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BJR

1734 Point I/O

8 posts in this topic

I haven't heard anything from my local AB support for a month on this so I want to run it by a bigger audience. Here's my problem... I'm having some trouble with an Ethernet panel lately that has been in production about 1-1/2 years no problem. In the last week it has "crashed" three times. 1734-AENT qty 7 1734-IB8 cards then 1734-FPD then qty3 1734-OB8E then qty5 1734-OV8E then qty1 1734-OW4 When it faults, the AENT Flashes a red light on POINTBus Status and every single one of the i/o cards flash red on their Network Status light. So when I read through the fault charts in the owners manuals and try to figure out what could be wrong it is pretty vague but at least I know it's not my Ethernet connection. It sounds like local hardware in that panel. I ordered a new AENT, a couple of i/o cards and a FPD just to start swapping out things since a "module missing" or a "node fault" could mean any piece of hardware in there. I've checked that everything is still tightly assembled and locked together but had no chance to stop production and take all of the bases apart and reseat them all. Is there anything I can do to help pinpoint or troubleshoot this instead of swapping out modules day by day?

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This may or may not be the problem but I thought that I would share it in the hope that it helps. I recently had to answer a call out (4 hour drive) where all of the analog points on a remote rack "froze". I was using an ENBT in the main rack and remote rack for remote IO comm. The remote rack had 4 analog cards and 5 thermocouple cards in it. This is what I found: (1) The remote rack was faulted. (2) I had forgotten to check the Major Fault on Controller When Connection Fails in Run Mode box so the PLC continued to run. (3) I had left the Requested Packet Interval set to the default time of 20ms Side note: The facility is remotely operated (unattended). Weeks after I made the change below the operators told me that whatever I did stopped the problems that they had been having with "frozen data". Apparently the system would freeze numerous times during the day but they never told anyone. Eventually the ENBT on the remote rack halted. When I power cycled the remote rack everything came back online. To fix my problem I set the RPI to 250ms. I think that the card "locked up" due to comm timeout. I had absolutely no luck with asking AB tech support or local support about the problem so I am just speculating. Since the problem went away I tend to think some version of what I think was happening is correct. ML Edited by Michael Lloyd

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If the system has been running for 18 months, the problem is unlikely to be firmware or configuration related. The POINTBus status LED solid red state makes the inter-module connections a prime suspect. While the POINTBus is more reliable than many small bus systems I've seen, I know that RA has begun to recommend that the modules be mounted so that the front and back edges are supported, so they can't rock back and forth on a 35mm DIN rail. If it were my system I'd disassemble it and check very carefully for wear or corrosion on all the sliding connectors. It might be easiest to just replace all the 1734-MB bases and leave the adapter and modules and RTB's alone. I know that the 1756 backplane has an error accumulating counter, but I don't know if similar diagnostics are available for the POINTBus.

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I had wanted to do this on one of the days it occured but didn't want to stop production. I took everything apart today and put it back together. There were two bases that seemed to have some dust between them and some of it accumulated on the copper. It didn't seem like enough to cause a problem but who knows. It has actually been fine since the last incident a few weeks ago but I would expect it to happen again in the future if I had not done anything to it. I think this is a good first step and may even help based on what I found. At this point I will wait and see what happens so I am only trying one thing at a time. I've got a few packs of bases on hand. If the problem comes back I guess they would be the next to be replaced and if that doesn't work would the AENT adapter be the next item to try?

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We have some new point I/O modules that have been doing fine, but I am interested in Ken's comment about supporting them. Do I understand that you meant to place something behind where the din clips are so they can rock forward and backward? I didn't install ours, so I did not get a feel for how much they might move, but they are "tall". I think Mike mounted them with screws to the panel back plate, but I am not sure. I will check tomorrow if i remember. Paul Edited by OkiePC

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It failed again this morning. I guess when production goes home I will swap out all of the bases for new ones as my first step towards solving this.

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I am going from memory so bear with me if I am off, but I think if you have comm problems with the AENT, then you blocks will all indicate network problems similar to what you are seeing. Has something changed with your ethernet network? Possibly flooding the AENT. Have you got a managed switch on the network? I know the AB drives are sensitive to their ethernet ports being flooded with packets and they will just stop communicating. Am I understanding correctly that you can power down the remote I/O and it comes back and works ok? If that is so, I think I would concentrate on what has possibly changed on your ethernet network recently. OK looking back at your post, why did you eliminate your ethernet connection/network as a possibility of causing the problems? Edited by PLCMentor.com

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Just because from the manual: POINTBus Status LED Flashing red = Recoverable fault occurred: <BR>1) At cycle power the number of expected modules does not equual the number of modules present . Recommend - configure chassis size<BR>2) A module is missing Recommend - check for missing module and reinstall as needed<BR>3) Node fault (i/o connection timeout) occurred Recommend Check for I/O module failure and correct as needed.<BR><BR>The PLC and 7 AENT cabinets are on a NTRON managed switch - however nothing custom was programmed or setup in the switch. It is my understanding from the manual that there is some optimization in traffic going on automatically. There is a VLAN network server on the switch for data collection in the room on a very large scale but each device is using a gateway address so hopefully that cuts down on problems as well. If the network is being flooded by the data collection system wouldn't some of the other 6 AENT modules fail from time to time? <BR><BR>If I open up the AENT webpage and check on diagnostic information what types of information am I looking for to check on anything being flooded? Some of it is Greek to me since I don't have a huge knowledgebase about servers/PC Ethernet networks, etc. I'd probably focus on the wrong item by just how the description sounds...<BR><BR>Some other machines were put on the same server but don't remember if that was before or after the problems started. Can my IT dept. monitor network traffic with any focus on this problem?<BR><BR>Yes. I did just pull the power connector on the AENT and put it back in to re-boot the "rack." Comes up working just fine.<BR> Edited by BJR

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