Steal power from the air

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Steal power from the air

Postby edugimeno » December 14th, 2016, 2:08 am

Hi!
Has anyone had any experience with "stealing" power from the air? Radiowaves/radiation/etc...

I was thinking of some idea to power a really low power circuit (3.6v, 25nA->90nW) and the name "joule thief" came to my head
When I googled "joule thief effect" I realized it was about to squeeze the last 0.5v-1v from a dead battery, stepping it up to 3 or 5v to power a led or something

What I was thinking of is some sort of coil (+ a rectifier and capacitor) that gathers power enough to generate 90nW. Seems like a small power but I don't really know if its achievable

So I was wondering if anyone has ever experienced with this topic to share his thoughts about it before I try anything (maybe it's just undoable)

Thank you!
edugimeno
 
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Joined: February 5th, 2016, 2:40 am

Re: Steal power from the air

Postby bandersnatch » December 14th, 2016, 3:06 am

Hi,

Yeah, there is so much EM smog in the air that grabbing some of this for your own use seems like a good idea.

In some places the EM fields are strong enough to light up flourescent tubes
( https://www.youtube.com/watch?v=cXhZvyGtMrk)

From a more practical perspective, this is exactly how RFID systems work.
The RFID transponder uses the RF field of the reader to generate enough power to send its code.
The generated power is tiny but just enough to drive the transponder circuit
G$$gle for "homebrew rfid transponder" for examples on how to drive circuits "from the ether" (!)
(e.g. http://makezine.com/2010/01/22/diy-soft ... rfid-tags/)

The main problem with "generically" grabbing power from the air is the huge variation of EM intensity
and frequency depending on your location.
Sitting under a 110,000 volt transmission line or outside your local radio station is likely to succeed...
50/60Hz EM fields are omnipresent in normal homes but you are gonna need a HUGE antenna (!) ;^)))
(Although the "ugly bags, mostly water" known as humans pick this up pretty well, just grab the input
of your stereo amp & crank up the volume...)

It depends on the power you need but I reckon its gonna be really difficult to come up with something that
works anywhere...

STFB.
bandersnatch
 
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Re: Steal power from the air

Postby asheets » December 14th, 2016, 6:14 pm

longwire, hooked up to a crystal radio, hooked up to a joule thief. YMMV
asheets
 
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Joined: February 17th, 2011, 4:30 pm


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