Tesla Coil Build Thread

[Sigurthr]

Most transformers don't like duty cycles over 50% in my experience, though it really depends on application.

 

[Fiddy]

Whats a typical on time for the application for this transformer you reckon?

 

[Sigurthr]

Ohh you meant that kind of duty cycle... I thought you we're driving it from a solid state inverter.

Just watch the winding temps, turn it off to cool before it reaches about 150F. The copper will be fine up to a couple hundred degrees, it's the insulation you need to be watchful of. I can't remember if obits ran continuously or not.

 

[Atomicrox]

Hey Fiddy,
I finalized the schematic today. Will start putting together the BOM soon now.

My hands are a little full debugging and designing a new white noise generator. The one we've been sleeping to for years is only pseudo-random and you can hear where it loops. Also, it generates some low frequency tones (100-600Hz) throughout its pseudo-random sequence, and they have higher gain than the rest of the spectrum. The result is really annoying sounds to sleep to, haha. I've got the basic white noise generator circuit hammered out, just need to design a proper semiconductor amplifier for it and construct it. Shouldn't take more than a day. Besides, the SSTC Driver BOM is not going to be fun, haha.

Forgive my ignorance, but why would you sleep listening to white noise?

 

[Fiddy]

Nah man its a spark gap tesla coil!

i guess ill find out if they like to run for a minute or so at a time i suppose.

 

[Sigurthr]

Haha, no problem, Atomic. White noise drowns out unwanted sounds rather well. We live a few miles out from a gravel pit, we're just off a major trucking road, and about 100ft out from our house is a bridge. When the gravel trucks go over the bridge it is loud as hell. Also, since we live with my mother in law we have to deal with her noise making while we're sleeping. She likes to get up and vacuum at 5am on her days off. The bathroom is also one thin wall from our bedroom and the closet door in it sticks, so it gets slammed a lot.

I don't have this issue but white noise with a truly even weighted audio spectrum can alleviate tinnitus for those who suffer from it.

The trick is finding a volume level you can sleep to that drowns out the unwanted noises.

Edit: @Fiddy I know your planned coil is SGTC but that doesn't mean you can't drive the obit electronically. Anyway, the spark gap electrodes limit the duty cycle for tesla coils. When the gap gets too hot the electrodes undergo thermionic emission and the gap ceases to quench properly. The big trick of SGTCs is to get proper quenching.

 

[Atomicrox]

Interesting, I live in a noisy place as well.
Let us know if you succeed

 

[Sigurthr]

Oh initial results are in, it works fine. Just gotta migrate it from a breadboard and rats nest of wires. I've got to play around with the gain loop as well to adjust for a better / different speaker.

 

[Fiddy]

Fiddy I know your planned coil is SGTC but that doesn't mean you can't drive the obit electronically. Anyway, the spark gap electrodes limit the duty cycle for tesla coils. When the gap gets too hot the electrodes undergo thermionic emission and the gap ceases to quench properly. The big trick of SGTCs is to get proper quenching.

I know you could but dont see much point to driving it electronically.
Never built a spark gap tesla coil or spark gap unit, ill probs make one at work with some perspex.

What kind of coupling do i need? im gunna use helical primary on a 70mm form and the secondary is 55mm form. Is that to high of a coupling?

 

[Sigurthr]

What most new coilers don't realize is that the Z axis has a larger effect on coupling than the X/Y axis. The percentage of overap of the two magnetic fields is the coupling ratio. The best advice I can give is to model it with JavaTC and see what it computes the coupling to be. Typically 0.08k to 0.2k is suitable for DRSSTC/SGTC/OLTC work. Most tend to err on the lower end of the coupling coefficient range as too much yields racing arcs which will destroy a secondary, where as too little just limits output power.

And as for the electronic drive of OBITs it has to do mostly with the construction of the said obit. Some have an exposed core like flybacks, so you can actually bypass the original primary and wind your own to greatly improve output (or to run it not on mains).

 

[The Lightning Stalker]

Here is my kit. Perhaps it will inspire.

 

[Speedy78]

Not sure if I should do a larger DRSSTC or go for a SGTC next.

 

[Sigurthr]

Fair warning about SG coils... THEY ARE LOUD. It doesn't matter if it is only 100W of power, it is LOUD!

 

[Speedy78]

Question for the master. At what point can you remove the breakout on a coil. I know oneTesla says it will cause too much stress on the IGBTs but I have seen some SS coils on youtube with no breakout. I also see SG coils with and some without. I think its neat to have the streamers shooting around everywhere instead of directed to the point of a breakout.

 

[Atomicrox]

The breakout point has always bothered me too... It's one of the reasons why my next coil will be an SGTC.

 

[Fiddy]

ive run my Nano SSTC with no break out point and it worked for a while but the switching transistors died prematurely.

I tried running my microbrute like that and it ran straight into the current limit at 350A and no breakout arcs at all.

I accidentaly had no breakout point on the Onetesla and turned it up a tiny bit then remembered there was no breakot point, pulled the bridge input power and control, went about verifying if the coil had no energy built up in the toroid and i could hear it start to conduct a arc when i went close with a insulated screw driver, i taped the toroid with the screw driver and it arc'd straight through the handle and into me....big tingle, surprised me more than anything! i use a ground wire to do this now lol