On Fri, Jan 19, 2007 at 12:22:11PM -0500, M. Adam Davis wrote:
> Out of curiosity (I like to have examples for when standard practices
> don't meet the requirements) what about this application precludes
> using a small plastic strip installed between the battery or cell and
> the contact that is pulled out when one wants to activate the unit?
> Given the button, mechanical action is necessary to start it, so why
> must it be a push motion instead of a grab, pull, and discard motion?

Easier mechanical design really. I also figured the device might be more
reliable in the long term if once activated, there is absolutely no
contacts or what not that could concievably corrode. As it is the
battery will be one with solder tabs on it, directly attached to the
PCB, and the whole thing (minus the switch!) will probably end up
encapsulated in polyester resin.

Aw heck, just reminds me, gotta find out if polyester resin is at all
conductive!

> I don't know if this idea would work or not, but note that some PIC
> pins don't have protection diodes, but can still be used as I/O.
> Attach the power input to an I/O without protection diodes, then use a
> button to temporarily power the PIC which turns the I/O output high.
> The I/O then shunts the power into the positive rail.
> 
> I haven't thought through the physics of running the I/O backwards
> like that - it may be a non-starter right out of the gate.  In other
> words, "This exercise left to the reader."

Great minds think alike, actually I think what you are describing is on
the piclist site already, under power supplies.

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