Profibus Issue

Hey,

I am having an issues with my profibus network with approx 20-30 nodes. All nodes are visable except a single MP277, which intermittently disappears.

The problem goes away if I move any 1 node from the network.

Hope this makes sense. Any advice would be appreciated.

Cheers
JD

Is the MP277 integrated into the STEP7 project ?
Or have you otherwise manually accounted for the MP277's presence in the calculation of the Token Rotation Time ?

Also, "approx 20-30 nodes" is suspect. The absolute maximum per segment is 32.
Try to provide much more information about the stations, distances, bus speed, repeaters and whatever else you might find relevant.

JayD

I am inclined to agree with Jesper that more information on the architecture of your Profibus system is required.

However the interesting point you make is that the fault is resolved when another device is removed. This could be one of many possibilities, exceeding 32 devices per segment, incorrect WD or bus timings such as TTR mentioned by Jesper, reflection issues.

If you need any further help you can get in touch via www.tyconautomation.co.uk and we will always be happy to help as much as possible.

Cheers

Scott
Tycon Automation Ltd.

Thanks for the replies.

The MP277 is integrated into the step 7, and it is actually 20-30 nodes in total, not per segment.

Bus speed is 1.5M, there are a total of 7 repeaters on system and the final length of the last leg is about 180m (which could be a problem).

A specific question is how many repeaters ('total') can you have on 1 DP system?

Cheers
JayD

At 1.5M the max is 200 meters per segment.

The maximum number of repeaters is 9.

Give us a screenshot of the NetPro configuration, zoomed out, and "with DP Slaves / IO Devices".
If that does not reveal something, then I think you need to have you profibus network analysed electrically.

Sorry for the delay in response. The senior Engineer has decided just to split the networks.