h a l f b a k e r yAssume a hemispherical cow.
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Not sure if this was previously submitted.
Why not a blanket with just one wire (standard 110V plug-in) to work like this:
Simple chip embedded in the blanket, and two (R/L) bluetooth controls
The controls would be used set the side heated and the heat settings which transmit to the blanket
chip
Blanket
chip would send Side and Heat settings to the blanket
I can't see anything but 110V for the blanket because battery life would be too short.
Truly wireless heating
http://www.fda.gov/...uides/ucm071626.htm
[mouseposture, Jan 22 2011, last modified Jan 25 2015]
Ahem...
http://www.halfbake...0Electric_20Blanket
[21 Quest, Jan 22 2011]
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The thing is, it's a bit inefficient to heat the blanket itself,
especially since the elements are insulated from the
sleeper by the inner layer of the blanket. |
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The human body has a resistance of a few tens of kOhms
(depending on lots of things). If you wanted 50W of
heating (adequate, considering a wasteful electric blanket
is 100W), then passing 700V between the hands (or, for
more uniform heating, maybe from feet to hands) would
be much more efficient. |
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You probably want DC, to avoid twitching. |
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//to avoid twitching// and fibrillation.
[MB] I see you're proposing a constant-voltage source. It'll
only
be DC if the
resistance is constant. Notoriously difficult to control the
impedance at the electrode-tissue interface with surface
electrodes. So I
recommend needle electrodes, that penetrate half a
millimeter or so below the skin. Lots of them, because,
being pointy, they have, individually, a bit of a high
impedance themselves. |
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I picture something resembling an
electrified bed of nails. |
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I think you could cope with a variable skin resistance - the
driver electronics could modulate the voltage accordingly. |
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Alternatively, you could use an extremely high-frequency
current which, I think, travels preferentially on the surface
of a conductor. This would generate the heat where we are
most accustomed to feeling it. |
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//the driver electronics could modulate the voltage
accordingly// Yes, that's a constant- *current* source (not
to
be confused with currant sauce). With that arrangement,
you couldn't control exactly where the heat actually went
(but, with surface
electrodes, I'm pretty sure most of it would be at the
point
of contact between electrode & skin, causing burns). |
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The high frequency idea is
interesting, and, in fact, maybe baked <link> |
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//Yes, that's a constant- *current* source// |
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No, we'd want a constant *power* source (which is just as
easy to make). |
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