PLC origins: Where did PLCs come from? 40th anniversary timeline

PLCs have undergone 40 years of convergent evolution, according to an article in the upcoming September issue of Control Engineering. See a graphic with a timeline of PLC development, a market that went from zero to more than $1 billion in a decade. Link to the full story.


Programmable logic controllers (PLCs) were more of a technology evolution than a startling discovery according to Control Engineering in the upcoming September North American issue. [See link below.] “The earliest robust, easily re-programmed industrial controller—which we know as the PLC—evolved nearly concurrently along three independent paths.”


Three tributaries converged to form today


Ball’s research for the


40th anniversary PLC article in Control Engineering

showed that PLC evolution involved five companies: Bedford Associates; General Motors Hydra-matic Division, Ypsilanti, MI plant; International Instruments Inc. (3I); Digital Equipment Corporation (DEC); and Struthers-Dunn Systems Division in Bettendorf, IA. He says that identifying the needs and early ideas first began to take shape in 1967. Documentation and actual building of prototype devices started in 1968, with early model deliveries and factory tests taking place in 1969 and ’70.
“Probably the most publicized early PLC development took place at GM’s Hydra-matic Division plant,” he says. “Several engineers there collaborated on a concept for what they called a‘standard machine controller.’ ” 
The GM engineers envisioned a controller to replace troublesome relay panels and provide a simpler interface between computers and machines.
Meanwhile, a second path was being pursued by Bedford Associates, a small New England company that today would be categorized as a control systems integrator. Bedford Engineers developed a controller to replace costly minicomputers and reduce programming time for various machine tool applications.
The third approach underway at the time occurred at the Struthers-Dunn Systems Division, which also had strong automotive ties and was well aware of relay and timer panel shortcomings.
Early on, the controller was known as the PC and publications such as the PC Insider popularized the designation. This was fine until personal computers arrived around 1980 and this office/consumer item stole the PC acronym. To avoid confusion, controls people reverted to a PLC designation — a term that had been registered by Allen-Bradley for their newer model controllers.“ Allen-Bradley has been quite gracious,” Ball says, “and has not attempted to restrict the use of the term.”
Shortly after the PLC debut, sales went from zero to more than a $1 billion in a little more than a decade.
C.G. Masi, senior editor
Control Engineering News Desk
Register here and scroll down to select your choice of eNewsletters free.


No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2013 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
A cool solution: Collaboration, chemistry leads to foundry coat product development; See the 2015 Product of the Year Finalists
Raising the standard: What's new with NFPA 70E; A global view of manufacturing; Maintenance data; Fit bearings properly
Sister act: Building on their father's legacy, a new generation moves Bales Metal Surface Solutions forward; Meet the 2015 Engineering Leaders Under 40
Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again
Pipeline vulnerabilities? Securing hydrocarbon transit; Predictive analytics hit the mainstream; Dirty pipelines decrease flow, production—pig your line; Ensuring pipeline physical and cyber security
Upgrading secondary control systems; Keeping enclosures conditioned; Diagnostics increase equipment uptime; Mechatronics simplifies machine design
Designing positive-energy buildings; Ensuring power quality; Complying with NFPA 110; Minimizing arc flash hazards
Building high availability into industrial computers; Of key metrics and myth busting; The truth about five common VFD myths

Annual Salary Survey

After almost a decade of uncertainty, the confidence of plant floor managers is soaring. Even with a number of challenges and while implementing new technologies, there is a renewed sense of optimism among plant managers about their business and their future.

The respondents to the 2014 Plant Engineering Salary Survey come from throughout the U.S. and serve a variety of industries, but they are uniform in their optimism about manufacturing. This year’s survey found 79% consider manufacturing a secure career. That’s up from 75% in 2013 and significantly higher than the 63% figure when Plant Engineering first started asking that question a decade ago.

Read more: 2014 Salary Survey: Confidence rises amid the challenges

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.