Alt-BEAM Archive
Message #13428
To: beam@sgiblab.sgi.com
From: Jean auBois aubois@trail.com
Date: Fri, 14 Apr 2000 20:37:30 -0600
Subject: Re: Solar powered pendulumn project
At 09:16 PM 4/14/00 -0400, Jeffrey wrote:
>The PM-1 from Mike Tilden--a super-cap and timing network
>contraption--looks like a fun little circuit and may be suited for
>this application.
I can think of a couple of bits:
1) Using a photointerrupter (LED/photodiode pair) to control the current
dumping trigger circuit. If the plumb is thin and flat with regard to the
plane of motion the sensor could be positioned underneath, with one element
on either side, the plumb causing the interruption. I think I've even seen
an aluminum circle used for this, counting on eddy currents to produce the
necessary magnetic field. If you thought it advisable, two sensors could
be used -- one on either side of dead bottom to make sure the "push" is in
the right direction -- if either of them times out ("another circuit" as
you say) perhaps it could then choose one coil for the initial push.
2) Don't presume that the pendulum will start by itself -- this may
actually be a problem if you run out of power. However, the idea above
might be helpful.
3) There is a lot of really ugly metal sculpture down in Santa Fe, New
Mexico that depends on very free pendulum motion. Even though I think some
of it is grotesque, I've got to admit that they've got the mechanics down
really well. Whatever damping force there is (friction, air resistance) is
extremely low and permits motion to continue for a very long time after you
push it.
All told it sounds like a cool idea.
jab
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