Joule Thief

[gadgetmall]

He dosn't understand that if that circuit is a selfrunning oscillator it is VERY useful .

[TinselKoala]

@ all

I a have question.. Why tesla coil doesnt self oscillate? If the tesla coil can create excess energy why it cant power itself without feedback from the secondary?

A good TC will "ring" for a (relatively) long time. But there are always wire and radiation (RF and heat) losses. Tesla's great idea was to use the natural resonance of the huge cavity made by the earth ground and the ionosphere to "pump" a large coil system, making it possible to extract injected power at any point on the globe. This cavity is a large capacitor, and the capacitance is capable of holding many tens of Coulombs of charge... and that's not chopped liver.
But the energy to drive that power -- to push charge into the capacitance -- still has to come from somewhere. I think that tidal effects caused by the Earth's rotation will cause the height of the ionosphere layer over any location to rise and fall on a daily basis, and this represents an injection of energy into the system that might be utilized by a _large_ TC system like he tried to build at Wardenclyffe. Tesla never claimed that his coil systems created excess energy, he thought they could enable "harnessing the wheelworks of Nature", but Nature would still have to supply the power, if it wasn't supplied by Tesla himself.

[TinselKoala]

@gadgetmall: many people build their TCs to do just what you say: make "cold electricity", lots of volts but very small currents, so little heating occurs. These systems are optimised for the spectacular long sparks and other typical TC effects.  However.... this is not the only way to build a Tesla Coil. My SSTCs that I call "TinselKoils" 1 and 2 illustrate that a Tesla coil can make "hot" electricity too.
These vids below are done with v. 1; the version 2 makes the same effect but more better, since I use a lower-aspect-ratio resonator to keep all of the secondary more in the field of the primary.
http://www.youtube.com/watch?v=3DjcRPSljB4
http://www.youtube.com/watch?v=7BMRJoqdy6E

The circuitry uses a 494 chip to drive an H-bridge current amplifier stage of pnp/npn transistors; the output of this stage drives two trifilar toroidal phase transformers; the outputs of the phase transformers drive another H-bridge of high power mosfets, which in turn drives the resonator's primary, which is just a few turns of heavy stranded wire close-coupled to the secondary. There is no spark gap or large capacitor in the primary circuit and the primary H-bridge is switching rectified line current, no high voltage (nothing over 200 volts and usually much less) in the primary circuit.

[NickZ]

  I've been hearing all this talk of "cold electricity", but every time I get shocked from my set ups, the room smells like burnt hamburger, (me). I've already burnt out my multimeter's higher amp setting, while working on the Exciter systems.  Big caps are also good, for short blasts...

[gadgetmall]

Thats definitly Hot Tk . it took seconds for the copper wire to get hot.I have a tesla Hv gen(flyback with push pull)l and i know if you let it spark on your hand in one spot it get hot or a glass bulb will burn through but i have never seen power like that in someones Lab. Very Cool and Big . Now i know this one don't run off an aa does it

I hear ya Nickz . I love getting shocked apparently.I can't even count the many times i was plugged by line AC 120 and 240 in the radio ,tv days it will make you dance if it's a wire (Slings Violently till it knocks it off)).. Getting blasted with a charged dc cap at 500 volts beats them all though. I can take these battery powered stings pretty good.