Re: MOSFET Coil- Ready..Set...

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

Original poster: "S Gaeta by way of Terry Fritz <teslalist-at-qwest-dot-net>" <sgtporky-at-prodigy-dot-net>

First, I would like to thank everyone who replied with links and
suggestions. I checked out the Maxim site, and the MAX parts are a little
pricy compared to other ICs, but I was allowed to order them in small
quantities. The 74HC14 (which is the correct # - Thanks Steve) was found at
futurelec-dot-com at dirt cheap prices. By the way most of their semi's are
cheaper than other places.

The circuit is Justin's design, and it is at
http://dave.golfbuddys-dot-com/hvguy/new/FBSSTC/sense_driver.GIF
I suppose that it is possible that driver transistors might be used somehow
in place of the high current inverting and non inverting driver ICs. A
friend suggested that I use driver transistors with a center tapped primary
on the driver transformer, use an inverting buffer to drive one transistor,
and use two inverters in series to drive the other one. I would be afraid
that this would introduce delay which would somehow mess things up. B892s
are commonly used to drive P460s.

I was also wondering why a feedback winding (coupled to the Tesla coil
primary) couldn't be used in place of the pick up antenna input where the
'human touch' is required to start the coil working? Somehow I don't feel
really comfortable with high impedance inputs on sensitive devices with all
that high energy noise floating around. If someone else touches the antenna
while I am playing with the arc, there is the possibility of MOSFET guts
flying all over the place, along with toasted driver components. I am also
guessing that the better coupling of a feedback winding might produce a more
reliable startup, and keep the coil going until you kill the power.

Sue

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, April 05, 2003 9:35 PM
Subject: Re: MOSFET Coil- Ready..Set...


 > Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<dhmccauley-at-spacecatlighting-dot-com>
 >
 >
 >  > Hi Dan,
 >  >
 >  > Thanks for the substitutions. I am going to try to look for those
later. I
 >  > chose this design because I liked the idea of a self adjusting, self
 >  > resonant oscillator, and it looked like a really simple circuit, but
the
 >  > component selection may be a little more exotic than I thought. I don't
 > like
 >  > designs with exotic components, especially in  things like a Tesla
coils,
 >  > where active components are expected to blow up on a regular basis!
:-).
 >  >
 >  > It also seems that the only place the HC74LS14 is mentioned on the
 > internet
 >  > is that particular circuit that I want to build!
 >  > http://dave.golfbuddys-dot-com/hvguy/new/P460Hbridge/schematic.GIF
 >  >
 >  > Thanks again,
 >  > Sue
 >
 > Another thing is a lot of times you'll see circuits on the web which are
 > created by international (non-US) individuals and a lot of times there
will
 > be components which are more
 > readily available in those countries than here in the US and vice versa at
 > least via their local distributors.
 >
 > Also, MAXIM is very good for free samples (in quantities of 2 usually), so
 > they might have the MAX913 IC you were looking at.
 >
 > I'm sure if you could get a sample circuit posted to the web, that myself,
 > Justin, or some of the other SSTC guys and gals here could help you get
 > substitute parts for your design.
 >
 > Don't feel bad.  Every day at work i'm forced to find different ICs for
 > designs I'm working on.  You need say an op-amp with this much bandwidth
and
 > this much slew rate and this voltage, you find one that fits the bill
 > exactly, and once you submit it to the parts engineering group they'll
 > reject it either because its on the future (<10 years) list to become
 > obsolete, they don't like the vendor, they don't like the reliability
data,
 > etc...
 >
 > The Captain
 >
 >