This microcontroller-based control circuit adjusts the speed of a small permanent-magnet DC motor to one of four speeds as selected by a pair of photosensors.

Using PWM allows precise current control in the windings. Hence, the output torque, which is linearly proportional to the average winding current, can be correctly controlled in coreless motors.

This DC servo motor controller can also be used with an external potentiometer or the integrated on board potentiometer. For applications with existing PWM signals available this can also be used ...