Subject:
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Re: What is RPM of Gear Motor???
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 7 Jul 1999 06:40:07 GMT
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Viewed:
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1018 times
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My memory is a bit fuzzy here since it was a while back, but according to
my notes...
* sensors are sampled every 3ms
* rotation sensor is a quadrature encoder with a 4:1 gearing in front of
it (one rotation of the axle yields 16 "ticks").
* sensor decoding software only handles +1/-1 tick. Opposite quadrant is
ignored (more sophisticated software could assume 2 in the previous
direction in this case, but Lego didn't think of that).
In order to never miss a "tick", sensor would have to keep up with ticks.
3ms per tick means 333.33 ticks per second = 20,000 ticks per minute =
1250 rpm.
This is all just theory, and could be wrong if I messed up on something
like the sensor sampling frequency, etc. I do however remember having
some trouble with the rotation sensor keeping up with 1750 rpm. I'll try
to reproduce this again.
Just curious - how are you getting 15,000 rpm - and what are you using it
for? Most of my stuff requires lots of torque so I'm always gearing down,
not up!
Dave
In article <Pine.SOL.3.91.990706225951.9139A-100000@bio3.acpub.duke.edu>,
Luis Villa <liv@duke.edu> wrote:
> On Tue, 6 Jul 1999, Dave Baum wrote:
> >
> > Keep checking the math. I clocked the motor at 330 - 350 rpm. I used the
> > rotation sensor driven directly by the motor. From analysis of the RCX
> > firmware, the rotation sensor should be accurate to 1250 rpm, so I'm
> > pretty confident of it being in the 350 range.
>
>
> Dave-
> Where are you getting that 1250 rpm upper limit from? While I haven't
> counted exactly yet, I'm dropping only 20 counts out of every
> thousand at ~15,000 rpm. I had assumed this was mainly gear slop,
> since it only appears to occur while driving the rotor in one direction
> and then stopping violently, which lets my gearing assembly roll a little
> bit even after the driving arm has bee stopped. Let me know about your
> analysis-
> Luis
>
> #######################################################################
>
> Profanity is the one language that all programmers understand.
> -Anonymous
>
> #######################################################################
> --
> Did you check the web site first?: http://www.crynwr.com/lego-robotics
--
reply to: dbaum at enteract dot com
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Message has 1 Reply:
 | | Re: What is RPM of Gear Motor???
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| (...) Oh! Math mistake on my part... 16 instead of 4. Hmm... the ~15K was an off the top of the head estimate, which would go down to ~4K if divided by four again like it should be :) I'll have exact numbers some time today. Like I said, it is (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: What is RPM of Gear Motor???
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| (...) Dave- Where are you getting that 1250 rpm upper limit from? While I haven't counted exactly yet, I'm dropping only 20 counts out of every thousand at ~15,000 rpm. I had assumed this was mainly gear slop, since it only appears to occur while (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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