Re: CNC Etch-A-Sketch, EggBot

Hi Bill, Ballendo,

That could work, if I follow you! And that reminds me, there are
"reflective optical switches", as used in the tach circuit, that would
be easy to use to digitize the surface of an egg. The MaxNC probe
doesn't use much pressure; I'm gonna chuck up an egg in my new sherline
4-jaw chuck mounted on a rotary table, and digitize it!

Ballendo, I had previously missed your comment, as copied below. Yes, a
cantileaver pen "tracker" would seem useful, however it imparts some
lateral motion as well as vertical motion to the pen.

Alan KM6VV


Bill Vance wrote:

>
> Just thinking about it, an optical sensor might be of use here. Normally, an
> optical cable Y connector is used for this version. Drill a tiny hole in the
> end of an LED, ans insert a piece of optical cable with a drop of clear cement
> on it, and let dry. Insert the other end into one of the top arms of the Y
> connector, and do the same thing to the other arm with an optical sensor diode/
> transistor. Attach more optical cable to the bottom arm of the Y, and use the
> other end for a sensor probe. When light from the LED is reflected from
> something close, a certain amount of light goes back up the cable to the sensor
> transistor, and gets electronically detected, outputting a signal.
>
> This is probably not quite accurate enough distance-wise, but a two cable
> version could be. Set it up such that the LED cable points light across the
> front of the tip of the sensor cable. When the sensor gets a reading you know
> that the tip is right next to where you want to be, and the pen needs only N
> silly millitweeters more travel to be in contact. When the signal goes away,
> it's time to bring it back down before continuing. Dead simple.
>
> Bill
>
> On Thu Jan 3 17:21:46 2002, ballendo, <ballendo@...> wrote:
>
> >Alan,
> >
> >The simple thing is to use a parallelogram (think rear
> >derailler,10speed) on the "pen" axis...
> >
> >Hi-tech would be to sense the surface, either by contact/retract (not
> >good as it marks up the egg!) or with a small "angular laser"
> >distance module...
> >
> >Hope this helps.
> >
> >Ballendo
> >
> >> > I'm wondering if any of our CAD/CAM *EGGHEADS* can suggest ways
> >to track
> >> > an egg's surface?
> >> >
> >> > Alan KM6VV