Re: Many questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Matt,

This sounds much better. The new cap size will be fine with a 720W
transformer. The MMC's are an
excellent choice.

The toroid dimensions differ from program to program. Some use radius, some
use outer edge diameter,
and some use centers diameter. E-Tesla6 uses center of tube, JavaTC uses
max outer edge. So for
JavaTC you should have a 6 x 30, and E-Tesla6 a 6 x 24. Program inputs are
partially decided upon
the type of equation used within the program itself (the other part is
personal preference).

I reran the new values and yes, 187kHz is correct as well as the primary
turns (looks like you put
in 6 awg at 1/4" spacing). Note, at this time, no program will throw out
187kHz for your coil which
is a full system design program. The external capacitances have to be
considered to pop this value
out. Assuming you build to spec, the tap should be right on the money. Be
aware, things change
during the build process. Just go back to one of the calculators and enter
the new values to keep
your specs updated.

One thing to look at is your h/d ratio. It's currently 9:1 (twice the
norm). Possibly you meant it
to be long for some reason, but thought I should point it out. (the
archives are full of posts on hd
- you might want to search through the opinions).

Take care,
Bart


Tesla list wrote:

> Original poster: "Matt Morrissette by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <yinzara-at-MIT.EDU>
>
> Ok, well I've redone my calculations.  I also have a new transformer
> because the old one doesn't work. The new transformer is 12kV 60mA.  I
> also am going to use the Geek Group MMC capacitors. I'm going to use 8
> of them in series to make .0199uF.  I redid the calculations using the
> same secondary coil and toroid. Turns out I was measuring the toroid
> wrong and it's 24" from center of the tube to center of the tube and 6"
> diameter tube.  I redid the calculations with the JavaTC and it says
> around 17 1/3 turns are needed to hit the 187.24khz frequency that the
> top coil is resonating at.  I will put the primary about 3 inches below
> the secondary. I'm going to run the coil outside so that I get basically
> no external capacitance.  WinTesla gave some different numbers but they
> didn't make as much sense as the JavaTC. Does this coil sound
> reasonable?
>
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Tuesday, October 08, 2002 9:59 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Many questions
>
> Original poster: "Barton B. Anderson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>
>
> Hi Jeremy,
>
> The transformer is small for trying to charge a 0.3uF cap size. That
> would
> be considered "huge" and would
> be better sized for large coils ( >18"diam.). Also, JavaTC recommends
> running E-Tesla6 to take into account
> external capacitances which directly affect the system and the tuning.
> In
> your case, your coil frequency
> (in a typical garage) should be around 207kHz with the toroid placed on
> the
> coil where the bottom plane is
> even with the top of the secondary and the coil itself about 20" off the
> groundplane. This changes the
> secondary resonant frequency and the primary must be tuned accordingly.
>
> If for some reason you tried the .3uF cap, then yes, you would need to
> tune
> to about 3.4 turns to hit
> 207kHz. However, you may never get that cap charged up. If it did, you
> may
> not want to be around when it
> discharged (67 joules = BANG!). Would be very dangerous, loud, and
> destructive.
>
> Now, lets say you want a cap size that your transformer can charge
> reliably
> without difficulty, then you'll
> need something around 0.005uF - 0.0075uF. Since 0.005uF is resonant, you
> may want to move to .075uF. But
> guess what, although the cap would be in the ball park, your helical
> primary would be 3 x taller than your
> secondary since you would need about 80 turns on it. The fix here is to
> drastically reduce the large
> spacing between turns.
>
> Say we move to 1/4 inch spacing (ball park). We then reduce the turns to
> near 25. Now your almost ready to
> spark, but coupling is pretty high at 0.24. So to get it down say to
> 0.15ish, raise the secondary up 3"
> from bottom primary turn. This will get you about 0.157.
>
> I'd like to say "your ready to spark", but there are other tid bits. For
> now, I would recommend wondering
> around some Tesla Coil web sites looking for similar component values.
> Try
> to take a look at what some
> other's in your power supply range have built (that works well). Some
> things worth looking at is the h/d
> ratio (my coils stay between 4 and 5), the type of primary best suited
> for
> the coil, and the cap size they
> are charging with their transformer.
>
> Take care,
> Bart
>
> Tesla list wrote:
>
> > Original poster: "Jeremy Neuringer by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <jneuringer-at-hotmail-dot-com>
> >
> > I m a new coiler and have done a great deal of research to design the
> coil I m
> > currently implementing.  I ll give all the specs and then ask the
> questions.
> > (please keep in mind the only part actually built is the primary, the
> rest can
> > possibly be changed by recommendation) The coil transformer is a 15kV
> 450VA
> > 30mA 60hz output neon light transformer. The capacitor is a 25kV .3uF
> box
> > capacitor I bought off ebay.  The primary is 7 diameter 6 gauge copper
> wire
> > wound in a helix with 4.17 turns and approx 1.2 space between
> windings.  The
> > secondary is 21AWG enameled magnet wire 1395ft wound on a 4.25
> diameter pvc
> > pipe 39 tall.  It is tuned to approximately 177kHz. The top load is a
> 30
> x6.25
> > toroid.  The spark gap is a collection of 10-½ copper pipes (1.5 in
> length)
> > screwed to a piece of plexiglass with around .025 gap between each and
> a fan
> > blown over the top.  I got all these calculations by playing with the
> TC java
> > tesla designer. However I m not sure if this is going to work
> correctly.  The
> > low amount of turns on the primary seems odd to me (I know if I use
> the
> > recommended .066uF capacitor (by another java designer) it says to
> wind 18
> > turns).
> >
> >
> >
> > Questions:
> >
> >
> >
> > Do you feel this should work?
> >
> > What wire should I use to connect it all together and what type of
> connectors?
> > I bought high voltage wire but it doesn t handle much current.
> >
> > Is the spark gap appropriate?
> >
> > What type of safety gap should I use?
> >
> > How can I discharge the capacitor so I can work on the coil safely? I
> think
> > shorting it would damage it. What can I use for a resistor to
> discharge
> it more
> > slowly?
> >
> > How and where should I ground it?
> >
> > Should I put a piece of Styrofoam in the inner part of the toroid and
> cover it
> > with aluminum tape?
> >
> > How should I connect the toroid to the top of the coil and should I
> leave
> some
> > blank pvc before the toroid?
> >
> > What do you recommend I use to coat the secondary?
> >
> > If you could change something on this coil, what would you change?
> >
> >
> >
> > Thanks for all your help,
> >
> >
> >
> > Matthew Morrissette
> >
> > MIT frat boy Sophomore in Comp Sci and EE looking for fun with a tesla
> coil