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I had an idea (which probably isn't original) that electronics could harness power from a signal or a wave (like a radio wave) or a ray or something like that instead of having to charge or buy batteries. How possible is this and what could be used to do this?

This would be along the lines of solar powered electronics, but what about other sources? Something that works like a solar panel that collects the rays or waves and converts it into electricity. Is there anything like this available or being worked on? Even something that used to be worked on but was forgotten.

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  • \$\begingroup\$ There is a way of energy theft from the power lines, using essentially the transformer effect when the primary "coil" is the power line and the secondary is your device. I repeat, it can be qualified as theft, since energy is not coming out of nowhere but produced for a specific purpose. \$\endgroup\$ – Eugene Sh. Apr 25 '17 at 15:10
  • \$\begingroup\$ Well Teslas experiments were surely one of the earliest tries to wireless power. If you think more along the line of a radio signal, there were people around using fluorescent lamps in garden sheds in front of large radio stations using the power harvested from the radio signal. This is not allowed in Germany however (like Eugene said it's thievery). And NFC is basically the same, you use the power of the electromagnetic field to activate the NFC chip. \$\endgroup\$ – Arsenal Apr 25 '17 at 15:35
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    \$\begingroup\$ There's not enough energy available from the devices to make capturing ambient RF worthwhile. The transmitter might send out 1Watt, but you can only capture a tiny (like 1/1000) part of that at best. \$\endgroup\$ – JRE Apr 25 '17 at 15:39
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    \$\begingroup\$ @JRE there's some interesting stuff in research that may or may not pan out, but definitely somebody believes in them. Things like sensors that use nano/microwatt average power, get their power from RF, and transmit using backscatter modulation of that same RF. \$\endgroup\$ – hobbs Apr 25 '17 at 18:16
  • \$\begingroup\$ The Russians did something like this during the Cold War: en.wikipedia.org/wiki/The_Thing_(listening_device) \$\endgroup\$ – altomnr Apr 25 '17 at 19:16
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The original "crystal set" AM radios were powered entirely by the received radio signal. You can still get crystal set kits today, though most replace the crystal with a modern signal diode.

See Wikipedia

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Essentially that's how RFID works, the chips in your debit/credit cards and so on. Those devices derive power from a transmitted wave and modulate it to return the read data.

The size of commercial transmitters for radio and TV are based upon the typical received signal strength within their intended coverage area. They're not spending any more money on transmitted energy than they need to. And radio waves carry little energy by the time they've travelled any reasonable distance, the losses are significant.

The closest domestic product I can think of that does what you say is the wireless mobile phone charger, of which I have several. They manage to travel a centimetre or so but put phone and charger apart any distance and nothing travels.

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