HELP DeviceNet Problems

I am new to the programming world and need some serious help with an allen bradley devicenet system. I have been having communication issues for a while now. At first i was getting a E78 fault on 5 of 6 nodes on the network. That problem has since been pushed to the wayside as now I am recieving a no transmission fault. Please HELP.

Bryan, could be useful to know more informations about your hardware...

Which CPU?
Which Scanner?
Versions (ser. Rev. Firmware etc.)
Software used (and Versions)
What type of nodes are the two with error?

Error 78 is related to the fact that a device is in the scanlist of the scanner but it isn't responding to it...
I have found sometimes this error on Devicenet, here some ideas that have solved these issues:

1. if the slave nodes have autobaud enabled, try to disable it and fix the right network speed on them
2. raise the interscan delay in the scanner using RSNetworx to 20 ms (default is 10ms); this to try to don't get a timeout from those nodes.

- [font=comic sans ms,sans-serif]fuzzy logic[/font]

If you are getting a No TX error most likely you have a bad cable or a wire loose. Try resetting the card and resetting the power supply to see if it will clear but my hunch is that the trunk line cable near nodes 5 and 6 make have a bad connection or be damaged.

Also at the end of the main trunk line should be a terminating resistor make sure thats not blown or damaged I agree however with LJBMatt check trunk 5 and 6 reterminate there may be a bad connection there

here is one troubleshooting guide

I have solved the transmission error problem. I found the terminating resistor loose at the terminal block of the scanner card. Now I am back to my original problem. The display on the scanner card is reading A#00 NoRX, N#1 E#78, N#2 E78, N#7 E#78, N#10 E#78, and N#11 E# 78. The only node that is communicating is node 12 and it is last in the series. We are running Allen Bradley Controllogix with a Logix 5555 processor (1756-L55M23) and a 1756-DNP scanner Card.

Your 1756-DNB scanner is just another node on the network, and should be connected to the network trunk-line just like any other node, therefore it should not have a terminating resitor attached.

The resistors (2 only) should be at the extreme ends of the trunk-line.

You are not getting data to/from nodes up to #11 - but the numbers don't mean anything, check the physical location of devices on the network, I would hazard a guess node 12 is the first node away from the scanner, and a break in the network wiring AFTER node 12.

There's a couple of quick checks to perform to troubleshoot network cabling problems.

1. Power-down the network and measure the resistance between CAN-H and CAN-L (the signal wires). You should get 60 ohms (or slightly less if quite a few devices attached), but not less than 50 ohms. Any higher than 60 and you have a missing or bad termination resistor.

2. With the network powered-up, measure the V+ to V- voltages at the extreme ends of the network, and where the network power supply is located. The maximum allowable voltage drop is 4.75 volts in each supply line, so a V+ to V- voltage of 15.5 V is deemed to be acceptable, although I would not be happy with less than 20 V

Brian.
If all but one node are not communicating my first suspicion would be that the Baud rate has been set incorrectly on the scanner. This used to be a common problem on the older scanners because people would mess about with the little button on the front of the module. The single node which does connect could have autobaud enabled. I would double check the baud rate for every device on the network.
Andybr

Ok here we go again. I am encountering more problems as I go. I have connected RSLINX and can see the scanner that is causing me issues. The LED display on the module is reading duplicate node failure. When I open RSNETWORX it sees the module but says it is not connected or communicating. Identity Communications Error 8000000A. Where do I go from here?????????

It seems that the DNB has the same node address as another device on the network...
If the DNB has a small pushbutton inside the cover, over its terminals, pushing and holding it give you the possibility to change the node address; then you will be able to connect the software.

If the module is a series C, then you may change node from rotary switches...

- [font=comic sans ms,sans-serif]fuzzy logic[/font]

Scanners can be picky once you find and fix one error. When you found the loose terminating resistor (it is ok to have the term resistor on the card if you are connected to the trunk contrary to what daba states) did you cycle your DNET 24VDC power or reset your DNB card by pulling it out of the rack and re-inserting. I find this clears a lot of erros as the Scanner tends to work better once an error is cleared on it by going through a power cycle and startup routine.

Don't panic, Bryan. DeviceNet can seem a little intimidating, but it is really very simple to use.

The scanner module's "Duplicate Node" error message means exactly what it says: your scanner is set for the same node number as something else on the network. This is probably because somebody pressed that little black button and incremented the node number by one.

Usually the scanner is Node 00. You can check that offline copy of RSNetworx for DeviceNet to be sure. Then, with the 24 VDC power turned on, press and hold the black button on the front of the 1756-DNB. It only increments slowly, so be patient and keep holding the button until it comes back around to Node 00.

Next go check the fundamental power and termination issues that have already been described.

After you have done these things, come back and describe your system in some more detail: the length of the trunk, the number of devices, what kind of devices, how you are supplying 24 VDC power, and the state of any indicator LEDs on your slave devices.

OK I really appreciate the cooperation as i am getting very frustrated with this issue. That being said maybe i can shed a little more light on this as I understand the system a little better now.

The network in question is a setup of four machines. Each machine has its own PLC rack. The machine that is causing the problem seems to be the master in the system. We have 4 Controllogix racks, and in each rack they have normal I/O cards as well as Ethernet cards (to connect to a Controll Desk where the orders are processed). Also all 4 PLC racks have a ControllNEt card. Connected to the controllnet in machine 1 is a HMI. Also according to the RSLinx this is what is controlling communicatins between all 4 machines. Machines 2 and 3 also have HMIs connected to the Controllnet. Recently the HMI in machine 2 was replaced and the program was uploaded from machine 1 HMI (no hard copy available at this time). Machine 1 HMI was set as the master and this parrameter was transferred to HMI 2. After we resolved that issue and changed the node address of the touch panel aswell as the Controllnet is when this Duplicate node failure appeared in the Devicenet. My question now is: Is it possible for there to be another parrameter in the HMI (A/B PanelView 1000) that could be affecting the Devicenet.

The trunk lines for the Devicenet are short and are all terminated well and the terminating resistors are within specs. There are 7 Nodes on the Devicenet in machine 1, 4 Nodes on the Devicenet in Machine 2, and 4 Nodes in machine 3 Devicenet. Machine 4 does not have a devicenet.

ANY HELP WOULD BE GREAT!!!!

Success

Thanks to all for the help. I have found the rouge node causing my problems. One of my slave devices was bad and causing all the communication problems. Thanks again to all that have helped.