One more question about RS2000

fishenguy

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Join Date
Nov 2007
Location
WESTERN PA
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125
Let's say I'm online using RS5000. I find that Output 5/28 should be on and the LED is lit but no power coming out of the terminal.

Now, I want to replace that output with 5/30.

I do a cross reference check and find that O:5/30 is used in 10 instances in various rungs. Can I do an on-line edit and replace all instances at once, or do I have to do 10 individual rung edits and hope I got them all, or do I have to go off-line do a Replace All and download the program?

Thanks for your help, Dave
 
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This is confusing. You say that 5/28 appear defective and apparently you would like to move it to 5/30 but 5/30 is already being used.

More importantly before you move an output is why it failed at the output it's at right now. They don't "just fail". The cause that took it out will probably happen at the new output.

You have some answers to determine before blindly moving an output.
 
Sorry, I just got home and I'm trying to unwind. What I meant was O:5/28 is being used in 10 instances. Regardless of the reason why it failed, (this is a theoretical question). How do I replace it with O:5/30 in all 10 instances?
 
What Bernie siad.....

But once that is addressed, no you cannot do a search and replace online. It (search and replace) can only be done offline. Online, it will require manual edits.


OG
 
I agree with what Bernie said. What brought this all about today at work was a coil went bad in a miniture air valve. Thus it also took out the PLC output. The air valve was replaced but then the output problem had to be adressed. Our daylight electrician knows about as much of the 5000 as I do, but he managed to get it going. Things were slow for me so I thought I would take some time to familerize myself with this problem in case it happens on my watch. So along with going on line and trying to figure it out on my own I figured I would consult with the pros.
Thanks for your answer OG. That helps

Dave
 
Suggestion for online edit

Where I work we have a method we use on machines that cannot be taken offline. I am assuming the changing of the output isn't affecting running equipment, of course. Also, I am assuming you are using aliased tags. If you are not, this won't work and SHAME ON YOU.

Step 1: edit your aliased tag and ad "del_" to the front. For example: "my_tag" becomes "del_my_tag". It is still aliased to the same output and the program automatically changes it in every instance it appears in the program.

Step 2: make a new tag with the old tag name and alias it to the new output number.

Step 3: cross-reference the "del_" tag and everywhere it appears, edit that rung, then edit that tag and remove the "del_" part. This will leave the 'new' tag that is aliased to the new output.

Step 4: Once every instance of "del_my_tag" is replaced, go to the tag editor and delete it.

This works most of the time but sometimes you will be unable to edit a tag - something about it being referenced elsewhere - I can't remember the exact error it throws.
 
The course of this thread has me thinking that there are four separate situations that each of which should be recognized and addressed: troubleshooting in the field, short-term programming modifications, long-term programming modifications, and programming practice.

For troubleshooting in the field, I agree with Bernie and have nothing more to add.

For short-term programming modifications - those ONLY USED to get the machine back up and running in the shortest possible time - you could simply parallel the coil of O:5/30 with the coil for O:5/28 and leave the other 10 instances alone. Of course you want to document this thoroughly and make sure that someone follows up with long-term programming changes when time allows.

For long-term programming modifications, I would do as operaghost suggests and do an offline search-and-replace and then download to the PLC. You need to be sure start with a copy of your most-current program before doing this. Also be sure you have a back-up of the existing program in case something goes wrong.

And finally for programming practice, while jemcneil has described a good technique for the use of aliases, there is another technique that, had it been used, would have prevented the need for all of this; the use of internal tags rather than referencing physical I/O throughout the program. Because field I/O often end up being different than originally designed, I like to have a single rung for each individual input and output that corresponds to an unique internal bit (or register) in the PLC and then use that internal bit (or register) instead of the physical I/O throughout the program. Then, in the event that a wiring change is required, as described by the OP, the program only has to be modified in one place.

Not only does this allow for quick and long-term on-line programming changes, it gives me as the programmer the ability to write my code well in advance of the machine being built, makes I/O checks much faster, and makes programs between similar machines more standardized.

Just my thoughts.

Steve
 
Simplest solution: Leave wire connected to O:5/28. Put a jumper between O:5/30 and O:5/28. Then insert one rung into your program:

O:5/28 O:5/30
----] [-----------------( )---



Draw the jumper on your electrical drawing and comment it in your PLC program. In the future if you replace the card its easy to undo.

Food for thought: You have probably wasted more resources on this route than if you had just replaced the card.
 
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For short-term programming modifications - those ONLY USED to get the machine back up and running in the shortest possible time - you could simply parallel the coil of O:5/30 with the coil for O:5/28 and leave the other 10 instances alone. Of course you want to document this thoroughly and make sure that someone follows up with long-term programming changes when time allows.

Steve, this is a great idea, I'll keep that in mind for future references.
 

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