History of PLCs

[Blackcountryman]

I'm writing a paper about the development of programmable controllers and looking for any published information from about 1968 to 1976.
I have searched the IEEE & IET(used to be the IEE) catalogues and the first reference I can find is an IEE Colloquium from 1976.
I have a copy of Dick Morley's book and more recent interviews with him.
Any help would be appriciated
John

 

[unclesyd]

Here are two sites that I found by searching "Modicon". This was the first off the shelf PLC that I saw in actual use.

Prior to the Modicon we had several PLC'S made by our instrument group to control very critical temperatures on processing synthetic fiber. The little temperature PLC's were made using minature vacuum tubes and stayed in service for over 20 years. The took the speed and temperature of a yarn toe, ambient temperature and adjusted the heating of a roller guide. Each machine had 48 of the PLC's and we had 17 machines.

http://www.plcs.net/chapters/history2.htm

http://en.wikipedia.org/wiki/Programmable_logic_controller#History

 

[IRstuff]

Perhaps, you need to explain what you mean when you say "programmable controller," or "programmable logic controller." "Switching Circuits for Engineers" by Mitchell Marcus is copyright 1962, which predates the period you're looking at.



TTFN

FAQ731-376

 

[unclesyd]

I forgot to add that prior to the electronic approach to PLC's there were several attempts to use fluidics in various form to get some logic at signal source. The first attempts were rather crude and didn't improve until micro fluidics came on the scene.

Prior to the advent of EDM, using our process for cutting metal we generated all types of geometric hardware for the fluidic crowd. I recall that we had a dozen confidentiality agreements at one time.

 

[Blackcountryman]

Thanks Gents,

IRStuff,
you're right I should have explained, I assumed people know what they are. We all know how dangerous assumtions are I should have known better.

PLCs are a software based controller originally for relay replacement but now much more powerfull and wide ranging. The two sites Unclesyd provided give a more detailed overview.

Unclesyd,

Thanks for those sites, the Wikipedia site I had not looked at. That has some interesting information.
I work for the organisation that owns Modicon so have access to our history which includes Telemecanique and April PLCs.
I had not thought about Fluidics thats another avenue. Where your early temperature PLCs software based?

From my present research I'm not finding any mention of PLCs in the accademic press/publications. It apprears that these devices where developed mainly by the compaines in the electrical industry Such as Allen Bradley, Telemecanique, Siemens, Texas Instruments and ofcourse Modicon.
Thanks again for your input
John

 

[unclesyd]

The earliest temperature controllers were not software based. The later models were programmable to some extent through a black box. The first controller that could be software programed by designed by an ex Motorola engineer who work in our electronic development group.

Back to the Modicon. On one of our process where we required a sequential controller that took several inputs we used a "Tenor" controller. This was a music box type system. Initially the Modicon worked in conjunction with this system until the Modicon was able to take over. If I recall all these systems were hard wired. There was some effort to use an IMSAI or ALTAIR to do some online programing.

I think that it corrected in saying that the electrical companies pioneered the software programmable devices. I had to solve a problem with the legs/leads on transistors being eaten off by HCl fumes in some of the early electrical boxes.

Just talked to one of the old hands and he told me that it was the mid 70's before we had a true software programmable controller. All the other systems were to simply change the logic by very small increments.

 

[IRstuff]

Intel's 4004 is reputed to be the first microprocessor:

http://en.wikipedia.org/wiki/Intel_4004

Prior to that, the only computers in general use were minicomputers, ala PDP-8:

http://en.wikipedia.org/wiki/PDP-8,

hardly the stuff that PLCs would have been made of.

There were no PLDs prior to about 1970:

http://en.wikipedia.org/wiki/Programmable_logic_device

TTFN

FAQ731-376

 

[Skogsgurra]

That's right. There was also the Fairchild PPS 25 system (my data book is from 1972, so it must have been marketed just about same time as the 4004 chipset) and the early bit-slice (or nibble-slice) systems used to produce something that could be called PLC:s. But they were all programmed in native assembler and they were not at all like PLC:s of today.

An attempt to standardise hardware and software was done by the Pro-Log Corporation of Monterey, CA. The name was derived from Programmable Logic Control and that was the first time I saw that combination of words.
They had a three-card system, the PLS-403, which I used to control measuring devices in robot cells. The measurements were handled by a Tektronix calculator with a very expensive I/O board. Slow, slow. But we were happy.

There was also a system based on a hardwired finite state machine with instructions in a set of 1702A 256 Byte EPROMS. That could have been called a PLC, even if there was no processor.

My old collection of catalogs from that time includes an intel 4004 manual from February 1973 and a catalogue from same time. One of the application examples shows a bottling machine controlled by a 4004 system. A PLC.



Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ozmosis]

Jim Pinto is always an interesting read:

http://www.jimpinto.com/writings/automationhistory.html