OTE won't light on true conditions?

Pinky · May 27, 2014

Hello everyone, I am new to both PLCs and PLCS.net, so please bare with me. I am currently using RSlogix 5000 as well as factory talk view for HMI integration.

The problem I am having deals with a few of my OTEs not lighting up (becoming true) when all of the preceding conditions are met. However, it still considers some of these conditions to be true on other rungs where it is used as an input (See rung 4).

The strangest thing to me is that I use this exact same logic (Minus tag names) in a different area of my code that works to some degree (the outputs still flash from on to off without me touching anything). This can be seen in the second image, if you'll notice the conveyor is running but the elevator is not.

Image one (Offline code):

Image two (Online with HMI):

Any and all help would be appreciated, thank you!

iant · May 27, 2014

welcome to the site
simple but not in plain site
these are inputs not outputs

tim2 · May 27, 2014

I think he's talking about rung 3, where all the XIO's and XIC's are on but the output local:4:O.data.6 is off.

Do you possibly use that address (local:4.O.data.6) with an OTE somewhere else in the program. That can cause problems with on OTE that looks like it should be on being off.

blperkins · May 27, 2014

rung 3 and 4 make me think the routine is not being called.

iant · May 27, 2014

Maybe but I am referring to rungs 1 and 2.
Which each share a contact in rung 3 and a resultant contact in rung 4

To me that logic can never work

califflash · May 27, 2014

Other than what iant has pointed out above, check the following.

1. Double coil syndrom. You should only use 1 ote per address for a program

2. Ensure the logic is not between an MCR instruction

3. Ensure the subroutine is being called

4. Make sure the jsr that calls the subroutine is not between an mcr instruction.

5. Ensure you are not using an OTU on an address that you are attempting to use an OTE instruction on. You will clear the on state until the ote is scanned again.

iant · May 27, 2014

Quite right
But this is an input being used as an output problem
With an OTL/OTU forcing the input into a quandary.

The other items you mentioned are the usual causes.

ndzied1 · May 27, 2014

Is the PLC in Run mode?

OkiePC · May 27, 2014

Yes, the rails are green, it is running, he is writing to input point data tags and so is the attached input card. With those cycles being asynchronous, I am sure the logic is stuttering at least occasionally.

iraiam · May 27, 2014

Do a "Find All" on that output and see if it's anywhere else as an OTE later in the scan. Or I see someone above already mentioned to look for an OTU.

I suspect the problem is something like this, If you look at run 4 The output is ON, but the rung is not true, this leads me to believe there is logic somewhere else operating these two outputs.

OkiePC · May 27, 2014

It's an input, guys, Ian nailed it.

You can't use a real world input like this, especially not in a Logix5000 controller. I don't care if it comes from a Panelview on RIO or how many OTE or OTL instructions there are; the only number that will work on that address is zero...examine it all you want, it is an input.

iraiam · May 27, 2014

OkiePC said:
It's an input, guys, Ian nailed it.

You can't use a real world input like this, especially not in a Logix5000 controller. I don't care if it comes from a Panelview on RIO or how many OTE or OTL instructions there are; the only number that will work on that address is zero...examine it all you want, it is an input.

I did not know that, although I have never tried to use an input like that, we always map a real world input or output to a virtual.

O I see, I should have read the tread more carefully, an input as an OTL or OTU aint' gonna work none too good

EDIT

I would also recommend making 2 ladders; one called inputs, and one called outputs. Map all of your inputs to a descriptive tag in the input ladder and map descriptive tags to your outputs in the output ladder. If you ever want to switch the input/output to a spare or different I/O point, you only have to change a single instruction. Plus as your program grows in size it is considerably easier to add and troubleshoot logic when it's structured, Something like this

osmanmom · May 28, 2014

Conversion program ?

iant · May 28, 2014

F F S
Wait until the OP tests the problem.

Talk about beating a dead horse.

Pinky · May 28, 2014

iant said:
welcome to the site
simple but not in plain site
these are inputs not outputs

Thank you very much Iant, this indeed was my problem. Also thank you to everyone else who posted in this thread, I really appreciate all the help everyone was willing to offer!

OTE won't light on true conditions?

Pinky

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iant

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tim2

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blperkins

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iant

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califflash

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iant

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OkiePC

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iant

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Pinky

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