Re: My TC So Far

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

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


You can get a lot of help by logging on to John Couture's excellent website.
He has a computer program that you can use free of charge.  You can do a lot
of "what-ifs" to see what works best for your application.

Calculate the impedance of your MOT transformer, and then select a cap
reactance value to give you 1.6 times the impedance match.

Dr. Resonance

 >
 >    Well it's been almost a month since I started working on this project,
 > to build my first-ever TC. I've accomplished quite a bit over the past few
 > weeks, and certainly learned a lot in the process. Needless to say, I
still
 > have a lot of learning to do and I already see some potential mistakes I
 > may have made. My TC won't be ready to power up for a few weeks yet, but
 > here's the story so far.
 >
 >    The first thing I started working on was the secondary coil. I was
going
 > by the bit of knowledge I had at the time, based mostly on recommendations
 > from a few sites. I had originally planned to use a 2" form, but decided
on
 > 4" instead, to accomodate more windings. Now being the cheapskate that I
am
 > (and living so far out in the country), I didn't want to pay big bucks for
 > a piece of some exotic material. I chose PVC, since I've heard it's the
 > choice of most coilers. The nearest hardware store only sold PVC in 10'
 > lengths, and wanted almost $20 for a piece of 4" PVC. Not wanting to wait
 > that long or spend that much money, I hunted around in the storage
building
 > out back and lo and behold, found a 10' length of 4" PVC. But alas, it was
 > perforated (~2 holes per foot). So after cutting the piece to use for my
 > form, and cleaning it up, I cut a bunch of small pieces off the remaining
 > pipe and epoxied them inside my coil form. Once dry, I filled in the
 > shallow! cavities on the outside of the form with plastic wood, and
 > thoroughly sanded everything smooth. I pre-coated the form with 3 coats of
 > Minwax Helmsman (high-temperature spar urethane - I hear polyurethane
isn't
 > so good). It took me a week to build the winding jig, but once completed
it
 > worked like a charm. It was run by an old variable-speed sewing machine
 > motor, and controlled by a foot pedal from the same unit. I even added an
 > electronic counter (purchased for $3.99 at an auto parts store) to
 > precisely count the number of turns. The wire used was Elektrisola #27
AWG,
 > and altogether I wound a total of 1,481 turns. The winding progressed
 > fairly quickly (about 1 hour in all), and once completed I added four very
 > thick coats of the same finish. (to avoid runs, I attached a low-RPM
 > turntable motor from an old microwave oven, and left the form rotating
 > until the finish was dry). Now all that remains is to glue on the end
 > plugs, and continue to the rest of the components - ! I hope.....
 >    Doing more reading today, I see that PVC is supposed to be "dried".
 > Well, this stuff was sitting in a well-covered storage shed for at least
10
 > years, and in the days before the coil was wound, I left the form near the
 > wood stove to allow the varnish to dry. I also wonder about the
 > perforations, but I'm quite certain that these were well-sealed, and
 > shouldn't be a problem.
 >    Now I can continue working on the other components. I'm having some
 > trouble figuring out what to build for a power supply. I had planned to
use
 > a very large old MOT, with a diode-capacitor voltage tripler (as described
 > on Greg's Garage). But I do not know how I would then determine what value
 > of tank cap to use, as well as what the primary inductance should be. All
 > the formulas I've seen, for determining the resonant frequency, require
 > that the current output of the power supply be known. When using a DC
power
 > supply, how does one determine the value of these other components?
 >    For the sake of simplicity, I may start out with a simple OBT power
 > supply and go from there.
 >    I can see I still have a lot of learning to do.
 >    Thanks for any advice.
 >
 >
 >