Review on 🔌 SunFounder 2 Channel DC 5V Relay Module with Optocoupler for Arduino R3 MEGA 2560 1280 DSP ARM PIC AVR STM32 Raspberry Pi: Expand and Trigger with Low Level Control by Travis Carter

Works great with Raspberry Pi project. > Connect the Pi's output pin to one of the relay pins > Set up the appropriate GPIO pins for the output > You change the state of the relay by setting the GPIO pin to False/True > There should be a nice click from the If you do this, I use it to switch the 12V power supply to the motor. Works perfectly. They are also often used as part of garage door opening projects. Google for it and you should see a few blogs.