ELEGOO Relay Module 4 Channel DC 5V with Optocoupler for Arduino UNO R3 MEGA Project 1280 DSP ARM PIC AVR STM32 Raspberry Pi

Compact, easy to use, well laid out and fair value for money.

Very neat little piece of kit. I'm using this module interfaced with IR detectors for train detection on hidden model railway storage loops. The IR detectors have an output which goes low when an object is detected and this module requires an input which goes low to activate the relay, so they work together a treat, all running off 4.5 - 5V. Also comes with a tiny screwdriver for the terminals and a ribbon cable for connecting up - very useful! I can't comment on the life expectancy of the relays though.

...came unexpectedly with a short ribbon and connectors to wire it up, and even a tiny screwdriver for the terminals, but no documentation or information whatsoever on the electricals or how to wire it up.I struggled a little to find information so resorted to the all-knowing-Internet to get me sorted (but not before sticking 5V the wrong way up my Raspberry Pi which thankfully survived).So, good value, worked eventually, but can't comment on longevity which other reviewers have questioned....

Beware that there is no documentation, and the relays operate when their associated control pin is driven to ground, not when it is driven high. I didn't realise this at first and assumed the unit was faulty. It isn't. Its a good system because it draws very little current from the associated microcontroller.

Excellent relays, opto-isolated etc. There is no way you could make something cheaper yourself. I have no idea how this is so cheap. Bought a couple, solid, reliable with or without Arduino.

Very good relay module. Have been using it with esp32 to switch lamps and ceiling lights. I use it very often and so far it’s still switching. I’m not sure why others say it breaks. Mines been fine. Comes with a tiny screwdriver for the terminals. All in all, it’s perfect.

I have both the 4 and 8 relay boards from elegoo and although they both look very similar as far as component layout, the 8 channel board has become unreliable after only a few weeks of use.

Like others the board is very good, but the relays have a tendancy to latch in a closed state if they have been energised for a period of time. I switched out the relays for OMRON G5LA-14-5VDC - you can't buy them here anymore as OMRON have discontinued them, but ebay has plenty of listings still from China (i used the seller smallpartsbigdifference) and they have been rock solid since.