History of PLCs

Today i have article that story in PLCs,Twenty-five years I was in my last year with Allen-Bradley PLC and a specialist and educator. I grew up with the PLC in 1774, the PMC. What a trip through the PLC-2, PLC 3, PLC 5, computer-based programming instead of a luggable terminal and a 10 MB hard disk for the PLC-3 GA module for remote data collection and programming remotely through the RM modules.

A laptop for programming (Data General) was more than $ 8,000. Hard drive space is outrageous expensive, and Windows will not be used. PCs were ahead, and programmers learned useful DOS software.
From 1977 to 1985 there was an enormous growth pattern that most had not imagined. Remote I / O, HMI, SCADA, and similarly, the PLC to the DCS world compromise. Servo Control was also available. Special keyboards set them up.
Bit-flipping was an art.

We had to do in ASCII module interfaces, and network modules with interfaces for mini-computers like the DEC VAX and PDP-11.

Some applications were too fast for the PLC, but not much. Everything was a good deal for the PLC and the companies and individuals.

In 1986 I founded my own company and am involved with the newfangled software arena. Life changes decision proved quite good.

ICOM, Tele-thinking, tender gray, Taylor et al. made DOS-based PC programming software. Moved to PC-based HMI and ARCnet came to town.

But what really changed since 1985? It depends on who you ask. Marketing vs Engineering is the battlefield, as hardware costs have fallen to the point of goods.

Let me table for the next month to develop a perspective on where we are and where we come from.

Applications that make use of automation changed, but some are not. The reasons for the use of automation, more enterprise-centric. This wish it was in 1985-it just was not easy to implement.

“Real time” a new meaning, so that access to data is crucial. It was, but the preservation of the data was primitive. OEMs developing and producing their own interfaces for the collection of data for customers. We just have easy access to such data today.


Electrician to resolve successfully the systems of fixed terminals. The documentation was found on the printed scale. Difficult to navigate, but they were successful.

Encoders, converters, control circuits and more linked (then and today) with special I / O. Today, however, there are I / O buses, remote I / O of something. Instead of treating a PLC data table for hiking or quantitative information, you get the data from the device. But the data is similar, yes?

At the risk has changed, old, I do not think much. ControlLogix is ​​no different than the PLC-3 from 1980. You can scan multiple cards to support redundancy, the use of special communication card, data collection and other languages. It is a remote I / O and remote programming possible in both.

Applications are available for client / server environments. Mainly based on UNIX, but they worked.

Then something really monumental happened changed the rules changed, the development cycle, and changed the operative work. This cycle / career change made changes, what we have today. We had the goods but few were in force.

The shift was monumental software. Windows 3.0, NT and IBM OS / 2 Presentation Manager creates a free-for-all. A small company called Wonderware HMI took over the company. Because it was so easy, PLC were targeted. Ethernet landed in the workplace, and ensure that each Ethernet PLC had to speak.

New and improved technology may not necessarily be a different function. get from 1985 to 2010 Oldsmobile Porsche both what you want. We want to buy different things with the data. This requires a number of different “things” and it’s slow, painful and not to the order indicated that to change much advertising.

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