DESIGN OF A PC-BASED DC MOTOR SPEED CONTROLLER

This paper is concerned with the interfacing process between a personal computer and a permanent magnet DC motor. A practical interface circuit has been designed and implemented in order to control the speed of a permanent-magnet DC motor using a C++ control program. The proposed circuit technique involves receiving the digital signals from the parallel port of the PC and providing them to a transistor driver circuit through an IC buffer. The transistors in the driver circuit are used to increase the current level of the incoming signals into an adequate value in order to drive control relays that are connected to the motor circuit. The control relays are utilized, in turn, to split or insert certain number of resistors connected in series with the motor circuit and thus changing its speed according to a prescribed digital sequence generated by the computer program. The circuit was implemented and tested successfully at the laboratory.