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Re: Not shooting for anything gloriuous, but... (fwd)
---------- Forwarded message ----------
Date: Thu, 15 Apr 1999 08:12:17 EDT
From: Hollmike-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: Not shooting for anything gloriuous, but...
In a message dated 4/15/99 3:12:53 AM Mountain Daylight Time,
tesla-at-pupman-dot-com writes:
>
> Please bear in mind as you read this message that I am not attempting
> to build a solid-state coil. The primary is unmeasured and hand
> shaped. The secondary is wound on a wrapping paper tube. I am not
> looking for help abot that - I know perfectly well that it is silly.
> However, I need some help regarding the capacitor. I plan to use
> something of the salt water type. If I put water in a two liter soda
> bottle and dissolve ordinary table salt (lots of it) until it stops
> dissolving, then wrap the outside with aluminum foil, will it worr?
> Should I use several in series? In parrelell? Please help.
You don't want to use plastic soda bottles for TC caps. They are made of
polyethylene terphthalate aka. Mylar. which is very lossy at high frequency.
I would suggest that plastic milk jugs would be better, if you can find some
without the handles. Might try juice bottles(Like Sunny Delight, eg). Any
of them that are translucent, but not transparent(look at the recycling key
and look for LDPE or HDPE). Your idea of salt water inside and aluminum foil
on the outside should work, although I have never tried this. You might need
to put some in series/parallel to reduce the corona, which will break down
the plastic over time.
> By the way - when a capacitor is measure in farads, what exactly does
> the number mean? I understand that it is coulumbs(forgive the
> spelling) per volt, but what does that mean, practically? What is the
> difference, say, between 0.002 uF and 25 uF? Any clarifying comment
> would help. Thanks.
>
> _
The important part of capacitance is the the energy it stores (and then
discharges into your primary circuit) is equal to 0.5 *C*V*V , in Joules.
For the same voltage, the 25 uF cap would store 12500 times as much energy as
the .002 uF cap. You need to know this for supplying power to your TC by
multiplying the energy times the breaks/second (could assume 120 breaks per
second for 60Hz charging) to get Joules per second, or Watts. Of course, if
your cap stores less energy than the max possible, it will fire more than
once per half cycle(that conservation of energy thing).