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Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
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Dr. Dark Current wrote ...
"...then drop back down when power was restored" The problem with strong magnets is that when they stick, the force needed to separate them again is remarkable.
One crude and ugly trick that probably works is just to have an electric motor- once the power is restored you move the equipment above the ceiling up until the levitation circuitry can float it again and then lower it back down again.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
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Incidentally, as the power fails, if you've balanced it to give near zero stability current on a permanent magnet, you could just have a charged capacitor, and when the power starts to drop off, you just discharge the capacitor through the coil and use it to yank the bulb up to the ceiling. Conversely, when the power initially starts, you could give it a lob away by the same mechanism.
However, for that to work, the energy in the capacitor has to exceed the energy the bulb has by virtue of its potential energy in the magnetic field; so you would need quite a neutrally stable field shape; that is tricky to achieve.
Registered Member #2529
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I bought a CFL and sawed the bottom off it to see the ballast, and found it's just a bunch of discrete components, which is good because i can repurpose it.
I also found a video of somebody driving a fluorescent wirelessly on the tube:
It looks like he just used an electronic ballast (which handly comes built into CFLs) a couple of coils, maybe some caps for the tanks, and (somewhat oddly) a transformer.
Not sure what the transformer is for, seems a bit bodgy, he presumably could have wound more turns on the receiver and changed the cap.)
Annoyingly there doesn't seem to be a circuit diagram, and there's still some stuff I don't completely understand about starting and how/whether that interacts with the transfer coils.
Registered Member #2901
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Is there any particular reason the guy from the video in the op and Marko use such high frequencies? Can this work at say 100 kHz as well? Dunno how it is in other countries, but at least over here LF is unlicensed for short range devices so it would have the advantage of being legal.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
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Pinky's Brain wrote ...
Is there any particular reason the guy from the video in the op and Marko use such high frequencies? Can this work at say 100 kHz as well? Dunno how it is in other countries, but at least over here LF is unlicensed for short range devices so it would have the advantage of being legal.
Yes, it can work at ~100khz. You need coils with more turns at lower frequencies, but I think 125 khz is one of the standards used for wireless power systems like this.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
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Or a bigger tank cap, a ferrite core would help as well, ideally you'd want a spherical form of E core (obviously the open ends of the coils would face eachother).
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
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At 100 kHz?
Any way they will also "focus" the field, improving your coupling factor and reducing the necessary circulating tank current and associated losses for a given power transfer ... kinda hard to predict which effect would win out.
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Levitating wireless powered light
