ELEGOO 4 Channel DC 5V Relay Module with Optocoupler Compatible with Arduino UNO R3 MEGA 2560 DSP ARM PIC AVR STM32

Works like it should

Worked with out a issue and wanted this for a simple Arduino project

Works as described. Ended up using these to control the popup headlights on my car with an Arduino.

I missed in the description where it says the relay is active low. This means you have to put the Arduino digital output in the LOW state to energize the coil and turn on the led on the relay board. Not what I would have preferred, but it was in the description and I just missed it. Prior to realizing that, I was wondering what was going on. An instruction sheet would have been helpful, though, because you have to figure out on your own whether the Arduino can power the VCC and GND pins, or if you need a separate power supply (spoiler: the Arduino can power it). Also, there is a jumper on the relay board with no explanation of what it does. You have to search the internet to find out. Again, a simple instruction sheet should be included.

Easy interface, saves time building. Used for added accessory control in my truck.

The relay quality was good, the price was reasonable as well. We used it in our ardiuno kit to create an assignment. It was not noisy, the documentation was ok.

I could never get this working. No diagram on voltage. I put in 9v, 5v, 12v. I activated the relay with an esp32. Nothing. Nada zilch. Did I break it with the 9v? There's no telling. Build in protection from 12v on a 5v unit perhaps? I'm no engineer, but I have common sense

Excellent components. Very good quality,