There are two tools for training systems, commercially available ones and those proposed by education. A review of both is useful. Portable training systems commercially available fall generally into two categories:
• Hard wired “kits”;
• Simulators.
Hard wired “kits”
A kit generally contains of a PLC incorporating banks of switches to simulate input devices and lamps to simulate output devices [5]. They do not facilitate interfacing industrial electrical components to the PLC. They are useful for teaching programming only, for experienced programmers to explore new programming techniques and for black box software testing. They do not for students of entry level programming, provide the experience of selecting and connecting actual components to the PLC and generating the Input / Output (I/O) List to document those connections. The I/O List is a vital part of the documentation required for effective program design and maintenance.
Simulators
Simulators may be sub-divided further in to two categories: PC based using an actual PLC. Simulators generally have a range of industrial processes (“virtual machines”) such as “pick and place” and “tank level control systems”. The programmer chooses a “virtual machine” from a menu, writes the program to control it and downloads it to the PLC. The simulator PC communicates serially with the PLC simulating the “virtual machine”. The PLC and the machine or processes are both “virtual” in the second type that is no physical PLC exists. Same as with the system previously the programmer selects a “virtual machine” from a menu, writes the control program on the PC based “virtual PLC”. The “virtual machine” is then controlled by the “virtual” PLC.
Generally Simulators can be used effectively for engineering training. However, for PLC training, as with the hard wired kits the simulators are best exploited by students who have the applied skills required to interface the PLC to peripheral devices, have some programming skills and want to develop those programming skills. The simulators in common with the hardwired kits do not provide the practical experience of wiring up the PLC, interfacing it to peripheral devices and generating the electrical drawings and the I/O List to document the system.