Re: [TCML] Table Top Tesla Coil

[Gary Lau <glau1024@xxxxxxxxx>]

Hi Amir,

"Optimal" may mean different things to different people.  As you described
your coil as a table-top sized device, it may be that you value
compactness.  Or, it may be that you place emphasis on achieving the
longest possible spark.  Or it may be that you are looking for the device
to achieve an appearance that only you can define.

Unfortunately you can't have everything.  In my experience in optimizing a
4kV/20mA powered coil, it has become extremely clear that bigger is better,
in all things, when trying to obtain the longest spark to a grounded
target.  When dealing with the lower-powered end of the spectrum, it's
tempting by way of convention, to use correspondingly smaller secondary
diameters.  I started with a 1.9" diameter secondary.  But when I
redesigned with a 4.5" secondary, performance improved significantly.  Same
thing with top load sizes, and primary capacitor values.  Making everything
big may end up with a coil larger than your sense of aesthetics is happy
with, but it will give you the longest possible sparks.

That said, while the sparks are longer, using a larger cap size results in
a slower BPS rate, and that will result in less-bright sparks.  And, a
larger top load will result in fewer, or a single spark, rather than
multiple simultaneous shorter sparks.  All depends on what you value.

Beyond that, I would urge you to consider a toroidal top load rather than a
sphere, unless the "look" is the decisive factor.  Also, with your tungsten
gap, I strongly recommend having some well-directed airflow through the gap.

Regards, Gary Lau
MA, USA

On Sun, Jul 14, 2013 at 7:06 PM, Amir Mojarradi <ln2guy42@xxxxxxx> wrote:

> Hi everyone!
>
>
> I would love to hear your thoughts on the table top sized Tesla coil I am
> in the process of building. Specifically, I was wondering if I have chosen
> optimal values for the primary capacitance and dimensions for the top load.
>
>
> Any other comments on improving the design would be incredibly appreciated.
>
>
> Here are the specifications:
>
>
>
>
> Power Supply: 5,000 Volt, 60ma Neon Sign Transformer (with safety gap and
> Terry Filter)
>
>
> Secondary Diameter: 2.5 inches (acrylic tubing)
> Secondary Wire Gauge: 29
> Secondary Winding Length: 11 inches
> Secondary # of Turns: 900
> Secondary Self Capacitance: 4.5 pF
>
>
> Primary Capacitance: 0.0499 uF @ 12,000 volts (MMC of (12)
> Cornell-Dubillier 942C20P15K-F 0.01 uF 2,000 volt capacitors; 2 parallel
> strings of 6 in series)
>
>
> Top Load: 8 inch diameter stainless steel sphere (11.4 pF)
>
>
> Spark Gap: (2) 1/8 inch diameter Tungsten Electrodes
>
>
>
>
> Thank you so much for your help!
>
>
> Amir Mojarradi
> Los Angeles, California
>
>
>
>
>
>
>
>
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>
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