Re: which commercial linear scale for EMC?

[Jon Elson <jmelson-at-artsci.wustl.edu>]

Doug Fortune wrote:

> I'm sure this has been answered before (ie before
> I joined the list), but it looks like I will be needing
> to get direct linear feedback into EMC.    A separate
> digital display head (such as in Dan Mauches' kit) is
> obviously redundant and so I'd like to avoid the DRO's.
>
> How is this done?  Serial port(s)?

Serial ports are too slow and not deterministic enough, in
general, for this application.  You need an encoder counter
card.  The Servo-to-Go card is currently supported.  I believe
that a cheaper, ISA-bus encoder counter card is either just now
supported, or will be, soon.

>  I would obviously
> like to go for a more inexpensive homebrew arrangement
> if it is immediately available and debugged, however
> time constraints may shortly be critical.  Anything
> 1 thou or better is sufficient.

The Servo-to-Go card is a little over $800 for a 4-axis card.
You also get a lot of digital I/O, plus analog output for servo
amps and analog input, which is not currently used in EMC, but
could be in the future.

> In that case, which commercial systems are known
> to be compatable with Linux/EMC?  The XYZ travels
> are 52"x15"x20" (on a Heckert FU-400V).

I don't know what you mean by commercial systems.  Do you mean
the whole motion package, motors, stepper drivers or servo amps,
and linear scales?  There really isn't anything that is a complete,
turnkey package at this time for EMC.  I am working on some
parts of that, but it is not ready yet.

> Future expandability to a 4th and 5axis would be nice too.

For only a slight increase in price, there is an 8-channel servo-to-go
card.

Jon