web.mit.edu/newsoffice/2007/wireless-0607.html

 

http://web.mit.edu/newsoffice/2007/wireless-0607.html
I can't see anything new there.

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This has been going around in news circles for a while now. There are some really big problems with it. Like what happens when someone with magstripe cards in their pocket goes near it? Or perhaps a metal spring in a physical device? If you're going to start ouptutting that much power in a magnetic field you're going to have to worry about long distance inductive heating of objects that have never been studied under these conditions before. The near fields devices that work over a few inches such as cordless electric toothbrushes are bad enough, and no matter what the articles say, much of this energy bleeds off into open space. Something like this is liable to completley destroy the existing AM broadcast radio spectrum. I doubt there's a perfect frequency that could be used that would avoid problems with all other currently used frequencies and common mechanical strucutures.

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The theory is all here.

I agree.

Using a sinusoidal wave of a non-AM radio frequency or IF should help reduce interference but then it will effect other electronic devices and you could probably hear it on the an udio amplifier.

I have a feeling that the LC circuit would need to be tuned to the same frequency as the transmitter so most mechanical structures should be a problem,

I don't know why this story has jumped to the headlines though because it's nothing new, I suppose the company's marketing department must be really good at generating hype.

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Did you all forget your schooling??? Nicola Tesla had this down pat 100 years ago. In fact his financier JP Morgan, upon realizing that he could not regulate and charge for wireless power shut down tesla, blackballed him and left him with nothing. The towers were already partially built and the operational principles were sound.

 

But it was never practical, they weren't overly concerned with efficiency back then!.

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That's exactly what I'm saying.

What's new?

Perhaps some new magnetic materials have been descoverd but I would think it's all hype.

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From what I remember of Tesla's work, he was very concerned with efficiency and economy. Documentation wasn't one of his strong points, did most of his work in his head. Considering the large number of his inventions we all still use, most haven't changed much in design in the past 100 years. And also the number of years he worked toward making wireless power a reality. I tend to believe he was on to something practical, and the key details died with him.

If I remember right, it wasn't about transmitting the power through the air, like radio, but through the earth. Something about charging the planet like a huge capacitor.

 

Thanks, but I'll stick with my 99.9% efficient power cord.

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There is no way to avoid the fact that the power is being transfered via a magnetic field. Could you imagine what would happen if someone's keyfob with some enamled wire or some such weirdness resonated? You'd inductivly heat the key's. Anyone ever burned by even a 30 watt iron knows they can get a little hot, and they're talking about 100watts as a goal. I finally found an efficiency rateing for the device which was about 40%, really respectable for wireless power, but the possible environmental interactons are impossible to determine until a full size power distribution network was tried, and so little is known about what extended exposure to strong magnetic fields does to living tissues. I've seen frogs magnetically levitated in super conducting coils, and it's kind of creepy to think how high the flux density must be to do that to organic tissue and what might be going on. You just can't pump that much power through something without expecting some sort of interaction. Perhaps some specific chemicals or molecular structures resonate, even at a harmonic some power will be absorbed.

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Wasn't it the "ether"? He theorized that the Earth's resonant frequency could be used to split the planet in half...

 

The jury's still out on whether strong low frequency fields are harmful but resonance of molecules can be ruled out because they are only excited by >SHF frequencies.

As far as RF is concerned, I've read tha the most dangerous frequency is around the FM broadcast range range. I didn't read why but I would assume that its because the average height of a human would from a half wave dipole at that frequencey.

Low frequency fields tend to pass though the body whichout loosing any energe because we're not conductive enough and EHF fields (>100GHz?) tend to be absorbed right at the surface because of the skin effect.

I don't know about DC fields but MRI scanners have been exposing patients and staff to strong DC fields for many years without any ill-effects.

The idea that huge amounts of energy can pass though a medium without having an effect on it doesn't seem so strange to me. You can pass 100A though a solid copper block and all it will do is heat up slightly, you can shine a very bright light though a glass windows and it will have the same result.

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http://www.electro-tech-online.com/g...al-energy.html

http://www.physorg.com/news100445957.html

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Yes it did have something to do with aether, and there is tons you can read on it. Actually tesla after making the discovery of "aether" abandoned all of his work on alternating currents. He found that he could charge certain metals from miles away from an electro radiant event (spliting the electron flow from aether) This was a large part of his system to send power wirelessly. Many people dismiss this, but it was important enough to telsa that he devoted the rest of his life to this study. Not only this but he also created and pattented devices such as "apparatus for the collection of radiant energy" that produced power with no input power, seemingly a overunity device. It is now theorized that this was more of a "solar cell" that used a field of energy other than light to power it. the aether maybe?

 

I don't see how the explanation is possible!

An antenna radiates in whatever pattern it uses regardless of whether there is a receiver except in some cases where the antennas are on the same scale as the gap- if there's a one sq ft flat antenna facing another one sq ft flat antenna 1" away then the receiving antenna can affect the transmitter's radiated power. Eventually when you're close enough you have a magnetically coupled induction pickup like the EV1 charger or some electric shavers use. The further away they get the leakage increases rapidly until the receiver has no effect on the xmitter. Then it's like a solar cell- the light bulb won't draw any more or less power when you pick up its light with a solar cell.

I see where they say they made the antennas do this. I know it's supposed to be MIT but I don't see how it's possible. Well, I could potentially make a transmitter than sensed whether a receiver was in its path and crank up the power, but that still has a lot of leakage unless the antenna is very directional and close up, and the amount of power radiated is not controlled by the load on the receiving antenna.

Nor does it address the problem that more than tens of mW of radiated power can be dangerous to people and electronics. Fatal? Naw... you might feel it. Might give you cancer one day, hard to say. Just not something that makes sense so you can plug in this xmitter on one side of the room and use your laptop without a cord... oh wait I can already do that for awhile with the battery.

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