Unknown Profibus Fault

E

Thread Starter

engr27

I have SST PFB CLX scanner, it has 41 slaves with 2 dp-dp coupler and 2 repeaters.

this happened after some welding job of our mechanical staff. the following day profibus scanner showing, COMM led is flashing green/red with 1 sec interval and SYSTEM led is off.

It was interesting and confusing, if I will load the original configuration the scanner will fails immediately, so I did some isolation, 1 by 1 slaves is communicating and without error and I tried to load without 32 slaves then network works fine, so I thought it might be the isolated slaves giving problem, unfortunately if I will load the slaves and remove other slaves also works fine.

it was really confusing and annoying so difficult to pinpoint what was the real cause.

I post it here, hoping to get some input and might somebody experience the same.

Thanks for reading.
 
J

James Ingraham

The same? No. Similar? All the time.

The usual Profibus trouble-shooting things apply. Make sure your cables are all the same impedance, and preferably true Profibus cable, not just random RS-485 cable. Make sure your segment lengths are reasonable for the baud rate you're running. Drop the baud rate if you can; I never go over 1.5 Mbps anyway, and if you can drop to 500 kbps even better. Check for proper termination. Make sure the terminated nodes are powered at all times. If possible, keep all nodes powered at all time. (You can cut the power voltage going to a drive, for example, but keep control voltage on it so that it stays on the network.) Check for damaged / misbehaving nodes.

Once you've done all that and still have mysterious problems, throw up your hands and switch to ProfiNet.

Good luck.

-James Ingraham
Sage Automation, Inc.
 
Thanks for the input Sir.

It was really confusing, since I have 41 slaves in the network, I tried to load 1 by 1 and each nodes is responding but when the full configuration is loaded, once the connector touches the scanner port immediately the COM Led flash and communication fails it seems that there is short circuit int he line.

But if I will load only 32 slaves for example 1-32, 9-41, 1-16/20-41 or any combinations of slaves there was no issue it works fine it seems nothing happens.

And, the full network cabling is intact I did not change the termination even I only load 32 slaves out of 41, it was been terminated and connected as is.

But I will give a try as you said, to lower the baudrate and might help,

I keep update if I found the real culprit.

Thanks for the input again.
 
You should not install more then 32 devices in one Profibus segment. Add a repeater to split your network into 2 segments. And remember that repeater also counts as a device.

Regards,
Jacek Dobrowolski
 
> Thanks for the input Sir.

> It was really confusing, since I have 41 slaves in the network, I tried to load 1 by 1 and
> each nodes is responding but when the full configuration is loaded, once the connector touches
> the scanner port immediately the COM Led flash and communication fails it seems that there
> is short circuit int he line.

> But if I will load only 32 slaves for example 1-32, 9-41, 1-16/20-41 or any combinations
> of slaves there was no issue it works fine it seems nothing happens.

Could it be that you are connecting all slaves ( more than 32) to a single segment? The maximum number of slaves is 32 for a single segment. The slave 33 - 41 must connected to a second segment which is connected by a repeater to the first one.

Best Regards
Armin Steinhoff
 
> You should not install more then 32 devices in one Profibus segment. Add a
> repeater to split your network into 2 segments. And remember that repeater also counts as a device.

Thanks for the inputs, there was 2 repeater, as I mentioned in the original post.

Kind regards,
Engr27
 
pl. check connector, cable laying,cable with high load power devices may cause link failure.

pl. ensure all your profibus network with proper shielding of profibus cable bec. it might drop your whole system voltage and failure of network.

another thing that repeater location. i think you need not required two repeater in the whole network. so reduced it by one and try to test your network.

another thing placement of repeater it should be in middle of your whole network as per length calculations.

another imp thing is that remove nods physically which is not in use for the production system.

and finally if your problem still there test on-line through profibus tester to check which nod is mal-functioning.
 
All nodes or connections and connectors check and with proper shielding.

The repeater, it is needed because I have 4 processor communicating

It is in the middle of the network

I remove nodes that is not needed,

I have the proficore and profitrace , unfortunately as I mentioned, once the full config is loaded the communication fails immediately. There is no use of proficore because I could not trace the line. Immediately cut off

It was really confusing, as I said, if i remove 8 nodes, no particular the network works as if no problem at all,

I tried to lower the baud rate to 500kbps, and even the scan time increase/decrease still the same.

And, one more thing, if the connecter is not connected to scanner it was solid green because no network, but once the connector touches the scanner port, immediately going to flash reed/green,

I remove all connectors to the slaves but still the same situation.

I make a test cable for test purposes, point to point, load the full config and connect to scanner, then to one slave, same problem,

My brain is totally drain and could not figure out the culprit.

My question is why even a single test cable from scanner and to one slave (point to point) the communication fails? absolutely there is no short circuit on the cable. new cable new connector

Scanner also change, dp-dp coupler and repeater as well change for testing.

I don t think config problem, as it is the running file for years.

maybe you have more idea to share??

Its interesting but totally confusing.

Hope to hear more

Thanks
Engr27
 
Dear

now try that direct node connection from master/cp to scanner with end to end connection with both node switch in on with completely new test cable. & if still problem then try to check scanner conf. In detail with its comm speed requirement. Then call Siemens people for solving your problem.
 
I did it, with a new cable and point to point (scanner - slave) and switch on the termination on both end. if the full config is loaded the scanner immediately fail. I did also to change the scanner the same output.

If I will load only the particular slave config (only 1 slave loaded for test) then it works fine. this has been tested for all 41 nodes (load 1 by 1)and no issues at all, works fine.

I have 4 networks in the particular plant. The other 3 no issue and working. I tried to plug the other network connector to the problem line and I had the same problem, comm fails immediately.

this totally insane, with new cable, single line, terminated both ends and only connected to one node but still communication fails.

I have reply, it might be scan time, I did reduce, increase but still same. even the baud rate also change but fails.

the PLC processor has been changed for test as well, L5561 controllogix. Scanner is sst-pfb-clx also changed.

it drives me crazy to resolved the issue.

As i mentioned earlier the network is working fine, if will remove 8 nodes (no particular, any node as long as more than 8, and it will work), just to run the plant.

But it must be resolved, how interesting.

by the way thanks for the input.

 
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