LAD, FBD, STL, and other?

[Jeebs]

Hi,

My knowledge is limited to STL, LAD, FBD.
What can be written in LAD/FBD I can understand in STL, what can't be written in LAD/FBD is a bit harder it get in STL....;-)
When I started learning PLC's I noticed the importance of STL, thus focused on learning STL and reading it.
Troubleshooting takes longer because you need to read it. But testing is faster. Commenting out parts or jumping over parts for testing is waaaay faster in STL.
Personal preference is STL.....

 

[Paulus]

I was under the impression that only Siemens has STL.

I believe that Siemens STL is their implementation of the IEC 61131 Instruction List.
Not to be confused with ST (Structured Text), which many manufacturers now support.

As for the vote, I've gone Ladder, although (as pointed out), it would be ST for complex math / string handling etc.
SFC is a very nice interface for sequential programming (with LAD or ST at its' heart.

Not really done much with FBD, and unfortunately, I am old enough to remember the tortures of using a hand-held programmer and typing...
LD I%0.00
AND I%2.01
ORNOT Q%5.02
OUT Q%5.03
...one line visible at a time, and no graphical interface!

 

[L D[AR2P#0.0]]

I believe that Siemens STL is their implementation of the IEC 61131 Instruction List.

Having tried to convert some STL to IL to run in a Beckhoff TwinCat PLC I would have to disagree.

 

[RMA]

Originally Posted by Paulus
I believe that Siemens STL is their implementation of the IEC 61131 Instruction List.

Although I haven't used myself, I believe Siemens claim that SCL is IEC 61131 compliant. They also make the same claim for S7Graph, which I have used. S7Graph has an option to allow you to write pure IEC compliant code blocking the Siemens extensions, if you want.

I have never seen any claim tha STL is IEC 61131 compliant.

 

[L-O]

I vote for FBD, but LADer is also ok, graphical programming is the best. Not so much possibilities for playing with "smart-solutions".

 

[PeterW]

I believe that Siemens STL is their implementation of the IEC 61131 Instruction List.

I disagree, as others have.

STL = Statement List = More or less machine code.

I have worked with Siemens, Allan Bradley and Modicon then going back a bit, Square 'D', Klockner, Mitsibushi, etc.

I have no experience of any other manufacturer using STL, although someone mentions Panasonic, which I have never used.

Unless the poll is meaning Structured Text, which I believe is ST.

Am I mixed up?

I voted STL, for which I mean't Siemens Statement List.


When I am given 100% freedom to write the code, which I'm not always (not enough), I would write the main code structure in Ladder, the bits which the Main... oops Bubba on this forum, can fault find with. But the repeated subroutines, the device drivers, would be written in STL.

 

[Paulus]

Guess when I'm wrong, I'm really wrong

Don't know why, I'd always thought STL was based on IL.
Who knew!

 

[JesperMP]

I believe that Siemens STL is their implementation of the IEC 61131 Instruction List.

I have actually examined Siemens claim to IEC 61131-3 conformance.
As for STL, siemens uses a cheesy statement like "not conformant, but with same function as IEC 61131-3 IL".

Like many other my "preferred" languages are:
STL for quick and dirty math, and some indirect adressing.
LAD for general purpose logics.
SCL for complex math and array manipulations.
I dont use HiGraph, but I think it could be intresting.

There is not one single language to suit every purpose. So I wont vote in the poll.

 

[Paulus]

I have actually examined Siemens claim to IEC 61131-3 conformance.
As for STL, siemens uses a cheesy statement like "not conformant, but with same function as IEC 61131-3 IL".

Vindication?

 

[ToolGuyFred]

I voted ladder BUT:

I wouldn't use a full bore rifle to go clay shooting and I wouldn't use a 12 gauge at 1000 yards. If the task can be done just as easily in any of the options then ladder is the one least likely to get me out of bed on a Sunday night...

 

[SLC_Integrator]

Coming from the DCS world to (also PLCs) I guess I did alot of FBD-style (all the old system shad their own 'interpretaions') coding and a fair bit of FST or CL. Im not sure exactly what the modern day equivalent is though.

Perhaps ST.

I find ladder useful for basic, discrete logic but when you get into alot of PID, complex control or alot of math if your using older or lower-tier platforms it can be extremely tedious (see my post on 'Momentum Scaling')

So I guess like other folks have said I pick whichever type of language best suits the application.

As for Mr 'Bubba'... I'm not sure posts like that (and it seems most of your posts are similar) are too helpful, but hey, if it makes you happy!

 

[BillRobinson]

LAD and FBD is the way to go! Usually structured text SFC require re-compiling, re-loading and re-booting, where as LAD and FBD can be changed on-line, on the fly.

 

[geniusintraining]

I was under the impression that only Siemens has STL.

Hi Peter,

Here is another version of STL by Automation Direct, I have now idea of why they have it, I don't think you can edit it just view but not even display the RIO, I'm thinking that you may be able to edit something like a CSV then import... I have not tried it yet

The reason I have gone from 60% STL to 40% is the additional PLC's added in the last 5ish years, I have added aprox 30 more none have STL, so in other words no S7's have been added only AD, AB's and Mitsubishi, soon I will get a S7300 very soon,

I love learning... or torturing myself

 

[allscott]

This is strictly a geographical and industry specific vote but ladder hands down.

My name is Bubba. What a lot of you programming/OEM types tend to forget is that when you sell me a machine, it is mine to look after for 10, 20, maybe 30 years. Hopefully the original programmer or an equivalent doesn't get hit by a bus tommorrow or your company doesn't go out of business, leaving me with a million dollar piece of equipment that doesn't work and no-one can fix.

We specify AB amd ladder now period. I really don't care if the original program can be written more efficiently in statement list or structured text. My guys don't understand that and I have a hard time as well. As the customer you, saving some time programming is going to cost my company $$$$ when something doesn't work.

Bubba ain't stupid, we just don't program PLC's all day every day. Some of the things we might need to do on a daily basis include;

1. Troubleshoot faulty limit switch.
2. Fix hydraulic proportional valve.
3. Replace blown up VFD
4. Wire 2MVA transformer.
5. Unjamb paper out of secretaries printer.
6. Change bearings in 100HP motor
7. Fix plant managers excel spreadsheet/monthly report.
8. Fix the A/C for the office.
9. Weld a broken piece of something back together.
10. Make a new X in the lathe.
11. Tune a motion controller.

To the poster that said "we'll find a different Bubba". I can do all of these things, can you? Should we hire another 15 people who are experts at all these things and then go out of business because costs are too high?

I phoned Siemens tech support about my other problem today (see Wincc flex). I might as well as phoned my mom, very sympathetic but no help...... I am sure that in a different geographical location I would have faird better.

So what kind of quantum physics are you guys doing in Siemens PLC's that is easier in STL than it would be with AB's CPT instruction. I would think that typing in an algebraic expression would be easier and less time consuming than trying to recreate it in STL, Bear in mind I am just bubba abd never found a whole lot of advantage in a polish calculator either.

 

[Paulus]

LAD and FBD is the way to go! Usually structured text SFC require re-compiling, re-loading and re-booting, where as LAD and FBD can be changed on-line, on the fly.

I know you said 'usually', but if it is an important consideration, then both a SFC and ST Program (as well as Ladder - no FBD as yet) can be online edited if you're using Omrons CX-Programmer!