Devicenet Power Supply Selection

I am trying to select a new power supply for a small devicenet network 10 nodes and it currently has a standard open frame power supply and we are having lots of problem dropping nodes.

This is not a devicenet rated power supply so i am almost 100% sure it is the culprit.

What makes a power supply devicenet rated? Is it the noise control /immunity?

Or is it more about the tighter voltage regulation or both?

I am trying to select between these http://www.clrwtr.com/PDF/Sola-Hevi-Duty/Sola-SDN-DeviceNet-Power-Supplies.pdf

I can not find any info on the power supply we have now so i do not know it's output rating.

Is there any harm in using the higher output supply on the network?

Price not being a factor i would just buy a devicenet rated/certified ps with the highest output rating i can find and be done with it. Any issues with this approach?

This is my first stab at devicenet and i want to cure these problems fast.

This is an all ab system with flex i/o and 1336 drives a slc 5/04 and 1747-SDN version 3.03 firmware.

My experience with Device net started out similar to yours, with nodes dropping out and my cures were

The screen wire on the Device net cable in the drawings is labelled as bare, and unfortunately when contractors install the tails on the cable thats exactly as they leave it, and allow it to touch earth, this tail needs to get an insulated sleeve.
Device net cable should only have one earth point on the screen.

The Flex Inputs and Outputs modules should have there own separate power supply that is not common with the that driving the Device net, as relay switching can cause issues.

Most good quality power supplies are adequate and going bigger is a good idea.
Don't allow your Net work cable length to get too long, or consider center feeding the power to your Devicenet cable, rather than feeding from one end.

Make sure you have two terminating resistor, one at each end of the cable.

OH, did I mention make sure the screen is only earthed at one point.

Persist with it it's a good network when installed properly.

When I taught DeviceNet seminars, I always used to say that the DeviceNet Media Design and Installation Guide was the "Moby Dick of technical manuals". Everybody's heard of it, but few have the patience to read it.

It's document # DNET-UM072, available from the Rockwell Automation Literature web server.

Chapter 4 covers power supply requirements.

Rule #1 of DeviceNet power supplies is to provide a power supply that is used ONLY for the DeviceNet.

If you use the power supply for other purposes, including bulk I/O power and network adapter power, you lose isolation and introduce noise.

Almost everything else in the network installation is of secondary importance. Yes, you should be sure the shield is grounded in only one place. The power supply needs to keep a steady 24V with little ripple and be sized so that it can bring the fully loaded network from 0 to 24V in under a quarter second. Observe dropline length, trunkline budget, and termination resistance rules.

Those things are important, but if you do them and ignore Rule #1, you're going to have trouble with the network.

The Sola "SDN" series of power supplies and the A-B 1606 versions with "DNET" in their part number are the ones I very strongly recommend. I have a strong dislike of open-frame PowerOne and Idec-brand power supplies for DeviceNet applications.

I ended up getting a sola sdn power supply from our distributor this morning and i am putting it in now.

Thanks Guys

I second the Sola SDN and AB 1606 "DNET" power supplies. Sometimes I think they're the same unit

Some Sola and A-B power supplies do look amazingly similar.

The explanation I heard was that Sola switched from a manufacturer in Country G to a manufacturer in Country C, and Rockwell Automation picked up the original Country G manufacturer's product line.

It is worth it if you can to put a scope of the V+/GND, V-/GND, and V+/V- connections and compare the original and the new power supplies.

Very interesting, we use the Sola SDN's frequently and I had no idea they were Devicenet rated. I've had good luck with the Sola SCP100S24X-DVN. It's a sealed unit and you do have to buy the cordsets separately, but I kind of like the design because it doesn't "look" like a power supply, so it's less likely that Bubba will try to power other things from it.

http://www.solahd.com/products/powersupplies/scpx.htm