> >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

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