Re: [CAD_CAM_EDM_DRO] Re[2]: digitising arm

HI,

I think I might have a play about with this sometime soon as it seems
interesting but I think I would be inclined to take a slightly different
approach. How would it be if we used a light but stiff wire (piece of music
wire) glued onto one end of the Xtal out of a phonograph needle assembly and
glued the other end to a stout mount. Then we could use the Xtal as the
resonant element in a simple oscillator and monitor the change in frequency
as the Xtal deformed under side loading and have a logic circuit to trigger
at a certain deviation thus indicating contact with the surface. In
principle it looks as though this could be very accurate as a very small
change in frequency could be detected. The Xtal would need a shielding tube
with just a small opening for the sensing wire to protect it from excessive
flexing (ham-fisted use!). These Xtals are really sensitive and easily
obtained cheaply - a few years ago I built myself a couple of microphones
using them to listen to watch ticks. All I did was to glue just one end of
the Xtal element to the watch movement holder leaving the other end free to
vibrate in air, and coupled up the wires to a simple amplifier. Even the
smallest ladies watch produces enough vibration through the mass of the
movement holder to give a loud tick at the loudspeaker simply by shaking the
Xtal.

Perhaps this is a daft idea - perhaps it would be an ideal 'PIC' project -
what do you think?

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk

----- Original Message -----
From: <ballendo@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
> Alan wrote:
> >About twenty+ years ago, we had "sonic digitizers" (2D) for use in
> >Radiation Therapy<snip>3d versions, and used a stylus which created