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In lugnet.build, Kevin Loch writes:
> This is awesome. What are you using for the control circuit? Any
> chance you could use an RCX?
I think that it would be possible to use an RCX. I used four op amps in my
circuit; the first amplifies the signal coming from the phototransistor, the
second differentiates the signal, the third takes the difference of the
proportional and differential signal (PD), and the last boosts the current via
a powere transistor.
Maybe it is possible to progam two of the RCX inputs to take the incoming
signal, and make one output combine them appropriately. It may even be
possible to use two Mindstorms light sensors to create the beam of light. The
only things that will need to be non-Lego are the electromagnet, and the power
supply (I don't think there is anyway of using an RCX to generate 400
milliamps)
I may try the RCX and the light sensors to do this one day (any of you
mindstorms guys know if this will work?)
anyway, thanks for looking!
Chris
> KL
>
> 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
> >
> > This device suspends small, ferromagnetic objects in midair using an
> > electromagnet and a beam of light. The beam of light shines on a
> > phototransistor, which translates via a control circuit into current to the
> > electromagnet. An object in the path of the beam reduces the amount of light
> > incident on the phototransistor. As the object falls, more light reaches the
> > phototransistor, and the magnet gets stronger; as the object moves towards • the
> > magnet, less light reaches the detector, translating into a weaker magnetic
> > field. The object reaches equilibruim, and hangs in midair!
> >
> > I used Lego to build the frame and the light shields. As it turns out, the
> > LED's and the phototransistors fit quite well into the technic holes. Using
> > Lego saved quite a bit of time, as opposed to machining an apparatus. It • also
> > allowed me to play with Lego while working on my final project! ;-)
> >
> > Sorry to all of the Purists out there - Lego does not yet make electromagnets
> > or Phototransistors or op-amps. Don't worry, I'll be back to building pure
> > Lego mecha in no time...
> >
> > Chris
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Message has 1 Reply:
 | | RE: Magnetic Levitator
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| We tried using the Handyboard (which is faster than RCX) and it could not do it. I think the RCX is not fast enough for UNSATBLE control systems such as magnetic levitation, etc. A while back, I proposed the inverted pendulum problem as a challenge, (...) (23 years ago, 7-Dec-01, to lugnet.robotics)
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