The MC68HC16Z1 is a 16-bit high speed microcontroller that incorporates a number of different modules. One of these modules is the General Purpose Timer (GPT), which provides various timing functions including pulse width modulation (PWM) output. PWM is very useful for motor control. This note describes a DC motor control system that provides for constant motor speed using PWM.
The control system uses motor shaft rotation period as its input, monitors motor speed, and changes PWM output duty cycle to either speed up or slow down the motor in order to maintain constant speed. The M68HC16 interfaces to the motor via the DEVB103 Logic to Motor Interface Module, which is described in detail in Motorola Application Note AN1300, Interfacing Microcomputers to Fractional Horsepower Motors.