The DFRobot single relay allows you to switch on and off a number of electronic modules. It can be used in interactive projects or to control lighting, electrical and other equipment. The modular design makes it easy to expand with the Arduino board (not included). The relay output state is indicated by an LED. It can be controlled through the digital I/O port with a simple HIGH or LOW signal to trigger a solenoid valve, lamp, motor or other high current or high voltage devices.