At a customer's yesterday, and he asks me to help him upload a program from a Contrologix in a machine someone else built. No problem, I say. The last programmer left an ethernet cable connected to a switch, just for programming. However, when I plug this ethernet cable into my computer, my mouse goes nuts (very jumpy and not responsive). So I unhook and my mouse goes back to being fine. I then hook up on the DF1 port, and as soon as I connect the serial cable to my computer, the same thing happens.
Everything appears to be grounded ok and the high voltage wires are not near the PLC or communication. Does anyone have any other ideas (I hate to get into a communication issue on a system I didn't build - we all know how much time you can spend chasing it)
Thanks

If the cable is currently connected into a switch it is probably a standard patch cable. If you want to connect directly from your PC to the CLX ethernet card you need a crossover cable. I would just get another patch lead and connect your PC to a spare port on the switch (if one is free).
Andybr

Sounds like what you are saying is that the CLX is connected to an external network using the ethernet switch, and that there was a cable left connected to the switch that you used to connect your computer. If that is the case, the noise could be coming from anywhere ahead of the switch, or even from the switch (not likely). If the system can tolerate you disconnecting it from the external network and connecting the CLX directly to your PC, and the problem goes away, you know which way to start looking. Even if you don't have a cross-over cable, this experiment should isolate the problem to either the CLX side or the network side (with no cross-over you may not establish comms with the CLX, but the mouse should not mis-behave).

Bill

Thanks for the help

The CLX is connected to an industrial switch, but the only other things on it are machine related (Computer for data collection & MMI, Flex IO, etc). It is not connected to a plant network.

I did try a crossover cable directly into the switch, but had the same erratic mouse problem.

I would like to try a crossover directly into the CLX ethernet port, but don't want to get involved too much yet (you know how that goes - then all the machine problems will become mine!)

If a cross-over cable from your PC to the CLX does not solve the problem, it would almost have to be a grounding/shielding problem. Are the CLX inputs wired with shielded cable? If so, are the shields bonded to equipment chassis at only the instrument end (shields should NOT be connected at the instrument AND the PLC, as you probably know).

An optical bluetooth mouse might solve the problem so you can do the data retrieval, but would not explain the root cause of the problem.

Bill

Was your laptop on battery or plugged into it's power adapter? If plugged in try it off battery. Some noise is a problem if the laptop provides a path to ground. Working off battery removes this problem.

good idea, but I was on battery (although I have seen similar problems when plugged into a machine in Mexico)