Re: [CAD_CAM_EDM_DRO] Simple DRO sensors - Cheap !

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