"Micro Cooling Fan" to provide the use of a DC power supply: DC motor has a stator and a rotor of two parts, there is a stator pole (windings or permanent magnet), rotor windings, the power, the rotor has a magnetic field (magnetic pole ), there is an angle between the stator and rotor poles attract each other in the rotor magnetic field (N and S poles between) the next, the motor rotation. "Micro Cooling Fan" to change the brush seat, you can change the angle between the stator and rotor poles (assuming that the angle between the stator pole starting side, the rotor poles to the other side, by the "Micro Cooling Fan" rotor stator pole point direction is the direction of rotation of the magnetic poles of the motor) direction, thereby changing the direction of rotation of the motor.