Microprocessor Based Digital PID Controller for Speed Control of D.C. Motor

This paper presents a simple scheme for implementing the speed control of d.c. motor using digital PID algorithm. Intel 8085 microprocessor based hardware is developed for the implementation of the controller. The system broadly involves interfacing hardware and the software for PID algorithm. A continuous PID controller is governed by an equation which describes the dynamic time varying behavior of the input or the error signal. This is digitized using numerical approximations and is programmed in the microcomputer. This system is a closed loop control system with feedback signal generated by a digital magnetic pickup, which gives a pulse output which is TTL compatible. A digital to analog converter interfaces the power control to the microcomputer. The PID algorithm along with the hardware achieves the speed control of the d.c. motor. The hardware and software are validated in real time by considering different speed settings.