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How small can a VTTC be?

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Steve Conner

Fri Jun 15 2007, 09:19AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yes, one important function of those chokes is to isolate the tubes from each other and prevent parasitic oscillations in a push-pull mode. By strapping the two plates together and then using a single choke, you're kind of missing the point.

ShawnLG

Wed Jun 27 2007, 07:13PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

Judging from all of these large VTTCs submitted, it looks like I am in the lead. The tube I am using is a 6BQ6GTB. It is being heated form a switcher using SMT components. This cuts down on size. Below are the pics of the switcher, fan patch and the HV tube board with interupter and EMI filter. The fan patch was added to boost the filament voltage to run the 12V fan under the SMPS. I could of added a 12 volt output in the switcher. I did not know I would need forced cooling during the design phase.

Dimentions:
4.5cm width
8cm length
14.5cm tall

Updated Video (5/9/08)

Marko

Wed Jun 27 2007, 07:41PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I admire that SMPS more than whole coil. It looks likle a forward converter? What IC did you use?

And how in world did you manage to etch that board like that, by hand or whatever? I get tired quickly drawing boards of similar size in eagle

And are you sure everything is OK with the SMPS? You shouldn't require a fan for few watts of output power. I ran my flyback converters at about 10W continuously with a small Dpak mosfet in free air with no heatsink at all.

Still freakingly awesome coil. I really doubt anyone will put that much effort into a mini VTTC...

...

Wed Jun 27 2007, 07:52PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

hey, no fair, you have more silicon that vacuum in that coil :p

In any case, that is a mighty fine SMPS you have there

Although if it were me I would have ran the coil off 12v (so I could use a battery later) and then to keep the part count down used a simple unregulated royer for for b+/filament. Also, I can't imagine why you would need a fan, unless your power supply is horribly inefficient, you only need <10w out...

But more worrysome is your spark output, you should be able to get WAY more than that. Did you try tuning it at all?

ShawnLG

Wed Jun 27 2007, 08:22PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

"And are you sure everything is OK with the SMPS? You shouldn't require a fan for few watts of output power. I ran my flyback converters at about 10W continuously with a small Dpak mosfet in free air with no heatsink at all."

I do not know exacly why it is running hot. I scoped the gate output and the mosfet on time is very short when under load. I can only assume that there is huge peak currents during these pulses. Also I do not know if the transformer core can source this much power. On the other hand, my fets on my DRSSTC ran cool with more abuse. The SMPS does run cooler with the gate voltage driven up around 15v, but I would need to rewind the transformer to supply more voltage to the 3842 chip.

"But more worrysome is your spark output, you should be able to get WAY more than that. Did you try tuning it at all?"

I did get better spark output around 1cm when the coil was on the protoboard. Since the transfer to PC it does not run too well. I guss the tube likes stray inductance and capacitance.

uzzors2k

Thu Jun 28 2007, 09:25AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Your tiny coils never cease to amaze me Shawn, and I think you're in the lead now too.

Brett Miller

Mon Jul 02 2007, 01:41AM

Registered Member #593 Joined: Tue Mar 20 2007, 12:32AM
Location:
Posts: 50

Shawn,

Excellent work on the mini VTTC and you are *definately* in the lead in my book.

I think the conservative contention that tube coils should be as solid state free as possible is ridiculous. We're building tesla coils here in 2007, for innovation, fun, learning, and sparks. The tube is just there to switch the power.....not to "sit there and be vintage". I build disruptive coils, tube coils, and solid state, and I love hybrid drives too. Removing "boat anchor" iron was the original boon of the OLTC topology, and half and full bridge SMPS based systems like the DRSSTC. However, we got the iron back with the Piranha, but I still like that since it showed a very failure resistant switching mechanism.

I love the SMPS supply! You should be able to tweak it for larger breakout and longer power arcs. The good thing about having a contest like this is the fact that people get creative and come up with great systems like Shawn's....coils that inspire future work.

So yeah, I'm not trying to hijack the thread by giving an opinion, but since it's on-topic I won't apologize. If this keeps dragging on (i.e. -- no deadline) I might build something, but I have so many projects planned for the near future, it will be difficult. In any case, Shawn and EDY19's coils are super cool.

-Brett
What I've been working on:

Vaxian

Tue Jul 03 2007, 02:42PM

Registered Member #635 Joined: Tue Apr 10 2007, 01:56AM
Location:
Posts: 85

I'm impressed.

I'm on vacation in PA now, when I get back I'll start the trophy for the winner.

Has anyone decided a time limit?

Dan

Experimentonomen

Fri Aug 10 2007, 04:48PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

Hey ShawnLG! Wheres the primary ? Or is it base driven like a plasma tweeter ?

ShawnLG

Fri Aug 10 2007, 05:08PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

"Wheres the primary ?"
The primary and feedback coils are inside the secondary.

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