28BYJ-48 Stepper Motor
The 28BYJ-48 is a small, cheap, 5 volt geared stepping motors. These stepping motors are apparently widely used to control things like automated blinds, A/C units and are mass produced.
Due to the gear reduction ratio of *approximately* 64:1 it offers decent torque for its size at speeds of about 15 rotations per minute (RPM).
With some software “trickery” to accelerate gradually and a higher voltage power source (I tested them with 12 volts DC) I was able to get about 25+ RPM.
These little steppers can be purchased together with a small breakout board for the Arduino compatible ULN2003 stepper motor driver for less than $5. Quite a bargain, compared to the price of a geared DC motor, a DC motor controller and a wheel encoder! The low cost and small size makes the 28BYJ-48 an ideal option for small robotic applications, and an excellent introduction to stepper motor control with Arduino.