1747_DNS

[Tinker 0]

I have a 1747-SDN that is doing many different things that leads me to think it needs to be replaced. First the voltage is 33 VDC for supplying the flat media and I wounder if this is to high. Second I was installing a PE on the Flat media with the system down and when I got done and turned the system back on the problems started. I removed what I had done to see if had an effect on the system and it did not. Some background, about 7 months ago the system died and all I did to get going again was reset the card and it was off and running until now. I can not get into the the card and if I do it is a short period until I loose communications again. Each time I remove power and re aply it gives me something different that it did before. Some of the combination of the highlighted below will come up. Edited 29 Oct 2007 by Tinker

[TimWilborne 108]

1747-DNS? Lost me. Thought you mean a 1747-DNB for Devicenet but an SLCs Devicenet part number is a 1747-SDN. The next closest thing I can think of is a 1756-DNB. Are you sure that's the part number? Anyway it goes, the solid red LED would lead me to believe this is an issue to take up with Rockwell Support. It may be a bad module but we would be guessing. Rockwell would know for sure.

[Tinker 0]

Fat fingers on my part.

[TimWilborne 108]

So which is it? 1747-SDN or 1756-DNB?

[Ken Roach 194]

33 VDC is too high for a DeviceNet power supply and could cause all the problems you are describing. It could also damage devices; in my experience 35 VDC is about the point where the transceivers begin to break down. DeviceNet is designed and advertised to work with a power supply voltage between 11 and 25 volts. I've intentionally done 27 VDC maximum systems that had DC battery chargers in them. Take the network power down and do a simple resistance check between blue and white to make sure your termination resistors are still solidly connected. You should read about 60 ohms (two 120 ohm resistors in parallel). A little lower is OK if it's a big network, but lower than 50 or so means there is an errant extra resistor out there or some damaged cable or devices.

[Tinker 0]

1747-SDN

[Tinker 0]

Well it turns out that all of these problems were caused by bad media. You gota luv devicenet............