Review on 🔌 SunFounder 4 Channel 5V Relay Shield Module: Compatible with Arduino R3 MEGA 2560 1280 DSP ARM PIC AVR STM32 Raspberry Pi by John Brazington

4 stars for: no documentation, overall OK build quality and good price. Would buy again. A good product for quick use to turn on/off a simple load with a PIC microcontroller. Note that a 0V/GND signal on any input on the relay board will energize/activate the relay, while a 5V signal will de-energize the relay. The relays are listed for 30VDC / 125-250VAC, both 10A, but I've never been familiar with tiny screw terminals of this magnitude. The board has a set of "VCC/GND" jumpers. I believe this is used to bypass the circuit from the output stage of the optocoupler to the input voltage of the optocoupler. You could probably remove this jumper if you wanted to isolate power supplies, but I haven't tested that. Moving the jumper 1 position simply short circuits the board ;). Finally, attach some general dimensions of the device if you are building a case or mount for it.