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Making my first coil, SGTC need help with powersupply.

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Estragon

Sun Aug 17 2008, 09:31PM

Registered Member #1391 Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40

Okay. Tonight i fired it up!

I tapped the primary around, what may be about 7 turns.
It did not arc into the air at all :( My RF-ground was just a pice of metal 40cm down in the ground, this needs to be improved. (But, I wanted to test it, anyway)

I was tired and also the weather looked unsure so I packed it up and took it inside, did'nt try tune it.
When I tried to check how it arced betwen the grounding rod (thingy) and the torroid i got some thik, good looking 7-10cm spark :)

I guessed it would be something like this I would get the first try, so I'll have to tune, and improve my grounding.

Tomorrow I wil put some pics of the kinda completish coil.

Also, none of the parts heated, (except the transformer, and the spark gap XD )

Arcstarter

Mon Aug 18 2008, 01:57AM

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

Did you use a rotary spark gap? Your toroid may be to big. Next run use a smaller or no toroid and you will probably get breakout. If you think your toroid needs to be resized do so but it will need different tuning than your current one.

rp181

Mon Aug 18 2008, 02:52AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

toroid does look a bit big. Is the coil varnished?

Estragon

Mon Aug 18 2008, 07:54AM

Registered Member #1391 Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40

Oh, of course!
I always read on most videos on youtube "you need a bigger torroid". So i thought: way not make a big one.
Silly as I am I made it even larger than it is one the pictures: I turned the donut into a dish, ufo-like thing.
And I did'nt even take the time to test the coil with the torroid removed :P
After school if the weather still holds I'm gonna try again :) (without toroid/with a smaller one)

The coil is varnished 10 times with some cheap spray-box varnish, I think i have read that spray-on is bad, because it contains acetone and some other solvents, who may destroy the coils original insulation. But I think it works well.
Also the where no racing sparks or visible corona "leaks" (it was really dark too, so I sure would have seen it if it where any.
Still, that surly was because the coil is so bad out of tune.

The spark gap is rotary, and I think it worked well, maybe it's to slow. Sparks only turned worse when I used the dimmer to slow it down.
Anyway, when I get the time I'm gonna make on with 6 or 8 bolts, and a more sturdy and traditional dessign.
The one I use not is a tungsten rod who rotates betwen 4 screws who are connected in pairs, it is both unnefective and fragile.
Yet, it looks awsome when its turnet on, it makes a cool-looking "illusion" of there being sparks everywhere on max-speed.
And on slow speed you can see the sparks rotate :) !

I did try the same thing with six screws, but then on slow speed it did not quench, it simply pulled the spark/arc around. The screws got to close and my plate was to small to improve this.

Thaks for all the help! :)

Edit: Another interesting thing is that when I tested the spargap without capacitors/coil, it had trouble sparking, to far distance betwen the bolts (the SG is the hardest thing I have ever made). But, when I added the capacitors it worked with 100% succes rate, on all the firerings. Do that means the soargap requires to much energy before the spark jump, or is it supposed to be like that?

Arcstarter

Mon Aug 18 2008, 04:48PM

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

So, what is your capacitor? That Chris Favreau's video used 11nf or something and steve connor used 12.5 nf and a quadrupler.

Let us know how everything goes!

Estragon

Mon Aug 18 2008, 05:30PM

Registered Member #1391 Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40

Uhoh! My capacitor is 15 nF, but I dont know how much I trust the multimeter, it is a cheap one. Still, I checked it on some comercial capacitors, and it was correct and accurate to the listed value of those, hmhm.

Arcstarter

Mon Aug 18 2008, 11:18PM

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

Oh, well 15 nf is good. Just ran my coil(not that this helps or anything). But it made me wanna see some other tesla coil beginner's tesla coils is what i mean :P.

101111

Tue Aug 19 2008, 12:09AM

Registered Member #575 Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263

I think you should use tungsten for electrodes even if you wont be using a rotary spark gap.

Estragon

Tue Aug 19 2008, 05:54AM

Registered Member #1391 Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40

The "thing who spinns around" in the middle like a rotor is tungsten. But I did not find a good way to mount the tungsten rods, in a stabile way. (they where easy enough to cut, no problem there).

In a traditional rsg, can't i just drill some holes in a wood circle and fasten some tungsten in the holes with glue? (connecting the to each other with common wire)
The important thing is that all the electrodes are equaly spaced, that is the hard thing to do XD
Also the spargap I use now vibrates so much wile it runs that the screws unthig themself. But i'm afraid to glue them, it requires constant adjusting :P

Estragon

Thu Aug 21 2008, 08:56PM

Registered Member #1391 Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40

Here is pics of the semi-assembeled coil :)
The pink platic is there just to cover up the spark gap, the wind where so strong it would not fire properly.
The grounding is a copper tube struck down 50 cm in the ground.

Well, I corrected the capacitors value, but with no noticable improvment.
No corona into the air with or without topload.
I tried to tap it many places around on the secoundary, then I noticed the transformer where getting kinda hot (appearantly it heats up a lot more when the sparkgap do not fire)
Then as I started pakking it up (I had moved the primary's tapping point again), I dessided i wanted to check without any grounding. And then it started displaying corona! (dident test with toroid) :) Kinda week, but.
Anyway I tried to reconnect the grounding, it still worked, so appearantly I have started to close in on the "resonacne point".
But, sparks did not visibly change in any way with or without grounding. They where exactly the same, what to make out of that?

The spark gap is ugly, unstable, uneffecive and not-working all the time. It annoys me a great deal! Arrr.

After this long test my tank capacitors diden't even heat (maybe because the coil aint working much yet XD ), anyway I think they are great! Loving them :P Thanks to the HV wiki turtorial!

On the pictures, can you see some mistakes with the settup or anything who requires change/remake?

Thing wich are on my to-do-list is: Grounding fix (possibly, I dont really know if it is bad, now I have tried two diffrent RF-ground with no improvment, the Copper tube and the iron-thingy) New Spark Gap and a way to keep the transformer cool, like maybe put it in oil or place a fan and heatsink settup on it XP, I thing it may be enough.
In the microwave oven on the magnetron, there is a part I can't guess is anything but a "heatswich" who stop to conduct electricity when it reaches a certain temprature, think it would be suitable to put on the MOT to prevent it from heating up to much, or would it flip out to fast? Anyway the easy way is just to check it next time I'm trying it.

Stil I'm having a lot of fun experimenting with the coil. Seeing some actual corona (even really thin cold sparks, 3-6 cm long) got my hopes up.

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