Talk:Programmable logic controller

message: A few years back, when I attended school, I learned about PLC's. I was shown three industrial PLC’s: one electronic (as on the wiki), one pneumatic and one mechanical. All three had the same functionality and could handle both digital and analogue I/O signals (by voltage, pressure and force). They are terribly obsolete today, but they are in my opinion very interesting and worth mentioning. Unfortunally I know very little about the pneumatic and mechanical PLC’s, perhaps someone does and whishes to add it?  —Preceding unsigned comment added by 87.208.51.83 (talk) 22:21, 15 February 2011 (UTC)
thread_title:  Pneumatic and mechanical PLC's 

message: 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)
thread_title:  Simple and representative 

message: 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)
thread_title:  Examples 

message: Could someone please comment on what standards for serial and or network communication exist?  Thanks.
:OK. Spalding 03:04, 15 July 2006 (UTC)
thread_title:  Communication Protocols 

message: I notice that Programmable logic controller has chosen to use asterisks to denote that PLC is a registered trademark of Allen-Bradley, and Unix has chosen to use the extended ASCII registered trademark character.  I'll let you guys duke it out, but we really shouldn't have two standards.--Superluser 00:35, 19 April 2007 (UTC)
thread_title: Trademark

message: There is not much explanation on PLC capability in delivering high speed output and receiving high speed input. This will allow PLC to control AC servo motor. This link might be helpful.
:::http://yourplctrainer.com
Tatau1234 (talk) 06:28, 11 December 2008 (UTC)
thread_title:  PLC compared with other control systems 

message: how they operate and thier functions  —Preceding unsigned comment added by 41.220.2.117 (talk) 13:30, 24 November 2007 (UTC)
thread_title:  microprocessors 

message: I changed the wording of this example a bit to be more clear. Am I wrong in thinking that it should be two series float switches (a logical AND gate) rather than two parallel float switches (a logical OR gate)? Schreineradam (talk) 15:03, 13 February 2008 (UTC)
thread_title:  Digital and analog signals example 

message: "PLC" from its original inception stood for "Process Local Controller" - somewhere along the line this has been changed by common usage to "Programmable Logic Controller" 81.151.17.6 (talk) 11:13, 21 August 2008 (UTC)
replies: text: Got a reference?  I've never heard of that story and the first time I got my mitts on a PLC was in 1980. Of course, credentials mean nothing on the Wikipedia. All the old Allen-Bradley literature that I had access to, called it "Programmable logic controller" and some of that went back to the mid '70s- pretty early on in the scheme of these things. As a check on my sanity, Google returns exactly 5 hits on the exact phrase "process local controller" and none of them are in an industrial automation context.  "Process control" usually meant analog loops in the old days, and PLCs weren't even usable for analog quantities for many years. --Wtshymanski (talk) 15:16, 21 August 2008 (UTC)
thread_title: Origin of name

message: That suppliers section is somewhat of a concern. It really doesn't fit with WP:NOT (business directory) and its a magnet for everyone to create and link spam in the article namespace. User A1 (talk) 13:19, 3 November 2008 (UTC)
thread_title:  Suppliers 

message: I suggest we add a magazine web site category page that is a great resource devoted controllers (automation), including technical articles, white papers, feature articles, webcasts, podcasts and other rich content related to PLCs and controllers. The top of the page has sponsored material but means you have to log in to view the material, no advertising. 
: External Links section - could someone please add links to:
::: http://www.automationworld.com/Controllers
:thanks (talk) 10:19, 15 January 2009 (UTC)
replies: text: This alink hbas been placed on multiple articles, and is clearly a commercial website, which has some educational content. This is not suitable per WP:EL. User A1 (talk) 00:54, 16 January 2009 (UTC)
thread_title: External Links

message: Please consider adding the following website link.
* PLC Complete Tutorial
Reason: A comprehensive tutorial on programmable logic controller (PLC) operation and programming.
Thank you.--41.234.63.19 (talk) 23:17, 10 February 2009 (UTC)
replies: text: This link has been removed by multiple editors multiple times. If you disagree  with the removal of the link, there are processes you can voluntairily follow to obtain a third opinion User A1 (talk) 10:11, 11 February 2009 (UTC)

text: I agree with the comments above by both Martynas Patasius and Athabaska-Clearwater, but at this time will not (due to real-life constraints) be adding the book as a reference in the article. To be clear, I have no objections to the direct use of the book at all, if it can be linked as a PDF. User A1 (talk) 01:05, 12 February 2009 (UTC)
thread_title: External Link Suggestion

message: It is stated on Functionality that a PC can replace a PLC "in some applications". This statement may imply that there are no (severe) trade-offs when doing so, hence I tagged it dubious. 201.37.106.228 (talk) 14:24, 15 March 2009 (UTC)
replies: text: Beckhoff Automation argues that their PC-based TwinCAT product can replace PLCs in quite a wide range of applications. — Wdfarmer (talk) 23:49, 28 February 2010 (UTC)
thread_title:  Dubious 

message: Page protection has once again been applied to deal with excessive adspam by User:Cartiman and his various sockpuppets. Apologies for the inconvenience. Euryalus (talk) 10:48, 26 March 2009 (UTC)
thread_title: Page protection 

message: Hello,
I'm kinda getting tired of continually sifting the wheat from the chaff when users are making edits to the "Suppliers" section. This section is a magnet for WP:COI edits, and doesn't really do much for increasing the reader's understanding of PLCs. I propose removing this section entirely, this article gets enough COI vandalism as is, and anything we can do to reduce the frequency of this would be nice. However I note that last time I removed it (without discussion) it was reinstated in a short time, hence this discussion. Can we have a discussion of the merits of this section, and whether it should be removed? User A1 (talk) 07:12, 9 May 2009 (UTC)
replies: text: Wikipedia is Wikipedia:NOT#Wikipedia_is_not_a_directory. This is the exact use that it should *not* be used for. If you want to find suppliers you should use a business directory User A1 (talk) 05:23, 14 May 2009 (UTC)

text: Ive pulled it. This discussion has been  up for two weeks, which I feel is sufficient to have recieved any feedback. I cannot see any reason that is inline with WP policy to keep this section. User A1 (talk) 02:05, 23 May 2009 (UTC)
thread_title:  Suppliers section 

message: Please stop doing this. North8000 (talk) 15:52, 18 July 2011 (UTC)
thread_title:  Somebody keeps taking out the history of PLC's and substituting the History of Modicon 

message: This article is focused on PLC usage rather than explaining what a PLC really is, or moreover, what a PLC is made of.  — Preceding unsigned comment added by 86.125.236.87 (talk) 21:49, 30 April 2012 (UTC)
replies: text: It's certainly not perfect, but I think it is focused on providing the common useful information.  A PLC is made of nearly all of the parts used to build any type of electronic equipment (resistors, capacitors, printed circuit boards, integrated circuits, transistors, diodes etc.) plus sometimes a few that are electromechanical equipment. IMHO the former is not very unique/informative regarding PLC's.   North8000 (talk) 03:03, 1 May 2012 (UTC)
thread_title:  PLC vs. What you can use a PLC at 

message: In the See Also section there is a link called "PLC vs PAC comparison chart at commons.wikimedia.org". This is confusing for two reasons:
1. Nowhere else in the article the acronym PAC is mentioned, let alone explained or spelled out.
2. The chart itself contradicts the article. For example it claims that programming is only possible via ladder logic while the article gives four more possibilities (under http://en.wikipedia.org/wiki/Programmable_logic_controller#Programming_2 ).
82.198.218.209 (talk) 14:34, 11 June 2014 (UTC)
thread_title:  PLC vs PAC? 

message: There seem to be some parts in this paragraph missing. The sentence "...incorrectly it can result in lost ols such as..." just doesn't make any sense. Perhaps some inadvertently deleted or copied parts?
192.35.17.13 (talk) 14:01, 2 April 2015 (UTC)
thread_title:  3.8 Simulation 

message: I'm afraid that there is a problem with the phrase
:A PLC is an example of a "hard" real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.
As far as i understand, a PLC could be used in a soft real time system, meaning a system where not meeting a deadline won't cause a total system failure, only a (possible) degrading of the system service quality.
Of course, due to its cost, a PLC is more useful in a hard real time system, but as far as i can see, there's nothing that would prohibit their use in systems with other real time requirements. 
Thanks,
--Hgfernan (talk) 20:55, 19 March 2016 (UTC)
thread_title:  Hard real time only ? 

message: Given the fairly recent emergence of Stuxnet, which infected PLCs, I think that there should be an entire new section that discusses specific viruses and the vulnerabilities they exploited. The only thing that was on the page now was a brief 3-line mention of security, which couldn't cover all the issues that have arisen. Thanks, Gluons12 (talk) 19:03, 7 May 2016 (UTC)
thread_title:  Proposed new section: PLC Viruses 

message: I think that there are numerous problems with the April 11th additions but I was hesitant to revert en-masse. It noted a problem with a particular vendor, and the complaint looks implausible.  The descriptions of timers look confusing and missing important pieces at best, and in conflict with standard timers at worst, and it appears that the terminology may be specific to one vendor. The counter section seems to base itself on vendor-specific terminology. In the up/down counter area it conflicts with the common "up/down" (bi-directional) counter-specialized input on PLC's which utilizes a quadrature input, not separate "up" and "down" inputs.  There is only once source used, off line and lacking in specifics with no info with respect to publishing, except possibly naming today's date as a publishing date.  North8000 (talk) 18:43, 11 April 2017 (UTC)
thread_title: Large amount of April 11th, 2017 additions

message: So, this was invented in 1968, then sent back in time for the IBM 1800 to come after in 1964?
Honestly, this article has a huge bias problem toward only certain application. I guess controlling a nuclear power plant doesn't count.  — Preceding unsigned comment added by 73.222.236.165 (talk) 07:14, 13 February 2018 (UTC)
replies: text: With respect to this question, PLC is basically a term used for combining the attributes described in the first paragraph. Because of that I think it's fuzzy / eye-of-the-beholder on when the first one was or who invented it.North8000 (talk) 12:11, 13 February 2018 (UTC)

text: PLCs are not the same thing as process control - they have merged in recent years, but not until the 1990s.  The IBM 1800 was not a PLC. Andy Dingley (talk) 12:22, 13 February 2018 (UTC)
thread_title:  Invented When? By Whom? 

message: reverted this change where I try to clarify what "Rockwell (Allen-Bradley)" means. The edit comment on the revert was "Confusing and possibly misleading. They Allen Bradley became prominent and leading in PLC's when it was not Rockwell." I have reverted that revert. What the ref says about Rockwell is, "Also involved was Odo Struger of Allen-Bradley, now Rockwell Automation. Rockwell became the PLC leader in the US through good marketing and development of strong distribution channels...". I think my version is more true to the ref. The original version has the problematic "Rockwell (Allen-Bradley)" phrase and also I think it is further from what North8000 claims happened than my version. I'm sure what I put up there can be improved further but I think my contribution was an improvement on what we had originally. ~Kvng (talk) 00:56, 11 December 2018 (UTC)
replies: text: The reference made a misleading statement.    AB had moved into the PLC lead prior to being Rockwell. But Wikipedia goes by sources, not wiki editor's knowledge.   So I agree that the misleading statement can stay in.  No biggee, and thanks for your work. North8000 (talk) 11:41, 11 December 2018 (UTC)
replies: text: Misleading is a generous assessment. I'm not sure this source is reliable. ~Kvng (talk) 02:34, 12 December 2018 (UTC)
replies: text: Regarding actual reliability (not wp:rs) I think that the source is overall pretty reliable on the topic but that that particular sentence was misleading or wrong. North8000 (talk) 13:22, 12 December 2018 (UTC)
thread_title:  Rockwell and Allen-Bradley 

message: Newly created page that has some useful information on PLCs. The contents of the article do not match with its title, so the info should be merged into the PLC article and the new page redirected. Bensci54 (talk) 17:31, 23 January 2019 (UTC)
replies: text: I agree.  But I guess "merge" could be a diplomatic and easy way to say "delete".  North8000 (talk) 22:44, 23 January 2019 (UTC)
thread_title:  Proposed merge with [[I/O module]] 

message: added these two external links. I have moved them here for now. The article doesn't (yet) cover PACs. This doesn't appear to be covered elsewhere in the encyclopedia. Maybe someone wants to add coverage and use these as references. 
* What’s the Difference Between a PLC and PAC?
* PLC
~Kvng (talk) 13:21, 30 August 2019 (UTC)
replies: text: I'm skeptical.  It appears that is it a general term with many uses.   The two links were to one specific company which purports to say it is a distinct class based on programming language. North8000 (talk) 18:55, 30 August 2019 (UTC)

text: It's been a while since this discussion, but I'll include few points of my own. From what I understand the PAC term hasn't really caught on with PLC vendors, and to me it seems that many devices currently on market sold as PLCs do include some/many features of PACs. So I think at this point it's very difficult to differentiate the two. Term was apparently defined by an advisory group in 2001. Perhaps back then this difference was much more relevant, but became irrelevant before becoming popular. -- DistilledBacon (talk) 16:06, 3 December 2019 (UTC)
thread_title:  Programmable automation controller 

message: I don't think that any such top level tags are warranted.  A short/medium length article with 23 references, written in wording that is pretty friendly to non-experts.  As far as "OR" the tagger should which part they believe is O/R.  North8000 (talk) 19:59, 11 February 2020 (UTC)
replies: text: I added this tags mainly as a response to the lates series of edits, but even before there were problems. About half of all statements lack any reference. At first, I just wanted to tag them inline, but there's quite many of them. I don't always question their validity, but the source is still welcome.  When it comes to WP:OR, section  Programmable logic relay (PLR) comes to my mind as it seems to come from personal knowledge or opinion.  When it comes to being too technical – it's not bad, but it uses jargon in places that I feel it can be avoided. I also dislike this bit: Examples of this would be an output address could be called “O”, “Y”, or “Q”. Some models of PLC have addressing in tables to organize data (N:7, DB12.DBW0), whereas other models permit you to use free text entry in a “Tag” format (ThisTagHere). Logic and process flow would operate the same between the differing models should the correct equivalent programming is entered. — K4rolB (talk) 21:28, 11 February 2020 (UTC)
replies: text: I think that those are all excellent and valid points. Except "more references" is pablum that can be said about 99% of articles, and this one looks mid-range regarding that.    But I still don't think that they rise to the level of top level tags.   I'd say lets improve it in some of those areas and then remove the top level tags. North8000 (talk) 14:37, 12 February 2020 (UTC)
replies: text: Well, we could probably argue for a long time about how serious the problems really are, but you're right. I didn't want to sound conceited. If I had time on my hands to just fix it, I would have done it. But now, with problems stated and discussion started, I will try to tackle some. — K4rolB (talk) 20:30, 12 February 2020 (UTC)
replies: text: Cool.   I fixed a couple of things to start. North8000 (talk) 14:05, 13 February 2020 (UTC)

text: WP:TAGBOMBING is not particularly productive. Thanks for highlighting specific areas needing improvement here on the talk page. I often review prior talk page comments (even very old ones) when making improvements. ~Kvng (talk) 14:40, 16 February 2020 (UTC)
thread_title: Three new top level tags put on today

message: I decided to work on some problems I saw in the article and it quickly became quite a big copyedit. I didn't want to just slap it on top of the existing article and it would be hard to add it in parts if it has to still make sense so I decided to create a workpage for it and ask for your opinions. It's very much work-in-progress but these are the main changes and logic behind them:
* Overview was divided between lead section and invention and early development, because it fits there, and from [WP:MOS] standpoint, lead section should be an overview.
* removed everything that wasn't invention or development from invention and early development. Future is there just for a moment, until I know what to do with info under it. Ignore it. I've read and improved all the references in the mentioned section and some unsourced info has found its reference! Also, I see that some part of history is missing and it should be completed, because at this point it kind of contradicts itself (Dick Morley created PLC in 1968, and Odo Josef Struger worked on it in 1958-60?)
* At least until I got a better understanding of it, I decided to put two subsections there: Modicon and Allen-Bradley as two independent paths of development. I think that until there is a Modicon article, that part may contain additional info about the company, but it's not the case with A-B.
* There were, I think, 4 places where IEC 61131-3 was explained. I'm in process of consolidating all of it under Programming.
* PLC topics was divided between existing sections, or new were created. I'm not satisfied with it yet.
* PLC compared with other control systems got subsections to make it more readable.
All in all, lots of text was moved around, merged and divided. Again, I'm waiting for some constructive criticism before I commit to changing the actual article. — K4rolB (talk) 18:13, 26 February 2020 (UTC)
replies: text: Kudos for the work.   From my standpoint, the big question is what, if anything, is being removed from the article.  Few have the time to do a compare-and-contrast wit a totally rewritten article or to review what happened when large changes are made in one day.  Suggest modifying the article incrementally spread over days.  North8000 (talk) 18:59, 26 February 2020 (UTC)
replies: text: I understand that, that's why I made a changelog. I will try to put rework in batches when it's more ready. Right now I just wanted to show the overall direction.  I try not to remove anything at this point. I tag things I have problem with. There are some things I would like to see removed as they might be outside of scope of the article or wikipedia. I will keep them now and discuss them later. – K4rolB (talk) 21:00, 26 February 2020 (UTC)

text: I agree with  that making these changes incrementally makes it easier for other editors to review and discuss. There are other advantages to working on the live article. Nevertheless, I have compared your new version to the existing article and I didn't see any obvious objectionable changes. I did not spend enough time with it to be convinced that the changes are a net improvement but the changes you describe above satisfy that and I will WP:AGF. ~Kvng (talk) 15:10, 1 March 2020 (UTC)
thread_title:  Article copyedit 

message: In case anyone was wondering why there are two rollbacks in the history, I had accidentally hit the Rollback button while viewing on a mobile device. KD5TVI (talk) 00:35, 23 September 2020 (UTC)
thread_title:  Rollbacks 

message: IMO the list should be reduced or deleted.  It has gotten bloated with companies that are not really in that business.  If it were limited to the top 5 or top 10 (and the section already has sources for that) that might be useful. But this list isn't and Wikipedia is not a business directory.  North8000 (talk) 19:48, 6 January 2021 (UTC)
replies: text: I agree and I'm going to make proper changes — K4rolB (talk) 21:38, 7 January 2021 (UTC)
replies: text: Cool. North8000 (talk) 22:21, 7 January 2021 (UTC)
thread_title:   IMO we should delete or pare the list of "PLC manufacturers"