Trying to build my first tesla coil!

[LordAlvin]

Hello! Well. as the title says I'm trying to build my first tesla coil. I'm a begginer in electronics and this is my first project.
I'm trying to build it following this video's steps:

/>The tools and parts that I have consist of a multimeter (with which I do all of my measurements) and all the parts listed in the video, with some differences my mosfet transistor is an IRPF360 (instead of an IRPF260n) and coil was made with 1.31 mm^2 enameled wire.
I have not been able to generate a spark (and as there is a strong magnetic field generated when the coil is powered on, I can't take any measurements with it operating). And I have a few quetions and concerns.
Should the diameter of the pvc pipe compulsorily be 3cm? My secondary coil was wound in a 1,5 cm pipe, it has aprox 500 turns and it goes over itself (I am a bit worried about this, though, I have not found found any info that says this affects the correct operation of the coil) something that could be of importance is that the inductance of the coil is 1.4mH.
The sources I have are a 19.5 V 2.5A charger from a laptop and an ac converter from an old printer that outputs 24V but only 0.8 A.
I'd greatly appreciate if somebody has some opinion to share or some info/link from wich I can get any answers.
Pd.: pls forgive my English, I'm from Uruguay and we speak spanish here, so if I don't use technical terms, that's the reason why.

[Mads Barnkob]

Hi Alvin and welcome to HVF!

Which coil is made with the 1.31 mm^2 wire? That is a too big gauge for a secondary coil on a small coil like this.

IRFP360 is similar in gate charge, double voltage, half current compared to IRFP260, this could properly do okay with a small coil like this. But given the high frequency of a small system, the 4 times higher RDS(on) (Ω) of the IRFP360 could be a problem.

By using a secondary coil form that is 15 mm instead of the prescribed 30 mm, you are doubling up the resonant frequency, making it much harder for the MOSFET to be driven that fast and possible spend all its time in the linear region and thus get limited output as you dissipate a lot of power in the MOSFET instead of letting it through.

Overlapping turns on the secondary coil is not a problem in regard to inductance and operation and for a small coil with relatively short spark output, there should not be problems with racing sparks or mid-secondary breakout due to a uneven surface for the overlap. You could give it a good amount of varnish to fix that somewhat.

[oneKone]

welcome to the forum Alvin.

This was also the first sstc i made! the mosfet i used was an irfp460 and i later made it midi controlled. Unfortunately 1.3mm^2 wire is far too large diameter. if you can i'd get some 30mm pvc pipe and some 30awg magnet wire.

[LordAlvin]

Thank you for your answers! I'll try to get some thinner wire, and the 30mm pvc. Btw, 30awg is equivalent to .25 mm, right? Here in Uruguay we use metric to measure almost everything, so if I go to the hardware/electronics store and ask for some 30awg they probably won't know what I'm talking about. Thanks again and I'll keep you updated!

[oneKone]

You are correct, 30awg is 0.25mm. Depending on what you buy it could have multiple layers of polyurethane and can measure 0.3mm. So 0.25mm nominal. Australia also uses metric for almost everything, I think wire size is the only thing i switch between imperial and metric! 

[Mads Barnkob]

Thank you for your answers! I'll try to get some thinner wire, and the 30mm pvc. Btw, 30awg is equivalent to .25 mm, right? Here in Uruguay we use metric to measure almost everything, so if I go to the hardware/electronics store and ask for some 30awg they probably won't know what I'm talking about. Thanks again and I'll keep you updated!

I made a list that compares metric and american wire gauge (AWG) with current capability: http://www.kaizerpowerelectronics.dk/theory/wire-size-table/

[LordAlvin]

Thanks Mads! Sorry I haven't updated the project this days. I'm studying for some mid term tests and I haven't got the 25mm wire yet. I'm going to try and build a wider coil with the wire that I currently have, and test it in one of the uni's electronics labs, and try to compare it to the one using 25 mm wire. Btw, i have not posted the circuit schematic.
Question: will 1uF be enough, or shall I get a capacitor with a higher C?

[Laci]

If I remember right,Keystone Science mentioned that an electrolytic capacitor will blow up due to the high frequency.As he said,use nonelectrolytic capacitor,however maybe paralleling them is enough.

Somewhere on youtube I've seen a guy making a similar coil,but interrupted with a 555.When he added a larger(maybe like 450uF)capacitor,much larger arcs came out.Not sure  if it's necessary for a noninterrupted coil,but you can just change the capacitor to a larger to see if it makes any improvement.

[Mads Barnkob]

The capacitance and ESR of the capacitor will determine how much peak current / pulse energy that is available for the MOSFET to feed into the circuit, just be aware that too large/low ESR capacitor will properly make the MOSFET explode

As Laci mentions, ripple current is bad on electrolytic capacitors, maybe not in this low power circuit, but to be sure, use a polypropylene capacitor (MKP)

[LordAlvin]

Yeah, as I saw the problems with the electrolitic capacitor in the video, I bought a polypropylene one.