Tesla Coil Build Thread

[Sigurthr]

Toroid

Minor Diameter-I don't know what this means but the outside of the doughnut is the entire diameter which is 14.75 inches.
Major Diameter-Is this the same minor diameter? Anyways, if this helps the duct is 3" flexible dryer duct, and it is coated with a lot of aluminum tape. The singe pie pan on the bottom, that is indented to about the middle of the toroid, is about 8 inches in diameter in the middle of the toroid. I'm using a metal bolt although I know I shouldn't, so for now, I'm covering it with electrical tape.

Center Toroid height is 14.50 inches.


Thanks.

Hey, in your earlier photos they were so poorly lit I assumed you had that sphere on top of the toroid, but now in your video I can see that you're not using a toroid at all! Well no wonder you're not getting six inch plus streamers, it's going to be out of tune! The 5.3Turns mark is for with the size of toroid you specified! With such a small sphere on top the secondary's frequency will be higher than the primary's, i.e. out of tune. You'd need more turns on the primary to compensate.

That being said your output looks good for such a small topload and being out of tune.

Also a small topload like that will NEVER give a single streamer because the radius of curvature of the top of the spheroid is too small, and you'll get charge accumulation like with a break out point. The reason the torus shape works so well is that the radius suppresses the uneven accumulation of charge which would normally prevent a single streamer from forming.

 

[USAbro]

I don't think it's out of tune. When I move the tap to the next turn out, the sparks are very weak. The next turn in and there weak as well. Also, my specs I gave you weren't quite accurate. I found the secondary was really 11" tall of wire.

The big toroid is too big for the coil, it causes no breakout, and arcs to ground are 1 inch. So what would be my best bet for a top load? A bigger foil covered ball? Or a spun toroid?

 

[Sigurthr]

Well, it's hard to say. You could be at a harmonic, or environmental coupling could be pulling your secondary frequency low artificially (most likely case, and this eats power invisibly).

In either event, try moving the tap two inches at a time, increasing the turns, as we know it won't be decreasing the turns. If you don't get any better performance, you've got nothing to lose.

To reiterate what Nospin said earlier though; you need a real topload on there!

 

[USAbro]

Bigger or smaller than this? 1" x 4" Spun Aluminum Toroid for Tesla Coil HV Project Marx Generator Polished | eBay

The problem with adding more turns, is there isn't enough room on the chassis, and how would I connect more copper tubing?
Also, I've found the perfect spot on the primary that works. And as I said, going to the next turn out decreases performance, I think I've found "Goldy Locks Tap."

 

[Sigurthr]

Those 1x4's are only good for SSTCs and VTTCs, unfortunately.

Yeah, sounds like you're seeing environmental detuning. Oh well, not much you can do at this point (you'd have to move the entire coil assembly to a free standing surface at least two meters away from any other object, which usually means for most folks placing it outside in the driveway on a milk crate or some such).

 

[USAbro]

Those 1x4's are only good for SSTCs and VTTCs, unfortunately.

Yeah, sounds like you're seeing environmental detuning. Oh well, not much you can do at this point (you'd have to move the entire coil assembly to a free standing surface at least two meters away from any other object, which usually means for most folks placing it outside in the driveway on a milk crate or some such).

And what should that do? Change the tuning? Also, how do you recommend adding more tubing on my setup. I have about ten more feet in my house, available for use, but I'm not sure what to do, as it would go off the platform. Also, I tried using on the driveway, but it was on the ground, not a milk crate. I have a crate though so is it worth a try? Would it lead to more output, or do I still need to add more turns?

 

[Sigurthr]

And what should that do? Change the tuning? Also, how do you recommend adding more tubing on my setup. I have about ten more feet in my house, available for use, but I'm not sure what to do, as it would go off the platform. Also, I tried using on the driveway, but it was on the ground, not a milk crate. I have a crate though so is it worth a try? Would it lead to more output, or do I still need to add more turns?

Well, here's the situation right now:

Your coil should be out of tune, but it isn't... The reason is the walls/ceiling/bench etc around it is creating a short path for the RF between the topload and the HV Return (secondary ground wire). So it's forcing the frequency of the coil low artificially by eating up power. The lower the frequency, the more turns you need on your primary to tune it properly (in other words you have to move the tap further out, to 6, 7, or even potentially more turns - bad).

Because your coil is where it is, your tiny sphere topload is working. If you move it out, it may not tune with that small sphere, BUT you'd have maybe 20-30% more power, the same amount that is being eaten by the environment right now.

Because you're using a tiny sphere you aren't storing enough charge in a topload for good output, AND you're getting multiple streamers instead of one long one.

So, you have a choice: Leave it where it is and call it finished. Or, move it outside away from things to couple to and place it on a milk crate (being too close to the ground does the same thing, it's another surface to eat power).

If you move it outside you'll have to retune it even if you keep the tiny sphere, but you'll gain some output because the environment isn't eating power. Outside you should be able to put on a proper topload, something in the neighborhood of 12" x 3" at least, if not larger, like the one you initially described to me, or like Nospin said to make with pie tins and dryer ductwork.

You should be ok sticking to the turns you currently have (7 max), but if you put on a very large topload or your tank capacitance changes sufficiently, you may not have enough turns to tune it, which results in a very big pain in the ass situation to fix. You will need to "sweat solder" on more tubing using a copper plumbing coupling designed for mating two pieces of that diameter copper, a propane torch, and a suitable plumbing solder/flux set. Since the platform isn't wide enough you'd need to get a larger one.

I had to do exactly this entire circumstance on my second SGTC, as documented in the first pages of this thread. I had taken the coil outside for a first full power test and got NOTHING for output because 1) I didn't elevate it off the ground, 2) I didn't have enough turns on the primary, 3) I added a large topload after initial testing. What did I end up doing? I remade the entire platform, soldered on four more turns, and retuned the entire thing. I went from 3" arcs to 17" lively streamers. It was a pain in the ass.

 

[USAbro]

Oh crap a larger surface. My dad has a oxygen acetylene torch and plenty of fittings for welding. I can't see a topload 12 inches being the right size. Do you really think so? I was thinking a 6" diameter metal sphere at most, then trying to tune it. And connecting more copper using aluminum tape and electrical tape.

Maybe it's not worth it. I can always work on it though, slowly over time.

Is it bad to touch the output? As you can see in the video I was touching it.

 

[Sigurthr]

You can't connect additional copper by mechanical connections, especially not by tape. Even though you're putting milliamps in, most SGTCs have a few hundred to a few thousand amps of current sloshing around the primary. Weak points will fail.

re: touching output -
Yes, it is bad, because it can cause nerve damage after years and years of exposure. No, because the likelihood of incurring damage is low and drinking pop is worse for you in the long run.

(Note, CW coils at exposure levels below RF MPE (determined by tissue heating at low fluid areas) is still totally safe).

 

[USAbro]

What are CW coils? Explain further please.

 

[Sigurthr]

CW or Continuous Wave is a type of operating mode where the device runs continuously without any interruptions or stops. Only two types of tesla coils run this mode: SSTC and VTTC. Arcs are short, brushy, and exceptionally hot and quiet. The most amount of power is consumed/transmitted in CW.

Your coil, any SGTC, any DRSSTC, and most VTTCs and SSTCs, as well as older or rarer variants pulse on and off periodically at various rates, typically between 5 and 300 times per second. It is the pulsation that causes long arcs and streamers to form, as well as what causes the nerve excitation we sense as pain, and causes a lot of interference to be generated.

Here's an example of one of my CW SSTCs; it's running at about 300Watts, and playing music through the plasma emision. https://www.youtube.com/watch?v=4-zt-P_nbuI


Here's another, with the coil set for auto-tuning, running at full 400Watts, lighting up a tube I made:
https://www.youtube.com/watch?v=Sg2i5HVN7_c

 

[DashApple]

Glad to see the SGTC working ,

This is a CW VTTC playing music -

https://www.youtube.com/watch?v=3d3Eha94Hvg

This is a CW SSTC playing music -

https://www.youtube.com/watch?v=ThrxfUzavfk

And a short run of my fullbridge mini SSTC in CW mode .

https://www.youtube.com/watch?v=_T6RZCv1he8

 

[USAbro]

Why does the VTTC output look so weird like fingers.

 

[DashApple]

Why does the VTTC output look so weird like fingers.

That's just how it ended up breaking out from the tin foil square top

 

[USAbro]

Hey guys, my coil is running as usual, but today I decided to put the caps in a milk crate and put the coil on top of the crate, as to make a nice setup. Problem is, the coil has no top load-to air output on my kitchen table, either way, with the caps in the crate, or on the table and the coil on the table, no configuration works even after moving the tap around a bit.
It still seems like that place I'm tapping it is the best place, no matter the circumstance, because moving it out to the last turn causes less output, and in causes less output too.

So I'm afraid that if I ever brought it to my schools science fair, it wouldn't work, because the only two places it works, are my garage work bench, and my rooms desk and on the driveway, with no crate.

Otherwise, output to ground is lame, 2" and there is no streamers to the air.

I need help!

 

[Sigurthr]

Unfortunately you being without a scope and a strong understanding of electronics there isn't anything we can really do to help you further than what we've said.

You kinda found a "goldilocks" arrangement of circumstances that cancel out the negatives and give you decent performance in those special cases. The real problem with that is as you said; you can't move the coil or it stop working. This is sufficient proof that you've got tuning issues (ones that can't be corrected by moving the tap alone). To "fix" the coil so it works reliably will involve considerable time and effort on your part. Primarily, you'd have to make or buy a large toroid, and retune as needed.

Since you're using salt water caps, don't forget to swirl the salt water to redissolve and redistribute salt that may have settled out.