Connecting the encoder index for a third axis

[NRocco]

I am having some trouble indexing an axis on our PCI-7344 card.  It is connected to a UMI-7764 breakout box.  The first two axis (#1 and #2) both work fine. They are tuned and finding the Index position properly.  The third axis (#3) is counting properly but not finding the index.  We have checked our phasing to make sure A and B are both low when the index is triggered to low.  We can see the index on a scope from the breakout box.  The controller doesn’t stop on the index position when we run the find index routine.  Under the encoder settings we have tried various encoder “Line State Polarities,” and under reference settings we have tried various “Index Reference Criteria.”

We have also attempted to configure the encoders on Axis #4 without any luck.

Thanks,

Nick

[Jochen]

It's hard to tell from remote what's wrong here as you have done so much testing already. If you haven't done that already, please connect your motion I/O signals from axis 1 or 2 to the connectors for axis 3. Does find index work on axis 3 now? Please try also to connect your motor and encoder that you have been trying to connect to axis 3 to axis 1 or 2. Does it work in this setup?

Best regards,

Jochen Klier
National Instruments Germany

[NRocco]

Hi Jochen,

I moved the working motor and encoder on axis 1 to axis 3 and the index was found correctly.  Then I moved the troublesome motor and encoder from axis 3 to axis 1.  It continues to miss the index even though the scope shows index nod low when A and B are both low.

Thanks,

Nick

[Jochen]

Nick,

at least this tells us that the board is not broken. So there must be a difference in the encoder's signal compared to the encoders of the working axis.
You wrote that you can see that the index is low while A and B are low, too. The standard Index Reference Criteria is Index is high while A and B are low. So if your signals never hit this state the index can't be found (e. g. if the index pulse of this encoder is much shorter than the index pulse of the other encoders). You can change these settings in the Encoder Settings menue in MAX.



I hope that helps,

Jochen

Message Edited by Jochen on 06-13-2006 08:53 AM

[NRocco]

Hi Jochen,

Thanks for answering my posting.  I was able to find the index with my existing setup but I had to increase the filter frequency to 25.6MHz.  12.8MHz also works but nothing lower.  I am not sure what noise the filter is cleaning but my index is working.

Thanks,

Nick