Re: mounting encoder with pulley

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
<spadnos@s...> wrote:

> Fred Smith wrote:
>
> >If the motor voltage fits within a 30vdc 5 amp rating, the DeskCNC
> >SV-500 with firmware build 7 will run 70,000 sps in 1X mode

(280,000

> >at the encoder).
> >
> >Fred Smith - IMService
> >
> >
> Well - it doesn't quite fit in that range - it's a 40V, 5.5A

continuous,

> 30A peak motor.
>
> Also, the SV-500 spec sheet I found says the step limit is 256

kHz. I

> would have assumed that's in encoder counts or multiplied steps,

not

The problem with building a divider for the encoder signal is that
you are actually dealing with two channels. Their relationship to
each other determines direction. Simple divider circuits (flop flop
or binary divider chips) would probably alter the phase relationship
with the two channels. The output of a channel gives squarewaves that
vary in width depending on the rotation speed. There is a
transision on the rising waveform and another transision on the
falling edge. The two sensors are ofset from each other so the
depending on the direction of rotation, the signal leads/lags the
other. You have to maintain that phase relationship. It might be
possible to build a circuit that ignores the trailing edge
transisiton on both signals and divides everything in half. Who
knows, you migh be able to further divide those signals down as long
as the phase relationship is maintained. On the other hand the
fastest and cheapest way might to be to find another servo motor with
an encoder count of 250 or 500. The last possibility is to shaft
couple a 100 count encoder to the back of the servo motor (if you
remove the existing encoder). I don't think belt coupling a rotary
encoder is the answer since they are not designed for even light
radial loading. You can get lower count rotary encoders from US
Digital at a reasonable cost.

> input steps.
>
> I'm not limited by the step generation rate - I have a USC from Jon
> Elson, which can do 300k pps (probably more if I want to change the

driver).

>
> - Steve