Subject:
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Re: Magnetic Levitator
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 8 Dec 2001 19:36:59 GMT
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Viewed:
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2241 times
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In lugnet.build, Mark-Jan Bastian writes:
> In lugnet.build, Christopher Snead writes:
> > Hello, everyone!
> >
> > I've finally finished a project for my Physics class:
> >
> > http://www.brickshelf.com/cgi-bin/gallery.cgi?f=8857
<Snip>
>
> Very cool! I was wondering, if you photographed the object using a
> flash, wouldn't the object drop a fraction of a second after that ?
The Phototransistor and diode are recessed deep inside the technic bricks,
which make very effective lightshields.
>
> Also, I understand that the light shines from the right side,
> and enters a photodiode on the left side (or the other way around).
> So, if the object is exactly in the middle, there is no
> relevant difference to measure, and neither if the object is getting
> too low.
The object is in the middle, but off of the axis formed by the phototransistor
and the diode. the object only partially intercepts the light beam.
>
> What are the highest frequencies you find on the output of the
> phototransistor ? This would give an indication if it was possible
> to do it all with an RCX, a lego lightsensor and lego lamp, with
> either a slow language like BrickCC, java, or LegOS. Oh, and you
> have to take into account the maximum sampling frequency of the
> light sensor. Since I read that the rotation sensor cannot be sampled
> with more than 300 Hz, there is probably a similar limitation for the
> light sensor. Dunno if this is hardware, or a timer value in software
> of the RCX firmware.
Without the dampening effects of the differentiator, the oscillations occur at
about 10-20 hz. With the oscilloscope, we couldn't discern any signals at
higher frequencies than this that weren't noise.
Chris
>
> Mark-Jan
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Message is in Reply To:
 | | Re: Magnetic Levitator
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| (...) Very cool! I was wondering, if you photographed the object using a flash, wouldn't the object drop a fraction of a second after that ? Also, I understand that the light shines from the right side, and enters a photodiode on the left side (or (...) (25 years ago, 8-Dec-01, to lugnet.build, lugnet.general)
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