Re: following error question

[Jon Elson <elson-at-pico-systems.com>]

Ray Henry wrote:

>
> I can understand why you want to make input_scale large.  It will
> integrate to a voltage better but with any EMC stepper module you quickly
> run up against the max pulse rate that your PC can spit out.  I'm certain
> that I don't understand the relationship but it seems to me that In this
> case, a max_velocity of four units per second and 40K pulses per unit
> means that your PC will need to spit out 160KHz for a rapid.

If this is true, I think he had better forget using software-generated step
pulses.  I can't imagine any CPU and parallel port able to handle that.
Even with a PERIOD set to .000003 (3 microseconds) the steps would
have to jump between 166.667 KHz and 111.111 KHz (two ticks per
step and 3 ticks/step) which sounds pretty rough.  That's a 33% jump in
rate!  I don't know if Gecko
drives can handle this sort of step rate.  I know some high-end
microstepping
drive can do it, at a high cost.  I guess a digital servo drive, in general,
can
do it, though.

But, for generating the step pulses, my universal servo board would be
what he needs (if these calculations of step rate are correct).  Running on
the
10 MHz standard clock rate, it would be dividing by 62 to get 161290
steps/sec,
or dropping down to a divisor of 63, to get 158730 steps/sec.  That is a
difference
of 2560 Hz, or 1.5 %, which should be acceptable to most drives.  This still

requires the driver to accept step pulse widths down to about 3 uS.

Of course, if one needed finer resolution, the clock rate could be easily
turned
up by a factor of 4 to 6 very easily.

Jon