Re: [CAD_CAM_EDM_DRO] Re: Simple DRO sensors - Cheap !

> $30???!!!
> I went to the site, and the "A2" was listed at $270!
> Could you please provide a part number? I am really eager to set up
> dros on my machines (and then do CNC), but I am just getting into
> this roll your own stuff...

Go back to www.usdigital.com and look around some more. There are
some in the <$50 range which mount on existing shafts and thus don't
have their own expensive bearings and don't need a shaft coupling..
They will also sell you the mylar code wheel for around $10 and the
read head for $25 or so, you build your own mountings.

They also cary linear encoder strip, but making protective housings is
a real pain. Their new EM-1 readhead module was still 'coming soon'
when I called them last week... tried to impress upon them that
getting the 500 lines/inch (2000 pulses/inch) resolution out the door
should be a priority as us experimental CNC'ers would snap those up
eagerly.

You can also scrounge a similar rotary encoder (with the same pinout)
from an HP500-series deskjet printer, but it must be one of the older
ones as the later ones have a low-res mylar strip stretched across them
that the printhead carriage reads directly.

Seeing as you will need to get these signals into the computer, do you
know about the Kulaga/Mauch interface board? This is based on the
LS7266 chip which US digital sells, but far cheaper than any of their
interfaces. See http://www.seanet.com/~dmauch

Chris

> Thanks,.
>
> --- In CAD_CAM_EDM_DRO@y..., Doug Fortune <pentam@h...> wrote:
> > Mark Taft wrote:
> > >
> > > Has anyone found any cheap sensors that can be used to make a
> home brew dro
> >
> > http://www.usdigital.com has high-resolution rotary encoders for
> > about $30 and also high resolution linear encoders for about the
> > same price (the linear 'tape' is $2/inch).
> >
> > As was pointed out by Dave WC0H yesterday, USDigital is coming out
> > with 500 LPI linear strips and encoders (giving 1/(4*500) ==
> 1/2000"
> > resolution in quadrature).
> >
> > Dave 'the newbie' Lantz wrote:
> > >um.... sorry, but what does 'DRO' stand for?
> >
> > 'Digital Read-Out'
> >
> > However in this list when they say 'DRO' usually they mean
> > TTL logic quadrature decoder.
> >
> > Thus the Kulaga/Mauch DRO board is more accurately a
> > TTL logic quadrature decoder ISA board (used perhaps
> > to display a Digital Read Out on a computer screen and/or
> > provide encoder feedback to EMC (a gcode interpreter program).
> > I always make the distinction by calling it a quadrature
> > decoder board (not a DRO board), because DRO display might
> > not be the purpose of the installation of the board.
> >
> > Sometimes on this list 'setting up a table for DRO' actually
> > means installing axes position encoders (either rotary
> > encoders on the screws, to deduce where the table might be,
> > or linear encoders alongside each axis to directly measure
> > where the table is).
> >
> > BTW, quadrature refers to a pair of logic square waves,
> > offset by 90 degrees. When there is movement, not only
> > can you tell the amount of movement by counting the transitions,
> > but you can also tell the direction (left or right) by
> > observing the sequence of changes.
> >
> > Doug Fortune
> > http://www.cncKITS.com
>
>
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-------------------------------------------------
Christopher C. Stratton
Engineer, Instrument Maker, and Horn Player
ccs@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html