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Wirelessly Powered Jacobs Ladder

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LAN_403

...

Tue Apr 21 2009, 12:41AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

We were playing around with my solid state tesla coil a few weekends ago, and tried setting a different random resonator we had in the lab next to it, to see what happened. I didn't expect them to have resonant frequencies at all similar to each other, (one had been wound me be about a year ago, the other wound at ucsb by a group of people I didn't meet until this year and of very different dimensions) but it looks like we got lucky and they were at least somewhat close. This of course gave rise to some interesting effects, which I honestly was quite impressed with.

Setup:
I apologise about the lack of specifics, I didn't really have the ability to take real measurements in the lab, but I did try to take a lot of pictures.
SSTC -> free space -> second resonator, with all of the ground tied to mains ground (a pretty bad idea, but it worked)
The sstc was my demo coil (its page is linked in the first paragraph), which was modified a while ago to be running fixed frequency fm (if that makes any sense). I am only using the VCO portion of the 4046 pll chip, with the vco input (pin 9) hooked up to a voltage divider that can be used to set the center frequency. If audio modulation is desired (it was not used for this demo) there is a rca jack input that is capacitively coupled into pin 9 as well (a dirty hack at best, but it has only fried one ipod and one channel on my eeepc so far so we are doing ok). The frequency was set for max current draw from mains when a an arc was present on the tertiary resonator, which which translated to about 3a idle (with minimal streamers on the coil) up to about 5a with a long arc on the tertiary (at this point there was usually no output from the secondary coil). I am not sure if the increased current draw is due to the coil coming closer to resonance, or the power being extracted from the secondary, but the effect was quite large

The tertiary was a coil that was originally used in the clubs sgtc, but seemed to have a resonant frequency fairly close to my coils. With a sharp object poking off the toilet bowl float on top I could get about an inch of streamers off the top, so while definitely not in tune it was pretty close.

Technical ramblings out the the way,
Some pictures:

A few arcs off the system

a pretty crappy gif of it in action, and the sytem spread out a little bit to better show the lack of wires connecting the two systems. Also note the heat ripples rising off the secondary arc, there is some serious power being transfered despite the ~.2 meter separation between the 2 coils

I also have a video of it in operation, but not much motivation to convert it nor space to put it. If you guys are interested I might be convinced to put some time into it.

Hazmatt_(The Underdog)

Tue Apr 21 2009, 08:10AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Looks pretty good to me.

Now can you put a 1R resistor on the base lead of that coil and measure the voltage across the resistor. It would be neat to see what the power transfer is. Now it won't be a very exact figure because you don't know the impedance of everything, but I'm a bit curious what you're going to find.

wicked alex

Tue Apr 21 2009, 11:59AM

Registered Member #1786 Joined: Tue Oct 28 2008, 03:23PM
Location:
Posts: 43

it dose not look like tesla coil sparks to me :/ moor like from a flyback. (tesla coils sparks are violet only at very high frequencys and thet transmittercoil dosen't look very high frequency)

sorry for my bad english

Plasma Lover

Tue Apr 21 2009, 03:33PM

Registered Member #1911 Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165

wicked alex wrote ...

it dose not look like tesla coil sparks to me :/ moor like from a flyback. (tesla coils sparks are violet only at very high frequencys and thet transmittercoil dosen't look very high frequency)

sorry for my bad english

It's okay to have bad english. However, it would be nice if you would use a spell-checker, if you have one for the English language.

The reason that the secondary's streamers look so much like ZVS arcs is that there's a lot of power-density in a SSTC. The reason is partially the high frequency of the streamers, paired with the fact that the high-current primary transfers, naturally, to a higher-current secondary. There are people on the forum who can explain it much better than I am able to.

MRacerxdl

Tue Apr 21 2009, 04:34PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

Hmm very good result!
I think you can increase the power transfer if you made the receiver coil at same Fres than the transmitter coil... At least, the arc's might be bigger.

Arcstarter

Tue Apr 21 2009, 07:22PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

That is very neat i think, '...'. Boy your name causes confusion! If only i thought of it first, i would rule the world. That sure is a nice hot arc on the receiver coil!

The reason is partially the high frequency of the streamers, paired with the fact that the high-current primary transfers, naturally, to a higher-current secondary.

Don't forget duty cycle! Also, a spark gap or dual resonant coil have much higher primary current, hence the longer sparks. They just use lower duty cycle, which of course lowers the wattage compared to high duty cycle and same primary current

Primary current does not necessarily translate directly to how hot the arc is, but more directly to the length, while high duty cycle makes thick arcs.

Renesis

Tue Apr 21 2009, 08:23PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

Would it be feasible to transform this HV resonance to a usable 230VAC 50Hz?

...

Tue Apr 21 2009, 08:36PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

It is possible, you can usually just add another coil to the bottom of the tertiary (tetranary?) which will work like a tesla coil in reverse and should be able to couple considerable power out. How much I am not sure, but 100w should be within reach, I may have to do some experiments over summer with a more carefully planned resonator and more controlled conditions.

Mattski

Wed Apr 22 2009, 09:25PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

In case you haven't seen it, this could be the same prinicpal in MIT's wireless power demo (resonant non-radiative magnetic coupling): News story, paper. Of course I'm sure the TC is also putting out a non-negligible amount of radiative power too, but that can probably be minimized if you design with that intent in mind.

It's a very cool setup! I'm at UCSB too so I'd love to see this at some point and even help you play around with it.

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