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my first personnal tesla coil

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paulj

Sat Oct 07 2017, 06:18PM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

Hello,

after being registered more than a year ago on the forum,
I would first like to introduce myself,

I am French, (sorry for my English translated by internet)

my name is Paul and I am a student in Art, I like high voltage.

I learned it using various kit (one Tesla, Eastern voltage reasearch) and an engineer's manual.

but for 3 years I want to take the step of breeding and build my personal resonator.

Here is the link from the site One tesla to start, then other photos will follow:

Do not hesitate to criticize and comment

Paul

Finn Hammer

Sun Oct 08 2017, 03:11PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Pierre,

You seem to be doing allright, there.
For a 2.1 meter spark you need at least 70cm of secondary coil, I would recommend one meter of secondary for that, so you might find that a longer secondary would be better.
The topload should follow, so that the major diameter is equal to the secondary length.
These are just numbers that have shown to produce great results, less is usable too.
Nice to see someone building a spark gap coil with mot power.
Cheers, Finn Hammer

paulj

Sun Oct 08 2017, 04:28PM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

Hello,

Thanks for the compliment, I hope it will work, because for me the simplest coils are the most robust

the goal is to build the most powerful coil for installation in a house,

I applied myself to the security components because it is very strict in France in public places.

ps:

the tube is pvc
the screws are nylon
the plates to plug the PTFE tube to support ozone and high voltage and wear time.
the base varnish (class 220) is made of special acrylic for use in high voltage and a large layer of polyurethane varnish has been applied (7 coats of varnish)

I am assured that no sparks are formed in the tube by placing any conductive wire inside the coil. and the screw above the secondary is not connected to the future toroid.

I've been working on it for years, for the 70 cm secondary coil, it's a 80 cm reel I have, do not rely on my JAVA, it's altered.

the only thing that scares me is the capacitors, I will use Maxwell 35349 brand new (very rare in France).

I will try to give you more information in the next month.

Sulaiman

Sun Oct 08 2017, 06:44PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Looks like you will have a very nice TC.

just a few minor side notes :

Long after you have forgotten reading this note,
you will find that a heavily insulated secondary can build up a shocking ammount of static electrical charge

It looks like you have a steel nut at the bottom of your secondary,
if so then it will heat by induction from the primary coil.
I have melted pvc like that.

Regarding capacitors;
polypropylene foil/film/foil capacitors are normal for most coilers
but at one time there seemed to be a lot of sgtc made in Germany successfully using much cheaper metallised mylar (MKT) primary capacitors.
I can not think of a url at the moment but I'm sure google will get you started.

Snubber capacitors for high power thyristor and IGBT 'blocks' have also been used.

paulj

Sun Oct 08 2017, 09:36PM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

I knew there was a risk of induction, the nut is in fact the earth plug, and the screw on it is also made of nylon.

But

Â the 4 screws at the top of the secondary coil are made of nylon, but for the base there are 4 steel screws because the base had to support the toroid and the secondary circuit because I designed it to be attached to the ceiling, a building.

For capacitors, I think to put them in parallel to modify more easily the turns of the primary coil.

paulj

Sat Nov 11 2017, 03:21PM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

Hello

here is the continuation of construction

the spark gap is finished, it's an improved copy of Terry's spark gap
- 1/4 inch pure tungsten electrodes
- The rotor is made of PTFE to withstand the heat and the ozone vapors, like the bakelite of the support which is a good insulator. I wanted to use cheaper polyethylene, but it not seems to be badly resistant to ozone and heat over time.
- a simple dryer motor animates the rotor.
- aluminum busbar for connections

I chose this design rather than a synchronous motor spark gap to have a total control over the spark using a variac, I can pass u, but also for its low price, and also its ease of construction.

the fan will be oriented differently than in the photo.

I tested it at 2700VA without capacitor, no problem for now

Finally, here is a picture of the set currently the toroid is not finished.
on the primary coil, it still lacks the strike ring.

PS: Finn Hammer: I respected what you advised me, the major diameter of the torus is equal to the length of my secondary coil.

1510411227 59353 FT180663 Img 20171109 123256

1510411520 59353 FT180663 Img 20171109 115452

Sulaiman

Sat Nov 11 2017, 07:21PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

A Request

I am of the opinion that with a flat spiral primary coil
inverting it changes the likelyhood of arcing from secondary to primary.

so

Could you please make provision for the flat spiral primary to be operated either way up
with little effort required to change orientation. ?

To determine for yourself if this is true or nonsense.

P.S. the primary turn spacing looks to make an adjustable tap difficult.

paulj

Sat Nov 11 2017, 08:36PM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

Sulaiman wrote ...

Could you please make provision for the flat spiral primary to be operated either way up
with little effort required to change orientation. ?

To determine for yourself if this is true or nonsense.

Hello Sulaiman

I misunderstood (my english is very bad, sorry)

reverse?
- invert the output poles of the primary circuit to the primary coil?
- to make a selenoid coil? (very bad idea)

Could you detail of yours request please?

Ps: I have about 1.2 cm spacing between the turns, it is temporary, with my two maxwell 35349 in parralel, I would not need so much turns.

everything will depend on the true resonant frequency of the secondary circuit

Hazmatt_(The Underdog)

Sun Nov 12 2017, 05:48PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

A flat spiral coil that is very dense is the best for a SGTC.

If the turns are not dense, then the magnetic lines of flux that are being generated from the ringdown are not as concentrated, so you basically radiate your magnetic field "away" instead of into the coil. I goofed on a coil I built for a customer with too much spacing between turns and the output suffered as a result.

You actually do not want any tuning taps, why? Because every extra inch of primary is lossy and reduces the energy in the primary inductor. Ideally (and this is the way I do it now) it is all primary and cap, no extra lead length at all. Any leads will have 200-300A pulsed and that energy is just being wasted in your leads ultimately reducing arc length.

Instead, you want to fix your primary and trim your secondary to be in tune, it takes a while but you have better performance when you're tuned within 10 Hz of the primary resonance. I do that with a synthesized generator like the HP 3325B which is not too expensive these days on ebay.

An inverted spiral, so Sulaiman means the start of the winding is parallel to the start of your first turn at the base of the secondary coil and the subsequent turns are lower, so it descends and the turns progress outward.
You can do that, but again you will have less flux density if you do it that way unless the angle is very shallow (<15 degrees), at that point the flux should approximate a flat spiral.

I always get criticized for my comments so go ahead, i'm not going to let it bother me.

I have gotten good performance out of flat dense spiral primaries and have not really needed a strike rail for protection, but that is with the caveat of running under 1500 VA, and a coil H/D ratio of at least 3.5.

Remember, the details are important with these things!

paulj

Tue Nov 14 2017, 07:29AM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

I understand better,

According to your advice, I will start tests with a flat spiral, I will see if I evolve on an inverted spiral.

I will finish the secondary circuit first and start the measurements.

Paul

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