Talk:Programmable logic controller
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[edit] Programming PLC
There is some info missing: PLC can be programmed not only in ladder languages or C, but there is a galore of possibilities:
- ladder logic (mentioned),
- structural languages - mostly C (mentioned),
- low-level languages- assembler, basic,
- block languages, like FBD, PD, FUP...,
- sequential function charts.
However, I don't feel wise enough to write more :D
There seems to be quite a few inaccuacies with this article. For one, complex programs need not always be done by a ELECTRICAL Engineer (It states Industrial Engineer). There are many highly skilled PLC programmers who are not Electrical Engineers. ProdigalSon
Also the IEC-1138 standard is not relevant to the topic, the actual one is IEC-61131-3; but there is no "structured C" there at all.
[edit] History
There seems to be some confusion about the history of the PLC. The present article seems to indicate that GM was the driving force behind the development of the PLC. However, in this article - http://www.barn.org/FILES/historyofplc.html, Dick Morley, its inventor, seemed to have had in mind the machine tool industry when he first envisioned it. Can anyone clarify this issue? Which came first - GM's proposal for a PLC or the PLC its self that neatly fit into GM's needs?
[edit] Simple and representative
We don't need to document all methodologies used for each brand of PLC. We all have our favorite system and after a while it seems like the One True Way. I programmed ZWorld controllers in C(more or less) to control gas flows. If you controlled cutting machines using GE Fanucs, everything has a slightly different feel. We don't need to document the different feels in this page. For example, I just whittled down a big mess regarding the labels we use for digital input values: On/Off, 1/0, T/F, 24VDC/0VDC. Any of these is valid. Including them all just confuses the un-initated reader. You control motors, I control valves but we don't need to list everything that is a digital output to communicate the idea of Digital Output. Same with programming languages, UIs, data storage, networking... Can we keep it simple and representative please? -- TomCerul 05:38, 21 July 2005 (UTC)
[edit] Examples
Okay folks, we know PLC programming is full of millions of details regarding how things can go horribly wrong. What examples should we use? My choice has been
- 1. DI/DO
- 2. AI/AO
- 3. Should we add an HMI example?
- 4. And now I'm thinking we should add an example and section describing the level of the complexity inherent to industrial control/PLC programming. Perhaps:"Now change the controlled fluid to gasoline. Extensive safety precations must be implemented. Overfill, vapor detection, catch pan liquid detector, exhaust monitoring, controller air pressure monitoring..."
I want to make most of the article clear enough for a layman. TomCerul 15:41, 1 September 2005 (UTC)
Since PLCs are never installed without a lot of accompanying electrical interfacing, some pictures of typical electrical control cabinets would help give PLC installations some context.
[edit] External Links
I suggest we establish external links - it may make sense to link to a few manufacturers and other useful non-commercial resources. See Also should refer to other entries in the Wikipedia. If no one has objections I will change link labels and start links to major PLC mfgs - AB, Siemens, Modicon, GE Fanuc, etc. - but would like to est a "policy" so this page does not become a link farm. VGarner 16:53, 5 April 2006 (UTC)
[edit] Communication Protocols
Could someone please comment on what standards for serial and or network communication exist? Thanks.
- OK. Spalding 03:04, 15 July 2006 (UTC)
