This motor speed controller uses a single IC LM1014 to control the speed of a DC motor. It senses the increase in the motor-current when the rotation of the motor slows down due to a load. The IC then increases the motor voltage so that the original speed is recovered. P1 potentiometer varies the speed of the motor.
Motor Speed Controller Circuit Schematic
LM1014 is a monolithic IC specially designed to provide a low cost motor speed regulator for low voltage DC motors.