DeviceNet and Phoenix Contact F.O. modules - Star configuration?


Thread Starter

Andy Sibley


We're currently running DeviceNet using thick trunk cables into very EMI noisy areas and have followed the usual grounding recommendations etc. The impulse interference we have is damaging some CANBus transceivers and although we've been successful with our own design of protection and C.M. filtering we're considering using the Phoenix Contact fiber optic modules to "shorten" the amount of copper we have in the area.

With the Phoenix modules we are getting mixed comments from Support. Basically we want a star distribution to satellite boxes via about 30m of F.O. to each box. Timing wise we seem to be ok at 250kb.

Has anyone on this forum used the Phoenix Contact DeviceNet F.O. modules in this way? I've used them in point-to-point the past with no issues.

Incidentally the DeviceNet cable spec only rates the braid at 65% coverage and despite the Al foil shielding we see huge levels of EMI (>30V). At our frequencies they go straight through the foil! Do the skin depth calculation.

We've adopted additional 99.5% braid on our drop cabling with some success. I can tell other stories about lack of input protection on some devices that will make an EMI engineer wince!

So anyone used the Phoenix F.O. modules in a star configuration?


asibley [at]