[Prev][Next][Index][Thread]
first coil experiments (fwd)
---------- Forwarded message ----------
Date: Thu, 27 Feb 97 07:06:36 UT
From: William Noble <William_B_Noble-at-msn-dot-com>
To: tesla-at-pupman-dot-com
Subject: first coil experiments
I (for the second time) tried building a small tesla coil - generally
following the plans I have uploaded from a 1964 popular electronics magazine.
I used a neon sign Xformer, and an acrylic 4" tube on which I wound about
45.5" of #24 magnet wire (that's 2100 turns according to my calculations)- it
seemed happiest with a 5 to 10 turn primary, at which point I could draw a 4
or 5 inch spark from the top of the secondary, but it would not arc into free
air. I'm using a 15KV neon sign transformer (30 ma, GE model 9tcx520at, a
,001 microfarad mica capacitor (cornell dubiller type PL?254-46, rated at
25KV, 25 amps at 5,000 kcs, 18 amps at 1,000 kcs, 11 amps at 300 kcs). This
is a fairly large aluminum enclosed capacitor with a 4" insulator and a large
terminal on it - don't know what it came out of, I got it at a swap meet for a
few dollars and cleaned it up.
so I have some questions:
1. from what I have read, this transformer (since it has AC ratings) should be
ok at 15KV, right??? or should I use it with 7.5KV transformers (I have a
couple of 25 ma 7.5 KV beer sign transformers)??
2. from what I have read, it would seem that my secondary coil is about twice
as long as it should be. so a 4" tube with 20" of 24 gague wire will give me
between 900 and 1000 turns. I'm inclined to repeat with such a secondary.
Comments??
3. Most of the neon sign xformers have the center tap of the HV windinds
grounded to the case - certainly this is the case with the 15KV units I have
looked at - this would seem to be a problem with a standard tesla circuit
because it prevents you from grounding the Xformer case and also the low end
of the coil. I presume that usually this whole mess is left floating???
4. should I wind a smaller coil - for example 2 inches by 10 inches with finer
wire first??? it's actually harder of course to use finer wire.
5. what kind of spark gap do you recommend?? I read that a rotary is not a
good idea for neon sign xformer based coils, so a multiple break static gap
maybe????