"Wireless" Power Transmission???

What are you assuming for M?

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John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

I could put a big mirror on the roof and slow down the rotation of the Earth. Or speed it up. Which do you think would be better?

The idea for that is to power low consumption law rate charging circuits. It is like using your power at night, while it is cheaper.

It is not meant to power a high consumption device. It trickle charges your devices (tiny amounts) while you are home or at other same such locales.

Every penny counts. Every electron counts.

yeah, but the "fuel" is free, or atleast very cheap.

Wouldn't k be more significant to you? Since k is dimensionless relating to M, L1, and L2; and M doesn't tell you much by itself.

I am saying more than I should, but STOP thinking in those terms.

As I wrote somewhere, it might be to impress the viewer that something unusual is happening. I really don't know.

Presumably, the "AC" that's powering the lights is at some much higher RF frequency than 60Hz. Estimating the resonant frequency of the giant coils might be possible if I knew the capacitance of the amazing ball shaped "tuning capacitor" sitting on the table next to the transmitter, but missing near the receive coil.

In my mis-spent youth, I had occasion to light up fluorescent tubes with RF, mostly at 27MHz (don't ask). I noticed some oddities. For example, with a 8ft long tube, ignition would start at the end nearest the RF source and progress towards the "ground" end as I approached the RF source. The light was also not very constant, and would vary in intensity and color depending on modulation and proximity to the RF source. There were also striations (dark bands) observed, which I guess(tm) might be acoustic standing waves. The basic problem was that without the aid of a filament to vaporize the mercury and disperse the vapor, the UV light produced, and therefore the phosphorescence produced, is uneven and erratic. That's not what I saw in the video.

Incidentally, if you feel like trying this yourself, just find an old tube type audio output transformer, and drive it with an audio signal generator to produce some high voltage. You can probably light a small 4 watt fluorescent tube with that. Start the show with the tube standing upright (like in the video), and watch the uneven lighting. (Note: I haven't tried this in a long time and don't recall the exact results).

See previous description. Long fluorescent lamps, powered by RF, without the benefit of filaments, starts unevenly. However, since the individual lamps each came on with the entire bulb illumined at once, and showing none of the uneven starting and uneven brightness I would expect if powered by RF. In my never humble opinion, it was faked.

Listen to the speakers commentary. He "simulated" the earth by covering it with conductive foil, essentially shorting the conductors.

What is the resistance of the earth or rather, how good a ground is the ground? This is an important question in LF (about 1MHz) antenna design. The range is 0.5 and 30 millimhos (or millisiemens) per meter over land. My area is 8 millimhos. So, if the demonstrator wanted show power conduction through dirt over the distance of about 2.5 meters shown in the video, he would need to pass 320 watts of power through: 1 / 0.008mhos * 2.5 = 313 ohms To directly light (no transformer shown in the video) eight 40 watt bulbs in series, he would need about: 8 * 117 = 936 volts or about 1000 volts which would require: 320 watts / 1000 v = 0.32A current going through the dirt. That would dissipate: P = I^2 * R = 0.32^2 * 313 ohms = 32 watts in the dirt. So much for efficiency and it gets worse as the distances increase and the RF starts to disperse. However, it might make a good way to keep your garden plants warm in the winter.

To be fair, through the ground wireless telegraphy, using ground conduction for one or both conductors, preceded radio by about 50 years, but nobody has ever demonstrated shoving huge amounts of power through the ground. The ground is just too lossy.

Those run at 19kV to 33kV, not the 1kV that I would guess the eight fluorescent tubes are running.

I once designed small fluorescent tube drivers for OCR illumination. Very educational. Found that one could 'start' a tube more easily *IF* you paced a GND next to the tube, then the tube 'fired' and the firing migrated down, along the tube. Pretty reliable. Think in terms of plasma and condutctive clouds of ??. Some area of the tube lights up [making that gas conductive] then high voltage is applied to another section of gas and that lights up and so on. Same thing kind of happens in a corona discharge where the air turns conductive [think in terms of conductivity] and it's like a sphere of metal suddenly moves outward from the actual metal pieces.

If the "fuel pump" costs enough, who cares if the fuel is free.

Yep. You were lucky with the scanner tube because it was horizontal. When cold, the condensed mercury is distributed fairly evenly along the tube. That's in contrast to what would happen if you tilted the scanner on its side and fired up the fluorescent tube. It will usually start at the lower end, where the mercury is piled up, and rapidly grow towards the upper end as the tube heats up. You can really see the effect with a common slow starting CFL lamp mounted with bulb up. The light starts where the mercury piles up, and grows from there. Tube with filaments vaporize the mercury and don't have this problem.

Also, here's a video of how an RF excited tube looks. Note that the tube doesn't light up all at once when the RF is applied at 21.8Mhz: "Quantisation of Fluorescent Tube Striations"

true, was horizontal. Also, learned it possible to 'bake' a tube that is going very non-uniform in brightness caused by mercury depositing near 'cooler' sections. seemed to redistribute the mercury backto near original, or better, and uniformity of illumination returned.

Or

You could also be sued by the FAA for interfering with air traffic.

Spice isn't even the right tool for the job. NEC2 or MagNET would be closer to the mark.

?-)

NEC2 is more for the 'far field' If you check out the software you'll find a lot of approximations that get in the way for 'near-field'

SPICE and NEC is usable combination.

When you stay within the modeling limits of NEC, you can use it. You may use a higher frequency as long as you stay well within the near field. The results from NEC or other (momentum) field solver you can put into SPICE by means of two coupled inductors.

or a quick experiment. Best-case coil-coil coupling vs coil spacing isn't complex; it would be a simple graph for equal-size coils, or a simple family of graphs for different sizes.

Better yet, just measure coupling at some distance that you could sell.

If MIT can't do it in the best part of a decade, and all the Qi folks are spending millions, there probably isn't a practical, efficient household wireless power transfer scheme. It doesn't make sense that there would be. If there were, all your neighbors would steal your power.

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If you've got something solid, it takes very little to file a patent application, after which you'd have investors galore.

(Heck, even a total crock would get investors galore.)

Grins,

Hey, range increased from 5 to 40mm! Yes we can!

"can be built into furniture, tabletops, cars, or found in charging pads, typically use magnetic induction or magnetic resonance transmitters to send power to the portable devices they're charging. Having the flexibility to choose from multiple transmitter designs allows companies to offer a wide range of Qi product types in consumer electronics, home appliances, furniture, automotive and other markets."

Somehow that description just screams "toilet seat," doesn't it? "Green toilet seat"--even better.

Cheers, James