AZDelivery 5 x 1-Relay 5V KY-019 Module High-Level-Trigger compatible with Arduino including E-Book!

Works well, does not get hot, low current requirement. I bought this (as a pack of 3, now I have a couple of spares!) to construct a sensor to detect whether power had failed on a particular electrical circuit. I powered the relay with an old 5V iPhone charger in series with a 22 ohm resistor. The relay contacts which are isolated from the supply I connected to a GPIO pin on a Raspberry Pi, such that I can sense the relay state remotely.

Out of the box two were faulty. Found soldering on the circuit board poor and shorts between adjacent PCB pads. One faulty one had a solder bridge between the 5V and input and the other didn't have a pin on the relay soldered at all. I had to repair these two myself. Once I'd done this all three working. Beware - check for short circuits and solder splashes to avoid damaging your arduino pin.

I needed a small relay board for my project, this does the job. The relay output offers ON\OFF connection, the relay is energised using a +5V signal.

It works as intended but it's poorly designed. It isn't true galvanic isolation (which you should expect when switching 240V mains!) so no optoisolator just a tiny transistor. Another thing is...why put holes for M3 mounting screws when a standard nut doesn't fit. Not worth the money, you could easily make your own.

These do not seem any good, I've had one fail already and it is less than 48 hours old and been activated less than 25 times. Junk!! good job I only needed 1 of the 3 in this pack, let's see how long the next one lasts.

So you have written your code, assembled your sensors and devices that the Arduino/whatever drives when the sensors tell it to, and you realise the Arduino does not have enough power.Not a problem with the relays, attach your power hungry device to a big power source (within the parameters of the relays, of course) and use the Arduino to switch the relays on and off and to power the logic of the relay board.Simples!

As specified and good delivery