RE: [CAD_CAM_EDM_DRO] digitizer debouncing

Alan -

The Renishaw model I've laid out has about 1/4" overtravel in X-Y
(depends on probe length), and about 1/16" in Z. I can't imagine
the probing routine would want to overtravel any more than a
couple thou., however, especially at those low speeds. Any more
overtravel, and it would have to backtrack after every move in
order to maintain high resolution. The accel/deccel should be set
to a fairly high value, IMO, in order to finish the scan sometime
this century. This is where the probe needs to be very rigid and
light, and the overtravel/switch contact spring needs to be fairly
stiff. Any (appreciable) oscillation at the probe tip would cause
a different kind of "bounce" we'd have to debounce. Can you see
what happens if you deccel within .001-.002" in your setup?

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Alan Marconett KM6VV [mailto:KM6VV@...]
Sent: Tuesday, January 16, 2001 2:37 PM
To: CAD_CAM_EDM_DRO@egroups.com
Subject: [CAD_CAM_EDM_DRO] Re: digitizer debouncing

Roman,

I have to disagree here. 555 timers are lousy anyway, there are
better
"timer" parts. What may be needed is a schmitt trigger, something
like
the old 74LS14 I've mentioned before. No caps across the
contacts. Run
5-20 ma. (1K pull-up) through the contacts.

The real "debounce" is in the software! If you sample the line
periodically (between steps), and take action on the 1ST one (and
only
the 1ST one), you have all the debounce you need.

Did it this last weekend. No GATES/TIMERS! Last night I got the
position latched, and decelerated afterwards to a stop. Did this
repeatedly, with good results. Which raises a question. How much
OVER
TRAVEL do we have with the Renishaw "model" we are building? My
little
micro switch got a little "up tight" with a longer deceleration!

Alan KM6VV