From: Harold Hallikainen <harold@mai.hallikainen.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Tue, 4 Feb 2020 13:14:34 -0800
Subject: Re: [EE] Power transmission
Thread-Topic: [EE] Power transmission
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True. However, this would reduce efficiency since the FET drain would see
a sine wave. An interesting approach I've seen in broadcast transmitters
is class F amplifiers where harmonic filters are added between the
transistor and the output. This is shown, for example, at
https://etd.ohiolink.edu/!etd.send_file?accession=3Dwright1422547511&dispos=
ition=3Dinline#page=3D15
.. This allows the transistor to have a square wave (drain voltage zero
when current high, drain current zero when drain voltage high) while the
output is a sine wave.

Harold


> A high q resonant circuit should help
>
> On Tue, Feb 4, 2020, 12:32 PM Harold Hallikainen
> <harold@mai.hallikainen.org>
> wrote:
>
>> I wonder about radio interference with several watts of 250 kHz square
>> wave. One nice thing about the Linear Technology designs (at Analog
>> Devices) is that they comply with EMC requirements.
>>
>> Harold
>>
>> > If you want to set up something simple for a test you need a mosfet
>> > driver,
>> > a coil of 20awg or so wire, about 30 turns in a coil about 3 inches
>> > across,
>> > a coil with about 200uh , a 200pf cap and a schottky diode.  That is
>> the
>> > sending parts and the receiving part is a coil as close to the first
>> 30
>> > turn coil in size and shape.  I can post more details if interested .
>> This
>> > will transfer about 3 watts using a frequency of 250khz  over a
>> distance
>> > of
>> > about 1 inch.   Of course you also need a frequency generator with
>> square
>> > wave output.    The most important part is the coils, the better the q
>> the
>> > more efficient it will be.
>> >
>> >
>> > On Mon, Feb 3, 2020, 5:44 PM Neil <picdude3@narwani.org> wrote:
>> >
>> >> I'm tinkering with power transmission for getting power from behind a
>> >> wall panel to in front.  For now I'm just experimenting with the
>> idea,
>> >> but I can't find much info on the relationship between coil diameter,
>> >> wire diameter, number of turns, frequency, and distance.
>> >> Anyone here know anything about this?
>> >>
>> >> Cheers,
>> >> -Neil.
>> >>
>> >>
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