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My First Dual MOT SGTC

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Dragon64

Tue Aug 26 2008, 09:55PM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

Well, I've finally decided to build a SGTC but since money was a problem, I decided to build a poor man's Tesla Coil.

As for the powersupply, I've decided to use Vasil's 2 MOT powersupply ballasted with a 100 watt 2k ohm resistor.
It will be a variable rotary sparkgap.
The only problem I have so far is the capacitors.

Would I be able to use a Salt Water Capacitor, or would I be able to use a couple MOC's in series?

And is this schematic correct?

Alexandre

Tue Aug 26 2008, 10:53PM

Registered Member #1228 Joined: Tue Jan 15 2008, 01:08AM
Location: Curitiba, Brazil
Posts: 162

According to what I know the scheme this correct ..

Prefer Cap of Salt Water, that the MOC's not working well, so I know ..

Iam build a simple tesla coil with a two MOT's:

Her is the link:

Alexandre

Firefox

Wed Aug 27 2008, 04:23PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

MOCs are meant for 2100V 60Hz duty. At Tesla Coil frequencies, they die quick deaths, sometimes spectacularly.

MRacerxdl

Wed Aug 27 2008, 04:57PM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

But you are thinking to use that resistor in the primary of the transformers (Like the schematic shows)? That is no good, you will limit the current for 24W that is not enough for nothing, that resistor you can use in the secondary of mot. About the MOC's, as Firefox say, it will blow quickly if you run it at higher frequencies. The Salt Water bottle its a better option, but not the best.

Arcstarter

Wed Aug 27 2008, 06:10PM

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

You could just buy some cde caps for 49 bucks off of ebay, but if you are like me and have no money, you can just make beer bottle capacitors. Problem with that is you are going to need quite alot of them to get the needed capacitance. You could also make the party cup capacitor, roll your own polyethylene one(you can get some polyethylene floor covering stuff from the painting isle in lowes or other hardware stores) like tesladownunder did with good success.

Dragon64

Thu Aug 28 2008, 03:22PM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

How much saltwater capacitors should I use?

Firefox

Thu Aug 28 2008, 04:00PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

Well, if you have capacitance meter, then the easy way would be to measure the capacitance and then divide that into 1.4 times the value of the resonant capacitance to get the number of capacitors you need. Otherwise, you'll probably have to rely on a best guess of (if I recall correctly) 1-2 nF per capacitor.

ArcLight

Thu Aug 28 2008, 05:25PM

Registered Member #341 Joined: Thu Mar 23 2006, 07:41PM
Location: Northern Illinois, USA
Posts: 69

For my first coil I used four MOTs and two of these salt water caps. Works great and I learned what I needed to know.

Regards, ArcLight

Dragon64

Fri Oct 24 2008, 11:56PM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

Well I have been delaying this project for a while but am deciding to build it soon.

If I was to use other capacitors then the salt water onces, what would you recommend being cheap?

Here are the spec's

-2 MOT in series with one MOT secondary shorted as Inductive Ballast

-Rotary Spark Gap

-7 Primary

-2050 secondary

-HV capacitor undecided

If there are flaws to this project, feel free to correct me.

LithiumLord

Sat Oct 25 2008, 01:00AM

Registered Member #1739 Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261

>one MOT secondary shorted as Inductive Ballast
pretty useless

>-Rotary Spark Gap
Good choice, also try making it a propeller one, not a disk gap - it's a nice design, but watch out for static electrodes and propeller rod balance

>-7 Primary

>-2050 secondary

Looks ok here, but keep track one the resistance - probably 2050 is too much, but, especially if you've already wound it, try it anyway.

>-HV capacitor undecided
Heh, here in Russia we have some trouble with good HVRF caps so most SGTC builders use an MMC of ceramic ones (hehe in Soviet Russia, an MMC can kill you by it's weight - by the way, this is NOT a joke, hehe), rarely - film caps, which prove to work way better as well as being transportable by one man. As far as film caps are easy to get for you, use them (as far as I know, Maxwell is a pretty common solution).

And....... DON'T FORGET THE RF CHOKE!!!!!

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