Re: T.C. design, and others.
Subject: Re: T.C. design, and others.
From: chip (Chip Atkinson)
Date: Mon, 5 Dec 1994 13:23:57 +0700
I finally have some time to respond to all the messages that have been flying
>> I consider TESLAC to be a tool, not a "crutch" it assists in coil
>> design, it won't do it for you.
Sorry. I didn't mean to denigrate your program. I know how much time and
effort go into something like this. What I meant was that before I use
a program, I would like to know what it is doing for me. I want the program
to do the drudge work that I could do but choose not to, rather than rely
on the program to provide some values that came from "somewhere".
(Message lost, content remembered):
The discussion of 1/4 wave length windings:
I was thinking of the 1/4 wavelength discussion and the discussion about the
wire "appearing shorter" when wound into a solenoid. I then thought that I
would take the specs for a working coil and reverse engineer it to see what
values I got for the wire length. I found that the length of the wire
closely approximated 1/4 of the wavelength of a light wave at that frequency.
(C = lf, or speed of light = wavelength * frequency). Initially this
seemed to contradict the "shortening" phenomenon. Upon reflection, I decided
that the purpose of the toroid on top is to "lengthen" the wire or drop the
frequency to a value where the wire length works out to the 1/4 light wave
length. So, the questions to those who know, are:
1) Is my figgering correct?
2) Is this a pointless consideration, that has no real bearing on the
real world of coil design? (I don't want to fixate on a hair splitting
issue, but if it is important to a good design, I want to know.)
>> check the draw with RMS volt and ammeters
Does any one know of a good source for ammeters that read in the tens of amps?
I have only seen milliamp meters, except for the expensive inductively coupled
>>> The first step in winding a coil is to select a coil form. The
>>> coil form should be a low loss material (we are talking RF
>>> losses) like polyethylene, polystyrene, or polypropylene, Lexan,
>>> or Plexiglas (acrylic): but a common material is PVC, which is
>>> high loss. Thin wall tubing is best regardless of material.
If one is using a "good" material such as HDPE, is the wall thickness as
critical? Am I better off just using very thin wall PVC and sealing it?
PVC is considerably cheaper.
I took a piece of thin wall PVC and sanded it down a little. Then, using
my mechanized winding apparatus* I started turning the form. While the
form was turning, I applied polyurethane. Because the form was turning
(30 rpm), I was able to apply a fairly heavy coating without runs. I left
the form turning for about an hour while the urethane hardened somewhat
(it was still tacky, but past the point of running when I turned off the
apparatus). I was amazed at how well the coating went when I kept rotating
*I have a lathe to do my winding, but a gearmotor would work just fine.
>>> I have a couple of large .04uF, 80kV DC rated caps that came out of an
>>> XRay generator and I was wondering if these would be good for Tesla
>>> coil work? They were used to filter the high voltage DC output to the
>>> XRay tube, so I'm not really sure if they would be good for pulse work?
I don't know about your caps, but here is some information on some caps that I
have that don't work very well at all:
I have two physically big caps, 0.015 and 0.030 uF. they have big high
voltage insulators on them, and I bet they could handle 60KV (dc). The problem
is that they have too much internal impedance. I could never get a coil
to work with them. They will hold a full charge for at least an hour, so
I know they aren't leaky. The problem is that they seem "slow". I figured
this out by rigging a spark gap across the terminals and listening to it
and comparing it to the sound of different caps that were known to work.
The caps that work are very loud and snappy, but the caps that don't work,
while snappy, are not nearly as loud. This is true even for smaller but
I am putting together questions (and hopefully answers) as time allows and
will send it out when I have something coherent to mail (No doubt it will
take several rounds to make sure it is accurate).