A Virtual Programmable Logic Controller |
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PLC Home A brief history Standards Applications Choosing a PLC Capabilities Principles of operation Hardware Programming and boolean operations Simulation 1 - Using the programming panel Simulation 2 - First steps in programming Simulation 3 - More complex networks Simulation 4 - Set/reset and impulse relay Simulation 5 - Using timers Simulation 6 - Using counters |
A Brief HistoryThe programmable logic controller (PLC) has a relatively short history. First developed in the early 1970's, it began as a simple device designed to replace electro-mechanical relays, and used integrated circuitry to perform simple sequential control tasks independently of other control and monitoring equipment. Millions of PLCs are now used around the world in this type of application. The PLC has now evolved into a complex system capable of handling almost any type of control application, including motion control, data manipulation, and advanced computing functions. The PLC no longer works in isolation, and can be integrated into complex schemes in which it is required to communicate with other controllers and computer systems in order to carry out plant management functions. |