Re: Kulago/Mauch DRO ISA quadrature feedback kit

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

Tim Goldstein wrote:

> > Dan has since emailed that confirmation.   Looks like the way to go.
> > The  LS7266R1  has  24 bit counters, so using a 0.1 um scale  I'm assuming
> > you'd  get (2**24 == 16777216  * .1e-6 = 1.67m)  ~ 66 inch travel.

24 bits seems perfectly adequate as .1um scales are pretty damn fine
giving a 66 inch travel which is pretty big.

> > The stepper controller brick posted here a few days ago by
> >  http://www.geckodrive.com  has a 200 KHz maximum step rate.
> >
> > What maximum typical step rate can EMC produce on a
> > 200 MHz (or 500Mz) Pentium?
>
> First to answer your question, I am running on an AMD K6-500 and can get
> speeds up to 90 ipm if everything is set just right. I have 5 tpi screws and
> a 2 to 1 belt drive run with a 200 step per revolution motor in half step
> mode, so that works out to 6000 steps per second.

or 4000 steps/inch == .00025" /step  which approximates the step size
required to match the   .000 196"    5um Redishaw scale pitch.   So if
around 6000 steps/sec was the max for a 500Mhz chip,  then gearing
down another 6.41 : 1  would match the  .000 039"   1um Redishaw
pitch (giving a max rate of 90 ipm/6.41 = 14 ipm) which is still ok for me.

The purpose of my gearing  down (for the big machine) is both for the
mechanical leverage (using a size 34 stepper motor to move an 80" table)
but also to match step size with the resolution of the 1um encoder
(ie speed is less important than resolution for my project).

Now 6000 half steps/sec = 3000 full steps/sec which may represent
the fastest your stepper wants to turn.   However, for the same
rpm with the 1/10 step (gecko microstep drive) now represents
EMC having to pump out 3,000*10 = 30,000 steps/sec

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 ?

Doug Fortune