The October 2007 issue of NUTS & VOLTS magazine has an article on tilt 
switches. The tilt switches (non-mercury, uses ball) are available from 
Electronix Express.

Peter Todd wrote:
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> On Fri, Nov 16, 2007 at 09:33:02AM -0500, Timothy J. Weber wrote:
>   
>> - An interesting solution to the same power switch problem I was 
>> studying with this project: <http://timothyweber.org/mancala> (also a 
>> 2xAA switcher for a portable device).  Olin's solution uses less weird 
>> hardware and cleverer firmware.  I think I was obsessing about having 
>> "no" current flowing while off; he's settled for "negligible" and made a 
>> much more elegant solution in the process - fewer parts, more 
>> flexibility in what's required for power-on.  I like it.
>>     
>
> I gotta agree with him too. I've designed two devices now that are fully
> sealed after manufacture, and need a one time activation to do their
> thing. After asking about no power latch circuits here on piclist, I
> settled with just having a pic in sleep mode waiting for that first
> button press. Both times I implemented the turn on with a reed switch
> and the turn on logic was that the reed switch had to be held closed by
> a magnet for 10s before ativation happened. The only problem I found was
> reed switches need the magnet fairly close to them to actually activate,
> for a device embedded in epoxy or acrylic it's tough to position them
> close enough.
>
> I'm thinking about ditching that setup for something a little more
> involved, but without magnet, namely mechanical tilt switches. Rotate
> the unit in a defined series of actions with timing. Problem is, as far
> as I can tell buying mechanical tilt switches is damn near impossible
> now. All digikey has is either very large ones for more industrial uses,
> or smaller photo sensor/hall effect based ones with current consumptions
> of at least 10uA, if not 20ma.
>
>
> Hmm... Just occured to me though... If you don't want your sensor to
> drain your battery, why not use a sensor that generates electricity for
> you? As in... solar. Looking at digikey I just noticed they have tiny
> solar cells in 8 and 16 pin SOIC packages for sensing and (according to
> the datasheet) trickle charging. With a 50uA short circuit current that 
> big lead acid might take a few decades, but it would be enough to 
> bootstrap a uC. That, or use one with one of the above 10uA tilt
> sensors! It'd make sure the device wasn't accidentally turned on during
> shipping!
>
>
> In any case, our Randy Glenn has one of those devices.. You turned it on
> yet? :)
>
> - -- 
> http://petertodd.org
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