Editing Programmable logic controller (section)

{{Short description|Programmable digital computer used to control machinery}}
{{Use American English|date=September 2023}}

[[File:Automate industriel WAGO pour un système de monitoring en industrie pharmaceutique.jpg|thumb|PLCs for a monitoring system in the pharmaceutical industry]]
{{Manufacturing}}

A '''programmable logic controller''' ('''PLC''') or '''programmable controller''' is an industrial [[computer]] that has been [[ruggedized]] and adapted for the control of manufacturing processes, such as [[assembly line]]s, machines, [[robotic]] devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis.

PLCs can range from small modular devices with tens of [[Input/output|inputs and outputs]] (I/O), in a housing integral with the processor, to large rack-mounted modular devices with thousands of I/O, and which are often networked to other PLC and [[SCADA]] systems.<ref>Tubbs, Stephen Phillip. ''Programmable Logic Controller (PLC) Tutorial, Siemens Simatic S7-1200.'' Publicis MCD Werbeagentur GmbH; 3rd ed., 2018.</ref> They can be designed for many arrangements of digital and analog I/O, extended temperature ranges, immunity to [[electrical noise]], and resistance to vibration and impact.

PLCs were first developed in the automobile manufacturing industry to provide flexible,  rugged and easily programmable controllers to replace hard-wired [[relay logic]] systems. [[Dick Morley]], who invented the first PLC, the Modicon 084, for [[General Motors]] in 1968, is considered the father of PLC.

A PLC is an example of a [[hard real-time]] system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation may result. Programs to control machine operation are typically stored in battery-backed-up or [[non-volatile memory]].