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PLC Courses are No Excuse to Dumb Down

A primary goal of a course in Programmable Controller Applications is to help the student find good employment. Another goal of the course should also be to support other subjects taught in the digital sequence as well as networking and programming.

The PLC was first brought to market around 1970 and the UAW went to the big three auto-makers with the proposition that they would endorse it if it was made available exclusively to electricians to program. This was agreed between the parties and the PLC was mainly programmed by electricians using existing control diagrams. In other environments, the PLC was programmed by engineers and later by engineering technologists (EET’s). The PLC never fully utilized in those early years the complete capability of the computer from which it evolved. There was a ‘dumbing down’ of the instruction set for many years and only recently has this trend been fully reversed.

From the author’s perspective in industry, there is a concern for the lack of student awareness of the high expectations of PLC work once the student graduates. It is commonly accepted that 90% of the jobs in the mid-west served by this university require some proficiency in the use of PLCs. One person who had hired over 20 EET majors in the past few years observed that the EET majors all had some PLC experience and knew how to ‘hit the ground running’. Most companies today do not want to spend money trying to convince the recent graduate that programming the PLC is something worthwhile. They want the student to already be convinced and willing to accept the challenges of program creation from day one.

The approach is in general more rigorous than that encouraged by most American PLC texts. Encouraged from the first is the writing of programs from scratch. Several clues are given along the way but students are encouraged to begin writing their own programs and debugging them in order to get credit for the project. Projects are used instead of labs. In a project the student must complete a working model in order to get credit. There is no guarantee that after an hour or two or three the program will be working and accepted. It may take longer – much longer. Programs include a traffic intersection, a simple cash register, and a simple candy dispenser machine. Programming moves to more difficult programs involving number conversion to bit logic and programs requiring the use of timing diagrams. Then more difficult programs including sequencing of data and moving data through tables are required.

The paper develops a list of topics that are covered in a comprehensive PLC course. Rational for inclusion of various topics are discussed as well as the name change to Mechatronics from PLC.