Schematics of the PBC microcontroller circuits.

(A) a power reduction circuit from 12 to 5 V to provide power to the MCU (microcontroller unit) chip; (B) the clock circuit for timekeeping; (C) the MCU pinout and circuit diagram; (D) the fan control circuit; with an additional diode (red), the same circuit design was also used to control the motor; (E) 3D print of the PCB microcontroller (top).

(TIF)