Devicenet Power

I have designed a lot of networks for DNET for Motor starters and MCC's. This is the first with a ton of I/O modules.

I have 30 modules of various types. None use external power, so all power will be consumed from the DNET PS. I will be turning on solenoids and lights with the outputs and have dry contacts coming back for inputs to the devices.

I have laid everything out but need some advice with power requirments. Total power consumption for the network is going to be 7500ma with about 600 ft of trunk line. Each drop will have a 3m cable so about 10ft. This will be a Class 1 system so we can utilize the 8amp requirements if need to but would try to keep each segment under the 4amp.

Question is should I use one 20 amp non DNET rated supply and inject power through the power taps where needed in accordance with the "lookup method" in most DNET power manuals. Or use multiple 8 AMP DNET rated supplies at each power tap.

I have never had good luck using a off the shelf supply on smaller networks and do not want to get into a situation where this system will be a constant battle.

Thanks for anyones input.

Sounds noisy with all the dry contacts and solenoids, I'd go with the multiples.

I would go further and reconsider using I/O modules that do not let you separate the I/O power from the network power.

The whole point of having the network power isolated from the I/O power is to prevent a noisy solenoid or contact from interrupting the network signal. This is a fundamental design principle of DeviceNet.

With a trunk line that long, the common mode voltage drop of a single supply will almost certainly be a problem. Use independent smaller supplies.