This is a 2 channels Relay module, which can able to control various appliances, and other equipment with a BIG current for 30A (250VAC/30VDC). It can be controlled directly by microcontroller: Raspberry Pi, Arduino, AVR, PIC, DSP, ARM, or TTL logic. For control of module need power 5V and logic operation 3.3V/5V. To isolate the microcontroller from the relay, we added an optocoupler. Now with this configuration, the microcontroller doesn’t have any physical connection with the relay, it just uses the LED light of the Optocoupler IC to activate the relay. This solution saves your microcontroller from a high voltage for VAC/VDC.