Re: I Need some Help.

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

Original poster: "Alexander Rice by way of Terry Fritz <twftesla-at-qwest-dot-net>" <alex-at-rices.myip-dot-org>

03/06/2002 15:05:33, "Tesla list" 
<tesla-at-pupman-dot-com> wrote:

>Original poster: "by way of Terry Fritz 
<twftesla-at-qwest-dot-net>" <TeraJoule-at-aol-dot-com>
>
>~Hello
>       I have been working on my first 
coil for a few weeks now.  I finished it
>and turned it on.  There was no discharge 
off of the Sphere on the secondary. 
>However there is a little arc (and I mean 
little) when I place a piece of metal
>next to it (something like a screw 
driver).  I've been wracking my brain to 
try
>and fix this problem and I was wondering 
if one of you fine gentlemen would
>help me.  I think it is something with 
the frequency of my circuits. I believe
>they are mismatched...
>
>The Dimensions of my coil are as follows:
>Secondary uses 30 gauge copper wire that 
is wrapped around a PVC pipe 7/8 in.
>diameter and 8.25 inches tall. (about 700 
turns) the sphere on top is .75
>inches in diameter.  
>
>The transformer is 9000 V NST and 30 mA.  
It's rated at 120 V. 
>
>The capacitor has 17 sheets of 5.5 in. x 
6 in. separated by .1 in. window pain
>glass.  (I don't know the dielectric 
value.)  If it makes any difference, only
>4 inches of the foil overlaps for each of 
the plates ( a 6 inch x 4 inch plate)
>
>The spark gap is non-rotary and can be 
adjusted to any distance it needs to be
>at.
>
>The primary is helical and is basically 5 
turns of wire.  3.5 in. in diameter,
>spaced 1 inch from eachother.  (I would 
be most willing to change this or the
>capacitor.)  
>
>I would be forever grateful if someone 
could help me work out the flaws in this
>design.  Thank you very much for all of 
your time.
>
>Sincerely,
>Alex

The best way to set the gap is to make it 
so the transformer you are using just 
jumps the gap if you connect it across the 
spark gap - this helps ensure you dont 
overvolt your transfromer and will prolong  
its life.

I really recommend against testing your 
coil by holding a piece of metal next to 
it - you could potentially get an unleasnt 
or even fatal shock under the wrong 
circumstances.

the secondary needs to be grounded at the 
base to a good RF ground such as a pipe 
griven into the ground (normal house 
ground is NOT suitable - you will destroy 
any sensitive equipment connected to it)

it sounds to me like your coil is out of 
tune - my calculations suggest a 
capcitance of 0.0064 uF which is a little 
under resonant with your transformer and 
should tune around 3.3 turns on the 
primary rather than 5 but trial and error 
is easiest here - start around 3 turns and 
hunt for best spark length. Really this is 
rather few turns and using a bigger 
topload would be very beneficial, 
increasing to a 2" by 6" toroid would drop 
the operating frequency from a rather high 
1.7Mhz to a slightly more reasonable 
1.1Mhz and increase the tap point to about  
4.5 turns - when doing this it is best to 
put a sharp point like a thumbtack on the 
top of the coil to ensure breakout.

You should get at least a 4" spark from 
this thing.

Some air blowing over the spark gap should 
also help
------------------------------
Alexander JJ Rice
Geek#-1232
Rank : G-2 (Wahey!)
http://www.TheGeekGroup-dot-org
"Because the Geek Shall Inherit the Earth 
!"?