Re: which commercial linear scale for EMC & S2G card?

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

Doug Fortune wrote:

>
> > You need an encoder counter card.  The Servo-to-Go card is currently supported.
>
> I am assuming we are talking about a linear scale attached directly to
> each axis.  I understand the S2G card can count encoder blips
> but I had assumed that was for rotary encoders only,  attached
> to the screw (and hence not guaranteed to be reading the position
> of the table).   You are implying that linear encoders do the
> same thing as rotary encoders,  and that the S2G is compatable
> with them as well.

The STG card will work fine on any linear encoder that produces
TTL-level quadrature pulses.  If the encoder has an index channel,
it should only generate one pulse every inch or cm or so.  Then
a microswitch can be used to qualify the specific location you want
to be your home position.

The STG card can accept either single-ended or differential signals.
If the differential signal version is not much more expensive, you
should get that, as it is a bit more reliable.

If the encoder runs on 5 VDC at 150 mA or less, you can power it
from the STG card.

I know that Heidenhain and Sony make scales that will provide these
signals.

> Or in other words, I am to find out whose 52" linear scales are
> compatable with S2G's card.
>
> **** Can someone save me the "experimentalism" and recommend a
> vendor for the linear scales (which has been tested successfully with
> the S2G cards and Linux/EMC) ?   *****

Other than calling Servo-to-Go, I don't know where you could get this
info.  I don't know of anyone in the EMC community using linear
scales with the STG.

Jon