Why is ladder logic still so popular?

DDHarrold · Nov 4, 2008

I'm an editor for Control magazine preparing an article for the January 2009 issue on PLC Programming. I have the feeling that despite the existance of IEC programming standards Ladder Logic still remains the most popular language for programming PLC's, I would like to hear opinions and thoughts from those of you who work with PLC's every day either as programmers and/or as maintenance personnel.
Also, I'd really appreciate full names of those replying. As you know, reading a trade publication article, the story always has more credibility when it includes thoughts, comments and observations from "real" people like yourself. Would you share you name, title, years in automation, and company affiliation? I promise NOT to embarress or make anyone look bad in the eyes of their employers.

Talk to me!!
Dave Harrold
[email protected]

Oakley · Nov 4, 2008

One of our reasons is the simplicity of troubleshooting, and commonality. A greater cross section of personnel that work on PLC's understand relay ladder logic.

The cost and effort to train people to understand function block or structured text has been deemed to great (by upper management).

DDHarrold · Nov 4, 2008

Thanks for the quick reply. I should have included in my post that I'd really appreciate full names of those replying. As you know, reading a trade publication article, the story always has more credibility when it includes thoughts, comments and observations from "real" people like yourself. Would you share you name, title, years in automation, and company affiliation? I promise NOT to embarress or make anyone look bad in the eyes of their employers.

PeterW · Nov 4, 2008

Ladder logic was based on electrical diagrams, therefore maintenance electricians in industry find it easier to fault find and manage code.

Still the case today.

DDHarrold · Nov 4, 2008

Thanks for the quick reply. I should have included in my post that I'd really appreciate full names of those replying. As you know, reading a trade publication article, the story always has more credibility when it includes thoughts, comments and observations from "real" people like yourself. Would you share you name, title, years in automation, and company affiliation? I promise NOT to embarress or make anyone look bad in the eyes of their employers.

Dave
[email protected]

Peter Nachtwey · Nov 4, 2008

Perhaps if you tell us who you really are.

I have never seen a magazine editor use a gmail address. If you used your real e-mail address then we can see if you are legit.
Provide a link to your magazine.
I searched for 'control magazine' and got
http://www.controlmagazine.org/
This looks like a student scam to me to get forum members to do home work for you. I must say it is creative.

cjd1965 · Nov 4, 2008

I concur with Peter. Why should members here provide 'full' details when the op doesnt... sounds fishy to me

Thomas · Nov 4, 2008

Standards

Why is the QWERTY keyboard still popular?

Ladder is still a popular programming method for PLCs because it has history on it's side.

It also is easily teachable to anyone who can understand basic electricity.

Additionally there are all sorts of "extensions" to the basic rll which provide a rich enough environment to satisfy most industrial machine programming needs.

DDHarrold · Nov 4, 2008

Want to learn who I am, try going to www.ControlGlobal.com and do a search for Dave Harrold. You will find that I have written lots of articles. Need more? Go to my former employer at www.ControlEng.com and do a search for Dave Harrold and you will find more articles. Need more? Go to www.isa.org and search past awards and you will find that in 1998 I received national recognition for my many years of automation contribution.
So why list my email address? Because I thought you might prefer to provide that information privately as opposed to including it in your post.
I'm not a student, this is not a scam, and I am who I say I am doing exactly what I said I was doing.

Dave Harrold

OZEE · Nov 4, 2008

I think the issue is that if you work for controlglobal.net, you will have a putnam.net email address like everybody else there, not a gmail address...

I can claim to be the Queen of England, start talking with a high-pitched British accent, and make a gmail address that looks like I'm the Queen, but I'm still not the Queen of England...

cjd1965 · Nov 4, 2008

While I accept you are probably who you say you are, why not simply post YOUR full details... after all your are pretty insistent on others posting theirs.

DDHarrold · Nov 4, 2008

Okay, this is getting out of control. Take a closer look at any major trade publications Web site and you will find contact information (including a publication email address) for the "full time" staff. Now take a closer look at various article bylines and you will find a plethro of "contributing" editors listed, usually three or four times as many as the full time staff. "Contributing editors" include paid freelance writers (such as myself) and recognized industry experts (such as Dick Morley). Sometimes contributing editors receive pay for the material they develop, sometimes they don't.
I don't know what more I can say to put an end to the FUD (Fear, Uncertainity, and Doubt.)
Dave

bulletin blues · Nov 4, 2008

main()

because i hate tabs;

andfor;

elsefor;

iffor;

downtime==1;

i like to """see" the "circuit""
AND avoid mgknmbrs;"""

endif;

endelse;

endfor;
return (1)

Steve Bailey · Nov 4, 2008

The way you phrased the question implies a level of disbelief on your part. In my opinion, RLL is still popular because it does a very good job of conveying the necessary information about the system it is controlling. It is reasonably intuitive, and provides excellent diagnostics.

That's not to say it's perfect, far from it. It is not my language of choice for math-intensive applications. I recently wrote some ladder logic for a Modbus ASCII master. I'll be the first to admit it's pretty ugly and there is nothing intuitive about it.

But when you're dealing with sequential operation of devices whose characteristic states are on and off, it's hard to beat.

curlyandshemp · Nov 4, 2008

DDHarrold said:
Okay, this is getting out of control. Take a closer look at any major trade publications Web site and you will find contact information (including a publication email address) for the "full time" staff. Now take a closer look at various article bylines and you will find a plethro of "contributing" editors listed, usually three or four times as many as the full time staff. "Contributing editors" include paid freelance writers (such as myself) and recognized industry experts (such as Dick Morley). Sometimes contributing editors receive pay for the material they develop, sometimes they don't.
I don't know what more I can say to put an end to the FUD (Fear, Uncertainity, and Doubt.)
Dave

Troubleshooting a complex rung such as this,

is visually easier than this troubleshooting Statement such as

Why is ladder logic still so popular?

DDHarrold

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Oakley

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DDHarrold

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PeterW

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Peter Nachtwey

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Thomas

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DDHarrold

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bulletin blues

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curlyandshemp

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