Everyday Practical Electronics http://www.epemag.wimborne.co.uk/ (or one of
its predecessors) had a design some time ago which Magenta Electronics still
sell as a kit http://www.magenta2000.co.uk/kits/864.htm .
If I can find the time I will try and find the original article. It would
appear to be pre 1996 from the quick look I have taken.

Regards
Chris

----- Original Message -----
From: "Reginald Neale" <rneale@MAIL2.NYROC.RR.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, September 02, 2000 6:26 PM
Subject: Re: [EE] Simple direction sensing


>    Brian asked:
>
> >As a simple project for my local radio club I've designed a PIC
> >Magic Wand that flashes 7 LEDs leaving a trailing message in the
> >air. The flashing (ie message) is triggered by motion sensored by a
> >mercury switch.
> >
> >Works fine if you wave right to left but moving left to right the
> >message is mirror imaged (of course).
> >
> >Any ideas on a simple (and cheap) method of detecting whether
> >motion is left-right or right-left so I can invert the message as
> >appropriate. 2 mecury switches mounted in some way so that the
> >leading edge triggered first seems the obvious solution but how to
> >actually implement this?
>
>
>    I have seen a commercial implementation of this that used a
>    piezo element for motion sensing. One part of the disc was
>    anchored to the circuit board. The center electrode had a
>    piece of circuit board fastened to it with a lump of solder
>    at one end. Presumably this acted as an inertial sensor;
>    generating positive volts for waving in one direction and
>    negative in the other.
>
>
>    Reg Neale
>
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