Re: Kulago/Mauch DRO ISA quadrature feedback kit

[Doug Fortune <pentam-at-home.com>]

Matt Shaver wrote:

> > From: Doug Fortune <pentam-at-home.com>
> > > > What maximum typical step rate can EMC produce on a
> > > > 200 MHz (or 500Mz) Pentium?
> <...>
> > So I return to my original question: how many steps/sec can
> > EMC pump out?   I think RTL has a limit of around 100,000
> > interrupts per second (with a 500Mhz processor),  and these
> > are probably shared among the 3 channels, so perhaps EMC
> > can keep up with 30,000 steps/sec per channel.
> >
> > Can anyone here with microstep drives confirm a higher
> > step rate than 6,000/sec ?
>
> >From a previous post of mine to the CAD_CAM_EDM_DRO list:
>
> > > What step rate can be expected with the present EMC software?
> >
> > It can step up to about 50kHz, but it's only usable (for me) up to 4-5kHz
> > because each successive increasing step is larger than the last. Since
> > stepper motor torque drops off as RPM increases, at some point the motors
> > won't be able to make the jump to the next speed (frequency). I have a nice
> > Excel spreadsheet that shows this effect if you're (or anyone is)
> interested:
> > http://users.erols.com/mshaver/stepfreq.xls
>
> On a 350MHzP2 I could run with PERIOD = 11, you might do better on a
> 500MHzP3. Plug this number into the spreadsheet and you'll see the effect I'm
> talking about.

Ok, I know there is a limit to how fast you can step a stepper (in rpm).  But the
point is that maximum (in rpm) could be  X fullsteps, or 2X halfsteps,
10X (1/10 micro steps) or 256 X (1/256 microsteps) - it won't affect
the top speed of the motor (but more microsteps will give a smoother
rotation) - but at some point at the same maximum rpm (but more of smaller
microsteps) then EMC on a 500Mhz processor is going to stall.

Anyway, for now I'll guess its in the range of 10KHz - 50KHz steps/sec
running 3 channels on a 500 MHz processor.

Doug Fortune