DeviceNet power supply

Hi I am trying to setup a DeviceNet network with 3 CN2DN and each CN2DN connects to 12 or 13 Schneider TeSys devices. My question is that I am using 1606-XL480E as a dedicated DeviceNet power supply (i.e. it is not being used for anything except powering the network) so will the 480E work in this case? The trunk is based on round thin type.

The only 1606 series power supplies that have been tested and certified for DeviceNet network power are the 1606-XLSDNET4 and 1606-XLSDNET8.

While the 20A supply you describe will probably work fine, the sheer size of it raises warning flags about what you intend to do.

Are these three CN2DN scanners and these 36 to 39 I/O adapters meant to be on the same DeviceNet segment ?

The three cardinal rules for DeviceNet power supplies are:

1. The power supply must be dedicated to the DeviceNet segment.
2. The power supply must be current-limited or fused to protect the smallest wire used in the network.
3. The power supply should be tested and certified by the ODVA or selected to meet the DeviceNet specification.

To expand in detail on #1:

The power supply should not be used to power devices that are not a DeviceNet transceiver. This includes the bulk power for DeviceNet I/O adapters, as well as HMI devices and PLCs and especially I/O circuits.

The power supply should not be used to power more than one DeviceNet segment. Signals from different networks can interfere with one another because they reference the DC Common of the network.

The worst thing about Rule #1 is that you can often break it and the network will run fine. But if you have problems with your network, the very first thing anyone in Tech Support or Field Service or any engineering capacity will make you do is go back and follow Rule #1.

Yup these CN2DN and devices are on the same segment. What I was interested in knowing is would this current fry anything? And if it were to do that could I limit the current by using a resistor and if so where would it be placed? I am assuming it would be placed in the loop that powers up the devices and not the signal loop. All devices in this network are DeviceNet transceivers so it isn't being used to power up anything else. Thanks.

PS I'm kinda new to all this so I greatly appreciate your advice.

Ken said... "While the 20A supply you describe will probably work fine, the sheer size of it raises warning flags about what you intend to do."

From the DeviceNet specs....

Max. Current in the Thick and Flat cables is 8A (4A for North America).

Max. Current in Thin Cable is 3A

I've been told that the cable should be able to handle that load but at any rate that is what I have. What should be done about it?

rehanmalick said:

I've been told that the cable should be able to handle that load but at any rate that is what I have. What should be done about it?

Click to expand...

choice 1 put in an appropriately rated fuse.
choice 2 get an appropriately rated power supply.
choice 3 do both of above 1 and 2.

The big book of DeviceNet media planning is DNET-UM072. I often refer to it as 'the Moby Dick of technical literature'; it's an important book but almost nobody slogs through the whole thing.

You might have to get your hands on that and determine how your cable system will work out, from scratch.

Having three 1788-CN2DN bridges suggests that you have more than one controller accessing these I/O devices. You could probably share the Input data table at the controller or ControlNet level just as effectively.

The general approach you need to take is to determine how much current each of your I/O adapters is going to draw from the DeviceNet, then provide a fused power supply for each segment that adds up to 4 amperes.

If you're set on using that 20A supply, you will need to provide a break in the red wire between each powered segment, and provide individual branch fuses for each segment.

Thanks for all your help guys!

Hello all just wanted to thank all of you guys' input on this little project of mine. Just to let everyone know that the design was changed from what I had initially posted. The latest setup has the 3 CN2DNs on a different segment each with its own power tap but all being powered by the 480E. All 3 devices were working fine and there was no cross-talk over the networks and all the I/Os were responding magnificently on the network. I know this goes against many of ODVA's recommendations but I had a hunch that it would work and I am glad that it has. It has cleared 2 of my doubts that I had before I began the project

a) the power supply need not be of the XLDNET kind, it can be any 24 VDC
b) multiple DNet degments can be powered using a single source as long as the source meets the load requirements (going back to Ken's earlier post.. I am not trying to negate his experience or suggestion but because of project constraints I had only one power source and putting all the CN2DNs on a single segment would have made me run into distance limitations, at that juncture something had to be done so I had to improvise on the design, cross my fingers and pray to God it worked)

just thought that I should share this with all and gather your thoughts as well. Thank you once again for all your input.