RE: [TCML] Suggestions for a mini-TC?, just right transformer

["Jim Mora" <jmora@xxxxxxxxxxx>]

Check this one out 5kv 20ma - one end grounded France. 140192837287 $58.00
As mention earlier. Simply use a small line filter (plug in line cord) and
ground the coil base, transformer to mains ground. The box sounds real cool.
It shouldn't be hard to stand off 5KV with plexi.

The solid state neons won't work in classic mode.
Jim  

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Jason Goodman
Sent: Monday, December 24, 2007 7:46 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Suggestions for a mini-TC?

A couple more questions...

Most large coils use exposed copper tube for the primary.  There  
should be no problem using insulated wire for this, right?  I'm also  
considering a design in which the high-voltage, high-current primary  
circuit is enclosed in a (ventilated) plexiglas box, with the primary  
coil mounted to the underside of the top of the box.

I've been looking at neon sign power supplies, and I see two basic  
types: big heavy clunky-looking boxes, and slim black plastic modules  
weighing a pound or two.  Am I correct in believing the latter aren't  
actually transformers, but some sort of solid-state voltage multiplier  
arrangement, and therefore no good for TC use?  (Going on the  
assumption that if they *were* good, everyone would be using them  
since they're tiny and cheap.)

How hard is it to go solid-state?  I gotta admit I'm no expert on  
semiconductor circuits, ideally I'd like some widget that I plug into  
a circuit and it "acts like" a spark gap, but I'm sure I'd have to get  
more complicated than that.  How much more?

Mixing quotes from several respondents:

> Consider building a pair of coils configured as a Twin Tesla Coils.   
> Each
> coil acts as a counterpoise to the other, and grounding of the  
> bottoms of
> the connected secondaries can be a connection to your power line  
> ground.

That looks like a fun arrangement: it'd also make the arcs more  
controlled, avoiding random strikes to the tabletop and nearby  
spectators.  Two coils are safer than one, eh?

So basically all I'd need to do is wind either the secondaries or the  
primaries (but not both) in contrary directions in each coil, right?

> I would consider using a 1.5 (7.5-9") or 2 (10 -12") form so that  
> you can
> get more turns on it with #30 and maintain the 5 or 6:1 aspect ration
> suggested for small coils. Someone jump in here if I'm off, but  
> usually we
> like to see closer to 1000 turns to get the secondary inductance up.

I noticed that JavaTC was giving me a resonant frequency for this  
thing that was up in the MHz, and it makes sense that the frequency  
would go up as the coil and topload get small.  Is there a fundamental  
problem with high-frequency coils?

A twin coil would help with this problem too, wouldn't it?  The twin  
secondary circuit should have a resonant frequency half that of each  
coil alone.

> I'm not sure a shoe box and in the
> office is too good of idea for an "in the office toy"...for a ground  
> plane
> you could use a counterpoise which should fit a desktop.

It wouldn't *really* be turned on on my desktop, the odds that I'd  
nuke my computer are substantial.  But something small enough to at  
least *display* on a desk would be nice.

> Lastly, as you said, 1kv is hard to start an arc and a microwave oven
> transformer is definitely a deadly toy if one gets bit(on the order  
> of 2+kv,
> ~2kw) certainly enough to kill you.
>
> Perhaps a 9kv 30ma old style neon transformer or an OBIT...anyone  
> got one? I
> like Steve's idea too.

MOTs and the big metal potted NSTs are physically waaay too big for  
this, and probably overpowered too.

> 	I made a little coil with an approximately 1-1/2" diameter by 6"  
> long secondary, wound with #36 wire as I recall.  I did it just to  
> see if I could get a decent winding and by luck I did.  Works out to  
> about 600 kHz resonant frequency with a 4" diameter toroid and puts  
> out about 4 to 5 inch streamers when excited with a 2.8 kV, 20 ma  
> transformer running about 50 watts input.  Pictures of it somewhere  
> in hotstreamer.

That sounds perfect.  I looked for a link in hot-streamer.com but  
couldn't find it.  Can you send me some details?  I'm especially  
interested in the source for your power supply.

> Here's a link to Gary's mini-coil page.
>
>  _http://www.laushaus.com/tesla/minicoil.htm

That looks close to what I want to do, maybe a little too big.  The  
power supply, an unpotted open core-and-coil neon sign transformer,  
looks like just what I'm after.  Anybody know of a good source for  
these?
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla



_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla