LAD, FBD, STL, and other?

[drspanda]

After considering very much....

LAD is better and useful with normal applications...trouble shooting is easy.

STL on other hand is the only choice when complex loops are to be formed.

A mixture is best and for normal boolean networks LAD is to be preferred...STL is to be used where we know the input and output relationship and is well documented...

Even for poor documentation, studying LAD is easier.

 

[S7Guy]

Ok, Let's break this down a bit (pun intended)

• STL is easier to program and faster
• LAD is easier to trouble shoot
• CSF is just weird... That was created by someone that was really board

Now lets look at three examples of the same logic and you tell me why STL is easier to trouble shoot (assumption of your thought by your post) how is a bubba expected to get this through that hard head of his???

I didn't say STL is easier to troubleshoot (although in some cases it is). I said that anyone who is capable of troubleshooting Ladder, pneumatic and hydraulic diagrams, and relay logic can learn to troubleshoot it.

In your diagrams, one thing you neglect to mention is that the STL code can be viewed all three ways anyway, so the troubleshooter can view it any way he wants. But in a case where boolean logic can't be viewed in Ladder, the first thing I tell the tech is "pay attention to the RLO". While online, it is very simple to quickly glance to the right and see which part of the logic is affecting the RLO. With a littlel practice, it is just as quick as ladder.

And when it comes to word instrucutions (math, shift, compare, etc), no one should have a problem either. I mean, who can't figure this out:

L MW10
L MW20
+I
T MW30

I consider myself a bubba (a very good bubba) but none the less, I have issue with someone making something hard 'just because they can'

I never make something hard just because I could if I want to. For one thing, I have to troubleshoot my own code while developing, so why would I make it harder? And GIT, I have read your posts, and I know you could understand every program I have ever written.

S7Guy, I disagree about the development time being shorter. SCL is the way to go. It is more efficient to buy a faster S7 to make up for inefficient code than to waste time shuffling registers around.

It depends on how you handle the pointers. I program symbolically and let Step7 calculate the pointers for me. If I change the addresses or alter the UDT and STRUCT sizes, I don't even have to change the code. In most cases, it isn't even obvious that I'm using pointers (or at least, you don't have to care that I'm using pointers if you want to change the code).

 

[ndzied1]

For those looking for a more complete example comparing different programming languages there is this thread:
http://www.plctalk.net/qanda/showthread.php?t=12067

 

[jvdcande]

jvdcande, how does one index into arrays in S7 LAD without a lot of pain and agony? I know there is an example on the disks that come with the Berger books.

That's exactly why I said "as much as possible". This is one example where S7 ladder is no good at all. Siemens can learn a lot from Allen-Bradley on that item.

Kind regards,

 

[BITS N BYTES]

I was a "BUBBA" until.......

Have always worked with ladder [20yrs] on numerous platforms [AB, IDEC,GE,OMRON, SCHNEIDER]
New project with OMRON CJ1M V3.0 series PLC required complex handling and sorting of Serial Messages and Mathematic calculations with REAL variables.

The messaging and math was initially written in ladder. WOW that was a challenge, difficult to write and for someone unfamiliar with the program difficault to understand [in spite of numerous rung comments].

Recently upgraded processor to CJ1M V4.0. This has Strucured Text Function Block programming that now includes STRING processing.
Just for "fun" I thought I would have a shot at writing my STRING and MATH functions in ST.

What a revelation!!

I WILL NEVER, EVER, EVER, DO THESE TYPE OF FUNCTION IN LADDER AGAIN.

 

[Outrage]

I voted for ladder. Simply because it was the first language I ever used for PLC's and I've stuck with it.

I don't considder myself a bubba (or whatever the British equivalent is) all the programs i've every written were in ladder and i've never had any cause to change it. Some might say that because i've never met the limitations of ladder that makes me a bubba because ive never written a program for a demanding application, i don't agree. I think that anyone that that has ever had cause to post here with a genuine question and not a shortcut for doing college homework is a worthy proffessional for taking up the challenge rather than just turning round and walking away from the scarey box with all the wires when things go wrong!

My past projects have typically involved me doing a whole range of jobs, from SCADA, PLC, Electrical design etc and it makes sense to me to program in what is essentially an electrical drawing format (since that's my background) and I know that the plant's engineers can understand the code and trouble shoot when i've gone rather then just being dazzled with a list of acronyms and numbers and simply closing the laptop and walking away.

Cheers chaps,

Lee

 

[monkeyhead]

I generally prefer ladder and can accomplish basically everything I need with it, but I've been thinking about learning some structured text for string handling and running big calculations. It's not that it's not possible in ladder, it's just really annoying compared to string handling in a text based language like C or OptoScript.

 

[controlled]

If it wasnt for poor programming and incompetent engineers, us bubba's wouldnt have a job....so......thanks!

In most of the plants I work in, if BUBBA's cant figure out the code, they get a different programmer to write code that BUBBAs understand. If us BUBBA cant maintain the machine, who will.

 

[testsubject]

About 8 months ago I had the opportunity to write a program using Structured Text. I wish all PLC manufacturers would provide it. It was the easiest, most intuitive method for writing code that I have come across so far. I did not have to worry about indexing or what word was used last. All I did was give everything intelligent variable names and let the compiler handle the rest. It was awesome.

 

[CharlesM]

I think this is a trick question. Its like asking who's better AB or Siemens. It all depends on what you are doing.

I voted for ladder. I think if you can do it in ladder it should be done in ladder. I think it is the most common and most people understand it. However it does have limits.

My question is:
In all the PLC's around the world how many were programed in ladder only?

I would guess 60-75% have ladder only.

 

[Stationmaster]

Umm...I'm kinda new here......is "Bubba" an industry recognized term or just unique to this forum....... : )

I have written some pretty extensive programs in ladder.......but then I work mostly with switches and coils. I have longed for something better when the math gets complex. (non-linear algorithms, analog I/0, custom PID feedback loops,etc) I learned programming in "basic" (showing my old age) and the most elegant things could be accomplished in basic with algebra 101 equations.... I miss that with ladder.
I used to work on hardwired logic stuff that was big on "sequence states". I find it useful to virtually "sequence" ladder functions. My "Bubba" programming style tends to be a combination of "basic" and "sequence" written in ladder. I will say that ladder makes it easy for me to trouble shoot my own stuff.........

I tend to find a lot of ladder stuff that is written by OTHER Bubba's to be kind of "woodpile" programming. All the inputs and outputs get thrown into one big woodpile....one change affects everything.....one log shifts and the pile rattles all the way through. With the advances in ladder options (and more to come I hope) I think most indusrial machine and plant applications can be "Bubba'd" just fine.

Stationmaster

 

[geniusintraining]

..In your diagrams, one thing you neglect to mention is that the STL code can be viewed all three ways anyway.

Yes very true, but only two of my programs are like this, I am sure you know... but for others, if the program is written in ladder it can be converter to other(s), but if the program is written in STL and does not have the NOP's in the correct place or if the segment is not broken down in the correct way, you can not convert...but again there are ways around this, such as when I am troubleshooting one of may many others that can not convert, I will open a blank segment or another program (empty) and just copy and paste, you still have to go back and forth a few times to compare the RIO but it works, I have gotten to be very fast at holding the ALT key and hitting the tab key

In all the PLC's around the world how many were programed in ladder only?

I was about 60% STL, but all the new machines coming in are ladder and the ones I install are ladder, so now I would say 60% LAD

is "Bubba" an industry recognized term or just unique to this forum

Industry wide, I even heard this when I lived in Calif. but its bigger here in the south

 

[CroCop]

In my spare time, I do Jiu Jitsu. Often in the JJ community, it is argued whether one should learn w/ a traditional gi on or no gi. There are passionate believers on both sides, & they argue endlessly. At my camp, we use both, as both have their purposes. We select the correct tool for the job.



Programming language is the same. I select the correct tool for the job at hand, and it's nice to have options.

 

[PeterW]

I was about 60% STL, but all the new machines coming in are ladder and the ones I install are ladder, so now I would say 60% LAD

I was under the impression that only Siemens has STL.

 

[testsubject]

Panasonic also has STL