Crowtail- MOSFET enables you to control higher voltage project, say 50VDC, with low voltage, say 5V, on microcontroller. MOSFET is also a kind of switch. There are two screw terminals on the board. One for input power source and the other for device you want to control. Crowtail- MOSFET will pass the power from one end to another when closed. But if outer power source is absent, your device can still draw power from microcontroller via the Crowtail interface. There is a mini fan that our customers can choose, you can do some interesting projects with the mini fan.