Structured Text on Controllogix 5000

OHUM

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Join Date
Aug 2005
Location
Oregon
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2
Has anyone had any experence using structured text on a Contrologix 5000 L62 platform. We have a new factory coming on line and they have implimented some of the equipment sequencing using structured text. We have always used ladder logic with our PLC's and I am wondering if this is a good standard to begin migrating to with new factories? How is it to make online edits and troubleshoot? I am used to the AB test untest edits.
 
OHUM said:
Has anyone had any experence using structured text on a Contrologix 5000 L62 platform. We have a new factory coming on line and they have implimented some of the equipment sequencing using structured text. We have always used ladder logic with our PLC's and I am wondering if this is a good standard to begin migrating to with new factories? How is it to make online edits and troubleshoot? I am used to the AB test untest edits.

I always believed Structured Text is for programmers, and not for plant maintenance personnel. Structured Text can have its place, such as a routine that does some sort of fancy algorithim, or where the power of a processor can be maximized using the Structured Text instruction set, but to be used for I/O logic, I personally think it is unfair to use, especially if the supplier is handing the code over to plant personnel. You will find way more 'guys' that can troubleshoot ladder than would be able to troubleshoot Structured Text.

Ian
 
The decision on using Structured Text for a programming standard should be decided by those who will develop, maintain and improve the factory equipment programming.

I will admit that Structured Text has its advantages but I usually don't use it unless the algorithm can be written easier and more efficiently. You will form your own opinion of ST rather quickly after you start using it.

You can develop any subroutine in RS5000 with ST. That is of course if you paid RA for the license. This has been around for quite a while and it is NOT something new with the L62 platform.

Try it out for yourself and form your own opinion. The combination of using Ladder, Structured Text, and Function Block all have their place in the programming world. Some prove more useful and more efficient based on the actual application.

Maybe the use of Structured Text as a 'standard' is not the real way go, but rather use it as another useful tool to improve (and help) your programming tasks. To set your 'standard' with only one programming structure (ST in this case) may end up as a real limitation.
 
Last edited:
I agree

I agree with the previous statements. Our Plant Engineering group decided in our programming standards not to allow ST unless approved by the group. The only reason being that it is much more difficult to troubleshoot a real world I/O failure issue in ST logic than in Ladder. FB is better for the programmer in most cased, worse for those left thereafter. If you will be the ones left to troubleshoot and modify the code, I'd recommend taking our approach. It has served us well.

Russ
 
Thanks for all the Replys

I want to thank you all for the information. It looks like we are not going to adopt the structured text going forward on our site. It will be interesting to see how this works out for the new site that is starting up using ST.
Once our factories are brought online they never shutdown so online editing is a must for expansions and product changes. I would still like to hear how online editing of ST compares to Ladder when the systems have to stay online without being bumped.
 
You have no problems doing online changes with ST. However I would never recommend ST to be used for machine control such as conveyors or sequential motor starting. Where it shines is as every one else has already said is in maths intensive routines. ie sort routines.
These are possible to be done in ladder but what takes 20 pages of code can be done in one page and when you are familiar with ST it is easier to follow than ladder for the right application.
Another thing is the comments all live in the PLC for ST.
With ST I have found because it is closer to VB or C in looks then graduate engineers try to do simple machine control with it. To a shift eectrician fault finding this can be daunting if they have not had the training or the exposure to ST.
Regards Alan Case
 

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