A permanent magnet DC (PMDC) motor, including: a motor body including a revolving shaft; a Hall sensing module; a gear reducer; and a gear assembly including an output shaft; and a magnet ring. The gear assembly is disposed in the gear reducer. The gear assembly is connected to and driven by the revolving shaft of the motor body. The magnet ring is disposed on the revolving shaft or on the output shaft of the gear assembly. The Hall sensing module is disposed on the gear reducer. The Hall sensing module is adapted to sense a signal of the magnet ring to detect the revolving speed of the revolving shaft or the output shaft, and transmit detected data with regard to the revolving speed.