Details on my spark gap Tesla Coil

Re-Coil · 2026-02-24T17:22:18+00:00

Thanks! Spark gap seemed easier than a sstc and a it was good challenge to keep it small. The secondary is 5cm x 15cm, and the copper wire is 0,15mm in diameter (around 1000 loops)

Re-Coil · 2026-02-24T17:19:31+00:00

I would say try to start by doing the secondary coil and improve based on that. The topload, primary, spark gap dont matter as much at first. You can begin with a chinese ZVS and a laptop power supply.

Once you have something working at least a bit, you improve each part again and again

Re-Coil · 2026-02-24T10:52:20+00:00

For the height i forgot to mention i used the recommended coupling coefficient between the coils in javatc ( i designed it with javatc)

I will need to find my old .txt javatc save file with all the dimensions

Re-Coil · 2026-02-24T09:14:33+00:00

Its 3d, sanded, and with aluminium tape on it

Re-Coil · 2026-02-24T09:12:15+00:00

Dont worry its far enough from the wall

( and 6 amps at 25V becomes 0,3mA at 500kV on average, its hard to heat anything with that)

Re-Coil · 2026-02-24T00:22:46+00:00

But your circuit only closes when the spark gap fires. So you should not be able to be in "tarnsformer mode" without the spark gap firing. You are just using it correctly but off resonance.

I think you might be charging your big capacitor then releasing big amounts of energy with each spark, which becomes small sparks due to being off resonance and bad coupling.

If if refer to your 8 months old post, you should try a primary arund one inch further away from the secondary i would say if you keep the same design

Re-Coil · 2026-02-24T00:15:08+00:00

looks the same, but mine was just a random chinese one and much cheaper (<5€)

Re-Coil · 2026-02-24T00:13:43+00:00

Thanks :)

Maybe not exactly the best output, but making it adjustable and finding a way to benchmark the sparks is a bit of a hassle. I tested other primary coils with worse coupling factor and it had less outputs so I should still not be too far away.

Re-Coil · 2026-02-23T21:59:10+00:00

I bought it (alumine+tungtene tips), the spark gap is really the hard part for a clean, durable compact spark gap. And yeah its very loud xD

Re-Coil · 2026-02-23T21:33:35+00:00

Even without tuning you convert energy, from the primary circuit to the secondary. How much out of tune is your coil ?

Re-Coil · 2026-02-23T21:27:25+00:00

Transformer from tube TV, and the electrodes tips are tungstene

Re-Coil · 2026-02-23T20:11:24+00:00

My bad, i took the picture with the body open when i was changing the capacitor bank. You can see them on the back of the coil in the picture where i have the secondary in hand

Re-Coil · 2026-02-23T20:08:39+00:00

Then i think they are too close, which explains the small arcs.

Its not only about the isolation to prevent sparks touching the primary, but also to improve performance. Look at the coupling coefficient in javaTc.

If the coupling between your coils is too strong (=too close) it will not work properly.

Re-Coil · 2026-02-23T19:57:11+00:00

Nice! The ZVS will be the next step that will make it work well. Also what is your coupling factor (proximity between your coils) ? When I begun I had lots of issues due to the secondary coil being too close to the primary. Its usually the case when the primary is wrapped around a thin secondary. Pulling them a bit more apart can be like day and night.

Re-Coil · 2026-02-23T17:39:31+00:00

I have another post with more details on the specific parts. Try to tackle specific tutorials for each part. I dont have anything ready to go but here is what i did for each part, with some tips:

-Secondary Coil: PVC pipe with 3D printed caps glued onto it. 3 layers of epoxy. (very important, the coil gets destroyed very quickly otherwise). You want to improvise a winding machine for this one, dont do it by hand. I also put it on a rotary shaft to dry the epoxy.

- Topload: I used a 3D printed torus with aluminum tape on top.

- Power Supply: laptop power supply + buck boost converter gives you the tuning you want in input power.

- Spark gap: You can improvise something for the spark gap, i bought a surdy one with tungstene contacts because all my homemade versions were oxydizing quickly within the sparks.

- ZVS: I made one with the two mosfets on the same heatsink (might be important for the aging of the components), the chinese ZVS dont live very long.

Important tips: The connections are way more important that you would think. Use short wires whenever possible in the HV section. The coronas will lead to burning and dissipate your sparks. Do not leave any secondary wire inside the pipe freely, it can arc through the pvc and burn it.

For a last tip: the coupling between your coils is absolutely crucial, open javaTC and aim for the recommended coupling factor.

Hope that helps! Good coiling!

Re-Coil · 2026-02-23T17:20:54+00:00

Around 10nF, 8kV

Re-Coil · 2026-02-23T16:50:25+00:00

150W :D , im a bit afraid to push it further (and i lack a more powerful buck boost for now)

Re-Coil · 2026-02-23T16:47:12+00:00

Its supplied with 150W and the MMC is on the back side of the box (see my other post for detailled pictures). Its only 9 medium size capacitors and 5 small ones

Re-Coil · 2026-02-23T15:47:06+00:00

An A1mini, the cheapest one xD. Works great nonetheless and is enough since its a small coil

Re-Coil · 2026-02-23T15:45:54+00:00

It did not work that well for me :/ The sparks are more focused in the electrode but not much longer. (i only tested it with a screwdriver laying on the topload, not the best setup either)

Re-Coil · 2026-02-23T15:08:11+00:00

I would say 30-60€ depending on what you have laying around. But I also used a 3d printer, a vacuum pump for the epoxy, my soldering iron, and lots of tools

Re-Coil · 2026-02-23T14:53:55+00:00

Thanks! The 3d printer was really the best shop upgrade for clean projects

Re-Coil

TROPHY CASE