Re: digitizer arm, w/ encoder?

Dave, Ballendo and the list,

I've been kicking around several sensors since the "center finder"
thread of a few weeks ago (yes I have and can now use a center
finder!). Strain gage, electrical contact, a "last word" connected to
an encoder disk, and latest, the photo-interrupter. Rudy's "Shop
Wisdom" book shows making a "dial indicator", an arm on a spring for
mechanical advantage from tip movement. SO... with the extra travel
(.5"?) of the "hand", I think the vane could cut the photo sw. fairly
fast. It might be practical, single axis of travel.

The mirror is a good idea! Let me think about that a little. 2 or 3
directions, probably not with this design. The strain gage could
probably give a couple of degrees of freedom. A clockwork gear
advantage (like a dial indicator) could directly turn an encoder wheel,
and would give mills of change. Lets see, can one even FIND a
mechanical watch for some small gears? Must give more thought! Any
clock makers out there?

Alan


dave engvall wrote:

>
> ballendo@... wrote:
>
> > Alan, list,
> >
> > The issue to solve with this probe, IMO, is how to allow 3 direction
> > sensing while accomodating overtravel. This way you can treat it like
> > a home switch. Probe 'til state change.(quickly) then retract and
> > probe for position (more slowly). Just some thoughts.
> >
> > Ballendo
> >
> > >I wonder if a "photo-interrupter" could be used? A little deflection
> > >would move the vain/tip out of the light path. Wouldn't give mills
> > >of deflection, but could still be useful.
> > >Alan
> >
> > Nice Idea!
> >
>
> Indeed it is!
> First time I read this post I though Alan was suggesting something else...use the indicator gear to move a mirror...on to or away
> from a sensor. i.e a led beam bounces off the mirror and is focused on a phototransistor. Might be more sensitive than the
> photo-interrupter.
>
> Dave
>
> ps. the real trick will any device like this is to minimize the tangential deflection upon contact. (long bearing surface on the
> probe ?)
>
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