Strange Communications Problem

[Old No. 7]

We have an OPC server getting data from a Compactlogix PLC. The PLC also communicates with a Panelview and a couple VFDs via Ethernet/IP. Everything seemed to work fine for a year or so and all of a sudden the OPC server stopped communicating with this PLC. It still works fine with a few other Compactlogix PLCs.

Here's the odd part. Unplugging one of the VFDs from the ethernet switch in the control panel will cause the OPC server to start working again. Plug the VFD back in and the OPC server stops. We suspected an IP conflict but we verified that everything is set correctly.

I'm suspecting the ethernet switch, but everything else on the same switch works ok.

 

[thingstodo]

We have an OPC server getting data from a Compactlogix PLC. The PLC also communicates with a Panelview and a couple VFDs via Ethernet/IP. Everything seemed to work fine for a year or so and all of a sudden the OPC server stopped communicating with this PLC. It still works fine with a few other Compactlogix PLCs.

Here's the odd part. Unplugging one of the VFDs from the ethernet switch in the control panel will cause the OPC server to start working again. Plug the VFD back in and the OPC server stops. We suspected an IP conflict but we verified that everything is set correctly.

I'm suspecting the ethernet switch, but everything else on the same switch works ok.

This sounds like a problem we had communicating ControlLogix to multiple Micrologix. We had run out of connections on the ethernet card (an ENBT). The message instructions were going into Enabled-wait state and went through sometimes, but sometimes did not. It caused a bunch of timeouts and other confusion.

It does not sound like you are using messages. Perhaps your ethernet card is running out of connections, as OPC ... I think .. opens and closes connections for writes, but keeps the connections open for reads?

I'm sure someone will correct me .. I don't think I have this correct

If I am correct, managing the connections would require another ethernet card on the ControlLogix side.

 

[Old No. 7]

Shouldn't be a connections or nodes issue with the L33ER. There are only two VFD's connected and a HMI. No messaging is being done to the drives.

It shouldn't be anything on the OPC side either. We've done much larger systems with 3-4x as many PLC's without any issues.

 

[Jim3846]

go to the controller in rslogix and check your connections. Maybe you are up against the max connections?