How to Find the Node in Devicenet

[Akif KC 0]

Hey Guys,

I am experiencing Devicenet problem in the plant, and it seems like its E78 followed by 2 nodes. I went inside the properties of Devicenet and there is those two Nodes selected in the properties. What I am confused about is if whether that nodes are faulted or have some sort of problem with that, how can I actually find that nodes? I have no clue what those nodes are connected to, can someone please help me out? Thank you very much.

[kaiser_will 65]

Do you have RSNetworx installed, to maintain your DeviceNet network?  Or are you using RSLinx?

What has changed to your system recently?  Have there been any additions or removal of nodes, or changes to a data interface terminal?  How many DeviceNet nodes do you have?

With DeviceNet problems, often they are physical in root-cause...damaged DeviceNet cable, loose terminal connections, failing DeviceNet interface board in a PC. 

[pcmccartney1 141]

The 78 is indicating that an "expected" node or nodes is (are) not communicating with the scanner.  The scanner is configured with the fore mentioned RSNetworks for DeviceNet software.

As far as finding the nodes,  the RSNetwroks is the best tool.  Without it, then the  PLC program might be well documented enough to point you to the faulted nodes.

Will's absolutely correct, there is more than likely nothing wrong with the scanner or the configuration.  More than likely there is a physical problem with either the wiring or the device has truly failed and needs to be replaced.  The majority of DNet devices have a set of rotary switches for setting of the node address.  You'll need to follow the truck cable and check every device's physical address to locate the faulted nodes, then diagnose the problem.

Again to Will's point, is it possible that the nodes have been decommissioned and removed?  If so then the DeviceNet scanner will need to have those nodes removed from it's internal scan list.  It is possible to write code to "deactivate" these nodes from the active scan list in the DNet scanner via explicit messages.

[kaiser_will 65]

Have you gone online with RSNetworx to analyze the network?  With a error E78, one would expect to see a node or a whole section of the network drop off.  Keeping in mind that a DeviceNet network may be addressed and wired in different manners.  I have seen the network "go to sleep" intermittently from the problem point on.  If you can pinpoint where, which node, the problem occurs at, then look at the nodes before and after, those 2 sections of DeviceNet network cabling is where I would be focused.  

Things to personally inspect...terminating resistors at both ends of the network (sometimes networks just work then one day then start giving you fits and you find out one resistor is missing or has a loose terminal), damaged trunk line or drop line (dig into RSNetworx to find diagnostic history).

While you are at it, take a few minutes to go back through your DeviceNet network design.  There have been occasions in which the root-cause of DeviceNet network failure was due to a poorly designed network (i.e., too long of trunk or drop lines, too many nodes on a drop line, wrong terminating resistors, etc.

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/dnet-um072_-en-p.pdf

[Akif KC 0]

Hi Will / Cartney,

Thank you very much for the valuable reply. Actually was really busy yesterday as I had huge headache because of the Devicenet problem in the plant. The cell was running production even with that E78 fault and when I tried opening the RSNetworx software, if I am not wrong , I screwed something up, which gave me E&77. That was really pain in the butt as I had to be in the cell for more than 5 hours looking what actually had happened and ended up remaking the scanlist for the cell.

Actually I had a bus off fault before that, I wish I could find why it is happening, as you guys already mentioned it may be some bad wiring or the noise, but it is really a huge network line to sit and check all the wiring !

Thanks again for the valuable replies, appreciate it.

Akif