Re: Insulating D-shell from chassis?

Randy,

I'm gonna disagree with those who say you shouldn't insulate your
dsub connector. At first, I was in that camp also; but here's what I
think may be being forgotten:

1) The computer cable with its preterminated ends may very likely
have the shell housing connected to the shield.

2) The xylotex drives do not have optoisolation.

3) If you ground the dsub at the control box (and 1 and 2 above are
true) you have connected the computer ground to your controller
ground. (Which is what we use optoisolators to avoid.)

So go ahead and leave things as they are, IMO.

FWIW, I use pc mount dsubs on my breakout boards, and cut a
rectangular hole in the housing the same size as the plastic around
the shell. Additionally, I am sure to have pcb mount holes and screws
close to the connector. The sum of these is to have an insulated dsub
that is strong "enough" and looks nice, with the added benefit of
easy manufacturability...

Hope this helps,

Ballendo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, zephyrus@r... wrote:
> At 11:14 PM 11/16/03 -0500, Dave wrote:
>
> >The last thing that you want to do is to isolate a chassis mounted
> >component from ground. My question is: do you know for sure that
you
> >have a ground loop?
>
> Oh yes, indeed. This is from the "random motor steps" discussion
from a
> month or two back. After properly star grounding the driver box,
using
> shielded motor cables (terminated only at the box end), making sure
I was
> using a proper parallel cable with all 25 leads and good shielding,
I was
> still getting occasional random steps on all 3 axes, especially
with the
> spindle motor running (oh, and I retrofitted the Sherline spindle
control
> box with a shielded power cord).
>
> Isolating the DB25 connector from the driver box chassis did the
trick. It
> is rock solid now.
>
> Best regards,
>
> Randy
>
> Randy Gordon-Gilmore ,----.___________ ______________
_________________
> ProtoTrains // = = === == || == == == = || == == ==
= == =|
> Rio Vista, CA, USA /-O==O------------o==o------------o==o----------
-o==o-'
> zephyrus@r... http://www.prototrains.com