Wireless Power Transfer

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Have have an interesting problem.

I need to transfer power (7V @ 20mA approx. 140mW) across a 2-3 inch
air gap without using a wire.

It will be in a high vibration and dirty (ie. greasy, oilly)
evironment.

Here are my ideas:

1) create an air gap transformer

2) use super bright LED's and a Solar panel

Does any one have any experience or knowledge in this area that could
offer some ideas and literature sources on implementing this.

Thanks,

Eric


Re: Wireless Power Transfer

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That would seem to indicate that your idea

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is a non-starter.  Light transmission and "greasy, oily" don't mix.

Setting aside really crazy ideas (directed air or liquid flow, cathode
ray tube, ...), magnetic power coupling, i.e. an air coil transformer,
is probably the only available option.

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

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I've seen a solid state laser used to transmit light on an optical fiber.
The output of the optical fiber illuminated a solar cell to provide local
power for a wide bandwidth active antenna.  The fiber optic solution for
powering the antenna was used to avoid contaminating the near-field of the
antenna and effectively de-tuning it.  This worked, but there wasn't any
grease to deal with.

If this is not rotating machinery, why don't you use an armored cable.  If
it is rotating machinery, then use something like a distributor in an
automobile.



Re: Wireless Power Transfer



Eric wrote:
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Convert the vibrational energy into electrical energy.





Re: Wireless Power Transfer
Hello Eric,

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Those are always the best, aren't they?

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That's the ticket. Make yourself familiar with series resonant
converters and their use in contactless power transfer. The essence of
this technology is that while the leakage inductance of your transformer
becomes huge with increasing distances it is more or less neutralized by
turning it into part of a series resonant circuit. TI carries lots of
the previous Unitrode chips that can be used to regulate the frequency.

You didn't say whether the other side needs to be regulated. Probably
not. If it does then the frequency typcially is varied to achieve this.

2-3 inches is a stretch but you could start out with fairly large
diameter core halves of a pot core. #77 material, Kaschke K2004 or
similar. Sometimes they offer a split plastic bobbin carrier which is
nice, saves you the trip to the machine shop.

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Sounds like brute force, lots of space and $$. Definitely not a viable
option in an oily and greasy environment. Panels may not like too much
vibration either.

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Use Google to find papers on "Inductively Coupled Power Transfer" and
similar topics. Lots of medical apps where they have to go through human
skin and tissue. I forgot the titles but there were some excellent
papers by Benedetti et al. back in the 90's. I believe they went up to
70mm which sounds like your distance goal.

The University of Auckland (New Zealand) has done a fair amount of
research in this area. You will have to become very familiar with
magnetics and switch mode power supply design if you go that route
alone. The good news is that your target power level is wimpy compared
to what we usually deal with. So if your transistors miss the zero
voltage switch point you won't have to have the fire department come out ;-)

Regards, Joerg

http://www.analogconsultants.com

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How much surface area do you have available for TX-RX on both sides ??
boB


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Have you looked at batteries as an option?


Re: Wireless Power Transfer
On 16 Aug, in article

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The main things you don't say

1/  Do both sides vibrate synchronously or asynchrously

2/  Is vibration constant due to operation of environment or like
    driving a car over a pot hole?

3/  What temperature range

4/  Size/volume constraints

5/  Inside or external environment or other special environments like
    aviation, automotive.

There are many ways to transfer or generate power but it depends on the
environment, becuase if this is constantly vibrating you could even consider
a 'shaker' genarator and rechargeable battery, like the shaker torches
that can be got. Similar in energy saving to clockwork radios, wind up
battery chargers etc..

140mW (7V @ 20mA) is similar power to a small torch.

Also if any other movements like circular motions could be used to
generate secondary power.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Wireless Power Transfer

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     Synchronously for the most part

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Like a car driving over a pot hole... the Vibration is a function of
the  environment this vehicle is in.

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-20 to +60 C

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Not really... smaller than a bread box.

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it is to be mounted on a peice of industrial equipment

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The 140mW doesn't have to be constant... because I was planning on
using this power to trickle charge a battery.

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Re: Wireless Power Transfer
Maybe Nikola Tesla has the answer?  :)


Re: Wireless Power Transfer

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Good reply.

Dan


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I think that by the time you get done with some exotic power coupling
system you would be way ahead to use a rechargable battery pack that is
easy to replace.  A typical laptop battery is 4000 mAH or more and 10 to
12 volts.  A battery like this would meet the requirement for a week.
Not nearly as interesting.

Dave Rooney


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