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Old March 20th, 2017, 02:36 PM   #1
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Need help understanding "Add on" instructions

Hello guys,

PLC 5 guy here who recently took a course through for some basic understanding on how to navigate through RSLogix 5000. The course was great, but definitely tailored to a beginners needs. Having year experience with RSLogix 5 and 500, the majority of the course was simple things I had already figured out on my own.

Of course, there were some great things in the course that made it worth while, but I do not have the cash flow to take the advanced training course. I'm currently having to troubleshoot a process water treatment program plant quite often. There are a lot of Add-on instructions that were obviously created by the programmer to use throughout the routines. I would like some knowledge on the subject on how to break these down and see how they work as an instruction.

I'm trying attach the .ACD program in a zipped file for you guys to have a look at but even compressed it still exceeds the limit at 1.1 MB. Is there any other way I can't get this file on here?

Some examples of the instruction are "add_on_analog_limit", "add_on_alarm_", "add_on_digital_pulse" etc.
Waste Water Automation and Control
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Old March 20th, 2017, 03:07 PM   #2
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Well, the logic that created these AOI isn't any more special then any other logic. What I see that creates most problem are locked AOI or when you don't have the proper 5000 package to read them. For instance, when the AOI is written in function block or structured text and you only have ladder.

If the AOI instruction is locked then we wouldn't be able to open it either.

ETA: The name of the AOI doesn't necessary mean much. After all, the programmer can name it anything. Are you able to browse to the AOI and see the logic?
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Old March 20th, 2017, 03:15 PM   #3
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I think you should first study


When done and after applying the newly acquired knowledge to your particular examples, if you still have questions, come back here and ask for specific details.
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Old March 20th, 2017, 05:13 PM   #4

nhatsen is offline
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Some videos from Rockwell website:

Introduction to Add-On Instructions

Creating Add-On Instructions

Using Add-On Instructions in a Routine

Monitoring Add-On Instruction Code

Changing an Add-On Instruction

Protecting an Add-On Instruction

Using an Add-On Instruction in a New Project
"If you can't solve a problem, then there is an easier problem you can solve: find it." (George Pólya)
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Old March 20th, 2017, 08:36 PM   #5
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I'm trying attach the .ACD program in a zipped file for you guys to have a look at but even compressed it still exceeds the limit at 1.1 MB. Is there any other way I can't get this file on here?


save it as an L5K (text export) file, then zip that to post on here. Anyone with the programming software can open (import) an L5K.

Anyway, there is no "mystery" in AOI's, they are simply pieces of code that you can run or execute from anywhere else in your application, even in different programs or tasks.

I'm tempted to say "just like a subroutine", but don't want to make that analogy too strong. AOI's go much much further than re-usable subroutines.

I strongly believe that once you get a handle on AOI's and how you can use them to your advantage, you will be using them like any other instructions... you just got to write, test, debug, etc. first.....
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