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...
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