Fiddys Tiny Tesla & TS Build/Feedback

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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby alexp » Fri Mar 20, 2015 2:10 am

Hello Fiddy,

Sorry to learn of another Failure !

I ordered a new secondary coil yesterday and plan to clean the Inside well and polyU it also.

I am concerned about having a coil that cannot easily be Tuned ...
I'm wondering if I should start working on a pancake style primary with adjustment ability ?

FYI, 785 ohms is what I measured for my secondary .. and from The Team, the AWG is 38.5
38.5 ga wire has a resistance of 780 ohms per 1000 ft, so the coil is evidently wound with about this length.
The dia of the form is 2.4" so there are ~ 1600 turns..

Alex


Fiddy wrote:Had bad luck today guys with the TS secondary, i had coated it with many layers of polyurethane over many days.

Went to run it today and i could see tiny sparks from the breakout with the minimum pulsewidth but then i saw just a thin stream of smoke rise, so i stopped to check the coil and found my secondary had arc'd inside the former almost all the way down.

I had cleaned the inside of the former previous, and checked the winding resistance before I ran, it was at ~780 ohms previous to running now its ~800ohm with the burn marks on the secondary, there's' no burning on the secondary at all.


Pretty peeved that it failed on the inside :(
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby Fiddy » Fri Mar 20, 2015 2:16 am

Yeah it sucks. I will order a new secondary this weekend.

At least i know my inverter is working.

Thats not a bad idea, will pay more attention to insulating the end caps and inside this time.

38.5AWG is crazy small no wonder why so many problems.

I wouldnt make a adjustable primary until i blew a IGBT, thanks for the info!
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby alexp » Fri Mar 20, 2015 4:48 am

Question :

I used JavaTC about 10 years ago to design the big coil .. but not since then...
As you seem to have a current knowledge of using it, I ask the following :

What would happen if the secondary was made from a more 'practical' wire such as
maybe #30 ? I think I can wind that, would not attempt # 38.5.

What is the Disadvantage to increasing the resonant frequency ?

The primary would just require less turns, and maybe made from wire = tunable.

It would be nice to have a 'user sustainable' design for the secondary.

Cheers,
Alex


Fiddy wrote:Yeah it sucks. I will order a new secondary this weekend.

At least i know my inverter is working.

Thats not a bad idea, will pay more attention to insulating the end caps and inside this time.

38.5AWG is crazy small no wonder why so many problems.

I wouldnt make a adjustable primary until i blew a IGBT, thanks for the info!
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby Fiddy » Fri Mar 20, 2015 4:54 am

alexp wrote:Question :

I used JavaTC about 10 years ago to design the big coil .. but not since then...
As you seem to have a current knowledge of using it, I ask the following :

What would happen if the secondary was made from a more 'practical' wire such as
maybe #30 ? I think I can wind that, would not attempt # 38.5.

What is the Disadvantage to increasing the resonant frequency ?

The primary would just require less turns, and maybe made from wire = tunable.

It would be nice to have a 'user sustainable' design for the secondary.

Cheers,
Alex


A smaller gauge wire will lower the inductance thus increasing the resonant frequency. I can wind 34AWG 200mm in abou 10mins by hand.

This can be countered by using a smaller value tank cap on the primary, or less turns on the winding as you pointed out.

Yes it would, good to have control of the primary turns.

EDIT

doing some rough calculations, if you rewind the secondary with 34AWG and changed the tank cap 2x sizes down to 0.033uF the frequency would be close, i can only guesstimate the primary wire diameter being a PCB trace tho.
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby alexp » Fri Mar 20, 2015 6:14 am

I just ran JAVA TC on the coil.

Looks like a wire gauge of '38.75' will make the 1600 turns and 1000 feet = 780 ohms. close enough

I physically see 3.5 turns on the upper and lower primary coils, but when I model it as a single
spiral of ( just a guess ) #20 wire, the program shows a need for 10 turns to match the secondary resonance.

It would not be too difficult to reduce the primary printed circuit board winding by half : just re-route power
to the upper/lower winding thru-hole area. As there is an N^2 factor with inductance and turns, that would change the freq by 2. Fn = 1/[2 Pi * sqrt( LC )] ... and dropping the secondary L by half or so ..

Might be worth while to work backwards : calc or measure the resonant freq of the primary based on using half its turns and then determine the number of turns (of larger wire ) needed for the secondary.

The disadvantage of lowering the capacitance value is that you drop energy storage - better to decrease L.

Yes, I remember winding #32 without issue many years ago, maybe #34 is not impossible either.

I plan to post the question about changing the resonant frequency (increasing ) vs performance to one of the TC groups today.
Alex
_____________________________________

A smaller gauge wire will lower the inductance thus increasing the resonant frequency. I can wind 34AWG 200mm in abou 10mins by hand.

This can be countered by using a smaller value tank cap on the primary, or less turns on the winding as you pointed out.

Yes it would, good to have control of the primary turns.

EDIT

doing some rough calculations, if you rewind the secondary with 34AWG and changed the tank cap 2x sizes down to 0.033uF the frequency would be close, i can only guesstimate the primary wire diameter being a PCB trace tho.[/quote]
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby gsklinger » Fri Mar 20, 2015 8:34 am

This is a issue with the design flaw of the end cap assembly. From the hvtesla.com site:

"Never take either ends of the secondary wire inside the tube it is being wound on. This always causes arcing inside and ruins the secondary coil."

http://www.hvtesla.com/secondary.html
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby KarlFlick » Fri Mar 20, 2015 11:45 pm

Ack! That's a real bummer!
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby alexp » Sat Mar 21, 2015 1:03 am

I believe what the comment means is to have a tube with sufficient top and bottom end length that the bolts. etc. used for the base and toroid mounting are beyond the coil region .. Its not really practical to "Never take either ends of the secondary wire inside the tube it is being wound on '

I took my coil apart, cleaned the Inside with alcohol and acetone ( quickly ! ), and then hot air dried twice.
I applied a heavy layer of polyurethane and finally, 'glued' with polyU a disk of plexiglass about 1/3rd down from the top to break up the straight line path from inner tube top to bottom .. time will tell if this works ..

That Fiddy's effort failed suggests there is an inherent issue .. perhaps the tube length should just be an added half inch longer at both ends to fit the recommendation ?

gsklinger wrote:This is a issue with the design flaw of the end cap assembly. From the hvtesla.com site:

"Never take either ends of the secondary wire inside the tube it is being wound on. This always causes arcing inside and ruins the secondary coil."

http://www.hvtesla.com/secondary.html
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby alexp » Sat Mar 21, 2015 1:26 am

I just did some changes to the JAVA TC model .. you can 'move' the toroid up by 1" and only change the
secondary frequency from 257 KHz to 253 KHz .. and that One Inch might be what is required to stop the internal arcing .. ?? I might implement this as I re-assemble the secondary .. can't hurt !

Alex


gsklinger wrote:This is a issue with the design flaw of the end cap assembly. From the hvtesla.com site:

"Never take either ends of the secondary wire inside the tube it is being wound on. This always causes arcing inside and ruins the secondary coil."

http://www.hvtesla.com/secondary.html
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Re: Fiddys Tiny Tesla & TS Build/Feedback

Postby Fiddy » Sat Mar 21, 2015 2:09 am

Good news everyone!

My varnishing and kapton tape is working well, no racing sparks even on high power.

Tinytesla is alive and performing very well with my vertical breakout!

Also playing some of my new midi's through it i havent released :-)

Watch on youtube.com


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