Such a coil with a capacitor tuned to 60Hz (or 50Hz) would resonate so
well that it may be able to be recitified and fed directly to the
shutdown input of the average switching regulator.  Some of these
regulators consume fewer than a few dozen microamps in shutdown.  Think
of it as a large transformer, the primary being the house wiring, with
the device's coil as the secondary.

-Adam

Ronald van Aalst wrote:

>It might. I do know that recently a VLF receiver was proposed in the
>hobby mag "elector" that consisted of nothing more than a large coil stuck
>in
>your pc soundcard.
>The main fuss was to get away far enough from power lines because it
>picked up that hum so wonderfully well.
>have a look at www.vlf.it and www.lwca.org
>
>it seems to me that all you need is a coil and a preamp, and maybe
>an analog filter (as opposed to some fourier stuff done in the chip)
>
>I wonder how you want to test it, though. it might not detect local outages
>(like
>the fuse at home).
>
>Regards,
>Ronald van Aalst
>
>
>
>
>>Can a battery-powered device with no AC line connection sense a power
>>
>>
>failure
>
>
>>by noticing the LACK of any 60Hz pickup?  Given sufficient care in battery
>>life preservation, that would make possible "stick up" emergency lighting
>>that didn't need to be connected to anything, which would be quite a neat
>>idea, IMHO...
>>
>>
>
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