Profibus problem

Renting a profitrace is also possible. We rented one when we had a problem which we just couldnt knack. With the profitrace it was quickly established that the common ground was floating, something that would have been near impossible to figure out by other means.
These things are remarkable. I dont do much Profibus anymore, but if I did I would definetely buy one.

That's a good suggestion. Something to keep in mind. I'd have to search for a place where you could do that.
 
Renting a profitrace is also possible. We rented one when we had a problem which we just couldnt knack. With the profitrace it was quickly established that the common ground was floating, something that would have been near impossible to figure out by other means.
These things are remarkable. I dont do much Profibus anymore, but if I did I would definetely buy one.


Where was this common ground located?
 
I'm assuming you have considered this possibility . . .
But I was injecting problems into a Profibus network so I could document what various problems caused what symptoms. And I switched a terminator switch to 'On' and wrote down my problems. Then when I switched it 'Off' again while the indicator read 'Off' it acted like it was still 'On'. (No Profibus communications beyond that point . . . ) Damn flaky little switch.

I also found that I could read a voltage level on the wires - and find a difference between where it worked and where it didn't.
Poet.
 
In case the real culprit isnt found, then you could consider to drop the speed from 1.5M to 187.5k. At 187.5k, Profibus is much more forgiving. Of course the TTR increases accordingly, but in many applications that is not so important.

If the above does not help, try to switch the Profibus Profile to User Defined, and then increase Retry Limit from 1 to 3. That will make the network much more resilient against noise, but it does mean it can freeze for 3xTTR when it encounters bus problems.
 
We never did find the problem. We decided to feed the slave unit with another slave, VFD combo down the line and it worked ok. The previous machines work only if we keep the last switch in the "OFF" position. I'm baffled by this but, it is what it is, I guess. I tried a new Profibus DP option unit on the Yaskawa V1000 VFD with no difference either.

At any rate all is well with a work around rather than a fix. :unsure:
 

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