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Hello everyone,

I am new to PLC programming and will start working on Allen Bradley PLC. I have an experience in computer programming languages. Will learning ladder logic be a better option or starting with structured text as i have some knowledge about the syntax and programming of structured text?

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Learn ladder logic.  It and structured text share share most functionality, but electricians and technicians who follow behind you will hate you for using structured text.

Learn the common patterns for holding single-bit state with a "seal-in" contact.  Prefer those over Latch and Unlatch coils unless you need that state to survive a power cycle.

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Learn ladder logic...unless you're a fan of 2AM phone calls.

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47 minutes ago, Joe E. said:

..unless you're a fan of 2AM phone calls.

Yeah.  That, too.

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Learn Ladder Logic and remember Elegant isn't always better.

I can write a process using a multi-dimensional matrix with indirect addressing and it takes up one page and works flawlessly.

BUT, BIG BUT, that 2am electrician and his grade school math sees it as a Black Box and wakes me from a sound sleep for a burned out light bulb.

Had I written it in the multiple pages of ladder logic he would have seen the issue himself.

Check out twcontrols.com and his you tube videos.  They're great.

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Gotta agree with the learning ladder.  That said, program to your audience.  If you have a staff of computer science experts then maybe structured text is the way to go.  Generally with PLC's you are going to be working with a maintenance staff with electrical knowledge and those guys are who ladder logic was developed to make things easier for.  As Bob said, you can do a lot of advanced programming with PLC's now days.  It's generally better to program things as simple as possible in order to make things easier for those with less programming capability than you have.  Also, at 2AM my brain doesn't operate well enough to remember what all that indirect addressing was doing!  So in reality you are programming simple for your brain at stupid hours when it needs things easy too.  In PLC's often simple, repetitive, well organized with good documentation is better than optimized and compact. 

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Ladder is foundational for PLC's. If practical I would write all programs on a PLC in ladder. I am an electrician who recently started programming mostly in FBD on a DCS. The more languages you know the more transferable your skills in the future. I would learn LD, FBD, then ST...since you understand syntax if you need to learn ST it will be fast. FBD has a bit of a learning curve to it and I see it used in PLC's more often then ST (in my limited experience). Just my suggestion. 

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Oh beginner tip from a beginner, though you are likely aware ... leave detailed notes about your code, I'm struggling through a poorly documented PLC program right now lol.

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Plus if you get "fancy" with your logic when you revisit it after a few years you may piss yourself off never mind anyone else!!!!!!!!!!!!

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Where do you plan to do most of your work? As a general rule of thumb, ladder logic is the most common here in the United States. But if you're interested in working in the European market then perhaps function block diagram or structured text would be the better choice.

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