On 7 Mar 04, at 11:26, Robert Young wrote:

> ----- Original Message -----
> From: "Denny Esterline" <firmware@TDS.NET>

> > I need some sensors to pick up vibration. Needs to be sensitive in
> > two axis, and capable of detecting being bumped with less than 1/8
> > inch movement. It'll feed a PIC so I can work with most any output,
> > but I only need a single pulse when it's bumped.

>
> I bought a cat toy that is a little ball, smaller than a golfball that
> has two flashing LEDs.  There is a small "vertical" wire soldered to
> the circuit board and around it is a coil of wire.  Normally the two
> don't touch but if you tap the ball they touch.  This triggers the
> flashing of the LEDs for the next 30 seconds.
>
> This may not be sensitive enough for you because you can pick up the
> ball and wave it around and it won't start to flash.  It seems to take
> a sharp movement to flex the coil.  With the ball on the floor I can
> tap it with my finger and it starts to flash.
>
I have seen a Piezo transducer, with a weight attached to its
centre, used to produce a movement detector.
 Two would give your 2 axis sensing. It might be worth a try.. the
ones I saw used were the very thin slivers of a transducer
commonly found in small telephone handsets and "musical"
greetings cards. The weight was a nut, about 0BA size, glued to
the centre of the Piezo disk.
hth, Mike

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