Re: small powered coil

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

I think you'd want to build a DC coil... Use the 4mA to charge a reservoir
cap, then have a series choke/diode combination to run to the tank cap,
primary combination.  Richie Burnett's page has all the stuff for resonant
charging.  Make the resonant frequency of the coil fairly high, so the
primary cap is small, and you can get a rep rate of 100 Hz or so.

Your supply puts out 40W (not a huge power...), so at a rep rate of 100 Hz,
you want the tank cap to store around 0.4 Joules.  With resonant charging,
the voltage will be twice the supply, or 20 kV.  Using Energy = 1/2*C*V^2,
we get 0.4 = 0.5 * 20*20 * C or C = 0.4/(200) or C = 0.002 uF (2 nF)

If you could scrounge up a good low loss transmitting cap in the 2200 pF
area, that would be a good start.

For the reservoir cap, it should hold around 10 bangs worth of energy (so
that the resonant charging sees a "stiff" source), or 4 Joules.. The
voltage is less (10 kV), so the reservoir should be 40 times bigger than
the tank, or, around 0.08 uF.  It doesn't have to handle AC current, so the
choice in capacitors is pretty open.  In fact, your power supply might
actually have a fair amount of stored energy (although, it is unlikely,
given the 200 kHz switching rate). One possibility that is cheap, but a
real pain, and probably unreliable, is to string up 30 or so of the
capacitors in disposable flash cameras (free for the asking at one of those
1hour photo places...Be careful dismantling...)  They run around 200 uF
each, so you'd have a pretty healthy stored charge on that string of 30
(serious hazard here...).



Tesla list wrote:
> 
> Original poster: "Chris Swinson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <exxos-at-cps-games.co.uk>
> 
> HI all,
> 
> I wondering if a power supply which is about 200Khz 4ma 10Kv will be enough
> to get a small output from a tesla coil.  I would assume the output would be
> really low but I'd still like to build it and see what happens. The only
> problem is the Tesla calculation programs wont match a tank cap to that
> supply. I am also not totally sure on what size the secondary should be, can
> anyone help me out ?
> 
> Thanks in advance, Chris