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Old 10-04-2018, 08:59 PM
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Originally Posted by Sputins View Post
G'day Gambier,

You could probably find a former similar in size to what Alexey has. Suggest a PVC pipe of 2 to 3 inch diameter of a certain length. Normally winding sparking coils one uses about a 1:5 diameter to height ratio, but Alexey's looks like it's a tad taller than that... So you could go ahead and wind your secondary coil and also your primary coil. Which is often only about 4 to 6 turns. Alexey simply used a bit of clear elephants trunk hose and used the wire coil that runs inside it.

Make a small jig (something to hold the pvc pipe while you can still turn it) and makes the task quite quick and easy. (Also good to clear coat the finished coil).

I'm simply using one of my existing coils made for sparking, which is wound on a 3 inch pvc pipe. I've made a new primary coil and the picture below shows it complete. (I'll remove the shiny cone and replace with a connecting wire).

However I am still working on the driving circuit...

From what I can see, it needs to have some feed-back from the coil to setup a constant resonance, either by some kind of Slayer exciter circuit (the neutral (base) output of the secondary coil triggers the base of the transistor) or from a separate feedback coil wound near the primary coil which provides feedback. So it needs that function. (I wouldn't normally say that btw).

The other important feature is that I believe it needs an adjustable duty. This is what Alexey adjusts so that for a given frequency or CPS, the on-time of the transistor can be set so that is it a very narrow pulse that drives the primary. This sharpness of the pulse maybe critical for the tuning process?
So this is what I'm looking at doing next. The driver circuit for the Tesla coil, that has positive feedback to keep resonance and also a duty adjustment.

So when I find the right circuit, build it and get it working, I'll post exactly what I've done.

A pre-built driver with these features would be the easiest thing to use. The one spacecase posted would work fine, but it may not have an adjustable duty cycle feature.

I hope there are others secretly building too.. (But then it would no longer be a secret if they say so).

I have some time off next week so things should progress hopefully.
if the pulse width is narrow, and put into a tesla coil primary,
you are making the induced electric field energy.
you do need to tune it to make that the most efficient.
from tesla's notes, you want to feed a pulse that is (when converted to a wavelength) is 1/4 the of the secondary coil resonance wavelength. and assumed here that you also designed your coil so that is near the secondary coil wire length.
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