Programmable Logic Controller A programmable logic controller (PLC) or programmable controller is a solid-state/ computerized industrial computer that performs discrete or sequential logic in a factory environment. It was originally developed to replace mechanical relays, timers, counters. PLCs are used successfully to execute complicated control operations in a plant. Its purpose is to monitor crucial process parameters and adjust process operations accordingly. A sequence of instructions is programmed by the user to the PLC memory and when the program is executed, the controller operates a system to the correct operating specifications. The first PLC system evolved from conventional computers in the late 60s and 70s. These first PLCs were installed primarily in automotive plants. Traditionally the auto plant had to be shut down for up to a month at model change over time. the early PLCs were used with other new automation techniques to shorten the changeover time....
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