GeeekPi 4 Channel Relay Board Module for Raspberry Pi, Power Relay Module for Raspberry Pi 4B/3B+/3/2B (No Programming Required/Programmable)

This board is unique in how it uses a shared I2C to communicate with the relays, instead of eating up precious GPIO pins. It is possible to stack up to four of these boards without needing any additional pins. That's a very valuable feature. It also means that driving the relays from C, Python, or even just the shell is trivial. Highly recommended.Note: While I love the flexibility of having both N.O. and N.C. contacts for each of the four relays, I find the labeling on the connector to be confusing. Make sure to measure connectivity with a multimeter before wiring up the terminal block.

I am using this board to control four 24VAC irrigation valves with a Raspberry Pi 3 B+ to fill (and not overfill) a 2000 gallon cistern and control the backflush of the filter when the output pressure drops (monitored using pressure transducers and an ADC). I really like that this board uses I2C to communicate with the Pi. It's easy to stack several of these boards to get additional relay channels. It has a nice pass through header, so you can still attack your other devices and sensors.Bottom line, it works perfectly. I highly recommend this board for applications where you don't need more than three amps per channel.

NO and NC labels on the PCB silkscreen are backwards.Terminals labeled "NC" are normally open, and terminals labeled "NO" are normally closed. Seems to work fine once you get that sorted out.

I liked how straight-forward it was to get working with my RPi 3B+. I only needed a single relay though, so $20 for a relay felt like a lot. If there were a single relay model, I would have given purchased that and given 5 stars.

Perfect fit and function. The LED indicators are very nice to show the relay is energized. hardware that came with it worked as expected and no issues with this. Only problem is currently unavailable and not sure if they will re stock.Hopefully they will.

First..this product is made by 52pi incase your looking for the wiki pages which are not listed anywhere on this amazon page.Second, i finally got around to using this hat, only to find that all of the NC terminals short to ground and do not switch from NO to NC. So ive got 24VDC hooked up to the NO and when the unit powered up i had no lights but the NO side was hot. So i used the i2cset command to turn that relay off, and behold the magic blue smoke. not even sure how thats possible but oh well.Far as im concerned this seller owes me another pi3b+ and a refund for this part.

Fits neatly on top of the GPIO pin headers. I needed a relay to close a connection on command from my Pi clone, and this works perfectly. I still have 3 more relays to play with, so I'm dreaming up additional tasks I can have my SBC do!

Would be five stars if the silkscreen was right, or at least the documentation mentioned that it was wrong. The NO & NC connections on the relay are reversed. However the board works great once you get around that