> >  Joe,
> >   As an alarm designer (fortunately it was a long time ago)
>
> It's your lucky Vasile, you may have the privilege of helping me ;-)
>
> I've got a little alarm project for a small vehicle that needs a
> movement detector and have day-dreamed about it for a day
> or two. It's a senior school project for a group of  young ladies
> (yes, I know, get over it) -
>
> Anyhoo....
>
> "We are SWIPE, a Young Enterprise team. Young Enterprise is
> a learning experience for secondary school students. They have to
> form a company; become directors; develop products and services,
> which they then have to market and sell"
>
> Someone they approached suggested mercury tilt switches, but in
> my limited experience with tilt switches, they aren't all that sensitive
> and aren't very good for detecting motion, like a small vehicle being
> moved. I've suggested that a pendulum trigger would be better.
> Simply a hanging wire in a ring (both gold-plated) that would sway,
> as it has far less inertia than a mercury switch (even if the mercury
> switch is set at some teetering angle). The wire/ring is how the TILT
> switches in pinball machines started off. And they work - I've lost
> many a 20p being too energetic


Have a look at the vibration sensors from Signal Quest ( P/N SQ-SEN-003P /
3PS / 3PS-XL)  http://www.signalquest.com/

They're basicaly a ball in cage design, but all the parts are gold plated
and sealed. I used some in another project - my only complaint would have to
be price, about $5 US ea in low quantities. But I'm sure they'd send a few
samples if you told them what you're doing.

There's also some app notes from Analog about using an accelerometer for
automotive alarm applications - but I don't have a link handy.

-Denny

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