# Wireless devices go battery-free with new communication technique



## ekim68 (Jul 8, 2003)

> We might be one step closer to an Internet-of-things reality.
> 
> University of Washington engineers have created a new wireless communication system that allows devices to interact with each other without relying on batteries or wires for power.
> 
> The new communication technique, which the researchers call ambient backscatter, takes advantage of the TV and cellular transmissions that already surround us around the clock. Two devices communicate with each other by reflecting the existing signals to exchange information. The researchers built small, battery-free devices with antennas that can detect, harness and reflect a TV signal, which then is picked up by other similar devices.


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## Ent (Apr 11, 2009)

I don't get it; it might not take power to transmit (dubious, it should still take energy to change state and adjust how things are reflected) but it surely needs power to do ordinary computing things. That is; supposing a phone uses this tech to send an SMS when the battery fails, you've lost power to the rest of the phone's systems (including, for example, the RAM that was holding the text of the SMS).


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## TheShooter93 (Jul 10, 2008)

I think the technology is far off from having some of the practical implications the article describes.

It's cool to see the beginning of it though -- interesting that it's even possible.


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## ekim68 (Jul 8, 2003)

As an aside, when I was young in the early 1960's they had little crystal radios that had one wire that clipped to metal pipes or grounds in your house, and when we put our ear to the radio we could the local radio station, not loud, but.......


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## ekim68 (Jul 8, 2003)

Of course it could have included the power source of the signal provided by the Radio Station, hmmm.....


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## Rob Pearson (Jul 10, 2003)

ekim68 said:


> As an aside, when I was young in the early 1960's they had little crystal radios that had one wire that clipped to metal pipes or grounds in your house, and when we put our ear to the radio we could the local radio station, not loud, but.......


I think I have an old crystal radio heath kit stored away some where that I never got around to putting together... You were correct -- no batteries.



> "Unlike other types of receivers a crystal set uses no batteries or power-line supply, therefore the sound that emerges from the head phones is derived entirely from radio energy picked up by the antenna. Use a long high antenna and a ground connection to a cold water pipe."


See images below...

















Image source here -- Awesome website btw with LOTS of plans on how to create more radios than just that standard one shown above.

Page title: Crystal Radio Plans and Circuits and parts of books ...This section contains 174 articles at the present time (articles are numbered) Many articles have multiple plans!

That reason right there is why it's so annoying that it's taken us so long to "figure out" how to obtain wireless electricity. Especially when Tesla was totally on top of the issue but his research on it never surfaced after his death and although he was totally brilliant I can't believe it's taken innovators this long to start showing serious prototypes of the proposed solutions... *blah*


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