Dampen the ping pong ball, then when on unleveled ground, the system would
slowly orientate itself.

Bill

----- Original Message ----- 
From: "Bradley Ferguson" <bradleyee@gmail.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Tuesday, May 31, 2005 2:52 PM
Subject: Re: [EE]:Trembler/tilt switch


> On 5/31/05, Jinx <joecolquitt@clear.net.nz> wrote:
> > > >Ball-bearing + ping pong ball + UGN3503 + magnet
> >
> > > Looks good.  How well does it work if the vehicle is tilted when the
> > > alarm is armed?
> >
> > So far so good. I'm looking at various ball bearing sizes to find what
the
> > optimum size is. Too small and it will be attracted too much to the
magnet
> > and not wobble enough with small movements. Big-ish (eg 8mm) seems to
> > be better. With any size, there's very little friction between the steel
and
> > the celluloid, so magnetic attraction is mostly the damping factor. My
only
> > concern would be the life-time of a celluloid ping pong ball, both due
to
> > material break-down and the bashing it's going to get from a ball
bearing,
> > but almost any other small plastic ball with a smooth regular inside
surface
> > will do. I've added an op amp for AC gain and a little HF noise
reduction.
> > The UGN3503 output  is very stable so it can be cranked up with gain
> > and changes detected with a narrow adjustable 12F675 ADC window
>
> The ball bearing could be damped with a fluid, which would also
> prevent damage to the ping-pong ball.  I would think silicone oil,
> which is available in different viscosities, might be a good choice;
> although, there may be material incompatibilities, the damping will
> change with temperature, and it's messy.
>
> I like this design, though.  And with the addition of more sensors you
> could know the tilt in multiple directions.  It would be an
> interesting project, but at some point an accelerometer seems better
> suited cost and size-wise.  It would be interesting to compare the two
> methods side-by-side, though.
>
> Bradley
>
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