RS500 Double Coil Issue

bikerdude

Member
Join Date
Jul 2003
Location
Indiana
Posts
315
Hi,
I'm having trouble with a program that was converted from PLC2 to SLC500 by a contractor. There is a double coil (latching). I'm trying to add a new pattern to the palletizer program. The output in question has erratic behaviour. Sometimes it works and sometimes it dont. I don't know if the double coil is causing the problem or if it lays somewhere elst in the 17 associated rungs. Does anyone know if the second rung will "unlatch" the bit, or am I barking up the wrong tree here?
Thanks for any ideas or help!

BD
B3_doublecoil.JPG
 
bikerdude,

That's a big no-no... You can have mulitple unlatch instructions addressed the same, but not latch bits. Try branching the two inputs on rung 0034 with XIC B3:3/15 from rung 0035. Then just delete rung 0035.
Hope this helps...
 
It depends... (I love that answer... :)

Looking at the address description "Clear Cycle Pulse", one could assume that they should unlatch B3:12/1. I don't know the operation of the machine though, so I am only going off the code you posted.

Do you have the old PLC2 program to go back and reference? If so, you could prob. determine which is the correct way.

If it is not supposed to be an unlatch bit, the way you have it shown in your last post would be correct...
 
bikerdude said:
HI,

Bob O

Here is rung 35
B3Unlatch.JPG

kbcombs,
You think this will be better?
B3_doublecoilMod.JPG

Thanks
BD

Either one is perfectly legit. The new rung 34 is easier to follow. You really aren't giving enough info to help troubleshoot your problem. I think the problem lies elsewhere in the program. It appears that there are two conditions to latch a bit and one to unlatch it.

You mentioned an output, but I don't see one in your posting.
 
Hi to all,
I have a SLC here on the workbench. I have tested it and it seems it doesn't make any difference, except the branch is easier to read & follow. They both work the same as far as I can tell. I have attached a slimmed down version of the file. Rungs 29 - 43 are the problem. Basically the latched bits (2), form a binary 1 to 3 value to move 3 different timer preset values to timer 15. The timer doesn't always hold the infeed belt long enough. Sometimes the case will run into the pusher bar and cause a jam. It doesn't always happen, just sometimes. The pusher bar grabs a row of boxes and pushes them into the layer forming area. On this pattern 4 rows are required to make a complete layer. The infeed belt motor needs to be off or "held" while this operation takes place. The other patterns work like they are supposed to. I must have screwed up the pattern SQO data table somewhere along the line. What confuses me is that the action is not the same everytime. It's always case #5, sometimes on the "even" layer and sometimes on the "odd" layer. I may have slimmed the file down too much for it to be of much use.
BD
 
BD,

I have noticed that there are no one shots (ons), you may want to add some.

Try latching B3:3/14 if it goes hi for one scan (I don't think you will see it) but it will latch B3;12/2 edit:(this latch will be just for a test, to see if its pulling in)

I have added the PDF for Terry Woods :)

I'll keep looking...

Edit: kbcombs said "That's a big no-no... You can have mulitple unlatch instructions addressed the same, but not latch bits."

I am not debating ,but I would like to know why(trying to learn)...reason is I just wrote a program with some..it works...???
 
Last edited:
kbcombs said:
bikerdude,

That's a big no-no... You can have mulitple unlatch instructions addressed the same, but not latch bits. Try branching the two inputs on rung 0034 with XIC B3:3/15 from rung 0035. Then just delete rung 0035.
Hope this helps...

Multiple OTEs in Rockwell software is a no-no.
Multiple OTLs & OTUs are perfectly legitimate.
 
i agree with Mark about the one shots, also when using (L) and (UNL) which ever one that`s true before the end of the scan will work. You might make sure your program at times isn`t latching and then before the scan ends unlatching the same bit. Sometimes just moving a rung in the program will make a difference.
 
CroCop said:
Multiple OTEs in Rockwell software is a no-no.
Multiple OTLs & OTUs are perfectly legitimate.

Thats what he had OTL's, maybe kbcombs did not see that???
 
geniusintraining said:
Thats what he had OTL's, maybe kbcombs did not see that???

Reread the post. He says no multiples on a Latch bit.

Multiple OTLs are common practice.
 
BD,

I would look at n7;11 and n7;12, What is your "Diagnostic Message Pointer" is it loading the correct values into your N7;XX...

I loaded your program and before I really screwed it up... it was working, I did not see any thing in the scan that I thought was wrong, try (if you can) loading a fix integer to see if it works properly


EDIT: OK, I read it again...he said bit's but...BD was showing (2) OTL's...never mind

BD, hope this helps,
 
Last edited:
Genius,

I think that N7:11 & 12 are timer values, adjustable from the panelview. Not sure what effect a "Oneshot" would have, or where I should try to use them. The message pointer also is for the panelview message banner.
BD
 

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