Tesla Coil Build Thread

[Sigurthr]

Here's a teaser.

http://img23.imageshack.us/img23/9836/ovl1.png

I think it is just about ready to submit!

I gotta work on posting the schematic and BOM for you guys now...

 

[Atomicrox]

Looking nice, Sig!

On a side matter, what do you guys think is the simplest SGTC setup using MOTs? I'm leaning towards building one in the near future. I want to use as fewer parts as possible (specially hard to find and/or build parts).

 

[Fiddy]

The board is pretty done ill let Sigurthr post some of the nice photos of the render

 

[Speedy78]

I hate being impatient! Lol

 

[Seoul_lasers]

Looking nice, Sig!

On a side matter, what do you guys think is the simplest SGTC setup using MOTs? I'm leaning towards building one in the near future. I want to use as fewer parts as possible (specially hard to find and/or build parts).

I am a co-inventor of the MMT ( Multi mot transformer-bank) so I am experienced with using MOTS in TC service....
*** However, I strongly discourage their use for beginning TC'ers as they are:
1) You have absolutely no second chances with MOTs, these are positively lethal in hands of inexperienced coilers due to their extremely high output currents.

2) poorly regulated (Secondary side ballasted with a large oil/paper filled capacitor) and can easily deliver well over 2A short circuited or until their windings catch fire!

3) You'll need at least a voltage tripler circuit to make any sort of working SGTC or carefully build MMT (multi mot-transformer).

4) When used ( in a 4 series) in a TC circuit they will require insulation oil and physical modification to make them run cooler. This requires the removal of their all their shunts and the complete removal of their low voltage filament windings. However this adds another layer of complexity to using them in a TC supply as you now essentially have a 4 x 2KVA pole pig needing ballasting via an shorted ARC welder. ( 1 gallon Shell dialex non detergent XMFR Oil is rather messy and quite expensive)

Sorry if I come across as being alarmist or condescending. I have had lots of experience around building TCs (SGTC). I have used Mots before and would never use them again. Period.


btw, the fellow in this video has balls of steel.
I have seen those caps CATO before pulling that much current. ( 15-20KW here? ).
An exploding cap bank can kill you from the flying sharp steel casing fragments.

 

[Atomicrox]

I have drawn arcs from MOTs before (from two in series and from a single resonant MOT) and I know how dangerous they are.

The thing is that I don't really have other good options:
-NSTs are too hard to find around here, too expensive when found and too heavy to order internationally.
-Flybacks, ignition coils and other "small" transformers are too limited, it's too much work to build a TC to get 10cm arcs, considering you could get similar sized arcs from the flyback without the TC.
-I don't think you can get a pole pig around here at all. At least I never heard of anyone getting one.
-I've built an SSTC, it worked but kept blowing up MOSFETs. I'll try again some day, probably when I buy a scope.

I'm willing to consider other options, if you know of any.

Are you sure you need at least a voltage tripler? I've seen many dual-MOT coils without voltage multipliers. That's what I have in mind, since I happen to have two MOTs here.

Won't removing the shunts increase the current and make the gap harder to quench?


Yeah, that guy is bat shit crazy. Nice video, though!

 

[Sigurthr]

It -can- be done with two mots (one as a ballast) and a voltage doubler, but no less than that; the air constriction of such close electrodes in the gap prevents quenching, if you can even build a gap to adjust finely enough for only 2.4kV.

I'd recommend for a SGTC beginner to work only with OBIT/NST just because things tend to go awry at least once, and once is all you get with MOTs. It isn't like arcing with a MOT when you make a MOT SGTC... should the secondary side ever arc to the primary side the arc will carry the full output of the primary with it; that is a resonant MOT's lethal current traveling on a normally harmless TC streamer.

But if you insist on trying a MOT based SGTC then do like you would do for a MOT based VTTC; only add enough voltage multiplier stages to reach about 10kV.

 

[Seoul_lasers]

It -can- be done with two mots (one as a ballast) and a voltage doubler, but no less than that; the air constriction of such close electrodes in the gap prevents quenching, if you can even build a gap to adjust finely enough for only 2.4kV.

I'd recommend for a SGTC beginner to work only with OBIT/NST just because things tend to go awry at least once, and once is all you get with MOTs. It isn't like arcing with a MOT when you make a MOT SGTC... should the secondary side ever arc to the primary side the arc will carry the full output of the primary with it; that is a resonant MOT's lethal current traveling on a normally harmless TC streamer.

But if you insist on trying a MOT based SGTC then do like you would do for a MOT based VTTC; only add enough voltage multiplier stages to reach about 10kV.

Yes right, however in doing a dual mot setup + voltage doubler route you'll need 230-240Vac and join the XMFR cases together to ground.
I tried this, it didn't run too well because of the problem you've just pointed out above, quenching. Flame (arc) outs were pretty common until moving to a RSG. (rotary spark gaps are an entirely different beast all together) - Really a Pain in the arse to set up. The other problem with RSPRKGaps are failing electrodes flying off and hitting things. At 7500RPM they fly off and travel ~300Km/hr. I got some nice holes in my garage in Canada from failed electrodes. Once we bolted (locked) them on a Phenolic disk this problem was solved.

See the link below. This coil in Singapore uses a very similar setup to our mot supply.
Notice that the doubler circuit diagram shows the use of filtering chokes.

http://www.loneoceans.com/labs/teslacoil2/

Our electrodes were ZrW, and melted down quickly due the the high current. We used a 170nF 35Kv rated cap.
Might have been a little excessive.

Obits will burn themselves out after a few runs. They tend to die quickly due to their thin windings.
Neons are pretty much the best you can get bang for buck wise.

 

[Sigurthr]

Those pancake chokes are ingenious! Never would have thought about winding them that way. That is a really nice coil, really cleanly built.

Yep, projectile electrodes is one of the reasons I swore off RSG's. Noise was the other main reason.

I've had luck with OBITs by running multiple in parallel and capacitively balasting them to limit current. It was a mess of wires that I never finalized into a neat form, but they held up well for many long runs. I eventually sold them off for cheap when I got my hands on a solid NST.

Btw, I still have connections to someone who had a SURPLUS of nonGFCI NSTs. Idk how much international shipping would run you on them, but he used to sell them for under $40 a pop for 12k/60s, which was a steal in and of itself.

 

[Atomicrox]

That's a great coil, man!
I was thinking of doing something similar to that.
Maybe using a "propeller" style ARSG instead of a disc.
I'm also thinking about not using a doubler. People on the pupman list say the diodes tend to blow up often. Not to mention 4x the amount of MMC caps.

Every now and then a member of the pupman list sells cheap NSTs around $30-50 but every time I checked shipping would double the price (not to mention the high chance of customs trouble with something that heavy).

 

[Speedy78]

A little Christmas music!

Hung two bulbs in the tree but the really neat part was the string of LED lights in the tree lit up. I guess the E-field was able to induce a current in that line to light them? Even the star at the top of the tree was getting some current and would light up.

Tried my best to sync it to the actually song. Had to slow the coils audio track down to match the song.

Anyway enjoy!

 

[Flaminpyro]

Wow that's a good one Speedy I will rep you when it will let me

 

[Atomicrox]

Fantastic work! The forum won't let me rep you either

 

[Speedy78]

I need a better camera than my 3 year old go pro. Works fantastic outside but in dimly lit areas or inside at all really its so fuzzy and grainy.

 

[Sigurthr]

Haha nice work! Gotta love e-field propagation!

 

[Seoul_lasers]

Nice coil!!

A video showing sparks to a grounded object with music would be nice as well!:wave::evil:

+1 rep for you!