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Re: Help...I'm having a lot of problems here...
Tesla List wrote:
>
> Original Poster: "Kent & Kim Schaffer" <santoken-at-bright-dot-net>
>
> Hello all...
>
> About six months ago my step son and I decided to build a TC for his science
> fair project. Boy, was that a mistake...
No... it's a learning experience...
>
> Furnace transformer or NST (I'm not sure):
> -10KVA
> -25 milliamp
Almost certainly an oil burner ignition transformer (you'll see OBIT in
the archives). You almost certainly want more juice for a coil your
size. I've had reasonably good luck using a variety of neon sign
transformers ranging from 7.5 kV -at- 30 mA to 15 kV -at- 30 mA with a coil
about your size and construction.
>
> Cap (set back for a good laugh):
>
> -12x 2KVDC .01 uf ceramic caps soldered in parallel for a
> total of 24KVDC
> -submerged in mineral oil in plexi box
I assume you mean series, not parallel? For the quickest solution, I'd
scrounge up some doorknob caps. They are not the most low loss in the
world, but they work, they are rated at a high enough voltage, and they
are easy to connect (just a machine screw in either end).. Alternately,
do the beer bottle saltwater cap thing (even faster, but a bit more
empirical and messy).
>
> Spark gap (another joke):
>
> -plexi box with three adjustable gaps in series
>
A good quick and dirty gap that is easy to build is to take 2 or 3
pieces of 1.5" copper pipe about 2" long and arrange them with their
axes parallel so the spark would jump from 1 piece to the next to the
next (2 series gaps). If you put the two outer gaps about 3/4" -1"
apart, the spark won't jump between them. Then, put the third one on top
(making sort of a pyramid). It is easy to adjust the gaps between the
single top piece and the two bottom pieces by mounting the top piece on
a bolt from some sort of insulating bridge. Something like a popsicle
stick makes a good feeler gage to gap it.
> Primary:
>
> -3/8" copper tubing
> -ID 7.7"
> -Wire spacing ..875"
> -5.5 total turns
> -wound flat (0 degrees)
>
This is just fine, although a bit large for your transformer.... You
will probably want more turns on the primary so you don't need a huge
capacitor to resonate your secondary. A good prototype primary can be
made from ordinary house wire (#12 or #14 solid, strip the insulation
off by holding one end in a vise and running a single edge razor along
it). Get some cardboard, arrange 4 or 5 pieces radially in a star, cut
slots every 1/2" to hold the wire in a flat spiral. Alligator clip for
tuning.
> Secondary:
>
> -4.2" diameter (thin wall PVC drain pipe)
> -21" long winding
> -22 ga wire - enamel coated
> -shellaced before and after winding
>
Wire is a bit fine, but it will work ok... once you've got the other
parts working...
> Toroid:
>
> -4" dryer duct
> -12" diameter center of tube to center of tube
Just fine...
>
> Now here is the problems we're having:
>
> After hooking up the cap the way all the schematics show I get no discharge
> at the spark gap at all. BTW, the way I read the schematics, one terminal
> of the cap attaches to the output of the transformer and the other attaches
> to the ground. Now, if I attach the cap in a series (one terminal input,
> the other output) I get spark at the gap.
>
> I have gotten absolutely no discharge at the torid whatsoever...sure does
> light a flourescent tube nicely though :-)
You don't have enough power to "break out" of your fairly large toroid
and coil. Try putting a sharp point on the toroid facing out (like a
thumbtack, or a drywall screw). Then, put a grounded electrode a few
inches away to spark to...
>
You've got 48 hours... no problem.. Nothing like the knowledge that you
will be hanged in the morning to concentrate the mind wonderfully.
--
Jim Lux Jet Propulsion Laboratory
ofc: 818/354-2075 114-B16 Mail Stop 161-213
lab: 818/354-2954 161-110 4800 Oak Grove Drive
fax: 818/393-6875 Pasadena CA 91109