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my secondary coil, is this OK?

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raff

Fri Aug 28 2009, 10:45PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

hi Herr
yes tagalog :)

back to topic: later ill be looking for nylon screws(if I do manage to find one on hardware store) . find a suitable material for toroid(or just a sphere) and plastic materials for use as HV cap...

raff

Sat Aug 29 2009, 01:15PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

guys,

After googling/reading for some time... my first rolled HV cap :) tommorow I will test this cap with my mazzilli flyback driver // spark gap

Aluminum sheet measures 18cm x 24cm and I am using OH transparency... measured capacitance : 7.85nF

"air trapped" shown in image is NOT from the foil/transparency, but from the cellophane tape...

raff

Sat Aug 29 2009, 05:04PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

here is a mock-up of my future SGTC ..bottom right showing the home-made cap...

will test the cap tommorow..1st things first.. then search again a way to mount the toroid (w/c is still BARE) .... then make a nice pancake primary... and lastly the sparkgap (maybe ill make a multiple gap)..

raff

Sun Aug 30 2009, 02:02AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

I see a small LIGHT already

testing my home-made cap... noisy old switches (SG) haha

can't wait to finish my flybck driven SGTC

raff

Sun Aug 30 2009, 05:56AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

guys

I forgot to ask this basic question:

since Im done with the secondary coil with 640KHz resonance(thanks MADS), HOW do I compute for turns on primary coil(flat pancake) and the tank cap?

Im having trouble understanding those java calculators around the net...

EDIT: btw I will be using flyback driver for this SGTC

Mads Barnkob

Sun Aug 30 2009, 07:07AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

You really just should invest the time to understand javatc, it is an invalueable tool.

This is how I would do it. (in metric)

surroundings: 200 cm in all of them, for small and medium coils run indoor.

secondary: the dimensions, I calculate turns number/winding length with the helical coil calculator:

distance between windings are 10% of the wire diameter, in general, a 0.5 mm wire will have 0.05 mm varnish.

primary: you can start off by having it 3 cm from the secondary and then keep 1-2 cm space between windings, try to aim for 6 - 12 primary turns depending on what you can get for resonance with your capacitor.

primary lead length, should be no problem.

topload, I suggest you turn both your tins so they form a toroid like form instead of having the sharp ends down and up, have them in the middle. try to approximate its dimensions with 2 discs and a cylinder.

you can now get javatc to tune your primary circuit and adjust coupling to the one it suggests

raff

Sun Aug 30 2009, 08:26AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Mads,

sorry but I have never seen those sites before...I guess I havent googled enough

thanks for the links.. will TRY understanding it :)

EDIT:
I was about to ask you what value I should put in the "distance between windings" until I reREAD your post.. :) cool! they are VERY close to the actual measurements I have made.. THANKS again!!

EDIT2:
another thing, is there a cap calculator for the LC primary? I have only found calc for NST... will my home-made cap (7.8nF) work for this? like If I adjust "taps" on the primary?

Plasma Lover

Sun Aug 30 2009, 09:09PM

Registered Member #1911 Joined: Mon Jan 05 2009, 06:30PM
Location: Salem, Oregon, USA
Posts: 165

raff wrote ...

Mads,

sorry but I have never seen those sites before...I guess I havent googled enough

As for 'Edit2', you will need to use the properly-sized capacitor to achieve near-resonance, otherwise you will not have an efficient coil and will most likely destroy your transformer/capacitor due to voltage reversals and spikes.

Arcstarter

Sun Aug 30 2009, 09:52PM

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

another thing, is there a cap calculator for the LC primary? I have only found calc for NST... will my home-made cap (7.8nF) work for this? like If I adjust "taps" on the primary?

I am not sure if there is a calculator, but usually you just get the capacitor that will charge to full voltage with the most capacitance you can, without the transformer not being able to charge it fast enough. Then, you tune the primary to resonate with the capacitor at the frequency of your secondary.

That way, you can adjust the LC circuit to resonate near the secondary, yet still have a capacitor that will charge fast enough, while still having enough capacitance to get the most out of the available power.

raff

Mon Aug 31 2009, 12:20AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

hi guys
I still dont get the point(how to get resonance) until I experience it in actual hardware.yesterday while I was playing with cap&gap, adjusting distance of "gap" varied the charge-discharge cycle..hence the "freq",right?

I also plan to use air blower to cool the gap and to quench the spark.

Im still looking for a NICE topload..cant seem to find those 'ducts' locally..too bad

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