Controllogix Flex I/O Reliability

Hey,
I was just wondering if people out there have had any major reliability problems with the Controllogix Flex I/O, in particular the ethernet versions.

It's just I'm working on a site at the moment and we seem to be constantly pulling our hair out because it seems every week a new Flex I/O module decides to behave strangely, even though it has been working fine for months.

Is it only the Ethernet version? Obviously with Ethernet you need to look at the network carefully and select the appropriate switch (based on size and traffic levels) and RPI rates. Can you give more detail about behaving strangely? Are you getting any IO rack errors?

Well, most of the problems are from the ethernet models. We seem to have a number of different problems, which all seem to be network related. We have taken a lot of time to examine our network, and are still in the process of doing so for some areas. The RPI rate is usually 50ms or 150ms and the network traffic isn't that bad. We are using Hirschmann switches, which were actually recommended to us by Rockwell.

We also have a few DeviceNet models on site, and they have also been known to just stop working. I need to investigate this further the next time it happens, but we currently know that the "ActiveNodeRegister" bit and "DeviceFailureRegister" bit are both healthy when this happens (which is curretly what we use in ALL of our code to detect when a DeviceNet module fails). The only way to fix the fault is to cycle the power, and then they can work fine again for weeks at a time.

We have found one big thing that has fixed a number of our problems over ethernet - turning off "auto-negotiating" of the network speed. We find that auto-negotiate has to be turned off in both the Flex I/O module and the switch. If we don't do this then we find that every few hours or so the module will fault for a few seconds and then come back healthy again (of course, by this time you have dropped out your motor contactors).

We only use redundant ControlNet Flex I/O in our applications, and haven't had any major problems. In our experience, with any Ethernet network you can't seem to stop people fiddling with it. Tim.

Sounds like an EMC problem. Are you using screened ehternet cable? are all the screens connected OK?