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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Tue, 13 Jul 1999 23:29:38 GMT
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Original-From:
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Luis Villa <LIV@avoidspamDUKE.EDU>
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Viewed:
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919 times
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On Tue, 13 Jul 1999, Dave Baum wrote:
>
> 650 ticks per second works out to about 1.5 ms per tick. I didn't think
> the RCX sampled inputs that fast - I thought it was 3.0 ms per sample. If
> so, this would mean that the RCX is capable of adding 2 to the rotation
> value during a single sample.
Nope-it's not. I use LegOS, and that only adds 1- I know that particular
section of code inside and out. Therefore, it must be the sampling time.
Or a really egregious error on my part.
> I'll have to look at the code again and see
> what I missed.
>
> The idea would be that you remember the direction of the last change (and
> assume some arbitrary one first off)...
<snips much code>
>
> If you're just slightly above 1 delta per sample period, then the
> occasional delta of 2 will get accumulated just fine. As you approach 2x
> the sample frequency, things start to get risky. An "instant" reverse
> will continue to count in the old direction.
Yes, but at this speed, you mainly need to count speed anyway, not total
rotations, so that small instant reverse probably won't damage your code
too much. Since we run out of ticks very quickly (less than one minute)
we can probably assume that knowing the wrong direction/speed for 1.5ms
won't hurt. Of course, that is only for my application :)
> Of course you could probably
> work out the system mechanically such that change of direction and a delta
> of 2 could never happen in the same sample period.
Uhuh. I has assumed that the easiest way would be to tell the code "you
are turning in direction X" and then reset it if there is an anticipated
change in direction.
Always in favor of new experiments-
Luis
#######################################################################
Profanity is the one language that all programmers understand.
-Anonymous
#######################################################################
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | Re: What is RPM of Gear Motor???
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| In article (...) I don't know anything about legOS - perhaps it has its own sensor sampling code. I was looking through the standard Lego firmware to determine the 1250 rpm number, and I verified it with a few experiments, but again using standard (...) (25 years ago, 14-Jul-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: What is RPM of Gear Motor???
|
| In article (...) 650 ticks per second works out to about 1.5 ms per tick. I didn't think the RCX sampled inputs that fast - I thought it was 3.0 ms per sample. If so, this would mean that the RCX is capable of adding 2 to the rotation value during a (...) (25 years ago, 13-Jul-99, to lugnet.robotics)
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