Programmable logic controller: Difference between revisions

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In 1968, GM Hydramatic,<!--Don't link hydramatic transmission--> the [[automatic transmission]] division of [[General Motors]], issued a [[request for proposal]]s for an electronic replacement for hard-wired relay systems based on a white paper written by engineer Edward R. Clark. The winning proposal came from Bedford Associates from [[Bedford, Massachusetts]]. The result, built in 1969, was the first PLC and designated the ''084'', because it was Bedford Associates' eighty-fourth project.<ref name=":9">{{Harvnb|Laughton|Warne|2002|loc=chpt. 16}}</ref><ref name=":0">{{Cite web |url=https://www.automationmag.com/855-the-father-of-invention-dick-morley-looks-back-on-the-40th-anniversary-of-the-plc/ |title=The Father of Invention: Dick Morley Looks Back on the 40th Anniversary of the PLC |last=Dunn |first=Alison |date=2009-06-12 |website=Manufacturing Automation |access-date=2020-02-23 }}</ref>

Bedford Associates started a company, '''Modicon, Inc.''',<ref name="b677">{{cite book | last=Group | first=Career Communications | title=US Black Engineer & IT | publisher=Career Communications Group | date=1993 | url=https://books.google.com/books?id=pESCcEtfrusC&dq=modicon%2520inc&pg=PA42 | access-date=2025-06-09 | page=}}</ref> dedicated to developing, manufacturing, selling, and servicing this new product, which they named '''{{visible anchor|Modicon}}''' (standing for "modular digital controller"). One of the people who worked on that project was [[Dick Morley]], who is considered to be the father of the PLC.<ref name=":1">{{Cite web|url=https://www.isa.org/standards-and-publications/isa-publications/intech-magazine/2003/august/cover-story-50th-anniversary-leaders-of-the-pack/|title=Leaders of the pack|last=Strothman|first=Jim|date=2003-08-01|website=ISA|url-status=live|archive-url=https://web.archive.org/web/20170808184918/https://www.isa.org/standards-and-publications/isa-publications/intech-magazine/2003/august/cover-story-50th-anniversary-leaders-of-the-pack/|archive-date=2017-08-08|access-date=2020-02-24}}</ref> The Modicon brand was sold in 1977 to [[Gould Electronics]] and later to [[Schneider Electric]], its current owner.<ref name=":0" /> About this same time, Modicon created [[Modbus]], a data communications protocol used with its PLCs. Modbus has since become a standard open protocol commonly used to connect many industrial electrical devices.<ref>{{cite web |title=Mobus Networking Guide: Introduction |url=https://development.libelium.com/modbus_networking_guide/introduction |website=Libelium.com |access-date=27 October 2022 }}</ref>

One of the first 084 models built is now on display at Schneider Electric's facility in [[North Andover, Massachusetts]]. It was presented to Modicon by [[General Motors|GM]], when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until after the 984 made its appearance.<ref>{{cite book |last=Chakraborty |first=Kunal |title=Industrial Applications of Programmable Logic Controllers and SCADA |date=2016 |publisher=Anchor Academic Publishing |___location=Hamburg |isbn=978-3960670247 }}</ref>