h a l f b a k e r yOn the one hand, true. On the other hand, bollocks.
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Back in the 1990s, I had a pretty little battery-powered
swing-a-ma-bob decoration. Only problem, it ran down
batteries in an egregiously ungreen way, so I cobbled
together an AC-to-DV power source for it using an unused
block plug, and rather than the typical soldered-on
connections and plugs,
some flat bits of copper and
sections of wood dowel that snapped in place of the
original AAA batteries, and insulated ribbon wire thin and
flexible enough to pass the edge of the battery
compartment cover.
Happy with the (which ran constantly for nearly a decade
‘til wearing its plastic swingy bits to ruin), I had ambitions
of packaging (more slickly than bare wood and copper) and
selling the arrangement in a world-changing
entrepreneurial tour de force, but being pretty a flea-
market-grade entrepreneur, if that, never realized it. A
bit of googling suggests that nobody else did, either, or if
they did, didn’t rise to fame and fortune from it.
Nice as this snap-in-place-of-batteries external power
system is, it has a downside of turning a pretty desktop
decoration into a pretty decoration with a thin cord
running from it to a wall socket. So instead of that, this:
same-size battery replacement powered by ambient wifi
signals.
A quick source check suggests this is asking a lot – a
typical wifi receiver has about 0.0001 W received power,
while a nominal 6200 J AAA battery discharged over 60
days gives 0.0012 W – but maybe not too much.
This idea is at best a silly variation on a serious,
promising idea in the oh-so-sexy internet of things family
of ideas
Mobile Gadgets That Connect to Wi-Fi without a Battery
http://www.technolo...-without-a-battery/
Aug 2014 MIT Tech Review story with some serious thoughts on Wifi power [CraigD, Oct 11 2014]
Swinging Sticks Kinetic Energy Sculpture
http://www.thinkgeek.com/product/e060/
A product page for arguably the best loved swing-a-ma-bob decoration much sold to date [CraigD, Oct 11 2014]
Wifi power harvesting
http://www.pratt.du...ergy-electric-power
I doubt this will fit in your device. [sdk16420, Oct 13 2014]
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Annotation:
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100 uW, but then there are conversion losses as well. You're
describing a crystal set, but operating at 2.4Ghz, where parasitic
capacitance has huge effects. And 802.11 uses a GPSK
modulation schema that spreads the energy over a frequency
range. |
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It's doable, but you need a local CW transmitter with a tight
frequency control and no modulation. Good luck getting a
frequency out of the FCC or the DTI for that. |
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A magnetron would be a good cheap-and-cheerful source, but
you'd have to hold the power way down - in the milliwatt range-
to avoid undesireable surface heating effects. And it's pretty
directional. |
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There might be some scope in the 27Mhz AM band in some
jurisdictions. |
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I love it when you talk like that. |
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I had to fan myself a bit too. |
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But back to the idea: I like a crystal set powered by
your own wifi. Wifi bases must differ in power.
Surely the big ones for convention centers have
more oomph than the one over there by the piano.
Or take a regular wifi and turn it up to 11? |
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I suspect that the original device described here is
one of those apes that pedal along a tightrope. |
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