This is 2 channels Relay module, can able to control various appliances, and other equipments with big current to 30A (250VAC/30VDC).
It can be controlled directly by microcontroller: Raspberry, Arduino , AVR, PIC, DSP, ARM or TTL logic.
For control need power 5V and logic operation 5V.
For isolate the microcontroller from the relay, we added optocouple. 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 save your microcontroller from high voltage for VAC/VDC.