Re: 60 vs. 30 ma - charging

From: 	Micheal Huff[SMTP:msnock-at-theonramp-dot-net]
Sent: 	Monday, June 30, 1997 12:07 PM
To: 	Tesla List
Subject: 	Re: 60 vs. 30 ma - charging

> From:   Pete Demoreuille[SMTP:pbd-at-cybernex-dot-net]
> Sent:   Thursday, June 26, 1997 9:36 PM
> To:     Tesla List
> Subject:        Re: 60 vs. 30 ma - charging
> On another note:
> I have almost finished my first coil:
> powered by a 15kV neon -at- 30mA
> Caps:  two crates of 14 snapple bottles each, each crate rated at 11uF,
>         which are connected in series to give around 5.5uF of capacitance

Way too much capacitance.  Each bottle cap is around 700pF if they are
the common beer   bottle size.  So unless snapple bottles are made from
barium titanate it is not likely that you are getting 11uF from 14
bottles.  With your 450VA neon the ideal tank capacitance should be
.0053uF.  No need to connect them in series.  Most bottles will hold up
fine to 15kV.

> One single spark gap made with 2 carriage bolts, housed in a box with an
>         exhaust fan at one end.
> Primary is 12 turns of 1/4 inch copper refrigerator tubing, at a 30
> degree
>         angle to make it ~4in high and 11in radius.
> Secondary is ~450 turns of plastic insulated wire, (couldn't find any
> enamled,
>         i am working on it) for a total wrapping length of 21.5in
> separation between primary and secondary is 2in
> Any suggestions, comments, improvements (I am sure there are many, I am
> working on getting some mica for making some real good plate caps, and
> making a better, closer secondary, and getting a new transformer)

Good luck getting the mica.  Make a new spark gap.  Use 9 pieces of hard
copper water pipe to form 8 gaps.  As far as the capacitor goes you can
get 6mil polyethylene drop cloth which can be stacked for 60mil (or
thicker) thickness.  There are several plans for these types of caps on
the web.  

> Any clue how much separation the spark gap should have, and where i
> should tap the primary???  Please HELP!  I have not a clue.

Experimentation works best.  Whatever gives you the most amount of
> If you could give a suggestion, that would be greatly appreciated,
> but if you could explain how you got the suggestion, that would make
> you a god.

Ok, I'll explain why you don't want alot of capacitance with a 15kV -at-
30mA neon.  To get a decent charge on the cap you need to match the
source impedance (the neon xfrmr) to  the load impedance (the
capacitor).  A capacitor's impedance will vary with frequency and
capacitance. You can match capacitors to a given transformer with these
simple equations:

Z = V(15kV) / I(30mA)

MaxCapacitance =      1
            2 * pi * freq(60Hz) * Z

So you will need about .0053uF.  8 parallel bottles should do the trick.

Happy sparkin',

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