Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>
Adriano:
I tried the same thing with 8" X 12" X.032" thick FR-4 sheets double
sided with copper. I stripped off the outer 1/2" of copper along all 4
edges and both sides to keep prevent cross-over. As you noted, each
sheet is a capacitor and I alternated the voltage on each board so that
"like" voltage copper surfaces would face each other.
Submerged in oil (5) sheets gave me 13.84 nF. Unit worked well for a
Tesla Coil. In air, the arc ran across the surface of the FR-4 around
the edge and back across the other surface.
My final copper area was 7" X 11" less an area to pass brass bolts
through to connect the thing together. This bolting gets difficult to
explain. I can send you a drawing of both sides of the cap if you are
interested.
Note: Most "List" subscribers hate Parallel Plate Caps!
Mark
>Original poster: "Dr. Adriano Mollica" <adriano.mollica@xxxxxxxxxxx>
>Hello list,
>i just bought on ebay a certain quantity of douple faces copper fiber
glass plate for very >cheap.
>i will like to use them to make a capacitor, and i believe that it is
possible.
>But i'm worring about the design. infact, every single plate is already
a little
>capacitor "as is", and if i'm right , the thickness of the fiberglass
will be 1.6 mm,
>that is very big (this will lead to a high punture voltage resistance ,
but low capacity). >So , how should i connect the plates one to another
in parallel cinfiguration trying to
>avoid any "corona" , and external spark? and so on, considering that
the plates will be in >a number of 20-40 and i cannot overlap them due
the double face!!!
Any ideas?
bye bye
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, March 01, 2006 5:53 AM
Subject: Re: rolled cap blowew out
> Original poster: Chris Estes <estescc@xxxxxxxxxxxx>
>
>
>
>
> Tesla list wrote:
>
>
> >Original poster: Adriano.Mollica@xxxxxxxxxxx
> >
> >
> >Hello list,
> >
> >after the last attempt to start the TC using lithuanian capacitors,
> >that used to explod very quick and very often, i made a homemade >
>rolled polyethylene cap. > >The dielectric thickness was 0.4 mm,
since 1 mm should resist 60kv, i > >thought that 0.4mm should handle
about 25kv. > >After the rolling up of the materials, i dip the roll
into a tube > >filled with synthetic engine motor oil, and by a vacuum
pump i > >removed all the air inside. > > > >unluckly, after few
successful sparks, the capacitor stopped working > >and started to
make a noise (probably an internal arc). > >i'm pretty disappointe
'cause i spend around 40 euros in materials, > >and many hours of
work! > > > >how can i built a cheap, reliable, and FAST pulse
discharge capacitor? > > > >i'm thinking about planar caps in air (
at least is the cheapest > >dielectric i know.! > > > >any
suggestion? > > > >how much is the dielectric costant of the air,
and its puncture voltage? > >37 nF cap wil probably be very large? >
>thanks! > > > > > > I've just finished an interesting design
thats yeilded about 6.7 nf > with I'm guessing 50 Kv strength. Its a
stacked plate cap that uses > corrugated cardboard and mineral oil for
the dielectric. I place 2 > pieces of cardboard between each plate to
give about 250 mil (3/4 cm) > spacing. All the pieces of cardboard are
oriented so that when looking > down on the stack you can see through
the corrugation if that makes > sense. then i place the stack in a
container and fill it with oil. The > orientation of the cardboard lets
the air bubbles flow up and out quite > nicely. The most expensive
component is all the oil and, I believe, > they will have a 'self
healing' quality. If theres a puncture, all I > need to do is shake it
around to jostle the oil a bit. The dimensions > are about 20cm by 35
cm by 35 cm for, as I said, about 6.7 nf. If you > wanted more farads
in less space then you could probably just use one > layer of cardboard
but I just needed about 7 nf for my NST resonant > condition and wanted
to be sure about the dielectric strength. I > haven't tried this out
yet as I'm still building the rest of my coil > but I can't see any
serious flaw in my design so far. Good luck and > happy coiling. > >