A geared motor consists of a regular direct current (DC) motor attached to a gearbox. The ratio of the gears is usually given in the datasheet if you look up the type number. Using gears decreases the speed of rotation but increases the available torque.

To change the direction of rotation, simply change the polarity of the power supply, or use a so called H-bridge motor driver controlled by a microcontroller.

A DC motor has a maximum supply voltage. You can change the the speed of the motor by means of a PWM (Pulse Width Modulation) signal.

Typical applications: toys, battery operated power drills, toothbrushes.

Common specifications

  • Motor voltage and current.
  • Gear ratio, as it is determining the Rotations Per Minute (RPM) of the outgoing motor shaft.
  • Diameter and shape of the motor shaft, as it needs to connect to other wheels, shafts, or gears. Typical shapes are circular and D-shaped shafts. D-shaped because of their similarity to the capital D. The flat side prevents the shaft from slipping to easily when applying higher torques.
  • Maximum torque.