Re: Digitizer probe progress

OK, the probe itself is screwed into a hub and from this hub protrude
three metal arms. These arms are insulated electrically. Each arm
sits between two bearings and hence makes an electrical connection
between them. The PCB clamps down onto the balls, holding them in
place and also making an electrical connection to them. There are
two wires from the probe one connects to one part of the pcb which
goes to just one of the balls, the current goes from the pcb to ball
to rod to ball ... until it leaves by the other wire.

i.e.

Wire
pcb
ball-rod-ball
pcb
ball-rod-ball
pcb
ball-rod-ball
pcb
wire

So if the probe tilts in any direction or is pushed up then the
circuit is broken and the computer knows to stop moving. The hub is
held against the contacts using a spring BTW.

I have uploaded pics of results now, see my other post.

Graham









--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Wayne C. Gramlich"
<Yahoo@G...> wrote:

> Graham:
>
> Every time I've looked at the digitizer.pdf file, I wind
> shaking my head and saying "I don't get it!" I guess some
> sort of electrical circuit is supposed to be made or broken,
> but I can't figure out how the circuit is supposed to operate.
> Could you explain where the wires are supposed to go, and
> what causes the circuit to be completed/broken? Am I correct
> in assuming that the goal of this digitizer probe is to
> detect any deflection in X and Y and deflection in one
> direction on Z? Any edification would be greatly appreciated.
>
> Thanks in advance,
>
> -Wayne
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler"

<eexgs@n...>

> wrote:
> > Just a quick post to say that I have my digitizer probe working.

It

> > is based on the one in the files section drawn by Carlos

Guillermo.

> > The file is digitizer.pdf.
> >
> > Based on this I built the digitizer out of Delrin on my little
> > Proxxon mill. I had been looking for 2mm ball bearings for the
> > pivots and eventually got these from smallparts.com (shame about

the

> > $25 postage, grrr). The probe works really well although I am
> > disappointed that I did not manage to get the probe part

concentric

> > with the shaft that is held by the mill collet. This means it is
> > only good for digitizing rather than edge finding etc. I may

rectify

> > this in the future and it was a function of my workmanship rather
> > than the design.
>
> [snip]