Talk:Ladder logic

message: There is no information here about who uses ladder logic in the sense of engineer demographics, a geographic sense, or controls company. I would like to see some discussion on that topic here. I would argue that ladder is all but dead outside of the US and within the US its use perpetuated almost exclusively by controls engineers over the age of 40 that grew up with Allen Bradly. I base that claim on my work in the industry in Germany, Austria, US, China, and various Latin and South American countries with several controls platforms. I have only seen ladder logic come out of US OEMs (not just on AB hardware), with everywhere else using IEC Structured Text, ANSI C, or automatic code generation from SimuLink. Within the US, ladder seems to only be used if the customer or OEM is or was dealing heavily with AB products. In addition, young engineers (nearly all of them proficient in text based programming regardless of their degree) seem to universally dislike ladder, even years after becoming proficient with it. In the US, I've seen integrators (whose engineers tend to be younger) quote 20% more to write a project in ladder vs a text based language and OEMs pay it. In Europe I have seen customers walk away from US OEMs that won't program in IEC ST or ANSI C.
I think the days of programming like you're using relays and coils are just about over; the new blood hates it, it takes longer, and the old blood is retiring. Companies still generating ladder code are setting themselves up for support issues down the road when they have to train new engineers in a language no one uses anymore for machines that aren't really that old.
173.67.240.90 (talk) 16:12, 25 April 2011 (UTC)
replies: text: You know what to do. Cite it and write it. --Wtshymanski (talk) 17:36, 25 April 2011 (UTC)
thread_title: Trends in Use

message: The article currently has a mix of contact symbols:
  --[ ]--
     X
  --| |--
     Y
  --][--
    Z
They all mean the same thing, right?
Should we standardize on one type ? The --| |-- seems least likely to interfere with Wikipedia formatting (so we don't need  tags).
(Note that the --( )-- "coil symbol" at the right of the rung is *supposed* to look different -- it does mean something different).
--DavidCary 18:06, 25 Jun 2005 (UTC)
thread_title:  standard contact symbols? 

message: What the heck does this mean?  A coil is just an electomagnet.  It can have contacts that are NO or NC but it can't be either. right?  TomCerul 18:11, 3 August 2005 (UTC)
replies: text: This is probably better called a "not" coil - if a not coil is energized by a rung, its normally-open contacts are open and its normally-closed contacts are closed (a regular coil will have NO closing and NC opening).  I ran across this on a Reliance Automate 35, where it was extensively used to save memory - though it made the resulting programs very hard to read (especially so as there was no documentation or variable names displayed by the programming panel that could have alerted you to the weirdness). I had to write my own documentation software for that machine as we only had the one and the manufacturer didn't support anything better. I'll see if I can fix the text in the article. --Wtshymanski 17:41, 4 August 2005 (UTC)
replies: text: I agree, it's a NOT coil. The proper use of NOT coils arises from the concept of "failsafe". One example is in machine tools. There is a circuit called an E-STOP string. All of the safety elements on the machine will have a set of NC contacts and be wired in series. The hydraulic pressure is NOT too low. The safety gates are NOT open. The drawbar that holds the cutter is NOT loose. If NO contacts were used, the control wouldn't be able to tell if a wire in the string were broken. In the old days, the string would control a relay. The output of that relay would go immediatly to another relay to be negated. Seán 03:51, 13 March 2006 (UTC)
replies: text:  Odd. We did failsafe design but we'd just use the other set of contacts on the relay. We ended up saying "Normally Open, Held Closed" a lot. TomCerul 21:36, 20 September 2007 (UTC)
thread_title:  Normally Open COIL? 

message: Just made a few minor changes and additions.  I can make graphical examples of the ladder logic shown in the article.  However, this would increase the load on the servers, and the present ASCI graphics seem to be sufficent.  Also, I am considering re-writing the article to be more streamined and organized.  Thoughts?Dudecon 18:26, 4 April 2007 (UTC)
replies: text: Decent SVG graphics (or at least PNG) would be appreciated. I wouldn't worry about the server load. If you feel like fixing the article, do it. You might want to see the PNGs on the Spanish and Italian versions of the ladder logic page. —Pengo 09:31, 24 July 2007 (UTC)
thread_title: Graphics

message: The name is based on the observation that programs in this language resemble ladders, with two vertical "rails" and a series of horizontal "rungs" between them. Ladder logic is popular in North America while in Europe it is more common to draw horizontal rails along the top and bottom of the page and vertical rungs sequentially from left to right.
Really? PLC programming software is not different (text localization aside) for American and European markets, and all the systems I've used (in Europe) draw and print out programs in the same way, with vertical rails. Horizontal rails are perhaps more common for electrical schematics in Europe, but no-one cares that ladder is drawn in the other orientation. --DavidHopwood 23:44, 28 August 2007 (UTC)
thread_title: Orientation of ladder diagrams

message: What do you think about merging "relay logic" into "ladder logic"?
The "relay logic diagram" on the relay logic page looks almost exactly like one of the "ladder logic diagrams" on the ladder logic page.
As far as I can tell, the subtle difference between the 2 heavily overlapping terms is:
* "relay logic" implies that something really is built with physical relays (almost always designed using "ladder logic" diagrams).
* "ladder logic" is a style of schematic diagram, standardizing the layout of "relay switches" and "relay coils". Any particular ladder logic diagram could be implemented with physical relays, but nowadays is more often emulated with a microprocessor interpreting the diagram and simulating the relays.
In this case, the thing, the diagram describing the thing, and something else that simulates that thing, seem closely related enough to cover all in one article.
--68.0.124.33 (talk) 16:47, 19 February 2008 (UTC)
thread_title:  merge "relay logic" into "ladder logic" 

message: So far, in the examples on this page, you've been using --[\]-- as a NOT, when all the ladder packaged I have used (DirectSoft, AllenBradley..) use a forward slash, as in --[/]--.  Even the example picture uses forward slashes for NOT.  Should this be fixed?  --Mainstreetmark (talk) 18:48, 20 May 2008 (UTC)
thread_title:  The "not" symbol 

message: I added a a couple of words to the descriptions of the normally open and normally closed contact instruction descriptions. Contact instructions are controlled not only by coil instructions whose addresses they bear, but by input signals as well. A minor addition, of course.  —Preceding unsigned comment added by Jharris693 (talk • contribs) 16:09, 30 July 2010 (UTC)
thread_title:  Example of a Simple Ladder Logic Program 

message: 1. In this section, the narrative appears to refer to the parens as "inputs", where they are actually outputs, and are described as outputs in the earlier section defining the symbols.
Example: 'When the "run" input becomes true the seal-in "run" NO contact in parallel with the "start" NO contact will'
2. The second diagram, at the end of the section, doesn't make sense.  It's supposed to show a latching scenario, but to do so the contacts/input labelled "Run" would have to be controlled by the rung's output. However, unlike the first example in this section, the output is not labelled Run, it's labelled "Motor", so from a diagram point-of-view, has nothing to do with the Run contacts/input.
Gwideman (talk) 12:15, 10 July 2017 (UTC)
thread_title:  Problems in section Industrial START/STOP