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How to increase the spark length of my tesla coil

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Electrikid221MnM

Fri Nov 04 2011, 01:34PM

Registered Member #4172 Joined: Sat Oct 29 2011, 05:57PM
Location: Narnia
Posts: 27

This is my new schematic.

Cain

Fri Nov 04 2011, 01:52PM

Registered Member #624 Joined: Tue Apr 03 2007, 07:50AM
Location:
Posts: 59

you dont want the rf ground to attach to the bottom of the primary. the secondary should only go to rf ground. you will just short your NST to ground otherwise.. part from that should work fine. although you would be better off with a safety gap rather than the rf choke

Electrikid221MnM

Fri Nov 04 2011, 02:22PM

Registered Member #4172 Joined: Sat Oct 29 2011, 05:57PM
Location: Narnia
Posts: 27

I've changed the RF ground but I have a question about the safety gap: Would the safety gap be in series on the bottom of the circuit instead of the top where the capacitor is?

Marko

Fri Nov 04 2011, 03:04PM

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

Hi electrikid,

your way of connecting the NST is suspicious to me - if your transformer has a ground wire on the mains side it is very likely connected to the senter of the high voltage winding, so grounding the primary like you did would short one of secondary windings out.

Regarding the spark gap, this is an easy way to build one:

Spacing is too wide in my case, use like 0.5mm or less, and about 7-8 of such gaps will be required for 8kV. You can use shorter pieces of pipe or those copper pipe interconnections you can get at hardware store.

Regarding transformer protection: you first need to find out if your transformer is center tapped construction (which I suspect it is) or not. If it is then it will have two output HV terminals and you'll be able to measure resistance between them and the yellow-green wire on the supply side.

Don't use a choke for your transformer protection, it's useless. Use 10 series 470 ohm 2W resistors in series with each HV leg of the transformer (wirewound or carbon composite resistors are ok, other types not so much). ALso, you can put a small leyden jar between each HV leg to ground, but even resistors do help a lot alone.

If you consciously set your spark gap (so that it just fires with the transformer alone conencted to it) and don't widen it later, you don't even need the safety gap.

I think the actually hardest part of constructing a begginer coil is building the primary. I wouldn't recommend to do what most people seem to end up widh as it's mechanically demanding and expensive.

I would instead make several helical coils with cheap wire and put them concentrically around the secondary, with increasing height of the windings for the outer coils - so the result is a sort of a cross between helical and inverse conical primary.

Strip the last few turns from a small bit of insulation (on the outermost winding) every 10cm or so for tap points.

Marko

Electrikid221MnM

Fri Nov 04 2011, 06:22PM

Registered Member #4172 Joined: Sat Oct 29 2011, 05:57PM
Location: Narnia
Posts: 27

Ohh. I already have the spark gap built i just wonder about placement in the circuit.

Marko

Fri Nov 04 2011, 09:01PM

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

Electrikid221MnM wrote ...

Ohh. I already have the spark gap built i just wonder about placement in the circuit.

Ok then, but what about your NST? I strongly suspect it's still wired wrongly, but some pics of it would certainly help a lot if you don't know how to describe it.

Marko

Electrikid221MnM

Fri Nov 04 2011, 11:03PM

Registered Member #4172 Joined: Sat Oct 29 2011, 05:57PM
Location: Narnia
Posts: 27

This is my NST. I think its an SSNST so that might be leading to my SGTC failure.

Polonium210

Fri Nov 04 2011, 11:57PM

Registered Member #3450 Joined: Sun Nov 28 2010, 05:01AM
Location:
Posts: 61

Electrikid221MnM wrote ...

This is my NST. I think its an SSNST so that might be leading to my SGTC failure.

That would indeed be a solid state neon power supply. This will not work for your coil. What you need to find is a big heavy iron core NST without the GFI protection circuit. You could also find a couple OBIT's to run in parallel for higher current.

Marko

Sat Nov 05 2011, 12:04AM

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

You could also build a simple flyback or ignition coil driver to power your coil. It's a learning curve on what you are at now, though, so it would perhaps be the easiest to find a proper transformer somewhere, or try hacks like powering a flyback from a solid state halogen lamp supply or powering an ignition coil from thatn dimmer based circuit (dangerous mains voltage though).

Marko

Electrikid221MnM

Sat Nov 05 2011, 12:50AM

Registered Member #4172 Joined: Sat Oct 29 2011, 05:57PM
Location: Narnia
Posts: 27

are there any ways of making it work with a ssnst? Im limited when it comes to spending. im limited to the 99 dollar range

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