RE: [CAD_CAM_EDM_DRO] Home switches.

One slight correction; that should have read "don't have to worry TO
MUCH about index/limit deadband". I wrote this with optical/hall limits in
mind, not thinking mechanical switches. When you setup a motor/limit/index
system test your limit switches for hysteresis; how far the index pulse is
from the state change and how consistence it is. If it's too close (less
that 1/4 turn) bump the limit over, if it's inconsistent (more than 1/2
turn) get new limits. Preferably optical but that's dependent on the
environment, Hall if you can guarantee that there won't be exposure to metal
chips, and lastly a really good enclosed mechanical one (Allen Bradley).
Of course all of this assumes you have a relatively backlash free
system. What's relative? The difference between what's limit switch
hysteresis and what's backlash?

-----Original Message-----

The software would have to be pretty quick on the draw to catch that
index pulse. Unless you read the limit switch, stop on state change, and
then slowly reverse until index pulse is seen. -OR- Stop on limit switch
state change, slowly rev until limit switch releases, then very slowly fwd
until index pulse is seen.
I prefer the later because it guarantees that you will always detect
correct index pulse because, you're always approaching the index pulse in
the same direction, plus you don't have to worry about index/limit deadband
(hysteresis, with no etymological link to hysterical for those women reading
the list) if you take the motor encoder apart.
Note: that the limit switch range could be several encoder rotations
wide.

Jack
www.lonestarobservatory.org