BF in ET200S

RAJATPALLAV · Jul 18, 2007

BF in ET200S
Abruptly once in a few days we get problem that :

In the last slave station BF flashes and SF glows steadily. We reduuced the communication speed over PROFIBUS from 1.5 Mbps to 500Kbps. The problem then shifted from last station to an intermediate station. In both situations the fault goes after a few minutes.

Anybody who knows what could be wrong?

JesperMP · Jul 18, 2007

As allways, investigate the diagnostics buffer.

Please state all relevant information about your network layout.

RAJATPALLAV · Jul 18, 2007

Diagnostics shows the station as crossed, with message - node does not exist.

JesperMP · Jul 18, 2007

You still have not described your network layout.
As you before wrote that the problem seems to be dependant on the speed, this points to that the problem is with the layout, or possibly noise.
We really need to know the entire layout.

RAJATPALLAV · Jul 18, 2007

The system has 2 nos. CPU414 in slots-3 and 4.
DP Master system-1 is OK is on CPU in slot-3.
DP Master system-2 on slot 4 CPU has stations ET200S numbered 2 to 8. Station 6 is the last. Station 6 is longest distance from CPU about 150 meters if not more and on moving drag chain system that moves about 30 meters back to front.

JesperMP · Jul 18, 2007

Max total segment length at 1.5M is 200m.
Max total segment length at 500k is 400m.

Something is drastically wrong, because at 500k you should not have any problems at all.
If there is no excessive noise source then I am guessing it is a cabling problem. A bad connector termination or a damaged cable.

If you cannot locate any such problems, then consider to buy or rent Profibus diagnostics tool. Such a tool can locate all kinds of errors including cable problems.

Taffy · Jul 18, 2007

Jesper,

Where did you get the max length for the different speeds from? I haven't come across a document for this.
Thanks

RAJATPALLAV · Jul 18, 2007

Thanks,I will try that.
Just one more query.
How to capture SIMATIC MANAGER screen and paste it to make the things more clear? I have tried the export import option but need help.

JesperMP · Jul 18, 2007

Taffy, Try these web based training courses:
http://www.profibus.com/pb/support/train/#index_9
Go to chapter 3 - Transmission technology - segmenth length.

PLucas · Jul 18, 2007

RAJATPALLAV said:
Station 6 is longest distance from CPU about 150 meters if not more and on moving drag chain system that moves about 30 meters back to front.

This might be where your problem lies, what is the bend radius on the drag chain? Too small a radius can cause problems with comms, also the type of cable used through the drag chain will make a difference, we use stranded cable through our drag chains. Standard profibus cable, solid core, does not like running through a drag chain system.

Paul

JesperMP · Jul 18, 2007

RAJATPALLAV.
Try ALT + PrntScrn.
Then open Paint (do not use Word or any other office program) and use CTRL + V.
Save As GIF image for the most compact file size (GIF images is best for computer screenshots).
Then follow the instructions in the FAQ section of the forum on how to add images.

RAJATPALLAV · Jul 18, 2007

Yes.
You have a point.
The PROFIBUS cable uses stranded copper wire.
In addition we have put a repeater RS485 to feed signal at its start. When that didnot help we reduced the speed from 1.5 Mbps to 500Kbps. Now the problem has shifted to an intermediate station. We are watching the development as the intermediate station has faulted only once.

JesperMP · Jul 18, 2007

In addition we have put a repeater RS485 to feed signal at its start

Where did you put the repeater ?
Where is it located in relation to the stations with errors ?

RAJATPALLAV · Jul 19, 2007

The hardware looks like,

We have put repeater after station 5 to feed station 6.Station 6 is last station.

Now the fault has come once in Station 3 which is just near CPU-2 on PROFIBUS DP MASTER SYSTEM (2)

JesperMP · Jul 19, 2007

The length of the segments are not too long, and there are not too many nodes in a segment.
Whoever designed the system was worried about the max length of station 6 and possibly also the drag chain. That is why he put the repeater before station 6.
The repeater means that the error cannot be directly related to station 6 or the drag chain.
I would check the cable all the way for damages, and I would check every single connector. If this doesnt reveal anything, then you need a profibus analyser, or a diagnostics repeater.

BF in ET200S

RAJATPALLAV

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RAJATPALLAV

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Taffy

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