
Plates vs. Coils – An alternative approach to wireless power transmission - luu
http://wp.josh.com/2015/07/11/the-other-way-to-do-wireless-power-capacitive-power-transmision-proof-of-concept/
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weland
> Q: What is the relative efficiency of the two systems? > A: I don’t really
> care for this proof of concept.

Looks like he'll have a ton of fun _after_ this proof of concept...

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somberi
From the last issue of The Economist (Edited by me):

"..a company called Wibotic that plans to recharge drones (and also earthbound
robots) without them having to establish an awkward physical connection with a
plug.... LaserMotive, another Seattle-based company, .. is developing a system
designed to replenish the batteries of drones that are still aloft, using
lasers and photovoltaic cells..

Wibotic’s answer is to use tuned electrical circuits in place of simple
transmitting and receiving coils. When such circuits are tuned to the same
resonan"t frequency, they exchange energy more efficiently. That permits power
to be transferred over distances up to the diameter of the coils, or even
slightly farther."

Reference : [http://www.economist.com/news/science-and-
technology/2165613...](http://www.economist.com/news/science-and-
technology/21656134-electronics-has-already-cut-data-cord-can-it-now-cut-
power-cord)

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kwhitefoot
>Note that we only need one LED for the inductive coil since there is a loop
though the coils, so the electrons can keep going around and around in the
same direction and never get trapped. Nonsense. The current in the secondary
coil is caused the changing the magnetic field. This cannot keep changing
indefinitely in the same direction so the current in the primary that
generates the magnetic field must be alternating and then so will the current
in the secondary.

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ksrm
The second LED is required for the capacitive example because without it all
of the charge would eventually accumulate on one plate. This isn't a problem
with the coil as there is a complete circuit for the charge to move around.

He is not saying the magnetic field is not alternating (he even says the coil
is being driven by a 1 MHz sine wave). The current in the coil is _not_
alternating, because of the LED.

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kwhitefoot
I see your point, and I was a bit hasty, very embarrassing.

That'll teach me to just skim an article quickly.

