~Setting a pin Low activates the relay, and setting a pin High deactivates the relay.~GPIO pinout:CH1 = GPIO 26 (pin 37)CH2 = GPIO 20 (pin 38)CH3 = GPIO 21 (pin 40)Pros:~Relay board fits good on raspberry pi (I've tested on an rp4).~Decent quality board and relays.~Has GPIO pin passthrough in case your project requires them.Cons:~Included standoffs and fasteners are complete junk~No documentation includedTest script:To test your relays, I've written a simple shell script that will cycle the relays High and Low.#!/bin/bash# written by D Smith# Check if the script is running as rootif [ "$EUID" -ne 0 ]; then echo "This script must be run with sudo." exit 1fi# Array of GPIO pin numberspins=(26 20 21)# Function to toggle a GPIO pin and print the statetoggle_gpio() { pin="$1" state="$2" raspi-gpio set "$pin" op "$state" echo "GPIO pin $pin set: $( [ "$state" == "dh" ] && echo "High" || echo "Low" )"}# Run loopwhile true; do echo # Set pins HIGH for pin in "${pins[@]}"; do toggle_gpio "$pin" dh sleep 0.250 done sleep 1 echo # Set pins LOW for pin in "${pins[@]}"; do toggle_gpio "$pin" dl sleep 0.250 done sleep 1done

It is working, advertisement is kinda weird, as it is mentioned that the "good quality" relay support 5 amp, and from the picture you can see that they support 10amp 250v or 15amp 120v, but hey, at least its conservative, not pretending supporting more amps than they do. But what are those hex stud screw for ? They re for another ! They re too small !!! Pass rigth through the hole.

Relays are assigned to pins 25, 28, and 29. In board numbering 25 is designated for ground, 28 is reserved (uncallable), and 29 is good for GPIO. in BCM numbering 25 is good for GPIO, but 28 & 29 aren't found.