Software control interface to a programmable logic controller

The authors summarize the design, development, and implementation of a software relay control system interface to a Struthers-Dunn Director One programmable logic controller. This system was designed to allow (1) program development on the Prime 6350 computer system in the Department of Electrical Engineering at the University of Alabama at Birmingham and (2) program execution on a personal computer which is connected to the programmable logic controller in the department´s Industrial Controls Laboratory. The development of both programs is discussed to understand the system design and implementation