Re: [CAD_CAM_EDM_DRO] Low cost DRO innerds

Alan Rothenbush wrote:

>Has anyone taken apart one of those low cost single axis 6"-12"-18" etc
>DROs sold all the time on eBay ?
>
>Specifically, is there a point where the raw quadrature is "extractable" ?
>
>

These are the things that are basically digital calipers without the
jaws? No, they don't work
on the same principle. The beam has a row of copper squares isolated
from the surrounding
metal by a 2 mm wide square gap. The squares are every 10 - 15 mm along
the beam. This
is just an etched piece of PC board material glues to the beam. The
sliding part has a piece
of PC board with the chip and display mounted to it, but the back of the
board is in very
close proximity to the beam. This PC board has a row of 25 or so
vertical stripes that
move across the place where the squares are. It uses the capacitive
coupling between
the stripes due to the presence of the squares to detect position.
Obviously, some type
of interpolation is used to detect position to .01mm or .001"

>I probably could do what I need via the SPC port, but that would mean decoding
>the SPC output .. being lazy, I'd rather do it the "traditional" way.
>
>

Well, the 'traditional' signals just aren't there. They may exist
somewhere inside the chip.
in fact, but they are not brought out, to my knowledge.

Jon