This is 1 channel Relay module, 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, Arduino, AVR, PIC, DSP, ARM or TTL logic.
For control of module need power 5V and logic operation 3.3V/5V.
For isolate the microcontroller from the relay, we added 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.