Part One: Rise of the PLC Systems

You are reading Part 1 of the History of PLCs series. In this series of blogs, we write about the PLC industry. Its challenges. And how to overcome them. Enjoy!

PLC (Programmable Logic Controller) control systems now dominate industrial automation. They are managing anything from simple semi-automatic devices to the most complex systems like nuclear power plants.

A brief excursion into the past The PLCs were born in the '70s to replace control through relay logic and hardwired electronics. They introduced a more scalable way and allowed logic to be changed by reprogramming. For example, the implementation of ladder logic (LD) made it easy to redraw the logic scheme instead of linking the physical wiring.

PLCs have revolutionized automation from wiring and soldering to actual programming. Their success came due to robust hardware, a variety of input/output devices, a simple model of operation, and deterministic behavior of the control program. Of course, a relatively low price compared to the computing devices of the time also played a huge role. The prices of PLC systems in the '70s were a fraction of the cost of existing computers.

In the beginning, it was common to use hardware solutions (buttons, switches, indicators, etc.) for user interaction. Later came; simple segment panels with membrane keyboards, followed by LCD panels, and finally industrial touch panel designs. Systems known as SCADA were used for more complex data collection and visualization. This scene has been relatively stable for several decades.

Historically, there were four good reasons to use PLC systems to control industrial processes: price (a fraction of the cost of computing devices like personal computers), robustness (resistance to damage and external influences), determinism (a guaranteed run of the program within a fixed time limit) and long life cycles (sales and support for decades).

Do these reasons still have merit in this current day and age? We will discuss that next time.

Part one: Rise of the PLC Systems
Part two: PLCs are Challenged
Part three: Differences in PLC Programming Languages
Part four: What Can Australian Natives Teach Us About Modern PLCs?
Part five: Will Industry 4.0 Save Us?
Part six: PLC Performance Challenges
Part seven: Why Beckhoff PLCs?
Part eight: Connecting PLCs to the .NET Environment

Tags: History of PLCs

Peter Kurhajec
CTO of Inxton

Peter Kurhajec

Hello! I'm the CTO of Inxton! More than a decade ago my pet project turned into a full-time job - INXTON. Now I'm on a mission to bring industrial automation and information technologies together.