RE: [CAD_CAM_EDM_DRO] Looking for scale interprolator circut

It appeared that the manual had all the theory of operation that one
would need to conceptually construct an interpolator from linear
(sine/Cosine) scales.

The implementation inferred is to digitize sine and cosine, then
multiply them together(read the part that mentions arctan) yielding a
larger numeric range than just the digitizing allows. Implementation
must throw away enough numeric noise to ensure not dropping steps on
reasonable inputs. (or provide means to produce extra steps when a
missing step is noticed.)

A discrete HW implementations could be:
use two ADC 8 bit converters to generate a 16 bit address to a ROM;
Program the ROM to output an absolute rotational position (based on
arctan, like 16 bits wide?)
Have an up/down counter increment or decrement to track the absolute
position from the rom (ROM data and counter feed a comparator that
indicates inc/dec/nop). QUadrature is generated from up/down count
events.... (width of the ROM and up/down counter should match; and
number of unique rotational positions the ROM is programmed with
dictates how much interpolation is done)

Added logic probably needs to handle wrap conditions.
One could through away the tracking counter if inputs are clean enough
and/or you through away some precision and avoid possibility of missed
steps...

Depending on speed of ADC and a cpu, the algorithm can be SW...



-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of th.carel
Sent: Thursday, September 08, 2005 6:18 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Looking for scale interprolator circut

Trevor

Not a great cheap issue , sorry , I had the same problem
with 2 glass linear scales from heidenhain + the need for
an extra Z.
I found a used Metrologic DRO wich work with sinus scales
and send the data through the RS232 to the pc (configured as terminal)
Metrologic today ,are more interested with the laser barecode devices
,and
it could be an idea to contact and ask for an "old" used unit sinus
compatible ?
(CMM =MMT in french)
Check for Metrologic group , MMT and directly to a technician.
They send me the connectors data , the setting , and the protocole
description !
(a setting for signal multiplier is included)

2/check Ebay for a heidenhain dro , more common ,(I found my Z for 220
Euros.)

3/Heidehain provide also some converting magic box (Ebay ?)

4/ checking the sinus dro input (for to act as you) , I found the trick
but
,to
cut all the analogic input part ,shorting the hooking and connect
directly
to
the appropriate CI pins was too tiedous (but possible !)

I suspect (maybe I'm wrong) you plan to hook your sin rulers to Mach2/3
,
as me , I suggest an other issue , keep your rulers as original and
through
a dro interface , send the datas when the rs232 input protocole will be
fully enabled ..?

thierry

----- Original Message -----
From: "protman16" <protman16@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, September 06, 2005 7:54 PM
Subject: [CAD_CAM_EDM_DRO] Looking for scale interprolator circut


> Group,
>
> Does anyone have information where I can find an interpolation
> circuit
> for converting a sine-cosine linear scale signal to square wave
> quadrature signal?
> Ideally the circuit would also have selectable multiplier for the
> output.
>
> Trevor
>
>
>
>
>
>
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if you have trouble.
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sister site to the CCED group, as many of the same members are there,
for OT subjects, that are not allowed on the CCED list.

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