This Relay Card circuit is the module connect to microcontroller board or various experimental board such as ARDUINO, PIC or AVR. The voltage released of about 5-12 volts will cause the relay to work as programmed in IC memory. Opto-Coupler device is the main advantage of this circuit. It is used to separate ground between microcontroller board and the relay card board. Making it possible to control noise and prevents damage to the microcontroller board.