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Re: Solid State - the business end.
Greetings:
I am interested to find out the best way to connect the solid state driver
to the Tesla coil.
So far I've tried driving a conventional primary (but large voltages sent
back from the secondary zapped FET's. Now I'm bottom feeding and
winding working transformers.
Rob wrote:
> I thought I'd weigh in on the discussion-
> even though in my own setup- a solid-state driver: the only resonant
> caps are in the oscillator circuit (a mylar 4700pf unit, and not
> really resonating: a relaxation osc) and the parasitic series resonant
> C from the coil to ground.
Where is this capacitor C and what's it doing and should I have one?
I'm bottom feeding - one end of the output transformer to the tesla coil,
other end to ground.
Paul wrote
>Harmonics from the switcher set up some mean nodes.
>That can burn up your secondary.
Paul wrote:
>PWM is a great way to regulate but not so good for tesla coils because
>of the off time.
Paul I'm happy to have got pwm working - can you expand on the problems
- is offtime a problem for conventional secondaries or for bottom feeding
as well. I do find that there is not a linear relationship between pulse width,
current drawn and spark produced, but I can't tell if this relates to my current
limiting jumping in or to the different harmonic mix produced by each pulse
width setting.
Thanks for the expanation of the advantage of the LC circuit.
I'm still not sure what the exact impedence of my secondary coil is -
I'm just trying to match to it by trial and error. (My DVM and even my analogue
voltmeter are
strongly affected by the Tesla coil - spark length, ammeter reading, and the
density of the smoke are the things that I'm going by. (I know I'll have to slow
down
and get some proper measurements but I'm having fun.).
I wound a larger coil onto a 5 gallon polythene bucket. With the toriod it
resonates at 104khz - alas I couldn't put much power into it - I suspect because
my transformers have too low an inductance at this frequency (current limiting
goes on).
Time to wind another output transformer (actualy I'm too mean to buy more
transformers -
I've got a couple of extra bobbins and one set of cores.) This time I'll put
multiple
taps on the secondary).
I won't get much chance to play for a couple of weeks - first my wifes parents
and then my parents are coming for a week :) but I've had to clear my
electronics
from the spare room :( .
Paul wrote:
>I really like the TelCom mosfet driver TC4428
>I just feed this thing a square and it drives like crazy. 1.5A peak.
>It has one inverted output and one not inverted
>takes in +5 cmos, puts out 0 or 12V.
I was using the TC4427 chip in this series (2 non inverted)
(And smoked 2 when the FET's blew learned to put a diode into
the 12V supply so as not to blow every chip on the line!)
But I discovered the TC4422 - 9A peak. It survived a FET blowing
as did the other 3 FET's it was driving at the time.
Paul if you >> just feed the 4428 a square
how do you do current limiting?
I won't get much chance to play for a couple of weeks - first my wife's parents
and then my parents are coming for a week :) but I've had to clear my
electronics
from the spare room :( .
Have fun,
Alan Sharp. (UK)