For nikisalli

The bugger, tesla coils are not normal transformers and in fact on my tesla coil that works at 576khz the primary inductance is under 3uh. There are special tecniques to not blow up everything and the most important is the interrupter that makes the tesla coil like 1% of the time on and 99% of the time off

Yes, to have a primary inductance of 1.5mH with a air core, with 5 turns 20mm tall coil, the diameter would be 27.5m. And a ferrite core is not suitable because of cost, histeresis, the coil will discharge on itself because it would be big enough to be considered a ground from the coil, and more

Yeah or you can just make the diameter 30cm, the height 1 or 2cm and the turns around 50 on an air core. P.S. To make an interrupter i don't see another way but to make it non self oscillating, with something to drive it. You also need power factor correction

You know what let me give you an idea. Buy a plasma lamp (I bought one for 3$ from aliexpress). It contains a high voltage transformer inside and a transistor and some other stuff to make it oscillate. The secondary has a piece of wire sticking out, that probably outputs more than enough voltage to make a spark. Use that as a spark gap exciter and make a coil the old fashioned way ;)

Yes, inside it there is a flyback transformer, but a tesla coil is far different. I did it and, as all 'regular' transformer it can make an arc only whith a second electrode, a wire connected to earth in my case. Tesla coil are different, they can output sparks without a real earth contact, the air sorrounding it is enough. Also in all tesla coils (there is only one exeption) a primary coil with a high impedence, high inductance and consequently high coupling is not good, it increse a powerlosses, decreas secondary transfer power and secondary maximun output voltage and thus way less sparks. There is one exeption thow, but it is a lot more complicated. P.S. for the interrupter a 555 oscillator with a very low duty cicle can be easily used to connect to gnd the gate of the mosfet, or a light dimmer with fase angle controll before the bridge rectifier.

Yes I wasn't suggesting you use the flyback transformer directly to induce spikes in a secondary. I was suggesting that you use the high voltage induced by it to make a spark gap exciter of a ,,Tesla Transformer''

Like in a spark gap tesla coil? Or I didn't get the point, again?

A tesla coil making lightning-looking sparks it's way way better then a stupid chinese plasma globe ;)

Yeah exactly a spark gap coil. A long time has passed since the tesla experiments, you don't need huge step up transformers and mains, just something to raise the voltage enough for it to arc. You can usually use a microwave transformer for the purpose but I don't recommend it.

I did one with a flyback transformer but it is not enough powerful (to much voltage and to little current), microwave oven transformers has to little voltage and to much current, they can destroy the spark gap in little time, so as you say are not recomanded. Also using solid state tecnology increases a lot the efficency, as a comparison a spark gap tesla coil at 10000V 50mA can reach 70cm sparks and a full H bridge solid state tesla coil at 320V can reach the same lenght, without even tune the primary coil as the spark gap one need.

Yeah the thing I like about spark gap tesla coils is that they usually don't need tuning since the arc has harmonics all over the place.

Wrong, they absolutely need to be tuned, otherwise you wont have any spark at all (experience).

I love solid state tesla coils because they can sing

Yeah they need a tuned circuit, but it doesn't matter on which frequency you'll tune it, because the spark contains them all. P.S. Yeah nikisalli they can be made to reproduce music. Sorta like plasma arc speakers

In fact my tesla coil sings ;)

Actually the primary must be tuned as close as possible to the secondary resonant frequency, otherwise the sparks descrease to almost 0 (experience again)

Yes but it's one less tuning man. You need to tune one of both to whatever frequency you want, which is not even a tuning, just leave it whatever, and only tune the other

Nono, them must be tuned at the same frequency, ontherwise no sparks will form. It is like to sintonize a radio, if you don't get the right frequency you won't be able to hear music

You're not getting what I mean I think. Yes a tesla coil is a resonant circuit therefore it must be tuned, but with spark gaps you automatically get the primary tuned to some frequency (no matter what) because no matter at which frequency it's tuned the arc will surely have a harmonic on it. You only need to tune the secondary to the same frequency as the primary was ,,autotuned'' to get it to work

Are you saying that doesn't matter the primary frequency because the sparks on tne spark gap contain all sorts of frequency, even the one where the secondary resonates?

No the primary will resonate at any frequency, yes because the spark contains them all, but the secondary needs to be tuned to the primary

It sounds as a countersens, the primary resonates at any frequency and the seconfary needs to be tuned to the primari. But both are a LC oscillator and thus they have only one, specific resonant frequency. My brain is fuming a bit XD

Okay let me put it in another manner. They both need to be tuned to a specific single frequency, but it doesn't matter which frequency this will be, cuz the exciter contains them all. So you just make a resonant circuit at the primary of whatever frequency you wish, and just tune the secondary to the same. Am i now making any sense ;d

Ok I think I get it, but there is a little issue, the secondary is not tunable and the primary is. So the primary needs to be tuned to the secondary and not the other way around. For the spark, it is just a crude switch, even if it emits radio waves it is not powerful enough to excite the secondary.

Well there are some tesla coils with multiple tuning points, so whatever, but usually yeah, you tune the primary. The secondary can also resonate though, due to parasitic capacitance

Well all the calculation on a tesla coil are based on the secondary resonant frequency, so it needs to resonate

Yes every real inductor has a self resonance frequency at a given point. That's because after a given frequency an inductor starts behaving more like a capacitor than an inductor due to parasitic capacitance, and at a given frequency the capacitance and inductance are equal in strength and opposite in direction (not to quote Newton) thus it starts oscillating. But other than adding extra capacitance to the secondary i don't see any other way to control its resonant frequency. That's why you usually tune the primary to match the secondary and not the other way around (not that it's not possible)

Exactely