Re: New Transformerless Tesla Coil

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Jolyon Vater Cox by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
> 
> New Transformerless Tesla Coil
> 
> Today I finished preliminary trial of new transformerless mini-TC built
> according to Antonio s calculations.

> Capacitor: 255pF
> L1: 61 uH
> L2: 5.482mH 1004 turns of 40SWG ECW on 1 1/8" diameter vitamin pill tube
former

This would be mode 9,10, as mine, but the terminal capacitance would
be just 2.8 pF. The secondary coil alone has probably 2 pF.

> Topload: 2" diameter plastic disc, coated with metal foil.

Did you try to add a breakout point to it?
 
> So far I have got faint 1/2 inch sparks to grounded wire with copious corona
> and ozone generation (are fine RF sparks and corona are better at producing
> ozone than bright low-frequency or DC discharges?); the TC is easily
capable of
> lighting a 20 Watt fluorescent tube from a distance.
> 
> Performance-wise, is this to be expected, only while it has been a bit -well
> "miniature" so far, judging from the spark length there is apparently voltage
> magnification and I am anticipating using the TC with bigger capacitors for
> larger sparks.

With a larger primary capacitance you can allow for more terminal 
capacitance, and more power available for sparks.
 
> Could L1 be better designed -is the Q likely to be low? If I use larger
> capacitor will a bigger topload bring it back into tune -or will it simply
> become untuneable?

If the ratio between secondary capacitance and the primary capacitance
is retained, the coil can be tuned for the same mode (in this case,
9-10,
menaing that the two resonance frequencies are in a 10/9 ratio and that
the energy transfer occurs in 5 cycles). For a different mode or a 
different maximum voltage gain one of the coils has to be changed.
For such low power, wiring losses are probably small, but thick wire
in L1 always helps. I used 1 mm wire.
 
> I would be interested to read of experience with transformerless TCs
especially
> with "mini"coils as I hope to build some easily portable designs capable of
> producing big sparks when running off integral batteries so maximum "bang per
> buck" would be an advantage.
> 
> And are transformerless TCs likely to be more common in future?

Their big problem is the association of the voltage gain with the mode.
High gains are only obtained at the cost of many cycles for energy
transfer. But is high gain really important if enough power is
available? 
How much voltage is really needed at the output of a Tesla coil?

Antonio Carlos M. de Queiroz