What’s most popular?

I'm just curious as to what most PLC programmers like to see in a PLC program.

Ladder Logic
Structured Text
Function Block

ladder logic is the most common and most familiar of the three

Well, considering the origins of the PLC, that question shouldn't even be necessary, lol. But yes, Ladder Logic is far more common.

Ladder logic and lotssssssssssssssss of comments.

Thanks - that was my guess but I'v got a X-PC programmer who thinks everything should be structured text

DavidBartel said:

X-PC programmer

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There's your answer right there. Sure, I've done some computer programming before as well, and that lets me better understand ST, but ladder logic is much easier to actually see what's happening. Computer programmers don't realize the value of being able to visualize interactions because they're used to things that are much more complex than simply scaling a number and turning on an output if it's within a certain range, etc. They're used to dealing with things that can't be easily visualized. And in some cases, used to using text to describe things that visual elements would describe better anyway (Anyone who has tried making layouts in Java knows how stupid that is).

The whole origin of PLCs is based around automating relay logic, which is traditionally designed in ladder logic, rather than heavy data manipulation, which makes ladder logic a more natural way to program it in the first place.

I am more used to ladder logic, but have dealt with sequence blocks before.

All the techs here want ladder logic hands down!

I would like to see stuff like this though:

http://micro.magnet.fsu.edu/creatures/index.html

Use what is most suitable available to use on task at hand. In general, ST for complex tasks, LAD for "simple" tasks, maybe SFC for Sequential tasks and so on.

I vote for Grafcet!

Just kidding.

PLCRookie said:

I vote for Grafcet!

Just kidding.

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I'm not Grafcet is great. But ladder is OK too. And a good programmer can turn any Grafcet into ladder without any problems.

Kind regards,

jvdcande said:

I'm not Grafcet is great. But ladder is OK too. And a good programmer can turn any Grafcet into ladder without any problems.

Kind regards,

Click to expand...

True.
I actually liked it once I learned it. It was great for the sequential machines that we had it on. I liked the mix of ladder within the steps. Ours was all documented in a foreign language (French), so I got the benefit of French instruction for no charge!

Use whatever you are familiar with and is appropriate for the task. Yes, PLC's are traditionally geared for LAD but there are just some things that are better suited to ST/SCL. This forum is full of ppl who will tout the benefits of STL, which I personally cannot stand and can write (and understand) anything in ST/SCL in a quarter of the time.

It all depends on your background and experience. In North America, Ladder seems to be the prefered method, although I have seen a lot of programmers with DCS programming backgrounds that prefer to use Function Block.

As I learn more about Siemens PLC's, it sounds like Europeans usually learn to program using Structured Text. Siemens PLC's seem to be geared towards ST, although they do support Ladder and FB.

I prefer Ladder myself as I believe it to be the easiest to troubleshoot. It can be quite difficult to follow someone elses code, especially if it's written in FB or ST.

I like nonukes post; lots of comments. I've also heard a quote, probably jokingly, that "If it was difficult to write, it should be difficult to read". Of course I don't agree with this philosophy but it might be worth a laugh...

Having come back to my old computer programming code with no comments, I've learned the lesson about commenting. It doesn't matter how awesome you thought hat hack was when you made it, if you don't comment it, your going to rewrite it next time you need to fix it.

It seems to depend on what you need. We use ladder and function blocks, depending on the need (i.e. FB for PID loops, etc)