On 10/25/23 08:24, Todd Zuercher wrote:
Hello,
It is my understanding that the step pulses generated by Mesa cards are always
the minimum pulse length set by for example hm2_5i25.0.stepgen.00.steplen, only
the space between the pulses is varied by the step rate, is that correct?
I was reading the manual for the new drive I was planning to use in my next
build and see that the drive calls a preference of a 50% duty cycle for step
pulse inputs. I am guessing that it may have something to do with how the
drive's pulse filtering system works, such that for maximum noise filtering and
step reliability having the pulse length be approximately equal to the step
spacing gives the best results.
So my questions are; Would it be possible to make a Mesa card output a 50%
duty cycle step pattern instead of the current default pattern? And would
doing this even be worth the effort?
Do yopu have a link to that doc?
In the drives I've played with using a function generator, a near 50%
ratio can help when pushing the drive limits, but generally the speed of
the opto-isolator is the ultimate limit, blurring the pulse into almost
unrecognizable signals, slowed by the response times of the opto device
used. For real dependability at 200 khz and up to the failure of the
opto, usually around 375khz, trimming a wee bit one side or the other
might get a motor with no load, just laying on the table some good,
getting it upto 2000 revs but unless the motor voltage is also cranked
uo, torque to do actual work at that speed is just a dream at 45 volts.
Some of the nextgen closed loop drivers can use 90-140 volts, overcoming
the windings inductance much faster, That makes it possible to make
usable torque at 3000 revs. Those higher performance transistors do
raise the price a bit. Particularly in the 3 phase versions. But they
run like casper the ghost is turning the cranks, Quiet.
> Todd Zuercher
P. Graham Dunn Inc.<http://www.pgrahamdunn.com/index.php>
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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