Mike W wrote:

> 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.

  I've seen similar, with one edge of the piezo disk soldered to the board, the
other edge had a longish bolt (at least the diameter of the piezo element),
soldered perpendicular to the disk surface.

  Works in three axis because piezo twist will register as well.

  Probably works out the cheapest option, but not the easiest (or cheapest
timewise) to manufacture if you need to make many, because human assembly is
required.

  It also could require a relatively subsantial amount of space depending on
how small the case needs to be and how the piezo element is mounted.  (the end
of the bolt can't be resting against anything of course)

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