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catzr900

Rslogix 5000 Output Question

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I am new to this so please bear with me. I watched a vendor modify a program "offline", and he used the same output on 3 diffrent rungs. This does not make sense to me. Can this program do this or when he goes online to download it, will it tell him there is a problem. I know that you can use outputs for an inputs, (relay with contacts) but seems crazy with multile rungs with same output. Thanks for your help Dan

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Logix 5000 will have no problem with errors caused by multiple outputs in different rungs. However the program will update the last output instruction scaned (for OTE). For example if the first two outputs scanned are ON and the third is OFF the output will remain OFF at the end of the scan If they are latches (OTL, OTU) then it is possible to have the same output controlled in different areas of the program using multiple instructions. In the example used above using latches the output would turn ON when the first OTL was scanned. Personally I do not care for multiple instances of the same output, makes it sloppy and more difficult to troubleshoot later on. Hope this makes some sense... having some trouble explaining this on paper Edited by TechJunki

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Thanks for the help. In this instance, the vendor used the same OTE in 3 rungs. It was for a indicator light, PanelView 1000 plus. This is hard for me because my boss will not let us have access to the program. They sent me to school, 5/500 & 5000 basic and M/T, but says that technicians do not program or need to use logix. Very strick that this is for Engineers only....... Dan

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Without seeing the code it is tough to tell if what was the purpose, or even if in fact it was done as you recall. Sort of odd to me that an idicator on a panelview would use an output rather than a bit, but I have seen it done on older systems were memory was tight and the unused output memory for a slot with an input module was used. Not my style, but it worked. Did you question the vendor? Does the device work as it is supposed to? I must admit that I have used rungs with duplicate outputs as a quick way to force a bit without having to have the red force light on or edit the original logic. When the problem was fixed then just delete the temporary rung without having to reenter the original logic.

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sounds like the boss has a very fragile ego.

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Thanks for all your help in this. One more question if I can: Can anyone give me an example of a situation that you would use the same output on diffrent rungs? Thanks again, Dan

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Possibly if the rungs are in different routines that are mutually exclusive. The mutual exclusivity can be managed with a sequential function chart or equivalent ladder design. Another possibilty is if the rungs are in "zones" that get skipped or jumped over depending on conditions so that only one OTE is actively scanned at any time.

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Thanks Gerry. That was what I was thinking but could not describe it. Everyday I learn a little more. Thanks again, Dan

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