On Wednesday 17 December 2008, Tom wrote:
>Gene Heskett <gene.hesk...@...> writes:
>...
>
>> Speed display widget in axis? Any thoughts, suggestions?
>>
>> Thanks.
>
>Gene,
>
>I am using a pyVCP panel in Axis that has a spindle rpm bar, lifted from
>Anders Wallins generously provided ini and hal files on his web page here:
>http://www.anderswallin.net/category/cnc/emc/
Bookmarked, thanks.
>Thus far, I can display 0 to 4000 rpm in a nice steady green bar, but as
>the spindle speed increases above that point (my spindle goes up to
>6000 rpm), the bar (and the floating point value of the "rev-scaled"
>hal pin that it is linked to) starts to bounce between extreme negative
>and positive integers. My diagnosis was that the frequency of the incoming
> pulse stream (m5i20.0.enc-03-position) was too great (120kHz) to be scaled
> accurately in a slow thread.
So the counter in the m5120 is overflowing. Maybe a compromise with a faster
slow thread? I've obviously not walked there though.
>Here is the hal file configuration as provided by Anders:
>
># load ddt for rpm calc
>loadrt ddt count=1
>loadrt scale count=2
>
>addf ddt.0 slow-thread
>addf scale.0 slow-thread
>addf scale.1 servo-thread
>
># 500-line encoder gives 2000 pulses per rev
>setp m5i20.0.enc-03-scale -2000
Which (the m5i20) I don't have here, only (I assume anyway) the duty cycle of
the pwm being delivered to the PMDX-106. Or the digital value that sets that
pulse would (I assume, there's THAT word again) should also be
available/usable?
In my case, this controller is very stiff, and you cannot hear the difference
between running free at .15 amps to the motor, and loaded up and threatening
to blow the 2 amp fuse. It might drop 2 rpm over that load range, a change
in pitch I cannot hear over the other noises the gearhead emits, combined
with the fans that cool my 4 axis xylotex board. Std psu fans, running on 19
volts, not only do a great job of cooling it, they are flat out noisy too.
At one point, working on a bit of steel, I had to make an ammeter so I could
stop blowing fuses since those 5x20 fuses can rapidly eat ones lunch money
when you have to buy the shack out of them, and the job waits till they get
some more in 4-5 days.
># RPM = revolutions per minute
>net ddt-scale scale.0.gain
>sets ddt-scale 60
>
>
>net spindle-pos m5i20.0.enc-03-position
>net spindle-pos ddt.0.in
>
># spindle position to motion-control for threading
>net spindle-pos motion.spindle-revs
>net spindle-index-en motion.spindle-index-enable m5i20.0.enc-03-index-enable
>
>net rev-count ddt.0.out
>net rev-count scale.0.in
>net rev-scaled scale.0.out
>
>
># 2000 Hz corresponds to 5400 RPM
># so scale Hz values by 1/2.7
>net rpm-scale scale.1.gain
>sets rpm-scale 0.37037037
>
>Stephen and Sebastian suggested using a new pin in Hostmot2 (ver.2.2.8)
>called "encoder.03.velocity" instead of the "m5i20.0.enc-03-position" pin
>used in the example above. That should alleviate having to sample/scale
>it in a slow thread.
>I will try that tomorrow.
>
>Tom
I haven't groked how to put an encoder on that spindle yet. Probably only by
an idler gear arrangement inside the head. Below the head there is too much
dirt, and above it is of course the drawbar bolt. Perhaps there is room
between the top of the spindle and the gears for something maybe 1/4" thick,
but I have not measured it. Pretty cheap, shove it around for quietest gears
as you tighten it, motor mount and top plate. Needs to be made into a belt
drive with at least a 4 or 5/1 change ratio, the gears are only 2/1 ratio.
I do have room to play in that gearbox since the VSR drive is now in a
separate box with the PMDX-106.
Or throw money the missus will scream about at it & get an X3. :) If I do
that, she will have to have yet another sewing machine, probably one of those
$7K computerized ones. She only has 3 now, and only one of them has >2 hours
actual run time on it. A retired school teacher, she has problems with
the "house mouse" scene. :)
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
No character, however upright, is a match for constantly reiterated attacks,
however false.
-- Alexander Hamilton
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