Devicenet Question - baud rate setting/config

[engr27]

Need some clarification regarding the devicenet set up
PLC is CLX with 1756-DNB scanner, trunkline using kwiklink flat cable with the micro connector for the nodes (direct connection to the trunk).

25 nodes consisting E3, DSA and VFD.
Total trunk line is approx 25 meters only inside the MCC panel
Baud rate setting for DSA is (auto) cannot be set to fix
E3 plus is also same but got some confusion regarding the next parameter which is (nonVol Baud rate)
Drives are manually set -- @ 500Kbps

I use IAB for simulation, I had 55m of cumulative drop length and when I run the cable wizard and set to 500kbps got error.

But powering up the system there was no error and the scanner is healthy condition, however, there is no particular time and got E78 from 1 drive and next day or week another drive in fault. intermittent E78 on 5 drives.

Need some advise please

Thank you

 

[Ken Roach]

Welcome to the Forum !

I always recommend being conservative with the DeviceNet data rate, especially when noisy devices like VFDs are present.

If you think that your cumulative dropline length is too much to support 500 kb/s operation of the network, decrease the network data rate to 250 kb/s or 125 kb/s.

Change the data rate for the 1756-DNB, and for the drives, then power cycle the DeviceNet power supply, the 1756-DNB chassis (or remove/insert it) and each of the VFDs.

Also check your termination resistors, of course. With the DeviceNet network power switched off, you should measure about 60 ohms between the blue and white signal wires.

 

[engr27]

Welcome to the Forum !

I always recommend being conservative with the DeviceNet data rate, especially when noisy devices like VFDs are present.

If you think that your cumulative dropline length is too much to support 500 kb/s operation of the network, decrease the network data rate to 250 kb/s or 125 kb/s.

Change the data rate for the 1756-DNB, and for the drives, then power cycle the DeviceNet power supply, the 1756-DNB chassis (or remove/insert it) and each of the VFDs.

Also check your termination resistors, of course. With the DeviceNet network power switched off, you should measure about 60 ohms between the blue and white signal wires.

Hello Ken,

Thanks for a warm welcome.
As per the topology I have 24 drops using 1485K - P1/P2/P4 F5-C direct connection to the kwiklink flat cable.
I will set it to 250Kbps,

Apology for newbie question, when I see the parameter box of DSA and E3 plus ( Baud Rate --. enable / disable) -- Do I need to set it via node commissioning tool??? And, what does the next parameter (NonVol -- wherein I can choose to set 125/250/500)???

Ken, do you mean that I have to set all nodes and the scanner with fix baud rate? And, I should not leave a single node with auto (enable) setting? Im sorry I hope you can correct me. I have to do it all via node commissioning tool of RSnetworx?

I actually really confused powering up the system --> all green. But as earlier stated. E78 appears intermittently.

Thanks

 

[Ken Roach]

The most common way to set up the DeviceNet Data Rate is to set the Scanner to the desired Data Rate, and leave all the slave devices set for Auto Baud.

The 1756-DNB always has a static data rate.

When the Scanner boots up, it will send out packets on the network that will be detected by the slave devices, which will adjust themselves to the correct data rate.

 

[widelto]

I have set up many DNET networks, and I always recommend this document:
http://www.cednebtrc.com/ftp_tshane/DNet Book of Knowledge.pdf

Though is not the latest revision , send me a PM I will send you latest revision.

 

[mellis]

If the topic is DeviceNet, Bob Law is the man to listen to (the document Widelto linked). As he is fond of saying, most DeviceNet problems have to do with physical installation of the media. Pay attention to the guidelines: trunkline / dropline lengths, grounding, termination resistors. Many of the "problem" DeviceNet networks I have seen violate at least one rule. My personal opinion for baud rate is you should start out at 125K and only raise it if you NEED to. The network is just more robust at 125K. The other thing to keep an eye on is the number of nodes. Technically, you can have 63 devices. I try to keep initial configuration at 20-25 for VFDs and E3s if all you are using is the command and status words. If you are using a lot of additional data, you might want to limit the number of nodes even more. If we are talking about simple devices like automated on/off valves I'll go to 40 nodes for initial configuration. In most cases, you want to leave some room for additions to the network.

 

[mellis]

Ken, do you mean that I have to set all nodes and the scanner with fix baud rate? And, I should not leave a single node with auto (enable) setting? Im sorry I hope you can correct me. I have to do it all via node commissioning tool of RSnetworx?

As Ken pointed out, leaving all the nodes set to "auto baud" is a good idea. This is the "normal" way to do it. It also makes much less work for the person that is commissioning the network. In general, all you should have to set on the devices is the node number. You do not have to use the node commissioning tool. You can set node number from RSNetworx. I usually set up a new DeviceNet by powering up with no nodes connected. Check that the scanner is happy. Then I connect one node at a time and set the node number using RSNetworx. Then I map the inputs and outputs in the scanner.

Most devices have a way to set the node number on the device (dip switches or rotary switches). This works fine as well. I just prefer not to open up the MCC to set them. Setting node address switches with arc flash PPE is a pain.

 

[engr27]

Many thanks for the input, highly appreciated.
I will keep the auto baud rate and will adjust only the nodes with fix parameters.

And, maybe this is the culprit of intermittent fault?
Fault happens without a particular time. which is really annoying and getting confused. it might be a single node, or couple of nodes in a week or sometimes after 2 weeks.

I will set first the baud rates to see the output.

Thanks a lot