Tesla Coil Build Thread

[DashApple]

For use with the NST and mmc? Even 1/8" tubing will do fine, there's little waste heat in a sgtc away from the spark gap. As for inter turn spacing I got away with 3/16" without issue. Yup always go two to three turns extra.

@Twirly yep trafo would work, but I can't afford a 3.5KVA step up trafo, haha. I'm not worried about upgrading or improving until I decide to make a new secondary. Then, and only then will I devote myself to going all out. I'm thinking full bridge of CM600s @ 75KHz, aiming for 5kW CW fixed frequency oscillator driven with audio modulation. Will be years before I can afford to do that though.

Yeah , I'm actually trying to do that now , but i'm using a 200A half bridge

 

[Fiddy]

i have a 240CFM Fan for my Microbrute

my plasma speaker coils use 32 or 34 gauge secondary wire! my spark gap tesla coil going to use 40AWG

Finished my spark gap, the fan is 105CFM.

 

[Sigurthr]

The fan motor puts a deadzone air pressure null in the center, offset the fan so that the exposed side is centered over the gap. That or add baffles and guides to converge the output to the gap. When the gap is quenched properly you no longer hear the 50/60Hz buzz (though you'll often need some capacitance on there to do this test, which is not advisable for a frail trafo).

 

[Fiddy]

haha yeah i noticed the air pressure dead zone from the fan motor. Seems to be working good at 7.5mm gap!

 

[Fiddy]

Also is it better to suck the air or blow? when i suck the air from the gap, i get ~20mm arcs drawn towards the fan, is that better for quenching?

My stainless bolts are holding up good too!

 

[Sigurthr]

Better to blow from my tests, sucking draws the arc out without breaking it most of the time.

The electrodes should hold, you've got no capacitance on there! Just wait until you've got 600A sloshing around, you'll start seeing real ablation.

 

[Fiddy]

Okie dokie!

yeah your right, cant wait to see it resonate, i must wind the coil in 0.09652mm wire about 180mm, hope the resistance doesnt get too high for decent sparks!

 

[Fiddy]

started making a enclosure/stand for the SGTC

 

[Speedy78]

Broke out the coil today and had a little fun.

 

[Sigurthr]

Heh, Speedy, you are going to be blown away by the e-field from a CW SSTC, I know it. That row of gaps... yeah you can do that with lightbulbs and people in between them. I used to run my big coil at about 900W, stand five feet from it, extend my left arm towards the toroid so my hand was about 18" away, and extend my right arm out towards a fluoro lamp... I could point to which lamp I wanted to light up and it would light up. My right hand was about two to three feet from each lamp.

 

[Speedy78]

Sounds interesting! How much longer do we have to wait?

 

[Sigurthr]

As I said before, the boards are off in fabrication right now. I expect to get the boards in the mail by January 6th or so. Assuming the parts orders from Mouser and Digikey arrive by then as well (they should), I'll need between one and three days for testing, depending on what all is going on outside of hobby stuff. The day the test board clears all my diagnostics and tests the single sale board will be available and the next batch will be ordered.

I just rebuilt my in-house ground and AC power network today to ensure all the issues I've had for the last year would be squashed. The circuit my office/lab is on was bridged to another circuit which had reversed hot/neutral lines and floating grounds. The people that wired this place were morons.

Now my office has fully code compliant wiring, solid grounding, and an additional low impedance RF ground tied in with mains ground.

I just have to pick up some new flexible 12-3 mains wiring and 3prong plugs to remake the power cord for my 3kW coil. I smoked the old stuff last year when the wiring fault cropped up.

I also have some Class-Y rated capacitors in the mail which I'll build into RF bypass boxes to force equal RF current sharing along the mains line. This allows any stray RF that gets into the mains wiring to find a low impedance path to the RF ground. I ordered enough for 5 boxes, with plans for only two of them right now (one at TC outlet, other at the outlet where the RF ground comes in).

I can link to these caps for anyone interested - they're not expensive. If you do not have a dedicated low impedance RF ground and plan to run your TC indoors it is a MUST have investment. It protects the rest of your house, and its wiring, from RF based faults/failures.

 

[Speedy78]

I would love to see the plans for that just to stay on the safe side. When I ran the coil in my garage last night my wife had some weird things going on with her laptop inside and it probly has something to do with that. When I build the sg coil for sure I'm going to have a dedicated line run to my house ground point outside. No reason to run something that loud indoors. Lol.

 

[Seoul_lasers]

I would love to see the plans for that just to stay on the safe side. When I ran the coil in my garage last night my wife had some weird things going on with her laptop inside and it probly has something to do with that. When I build the sg coil for sure I'm going to have a dedicated line run to my house ground point outside. No reason to run something that loud indoors. Lol.

Actually I was just going add something to your interference experience.
I have on several occasions opened and closed my Garage door in Canada from running Tesla Coils too close. On one occasion I permanently magnetized a relay switch use to control the door. That was rather expensive to get fixed.
:evil::evil::evil:

 

[Sigurthr]

I would love to see the plans for that just to stay on the safe side. When I ran the coil in my garage last night my wife had some weird things going on with her laptop inside and it probly has something to do with that. When I build the sg coil for sure I'm going to have a dedicated line run to my house ground point outside. No reason to run something that loud indoors. Lol.

It is pretty simple, really. Capacitors pass AC while blocking DC. The size of the capacitor determines how much impedance it presents to a certain frequency of AC. The trick is to pick a value that presents little impedance to the RF from your TC, but a very high impedance to the mains AC power at 50 or 60Hz. The formula for capacitive reactance (impedance) is 1/(2piFC), where F = frequency in Hz, and C = capacitance in Farads.

In choosing a capacitor for an application there are a lot of things to consider, but foremost you have the voltage ratings, which must never be exceeded, and the polarization (if any). Polarized caps are to be used with DC, or where the DC offset exceeds the amplitude of the AC superimposed on the DC.

For this application, the capacitor will be directly connected to mains, so the DC voltage rating needs to exceed the peak voltage of the mains cycle, and ideally the capacitor's AC voltage rating should exceed the AC Vrms of the mains. To determine the peak voltage of a sine wave multiply the Vrms by 1.414. Now, they make capacitors designed specially for mains connections that are engineered to have failure modes that do not result in fires or explosions, these are Class-Y and Class-X rated. Class Y is for mains to earth or mains to mains, and Class X is for mains to earth only. We'll be using a Class-Y2 rated capacitor with 1.25kV DC and 300Vac ratings since I'm on 120Vrms service.

Here is the capacitor I selected/ordered:
Invalid Request

These caps are only 0.1uF, but Class-Y film caps are hard to find in large values, and quickly get expensive. At this capacitance they will present a 26Kohm impedance to the mains AC power. That means only 4.5mA of 60Hz power will seep through. At 200KHz, the f0 of my large TC, this 0.1uF is only a measly 8ohms, and while you wouldn't want 8ohms between the secondary return and true earth as this would seriously limit the flow of RF current to earth (due to the low voltage and high current output of the secondary return), it works marvelously for the high voltage and low current that the mains wiring in the walls pick up due to capacitive coupling from the toroid. At 750KHz, the frequency of most small form SSTCs with no topload, this capacitor presents a paltry 2ohm impedance. If I were to be running a SGTC or DRSSTC, which operate at much lower frequencies typically, I would want a larger capacitance, on the order of 0.68uF at minimum, perhaps up to 3.3uF or so for a 50KHz coil. *See note below about pulsed coils.

Implementation of the capacitor RF shunts is simple: Simply connect one capacitor between the HOT and Ground lines and another capacitor between the NEUTRAL and Ground lines. A third capacitor (X/Y or X rated) can be added between the HOT and NEUTRAL lines but it is not necessary from my experience. I'll be using a completely plastic project box to enclose the capacitors and connections. I'll use a heavy gauge three prong mains plug and a few inches of 12/3 or 14/3 extension cable for easy connecting and disconnecting from the outlet. Ideally you want one of these at the outlet the tesla coil is plugged in at, one at the outlet where any additional ground connection is made (sink, dedicated line, etc), and one at the outlet where any potentially sensitive equipment is located. You can add as many as you like with no detriment (other than to your wallet).

*Pulsed Coil operation (Staccato VTTC, DRSSTC, ISSTC, OLTC, SGTC) causes RF noise at the pulse frequency, its harmonics, the resonant frequency of the secondary (f0), and wideband noise if there is a spark gap. These lower frequency components will see a larger impedance than the f0 and will not be as effectively filtered out by the capacitor shunts. A typical spectrum for a SGTC will see peaks at the mains frequency and harmonics, the break rate, sever orders of harmonics at both even and odd intervals of the break rate, a continuum of white noise from DC to several GHz, the quarter-wave and half-wave frequencies of the wiring between the SG and primary tank, and the f0 of the coil. This LF section, numerically, would look like: 60Hz, 100Hz, 120Hz, 200Hz, 240Hz, 300Hz, 360Hz, 1KHz, 1.2KHz, etc. All of these noise components will find there way onto the mains but will not see a low impedance path to ground through our shunt capacitors.

 

[Fiddy]

Got me tank caps today! 20kV @ 0.03uF ordered a couple extra just in-case.