Free Batteries?

[alisarhangpour]

Is it possible to convert electromagnetic waves around into a free power supply? (Not a MegaWatt one of course!)
I've heard about some circuits which do so...
Thanks, Ali

 

[Sebi]

Yes, if You live nearby a middle-wawe transmitter (over a kW), with tuned aerial - possible lighting.
Many years ago i've built a receiver (MW) without battery.

 

[alisarhangpour]

Any circuit diagrams? :?:
Thanks Again, Ali

 

[Nigel Goodwin]

Any circuit diagrams? :?:
Thanks Again, Ali

You just need a tuned circuit, and tap off at a suitable low impedance for what you want to drive.

But you need to be VERY close to a VERY high power transmitter.

The radio Sebi mentioned is called a 'crystal set', they simply use a tuned circuit and a rectifer, feeding either high impedance (2000 ohm) headphones, or a crystal earpiece.

The very early domestic radios were like that (before valves), the rectifier was a piece of crystal, and you made contact to it with a 'cats whisker', a very fine piece of wire - apparently the skill was in finding a sensitive part of the crystal. I'm sure searching for 'crystal set' will find loads of hits!.

 

[tansis]

Solar cells are getting cheaper to buy but you
can build your own, this link is for titanium oxide versions..
https://www.solideas.com/solrcell/english.html

An even simpler method does exist that uses cuperous oxide
but the power output is very small.
https://scitoys.com/scitoys/scitoys/echem/echem2.html#solarcell