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Re: tesla coil



Original poster: "Joshua Lovato by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jlovato-at-newmexico-dot-com>

Hey thanks for the help, I got my little coil putting out arcs over 5 inches
long! (better then the 3 inches it was doing before :-)) I found that one of
the things that seemed to make the most difference was the terminal
(toroid). I tested it by placing a large tin can like those used to hold
Christmas cookies on top of the coil. This made a big improvement in
performance. Does anyone have any ideas on how to make a small toroid that
has a relatively smooth surface? I was thinking of constructing a toroid out
of an 8" doughnut shaped Styrofoam ring and wrapping it with aluminum foil.
Would this work? Also I would probably have to figure out the capacitance
that the toroid would have right?

Also another thing that I would like to ask is about grounding. Right now I
don't have my small 8 inch coil grounded to anything (I use a wire near the
discharge terminal that is attached to the bottom connection of the
secondary to draw arcs) I know this is probably not the best (or safest) way
to do things. However I an afraid to use the household ground for the coil
(don't want to blow up the computer or entertainment center). I do have a RF
choke on both output terminals of my neon transformer with safety gaps.
Would this provide enough protection? Would MOV's on the 110 volt connection
from the transformer help? Or should I use a separate grounding system (a 4
foot rod in the ground)?

Thanks,
Josh

P.S. I will have more pictures soon on my website at:
www15.brinkster-dot-com/thebytefiles/





----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, January 02, 2001 9:32 PM
Subject: Re: tesla coil


> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
> Hi Josh,
>
> Neat!  Let's see what we have.
>
>
> At 07:40 PM 1/2/2001 -0700, you wrote:
> >Transformer voltage: Some where between 9-10kv. The transformer was given
to
> >me by a friend of mine at the local radio station and has no name plate
or
> >any type of label on it :-(.
>
> Is this a NST type or current limited type transformer?  I will assume it
is.
>
> >
> >Transformer current: 20-30mA, is there a way for me to measure the
current
> >of the transformer? possibly by setting a meter to read current and
> >connecting it across the transformer before plugging it in?
>
> You can measure the current with a meter but if anything is set wrong or
> anything is not just right, it will fry the meter.  Best just to assume
the
> voltages and currents are ok for now.
>
> >
> >Primary coil inner diameter: 5 inches
> >
> >Primary coil turns: 3 made of 12 AGW wire.
> >
> >Primary coil distance between turns: .25 inches
> >
> >Primary cap size : 12nF
> >
> >type of spark gap: Multi point spark gap made with 8 1/2" copper tubes
> >bolted to the inside of a 3 inch PVC pipe
> >
> >Secondary coil diameter: 1.75 inches
> >
> >Secondary coil turns: 680
> >
> >Secondary coil length: 8 inches
> >
> >Height of first turn of secondary coil above primary coil: 1/4" from the
> >bottom of the primary (im using a Helical primary). I found that if i
lowerd
> >the secondary coil further into the primary the output increased
dramaticaly
> >( from 1 inch sparks to 3 inches).
> >
> >Terminal diameter (side to side): You guys are going to laugh but I am
using
> >a 1.5 inch Styrofoam ball wrapped with aluminum foil.
> >Height of terminal (center) above primary coil: 10.75"
> >
> >I will be posting some pictures of the coil on my website as soon as I
get
> >it updated :-)
> >
> >Thanks for the help,
> >Josh
> >
> snip...
>
> Here are the numbers I get using a bunch of programs and formulas:
>
> Your secondary coil's inductance is 4.03mH
> The total secondary system capacitance is 4.56pF
> Your secondary system frequency is 1.17MHz
>
> For the primary to be tuned at 1.17 MHz you would need to tap the primary
> coil at 2.38 turns with a 12nF cap.  That gives a primary inductance of
> 1.53uH and a primary system frequency of 1.17MHz like the secondary.
>
> The primary to secondary coupling is around 0.08
>
> So, I would try moving the primary tap point in to around 2.4 turns but
try
> a bunch of places around there to see where you get the best spark.
>
> If that does not seem to help much I would try drawing an arc from each
leg
> of the transformer to ground to be sure it is working properly.  However,
I
> am assuming you have a current limited NST and can do such a test safely.
> If not, we can help you out there.
>
> The cap may be the next suspect.  If it gets hot or does anything odd,
that
> would be a bad sign.
>
> Pictures would be great and help too.  If you send them as attachments to
> (now with virus scanning ;-)):
> terry-at-hot-streamer-dot-com
>
> They will show up at:
> http://hot-streamer-dot-com/temp/
>
> So that is the first shot at figuring it out.  See how it goes...
>
> many of the numbers above are from formulas like those at:
> http://home.earthlink-dot-net/~electronxlc/
>
> Cheers,
>
> Terry
>
>
>
>