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Guest Daniel

Problem with unlatching bits

15 posts in this topic

Hello I'm having some trouble with an unlatching problem. The first time i ran the program on the SLC5/04 it goes well. After a few weeks, I'm getting complaints from the factory floor that tyres aren't moving. And its due to bits not unlatching properly. I've examined the program throughly and still it is not unlatching properly. It occurs at random. And usually happens around once a day or twice a day...or maybe more often than that. Too hard to keep track of. I've use a counter to register occurances. I was wondering could it be the rack interconnect cable causing problems. Cause the electricial broke a couple of pins while installing the new rack. But it ran the input cards and output cards with no problem until now. Any ideas would be very much appreciated. Thanks.

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Guest_Daniel: Please register at MrPLC.com and join the MRPLC.com community Register at MrPLC.com When the latch bits failed to unlatch, does the program reflect the latched condition of the bits? Or are they in the unlatched state? If they are in the unlatched state, you definitely have rack problems.

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Also remember: "The program never fails..." Can you post your code? I'd like to see your latches and see what's going on in your PLC. It could be hardware, but it might be a condition in your software to. Can we see?

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Just don't use latches...

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How do i post the code? When we see the tyre stuck on the conveyor for no odd reason, I log onto the PLC and i see a few bits that are still latched when they shouldn't have been latched. After you clear the problem, it runs fine...until the problem occurs again.

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Just attached the RSS file to this thread. You have to register however to attach any files. You can post questions as a guest, but in order to attach files to this board, you have to register. Attach your RSS file, tell us which RUNG is having the problem.

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Don't take this personally, but I'm sure that the "problem" is that you haven't catered for all of the possible operating circumstances in your program. You now need to consider some 'what if' scenarios that could lead to the program state (or states) that you're seeing. It could be anything from a dislodged sensor to something unexpected that the operators are doing. Observe. Talk to the operators. Find out what preceded the stoppage. Be humble.

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Here is the file. I've excluded some other conveyor operations. Its quite a huge file. The file i am having problem is file No.21 TUO CONV. In that file..problem occurs in rung 0018 to 0036. Its basically bits associated in transporting the tyre to #5 TUO or the Reject Conveyor. I've talked to the operators. And after discussing with the electricians, they agree its the unlatching bit problem. It maybe due to my bad programming skills, but in following the logic in the rungs, I still don't see why its not unlatching. Just out of curiosity, what kind of problem would you get if you broke a couple pins off the rack connector port and use that same port to connect to another rack? CONVEYOR_NETWORK_file.RSS Edited by daniel

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Daniel, I think I found your problem. It's bit B3:1/0 You have an OTE twice for that bit. And your using the XIC of that bit in rung 36. Rung 36 is where you UNLATCH everything. You can't really have TWO OTE (B3:1/0) in the same program. That tends to screw things up at any given moment depending on the PLC scan. Right click on Rung 33 on the B3:0/1 bit, and do a FIND ALL. You'll see that there is an OTE on rung 33 and rung 44. See my screen shot.

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Bravo, Senior Super Admin! Keen eye!

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Hey thanks, Omron swamie expert! I hope it helped out Daniel.... Hey Daniel. You gotta report back to us and let us know if that was it or not. Good luck!

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Hey guys, sorry about the late reply. I've been swamped with work over the past few days. Thanks for the suggestion. But I have tried it. But its doesn't solve the problem. To make matters worse, I'm having major faults every now and then. I've called the support line. And they say its the rack. So its going to be replaced later this afternoon. Hopefully it solves the major faults...AND...the unlatching problem.

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What are the "major faults"? Processor faults or faults that you programmed?

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There is also two unlatch bits B3:1/5 on rung 40 and 41 just combine the two rungs together.

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I am happy to say that we have replaced the rack with a new one. And it is safe to say the problems have dissappeared. Just one pin missing from the interconnect port can make a whole lotta difference...

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