'POWER from AIR' backscatter tech now juices up Internet of Stuff Wi-Fi gizmos Researchers who last year demonstrated they could harvest stray RF signals to power RFID tags have scaled-up their technology to power Wi-Fi devices. The University of Washington team is pitching their ultra low-power “backscatter harvesting” technology with the inevitable Internet of Things (IoT) tag, since if it could be …
Health and safety laws around the world limit the allowable level of 'background' radio signals to something of the order of a few watts per square meter, weak but potentially usable with skill.
Solar cells + batteries are cheap, easy and much, much more powerful (unless you live underground).
I rest my case m'lud.
You are right, the Health and Safety people should do something to regulate the output of the Daystar. I don't see why we should pay to maintain such a potentially high level of background radiation when millions of users experience daily outages, for hours at a time even. Who is running this thing anyway?
It was used in WW2 for remotely powered spy microphones. A carbon microphone in the middle of a dipole antenna (hidden in an enemy office) AM modulated a RF carrier, which is detected with a (remote) receiver. The point being you did not have to access the office again to change batteries.
I recollect this from an old magazine article, someone else also recollects this:
http://www.vintage-radio.net/forum/showthread.php?t=64056
The individual remote boxes (window sensors, IR etc) ate batteries..
Frankly if the IoT is going to take off people won't want the huge PITA of changing batteries, all of which will no doubt be different between different products, making buying them in bulk to do a mass replace impossible.
o.k. I can see that would work for one sensor but what happens if you have 2 or 20 such devices in the same wifi zone. Interference and increased overhead as every IOT will need a mac type address.
If IOT is going to catch on you could have hundreds of devices within a WiFi zone!
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