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

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

Original poster: "Justin Hays by way of Terry Fritz <teslalist-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

Hi All,

I believe an SSTC that uses a feedback coil on the same coilform as
the primary, has been successfully tested by Italian coiler Mazzilli
Vladimiro. I'm not sure how his circuit is/was set up, but I think
there are pictures in the www.pupman-dot-com "Images from the list" page.

You can sample current from the resonator ground wire using a
current-sense resistor. You would need an op-amp (2-5Mhz UGB or
so...TL08X would work good) set up as a differential amplifier to
amplify this signal (and also any noise present), and then finally a
comparator to square it and detect zero crossing.

I would think that using a feedback coil would be difficult, mainly
due to ringdowns and spikes that it would pick up from the primary.
You would have to filter this stuff out, which would add phase lag
that would push the system farther away from perfect ZVS. After
filtering, you're looking at amplification then comparison.

The antenna method isn't too bad really. I use a BNC connector on
top, and a little whip antenna I made. I can wrap my hand around the
antenna (which is only a few inches long) and nothing changes...it is
lower impedance than you think ; ) and the simplest I've found yet.

Justin Hays
KC5PNP
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com