Brian,

Not so cheap but ADXL202
http://www.analog.com/industry/iMEMS/products/ADXL202.html
looks like a good solid state solution.
Or, you can use a spring and 4 screws...
(use a fixed font to see the schematic)


                 0 <-screw/ground
                 | <-spring
                 |
    contact-> 0  | 0 <-contact/pulled-up
                 |
                 |
                 |
                 0 <-screw

stress or relax the spring as needed...

Hope this helps.

Ricardo Seixas


>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?
>
>Thanks
>
>Brian
>Brian E Jones
>Centre for Java Technology
>IBM HURSLEY

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