Review on 🌐 MCIGICM 2 Channel DC 5V Relay Module: Optocoupler Low Level Trigger Expansion Board for Arduino UNO R3, DSP, ARM, PIC, AVR, STM32, Raspberry Pi by Jeff Kersey

I use this module to control the power of a computer fan. I won't go into details but suffice it to say that the module works great. I removed the jumper to electrically isolate the electromagnet circuit from the relay logic circuit. I then used 5V from the computer's power supply to power the electromagnets, using the JD-VCC and GND pins on the 3-pin header, with VCC on the 3-pin header was not connected. To power the relay logic, I connected 5V and ground from the Arduino Nano to VCC and GND on the 4-pin header. Do not confuse 3-pin connectors with 4-pin connectors when the jumper is removed. (If you leave the jumper between JD-VCC and VCC, the 4-pin VCC connector also powers the electromagnet and you don't need a separate 5V for JD-VCC on the 3-pin connector.)