Ladder code doesn´t work. Why is it ?

giovani

Member
Join Date
Jun 2003
Location
Rio de Janeiro
Posts
18
Hi everyone !


I´ve just begun to develop a ladder program for a SLC 5/03 PLC and I´m facing the folowing problem :

The application I´m developing is indeed a revision of the actual running code, which has some bugs to be fixed, but there´s a portion of it which I don´t need to rewrite since it´s error free. So I decided to copy this code portion and test it alone, but it doesn´t work, i.e, the ouputs are not set or reset according to the code, despite rung continuity. I don´t understand why this happens since the parameters of every instruction used by the code portion are digital inputs and digital outputs.

I know the info given above may sound a bit confused but any help you guys can provide will be deeply appreciated and, if some of you think it´s necessary, I´ll post the code portion here.

Thanks in advance !! :)
 
Maybe you missed out some set/reset coils that would hinder the output(s) from deactivating. Those coils could be just memory address, but they could well be the address meant for resetting or setting of the output(s).

I could sound just as confusing.... :p
 
This "portion of the code..." that is not executing; is it in a Program File other than #2? If so, you should have logic like shown in the attachment in file #2 to ensure that that particular file is executed.

jsr.jpeg
 
First of all, I´d like to thank everyone for the input !!

I decided to post the ladder code which I´m talking about to clear things up.

Here it goes :


This portion of ladder program is responsible for the control of a pump and for reasons unknown to me it doesn´t work on my knew program, although I copied it exactly like it was on the original program. The only difference betwen both of them is that in the original program the rungs are not one in the order shown above :

My program Original program

Rung #50 Rung #0
Rung #51 Rung #1
Rung #52 Rung #2
Rung #53 Rung #3
Rung #54 Rung #4
Rung #55 Rung #85
Rung #56 Rung #86

Thanks again for helping me out !!!

ladder_portion.jpg
 
Sorry OT

🤷

Sorry for hijacking this thread..

Ron

I just noticed you changed your avator..

For a moment there, I didn't think it was the 'real' rsdoran that had replied, but some imposter! Then I noticed the post count.

Who is that in your avator?

Paul
 
Greetings giovani,

we’d be able to offer a lot more help if you’d post the entire .RSS file ... the screen shot you posted is really too grainy for my tired old eyes to read ... plus we’re only able to get a very small part of the total picture ...

if you have any trouble making the .RSS file post, this should help ...
 
I must be missing something.

I looked rather quickly through the code that giovani posted. I don't see any outputs in a state they shouldn't be. It all looks right.

Or are you saying that the outputs are on as displayed in RSLogix but the physical outputs are not on? Which output(s) are causing you trouble?

Keith
 
Once again the members of this forum helped me solve my problems !! :)

On my last reply I forgot to give some information which would make it easier to understand the ladder portion I gave. Thanks Rube, rsdoran and TimeFluxCap for letting me know it.

I want to give the additional information :

The bits N7:18/0 and N7:18/1 are used to to turn off and to turn on the pump, respectively, and are set true or false by the supervisory system I´m designing. But, even if I set the bit N7:18/1 to true by right clicking on it and choosing Toggle Bit the pump are no turned on, although all the other bits involved in this operation are set accordingly, i.e., their states are such that there is rung continuity.

Also, I decided to follow Ron Beaufort and will post the original .RSS file and also the .RSS file of my design. But I need to tell that some of the bits involved are different although their functionality remains the same. They are the following :

My program Original program

B3:0/12 B3:0/0
N7:18/0 N7:0/0
N7:18/1 N7:0/1

If any other information become necessary - for example, a brief description of the way the pump should operate - please let me know.

Once again, thanks to all of you !!
 
giovani said:
But, even if I set the bit N7:18/1 to true by right clicking on it and choosing Toggle Bit the pump are no turned on, although all the other bits involved in this operation are set accordingly, i.e., their states are such that there is rung continuity.

I don't see any immediate problems in your program, the logic is in LAD2, there are no MCR's, JMP's or other headache instructions....

Are you saying that when you toggle N7:18/1, B3/320 comes on, and in rung 53 turns on O:18/4? Does O:18/4 turn on in RSLogix?

You are running the logic in a SLC aren't you? Is the SLC in Run mode (or REMRUN)?

Is the Pump motor starter wired to the correct output?

I am thinking you have a physical problem between the PLC and the Pump.

Do you see:

rsl500.gif
 
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In rung 51 try a parallel branch with an XIC bit (non integer) around the N7:18/1 integer and toggle that. See if the pump comes on then.
 
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