Re: Position Readout Question and Introduction

acu-rite scales put out 5v half quad signals i have hooked up
rotary encoders to acurite readouts worked fine

mike

Matt Shaver wrote:

> From: "Matt Shaver" <mshaver@...>
>
> > From: George Potter <gpotter@...>
> > Is anyone using the output from a DRO as the position indicator in a
> > servo system. I've been contemplating this for quite some time, and
> > am fascinated (specially because I have the DRO installed on the Mill).
>
> It's done all the time on large cnc machine tools. What I mean is that the
> output from a linear scale system (such as Sony's Digiruler) is translated
> into a quadrature format that mimics the standard output of rotary
> encoders. This is then used as the source of position feedback to the cnc
> control. I once worked on a machine that had a Mitsubishi cnc control which
> had also been retrofitted with Sony scales. You could select from either
> feedback source by changing a parameter in software. The problem you will
> have with using a regular DRO this way is that the scales themselves don't
> present a useable output at their connectors. Additional circuitry inside
> the readout box amplifies and otherwise conditions the raw scale signals
> into essentially step and direction signals that it can count and display.
> Unfortunately, I don't know of any DRO maker that provides an output jack
> for auxiliary connections. It may be possible, with a little reverse
> engineering, to tap into the digital circuitry in the readout box to obtain
> a useable signal (abandon all warranty hope, ye who enter here!). You may
> get the idea to build your own scale to quadrature box, but AFAIK all the
> different scale makers have different, non-compatible scale electronics. It
> would also depend upon whether the scales are optical, capacitive,
> inductive, etc. The above mentioned Digiruler system can be had with
> quadrature output, but the cost makes further discussion inappropriate for
> the audience to which this mailing list is directed ;). There remains the
> linear encoder/mylar scale system available from http://www.usdigital.com
> which, despite its peculiar native resolution, is being successfully used
> by some other list members to achieve a do-it-yourself DRO setup. This is
> maybe the best, easiest method of achieving what you have in mind since the
> encoders used have quadrature outputs.
>
> Let us know more of your plans and you won't want for opinionated comments
> on them!
>
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