Wireless Electricity!

I'm playing around with the idea of wireless power. It should be easily do-able over a short distance- my plan is to be able to charge something like my cellphone through induction, by placing it on a powered surface.. But- I don't know a whole lot about induction, so I was hoping someone could help me out a bit. Here is my setup: I'm using coils from old 5 1/2" floppy drives. I used them once before in a BEAM bot pendulum.. I set one coil on top of another. So far, by pulsing 9v DC through the coil, It sparks a little (because its shorting I assume) and the multimeter in the adjacent coil gives me a small spike of voltage, but quickly returns to zero. Zapping repeatedly gives me at best 2.5v, which is totally acceptable, if only it was sustainable. I've tried using AC 9v.. but I didn't seem to work either. I also tried some different on/off cycles with a BS2.. no luck. Any info would be quite appreciated..

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Marconi originally made the radio but he used 13 of Nikola Tesla's patents to make it work. I suggest making a Tesla coil. Use a whole lot more electricity than 9V...lets try about 100KV next. Get a neon sign transformer and a high voltage capacitor. Look it up online or something. And try that.
tesla coil primaries for ameratures are usually around 15kv
sam (author) 10 years ago
It looks as though MIT is a little ahead of me.. they have wireless electricity working much better than I could have hoped.

I'm not surprised, but I wish I could go there.. At least my ideas are on the right track, even if I don't have the resources or collective of minds that are necessary.

Imagine a future in which wireless power transfer is feasible: cell phones, household robots, mp3 players, laptop computers and other portable electronics capable of charging themselves without ever being plugged in, freeing us from that final, ubiquitous power wire. Some of these devices might not even need their bulky batteries to operate. A team from MIT’s Department of Physics, Department of Electrical Engineering and Computer Science, and Institute for Soldier Nanotechnologies (ISN) has experimentally demonstrated an important step toward accomplishing this vision of the future. The team members are Andre Kurs, Aristeidis Karalis, Robert Moffatt, Prof. Peter Fisher, and Prof. John Joannopoulos (Francis Wright Davis Chair and director of ISN), led by Prof. Marin Soljacic. Realizing their recent theoretical prediction, they were able to light a 60W light bulb from a power source seven feet (more than two meters) away; there was no physical connection between the source and the appliance. The MIT team refers to its concept as “WiTricity” (as in wireless electricity). The work will be reported in the June 7 issue of Science Express, the advance online publication of the journal Science.

The story starts one late night a few years ago...


LasVegas10 years ago
You'd need an oscilloscope with memory to read a single pulse. You'd also need to broadcast quite a bit more than 9v to get much of anything at your receiver. Do a google search for "Marconi" to get an idea about how it works.
sam (author)  LasVegas10 years ago
Ok, I have access to an oscilloscope.. I'm not certain whether it has "memory to read a single pulse" Is that a fairly common feature?

As far as Marconi goes, are you referring to the man or the company?

LasVegas sam10 years ago
Guglielmo Marconi! The father of radio! Your experiments are directly reflecting his early work in spark gap radio.
sam (author)  LasVegas10 years ago
Ok! I was just checking.. but from what I've read, he was trying to send signals (morse code), whereas I'm trying to send a constant stream of power.. From the schematic on wikipedia's spark gap page- It seems that I would just omit the antenna. Is there something other than a spark gap to get the desired effect? ( a more modern version.. ) I also have no idea where I can get a spark gap "component" if such a thing exists..
LasVegas sam10 years ago
A constant stream of power between two coils is called a "Transformer." Yes. You could use air in place of an iron core, but it would require much higher voltages and frequency (Look up Tesla's experiments). A spark-gap can be easily constructed using a block of wood, two L-brackets, two bolts, four nuts and two brass threaded balls. All of which can be purchased at home depot. It's calabrated by adjusting the bolts so the balls are close, but not touching. The closer they get, the higher frequency you achieve. The brass balls are needed to prevent melting. Yes; There are more modern techniques. They're called Radio Transmitters.
sam (author)  LasVegas10 years ago
Ok, well I did some more experimentation last night. I took Andy’s advice of connecting a bridge rectifier with a smoothing capacitor, which I took from an old 9vdc wall wart transformer. I stepped the voltage up to 24vdc I tried putting a chunk of metal rod in through the holes in the coils.. things started to levitate.. I also got shot by a rare earth magnet.. This improved the efficiency quite a bit. To attain a rudimentary spark gap, used the small levitation of the coils to connect and disconnect power to the coils, in a way that it started to oscillate quite fast. I got a pretty good output from the diode bridge. The cap helps smooth things a lot. Output hangs around 3v.. not too bad.. The coil starts to get really hot.. which needs to be fixed- any ideas? heat sink? circuit? Also- putting a nut in the middle of each coil, even when they are separated by 1/4" of wood, greatly improves the efficiency. I'll try a proper spark gap next, but I think I need more circuitry for that, correct?
Yay for Marconi!!
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