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dogleg43

Duplicate Coils in RS-Logix5000

22 posts in this topic

Is there an setting in RS-Logix5000 to keep you (or at least warn you) from using an OTE output address more than once in a ladder file? I understand that latch/unlatched coils need to use the same address but using the same address twice for a regular OTE coil usually causes problems. Thanks for your responses.

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Tools, Options. Highlight Application and check the "Enable Duplicate Destructive Bit Detection" box

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Emphasis on usually. I have seen some very well written code with multiple OTE's of the same coil. The trick was each OTE was in a seperate Subroutine and subroutine calling was strictly controlled and sequenced.

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OOPs, I meant RS-Logix 5 for PLC 5's. The path you described does not exist there. Also, I searched around in that area and did not see anything similar to prevent duplicate coils in RS-Logix 5. So for me the question remains: Is there a way in RS-Logix 5 (ver. 6.30) to prevent using duplicate coils. Sorry for the mixup.

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We have duplicate OTEs in 2 of our PLC5s. The logic was written by the German oem. They do it by including the OTEs B3 address is the first XIC in the next rung. They can have as many as 5 rungs like this. They only use discrete bits, never real outputs. ...........bla bla bla.............( )... --| |--... bla bla bla..............( )... --| |--....bla bla bla..............( )... --| |--....bla bla bla..............( )... --| |--....bla bla bla..............( )... Their explanation is that it's a leftover (canned) logic from the old days of the T3 (?) terminal that only allowed you to see a certain width rung. This way they could see it all. Works fine although can be confusing if you haven't run into it before. I personally never do this.

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I don't understand where are duplicated OTEs in this example. Explain, please. Edited by Sergei Troizky

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In my example, all of the --( )-- and --| |-- have the same bit address.

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What's going on here is that this particular group of rungs doesn't actually do anything. It's just a method of packing a bunch of addresses into the limited space of the T3 terminal for monitoring. The duplicated coils are non-functional. Think of it as a crude custom data monitor. Edited by mellis

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Not quite I have seen this done in RSlogix a few years ago, especially when 800x600 screens where being used, say you could see 8 contacts on screen without scrolling but the rung needed lots of contacts in series:- -[/]--[/]--[/]--[/]--[/]--[/]--[/]--[/]-(B3:0/0) -[b3:0/0]--[/]--[/]--[/]--[/]--[/]--[/]--[/]-(B3:0/0) -[b3:0/0]--[/]--[/]--[/]--[/]--[/]--[/]--[/]-(B3:0/0) -[b3:0/0]--[/]--[/]--[/]--[/]--[/]--[/]--[/]-(B3:0/0) Only if all contacts are in closed state is B3:0/0 on when the rungs have been scanned If any contact is open all the B3:0/0 coils will appear to be off all the time to the programming package, and would be off for all other rungs thoughout the program. Now we tend to have acres of screen space it is rare for a rung to exceed the size of screen. Its easy to forget what we had to work with in the old days... any wonder progs from a few years back can look so messy when re-opened on modern equipment. Edited by Snerkel

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In one of my recent projects I did this quite a bit. I had about 8 different programs each with about 10 subroutines. I used OTE of the same coil in different subroutines, becuase they were called differently depending on what operating mode I was in. $

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If you go to Tools, then Options, then the Xref/address tab, and check both cross refrence on line and cross refrence off line boxs then it will show up with a ladder and rung as well as the OTE, XIC,XIO, ECT... Then you would know if it is used anywhere else.

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Let's get back to dogleg43's origonal question because now I'm curious. Is there not a way to set up warning for duplicate destructive bits in RsLogix 500 like you can in RsLogix 5000?

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Greetings to all, sorry that I didn't get a chance to mention this earlier - but I've been busy with some other projects ... and yes, I know that the original poster was actually interested in something other than RSLogix5000 ... the following quote came in from our good friend TWControls ... as far as I know, the answer is "no" ... if I remember correctly, the older "AI" software for the PLC-5 used to sound an annoying "beep" whenever you programmed a "double-coil" transgression ... but now things have been "new and improved" so that particular feature is no longer available ... moral of the story: be careful about using double-coils ... and I know that's too simple - but basically it's "all-I-got" right now ...

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Thanks for the clarification Ron. I knew I couldn't seem to find it.

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To all, Thanks for your help on this topic. I'll just have to be careful. The project I'm working on now is to go through existing programs to clean up some programming issues and bring them up to our customer's latest standard which includes making internal coil addresses match the ladder file they originate in (LAD-30 has all N30:xxx/yy coils, LAD-40 is N40:xxx/yy coils, etc.) Many of these coils exist already but in the wrong place. So it will just go a little slower. By the way, in my 20 years of experience in this field, none of the customers I've ever worked for who actually had a programming standard would allow you to use duplicate coil programming. These are both large and small companies. I'm sure there may be justification for it somewhere but it can usually be avoided by using working (intermediate) addresses and then writing to the real world outputs only once. thanks again.

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On thing you can do is use the cross reference and make sure that there is only one OTE per address, but don't forget to check at the word level too

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Definitely take TW's advice and use the cross reference. I suggest that you run a cross reference report on the range of files you are working with and print it. Scan through it and mark any problem children that already exist (OTE in the wrong program file) and also mark any that already have a duplicate OTE. Then as you begin to work on each program file, you can refer to the report and resolve any pre-existing conditions as you re-assign the coils in that file. Good luck,

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The way I actually keep it from happening is I have a Routine just for outputs. Say we are dealing with a 16 output Micrologix, rung 0 has output zero, rung 12 has output 12, rung 15 has output 15.

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May I suggest thast you make your changes in an exported CSV format file not in logix. This will allow you to go ladder by ladder and change all out of place coils for example N7:1 in ladder 3 can become N254:0 with the understanding that all n254's must be assigned later to a real vlaue. In others words it is a two pass process. pass 1 change all out of place values to N254 and then pass 2 reassign all values. Should go fairly fast working in excel with global search and replace. Just curious for Ladder 3 to you use N30 ot N37 you might want to use B33, C34, T35, R36, N37 and F38 in aldder 3 just a thought. Saw a standard like this once. Was pretty cool. Edited by BobLfoot

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I loved my T3's. Except for the lack of documentation, and the fact that they weighed 3 tons, They were the awe of the age....

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This thread is from 2006. Although there is a way to do this with Logix 5 (turn on the online cross referencing stuff and when you go to type in an address, Logix 5 will automatically fill in an UNUSED address for you), I doubt the original poster really cares any more.

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