Controllogix to OPC Connection Issues

Jmcwethy

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Join Date
Jan 2021
Location
MN
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6
Hi, I have been banging my head on this problem for months, hoping to get some help from the experts here. I will try to make this short.
The Problem: PLC network connection to Top Server OPC constantly drops out for a second or 2. Happens roughly once every 10 minutes on avg. Going live with the processor in logix designer is also painfully slow.
The System: Conveyor system consisting of a ControlLogix L73S V28, 14ea PowerFlex 527 VFD's, some Cognex imaging devices, a handful of remote I/O racks in a DLR, and a stratix switch as the DLR supervisor. The OPC connection is made through a NATR module. The main task is a continuous task with a 25% timeslice, reserved for comms. Task monitor shows around 10% null time, comms usage is below 15% as are the en2t modules, and the stratix shows at worst, 2% utilization.
Other facts: We have several other systems all with similar Allen Bradley hardware and identical connections to OPC with no problems. Occasionally, an attempt to go live gets stuck on "correlating", removing the DLR cables from the stratix unfreezes it. Oddly enough, if it happens when the connections are already removed, reinserting them unfreezes it. Does not matter if you are connecting with Ethernet or USB, same behavior. The VFD's are controlled using motion instructions, not a fan of the way it was implemented. The symptoms seem to all be communication related, but removing the networked devices does not improve the connection, plus utilization is really low. The CPU utilization is within acceptable levels as well. Any insights would be appreciated, I'm out of reasonable options. Thank you.
 
When you say connection drops out, does the link go down? LED's go off? Connection properties shows unconnected? or is it not receving? sending? data anymore but the link is still physically present? I have seen "intermittently" faulty patch cables before, sometimes the jack, sometimes the connection inside the rj45 end.
 
Can you try to use an OPC Client that can report in detail the error reported by the OPC server. This could provide valuable information, as the number of issues that can cause the problem you report can be significant. I can point you to a very easy-to-use and free OPC CLient.
 
Can you try to use an OPC Client that can report in detail the error reported by the OPC server. This could provide valuable information, as the number of issues that can cause the problem you report can be significant. I can point you to a very easy-to-use and free OPC CLient.

Can you point me to an easy to use and free OPC client please?
 
When you say connection drops out, does the link go down? LED's go off? Connection properties shows unconnected? or is it not receving? sending? data anymore but the link is still physically present? I have seen "intermittently" faulty patch cables before, sometimes the jack, sometimes the connection inside the rj45 end.
The OPC server reports "device is not responding", then within a second or 2, a connection event for the device is logged. We have replaced all ethernet cables between the PLC, NATR, Stratix, and plant switch. This causes issues when change events occur during the time the plc is not responding.
 
Can you try to use an OPC Client that can report in detail the error reported by the OPC server. This could provide valuable information, as the number of issues that can cause the problem you report can be significant. I can point you to a very easy-to-use and free OPC CLient.
TOPServer reports that "the device is not responding" and then reconnects a second or 2 later.
 
Can you point me to an easy to use and free OPC client please?

This is the OPC UA client
https://data-intelligence.softing.c...orm/opc-ua-demo-client/#tx-dftabs-tabContent1

The OPC (Classic) client is shown below:
https://data-intelligence.softing.c...server-sdk-for-windows/#tx-dftabs-tabContent2
(OPC Client Demo Client package)

You need to register but both are free of charge and run without limitations. You can save the configuration of the client. They do not allow you to perform logic. You can write data to the server with the keyboard. I hope this information is helpful.


Addition: If you have any problems setting the OPC client, please create a new post (not in this one) explaining your problem, and I will give you a hand. Its late here in Japan, so my reply may take some time.
 
Last edited:
Go online to the processor with a web browser (just type in the Ethernet modules IP). See how many connections are in use.

That sounds a lot like a connection issue to me, but the browser will also show Ethernet diagnostics, which might indicate faulty cabling or some such.
 
I wonder whether you can provide more specific information, such as a standardized OPC or OPCUA error code. Something more or less like what I show below.

At the tag level, the quality is good. I assume if I was looking at it for the 1 or 2 seconds that the connection was dropped it would show bad. I ran diagnostics for hours, and during these drops there are a bunch of failed reads. Makes sense, but no other errors recorded.
 
Go online to the processor with a web browser (just type in the Ethernet modules IP). See how many connections are in use.

That sounds a lot like a connection issue to me, but the browser will also show Ethernet diagnostics, which might indicate faulty cabling or some such.

All cables have been checked/replaced.
Here are the connection stats:
connections.PNG
 
Update: I started logging VFD motion timestamps, and compared them to the connection drop timestamps, There is a definite correlation. 100% of the drops occur during VFD motion on one of the 14 drives. One of the things I noticed earlier, was the MAFR fault reset motion instruction was constantly enabled when the drives were off, sending reset instruction many times per second regardless of fault status. I've changed this logic to only reset when a fault is present, but I wonder if excessive motion messages to the drives would cause this. I also noticed that every activation of the drive, the Enable bit goes true to false back to true within the same second before staying true during the MAJ jog function.
 

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