Reverse limit switch always active.

[ecouser]

Dear NI,
we have a problem in one NI driver board, specifically the model MID-7604.

In our lab we have two of these boards: one worked regularly for years, we are trying to setup the second one using it in the same systems (positioning with 3 axes).
We replied the cabling of the working board in the second one, but we have this issue.

The issue is: 2 axes work regularly forward and backward, but the third axis doesn't move backward because we always detect active "Reverse limit switch is active".
The behaviour is the same using our moving software or NI Max software.

Do you think the issue can be more software related or HW-cabling type?
Is there some further test we can try?

Thanks for the attention.

[ValeS]

Good afternoon, sorry for the delay in the reply.

If the limit is not phisically reached, the problem could be due to the Reverse Limit Switch, as you can see in figure 10 (pag 16) of the following document:

http://www.ni.com/pdf/manuals/372454g.pdf

During normal work, the switches should be closed, so the pin are connected to digital ground. If the switch is open the limit is active. Could you check if the switch related to the Reverse Limit Pin is open or closed? If you can't establish it, you can connect through a wire the Reverse Limit Pin directly to digital ground and see if the third axes moves backward.

[ben64]

It may just be a reverse polarity. You can change it in MAX, go to the Motion I/O settings for this axis and change the reverse limit switch polarity to active high or active low.

Ben64

[ecouser]

Thanks all for the replies,

the SW configuration was good as expected.

The reason was an unplugged capacitor in the rear cabling of the board: once replugged the capacitor, the NI board started to work in the correct way: very good result!

I hope your replies can help someone else.

Thanks a lot.