Programmable logic controller: Difference between revisions

Revision as of 15:27, 7 August 2003

Revision as of 23:47, 7 August 2003

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-A '''programmable logic controller''' or '''PLC''' is a small [[computer]] used for [[automation]] of real-world processes, such as control of machinery on factory assembly lines. Where older automated systems would use hundreds or thousands of relays, a single PLC can be programmed as a replacement.

The PLC is a [[microprocessor]] based device with either modular or integral [[input/output]] circuitry that monitors the status of the field connected "[[sensor]]" inputs and controls the attached output "actuators" (motor starters, solenoids, pilot lights/displays, speed drives, valves, etc.) according to a user-created, logic program stored in the microprocessor's battery-backed [[RAM]] memory. The functionality of the PLC has evolved over the years to include capabilities beyond typical relay control; sophisticated motion control, process control, [[DCS]] and complex networking have now been added to the PLC's list of functions.