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First Tesla Coil - problems getting streamers

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void109

Wed Jul 21 2010, 02:22PM

Registered Member #3016 Joined: Tue Jul 20 2010, 01:55AM
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Posts: 9

Ok, that's a lot of information that's new to me. Which is great! I thought two series inductors were simply summed, I didnt realize their proximity to each other affected how their inductances were integrated. :D

And yes, they are both wound in the same fashion, clockwise from center to perimeter.

Herr Zapp

Wed Jul 21 2010, 06:09PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

void -

OK, so your two flat spiral primary coils both have the same winding direction.

Please confirm how the two coils are series-connected to each other.

e.g. is the innermost turn of the lower coil connected to the outermost turn of the upper coil?

In asking about the length of the interconnecting wire in your primary circuit, I meant just the interconnecting wiring, not including the primary coils themselves. This is now a moot point, as your resonant frequency measurement technique appears to be correct, and would incorporate the inductance of all your interconnecting wiring.

Klugesmith -

I could swear that sometime in the dim past I had cracked open a large tubular ceramic high-voltage resistor that was described as "non-inductive via Ayrton-Perry winding technique", and that there was only a single winding. One half of the resistor was wound as a RH helix, and the winding direction reversed at the center of the resistor with the second half LH wound. This winding technique would seem to be not as effective in reducing inductance as physically overlaying two layers of windings with opposite winding directions.

Was this a variation of the Ayrton-Perry winding technique, or something entirely different?

Regards,
Herr Zapp

void109

Wed Jul 21 2010, 06:13PM

Registered Member #3016 Joined: Tue Jul 20 2010, 01:55AM
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Posts: 9

Hello good sir, as you said, the innermost turn of the bottom coil is connected to the outermost turn of the top coil. Do you think this could be the source of my trouble? If so I can start building a new primary.

Herr Zapp

Wed Jul 21 2010, 08:28PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

void -

No, with both coils wound in the same direction that is the correct "series" connection.

So far, there is nothing obviously wrong with your system.

During your attempts at "tuning", did you have a breakout point in place? Make sure that your breakout point extends at least 8" beyond your toroid surface, and that you have a dark background so you can see even the faintest hint of discharge.

During tuning, how far away from the tap point that yielded a 130.9KHz resonant frequency did you go? Since you haven't been able to generate any visible streamers, I'd perform a preliminary "search" by moving your tap point in 1/4 turn increments both inboard and outboard of your initial tap point. Once you abe able to generate a visible discharge from your breakout point, "homing-in" on the opyimum tap point should be relatively easy.

All that being said, I've never had a coil that was initially set up with o'scope & signal generator NOT generate sparks at first power-up. Very odd, unless we've missed something obvious .......

Double check all primary wiring for any high-resistance connections, and verify that your secondary shows continuity from the surface of your toroid to the bottom (ground conection) of your secondary.

Herr Zapp

void109

Wed Jul 21 2010, 10:52PM

Registered Member #3016 Joined: Tue Jul 20 2010, 01:55AM
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Posts: 9

I will check that - unfortunately I'll have to wait til Saturday to set everything up again. For the breakout point I just taped a screw to the toroid surface upside down, 2" screw. I didnt think 8" was needed, I'll try that.

I'm also actively shopping for a bigger supply since the secondary/toroid are so large, a 15k 60ma would be fine indeed.

Arcstarter

Thu Jul 22 2010, 07:22AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

If you want a straight forward answer, you are not spending enough money for it to work. Not only do you have to be smart, but have to have moneh too.

You need some real caps! CDE, Panasonic, WIMA... They make good caps.

void109

Fri Jul 23 2010, 05:25PM

Registered Member #3016 Joined: Tue Jul 20 2010, 01:55AM
Location:
Posts: 9

The painful part about what you have said is I'm already quite invested in this project. I didnt purchase caps because they werent readily available, and Leyden jars were good enough for Tesla, I figured they'd be good enough for me.

dmg

Fri Jul 23 2010, 05:47PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

Is it possible for you to order some online?

also, can you give us some pictures of your setup? I think it will help many people here understand more about your system.

quicksilver

Fri Jul 23 2010, 06:13PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

There is a fellow who makes replicas of the various antique HV machines. From the original species of wood to the Bakelite components, he pays painful attention to detail. The end results of his efforts are fantastic but it takes him a very long time to duplicate the depth of workmanship of that period in history.
I certainly don't want you to think I am in any manner denigrating your workmanship: I'm not.
But as you know, the level of time and effort that was put in was actually the highest level of science at that point in history. The Leyden Jar issues was a hidden problem for me & I learned it simply wasn't worth the headache.
The use of an MMC is simply a guarantee of performance (or pretty close) from that component of the TC. And certainly the cost factor can be minimized; if you hunt. Unless you were directing your efforts to truly classic design: I'd keep my options open.

No one likes putting that much energy into a project & then get stymied by a thing like that but unless you knew for a fact that your Leyden jars are at a solid level of performance, it can be a great deal of frustration.

There may be some caps available (from private parties here) that would take the sting out of that cost factor. If you keep on checking he Board you might get very lucky!

void109

Fri Aug 13 2010, 05:34AM

Registered Member #3016 Joined: Tue Jul 20 2010, 01:55AM
Location:
Posts: 9

Just for anyone reading this thread with a similar dilemna-

I replaced my snapple bottles with standard TC CD capacitors, as well as vastly improved my spark gap. While both of these were good changes and I did get streamers, they were poor, and often weren't even visible. More often than not I couldn't get anything from the coil.

To cut to the chase, ultimately the reason I was having trouble was primarily - crappy workmanship. Very sloppy all over the place, I was leaking power everywhere (to start, the frame had metal in it). Wire placement (high potential wires leaking power even though there's no arcing ocurring), size (make sure the heavy current areas can push their current), length, these were all big pitfalls for me. Once I cleaned up my wire placement, lengths, sizes, etc. it worked beautifully. I didnt get close to my theoretical maximum, but I did get 2.5-3' streamers.

I've learned how unforgiving high voltage can be with design, and I've gained a valuable education in being meticulous in your build.

Thanks for all of the above advice, and I hope this helps someone in the future. The DETAILS are oh so important!

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