Fan having rotation sensing

A fan having rotation sensing comprising:

• a casing having a first mounting surface, a second mounting surface, a third mounting surface, a fourth mounting surface, a space, and a shaft mount contained within the space, wherein the first, second, third, and fourth mounting surfaces are defined by four sides of the casing, respectively;
• a motor disposed within the casing and having a shaft pivotally connected to the shaft mount;
• a rotation sensing unit configured to detect a first rotational position of the casing with respect to a contact surface of an electronic device and to correspondingly output a first sensing signal;
• and
• a control unit having a controller electrically coupled to the rotation sensing unit and the motor, the controller receiving the first sensing signal according thereto to control the motor to perform a first operation mode selected from the group of operation modes consisting of clockwise rotation mode counterclockwise rotation mode, voltage-controlled rotational speed mode, PWM-controlled rotational speed mode, temperature-controlled rotational speed mode, halt, rotational speed increasing, rotational speed decreasing, timed activation, timed deactivation, and sleep mode.