[Noisebridge-discuss] Long-lived, battery-powered AVRs

[e at eden2.com]

If you want to use a magnet, could you just use a reed switch?

On Jan 30, 2012, at 1:09 PM, Jonathan Lassoff <jof at thejof.com> wrote:

> On Mon, Jan 30, 2012 at 11:42 AM, Casey Callendrello <c1 at caseyc.net> wrote:
>> What about using the gate latch to trigger a Polou switch?
>> (http://www.sparkfun.com/products/8903). This was used by the famous
>> Reverse Geocache to save battery life. It's a clever little switch that
>> can be used to let a microcontroller turn itself off. When off, it draws
>> (according to spec) .01ua.
> 
> That's more or less perfect for an application like this, though I
> think it may not be a good contender, physically. Since this is to
> detect a gate swinging open and shut, we were thinking of placing a
> small coil-based sensor on the frame and a neodymium magnet on the
> swinging gate.
> 
> Thank you everyone for some excellent suggestions. Sleeping the AVR
> seems like the way to go, but waking it back up will be the trick.
> Since I hope to use the small charge that will build as the magnet
> passes over the coil, I was hoping to flip a small transistor. The
> only problem I'm having is finding something that will trip with just
> the slightest charge.
> Would it be crazy to try and bias the gate of a small MOSFET so that
> it's nearly triggered?
> 
> --j
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