Teaching programmable logic controllers using multimedia-based courseware

International Journal of Electrical Engineering Education, Oct 2000 by Blakley, J J, Irvine, D A

Abstract In this paper the development and use of multimedia-based courseware to support teaching and undergraduate laboratory sessions in the subject area of programmable logic control are discussed. The multimedia-based courseware described is designed to be used by undergraduate students meeting programmable logic controllers (PLCs) for the first time. Two developed prototype multimedia packages are described.

Keywords multimedia courseware; programmable logic controllers; teaching aids

Programmable logic controllers (PLCs) have progressed rapidly since their inception in the early 1970s, and are now widely used in the manufacturing, process and utility industries. Consequently, a detailed understanding of the operation and use of PLCs is important for many undergraduate students, particularly those who seek eventual employment in these industries.

Collins and Lane1 have noted that a recognised obstacle to the fullest possible benefit of programmable logic control is one of education and training. Difficulties arise, in part, due to the rapid pace of PLC technological development, with new models and innovations continually being introduced by manufacturers. Further, PLCs are dedicated industrial controllers and, unlike personal computers, once purchased for laboratory use cannot be employed for a wide range of other useful applications. Costs incurred in the setting up of comprehensive and modern PLC laboratory facilities, and in the required periodic updating of teaching material and equipment are, as a result, very high.

With one definition of the term, 'multimedia' is defined as any combination of text, audio, graphic images, animation and video that can be delivered by computers to present teaching/training material. Although there are challenges and barriers to overcome,2 multimedia technology provides a valuable resource to enhance the teaching and learning experience. The introduction of multimedia technology into PLC laboratories, for example, has the potential to reduce costs and to enhance the quality of laboratory learning and its integration into the total undergraduate learning experience. In the control laboratory at the School of Electrical and Mechanical Engineering, University of Ulster, development of multimedia-based courseware in the form of two prototype multimedia-based software packages has recently been undertaken to pilot future use of multimedia technology in PLC laboratories. The first package is a PLC simulator, PLCSIM, designed to assist in the teaching of ladder diagram programming in a laboratory setting. The second package is a teaching package, PLCTUT, in which interactive hyperlinked notes, supplemented by animations, audio and video, are provided to support teaching and the student laboratories and coursework undertaken. Both PLCSIM and PLCTUT packages require Windows 95 to run and are written using Visual Basic and the multimedia publishing package Macromedia Director, respectively.

Previous attempts to introduce innovative methods into teaching programmes involving programmable logic control have included: the use of PLC control of laboratory scale models;3-5 and the development and use of PLC ladder-logic simulators.6,7 Also, recently, a commercially available ladder logic editor and PLC simulator has been developed by the laboratory equipment developers and manufacturers Bytronic.8

The programmable logic control simulators described in the literature6-8 are, in general, designed to represent only a subset of the capabilities of most industrial PLCs. Whereas, in the PLC simulator described in this paper, an actual PLC representative of many small PLC systems currently available on the market, the Toshiba EX20PLUS, is used as a model for the simulator. A complete specification of the EX20PLUS can be found in Ref. 9. Currently, at the University of Ulster, the Toshiba EX20PLUS PLC is one of a number of small PLC systems used to teach students the basics of ladder diagram programming and to introduce PLC implemented devices such as contacts and coils, timers, counters, flip-flops, shift registers and step sequencers. Subsequent laboratories entail study of more advanced functions available from a range of PLCs and their interfacing to and control of laboratory scale models. The approach adopted has the advantage that groups of students can use the PLC simulator (PLCSIM) in parallel with those using actual Toshiba PLC hardware. Further, use of the two multimedia software packages, PLCSIM and PLCTUT, alleviates safety concerns that arise when groups of inexperienced student users experiment with actual control equipment, and offers the possibility of reducing the dependence on the expensive laboratory scale models and control rigs required for control experimentation.

In this paper, a description of the developed multimedia courseware packages is given in the next section. Examples are then presented to illustrate typical screen output resulting from student application of the PLCSIM and PLCTUT software packages, Finally, some concluding remarks are given.