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Re: A SSTC Ground ?
Original poster: "Gavin Dingley" <gdingley-at-ukf-dot-net>
Hi Steven,
this 60 degree phase shift, is the coil the primary or secondary? This would
be due to the fact that there are reactances involved. If it is the primary
coil, the output decoupling capacitor and primary coil will develop this
phase shift?
Cheers,
Gavin
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, September 17, 2003 5:20 AM
Subject: Re: A SSTC Ground ?
> Original poster: "Steven Ward" <srward16-at-hotmail-dot-com>
>
> Hi Finn,
>
> some comments within:
>
>
> >I don`t yet make any conclusions of this, other than it is possible to
> >make measurements, that it is useful.
> >I know that Stephen (hi!) has made great results with the same circuit,
> >so it can be tweaked into working, probably by adjusting distance from
> >coil and antenna length.
>
> At one point i had the twin coils working off of a breadboard, i made no
> measurements of any kind. Then, i built a PCB for it and checked this
> exact same thing you did, the phasing between the driver and the
> coil. Indeed i saw a huge phase shift! I was freaked and thought surely
> something was wrong here! So scared that i scraped the poorly made PCB
and
> put it on some perf board. Again, the same phase shift (and it looked to
> bo 60 degrees or so). With a teslathon the next day i figured, i may as
> well see what happens. I cranked her up to 120vAC input, and it
flawlessly
> produced bright 34" sparks! The heating was not a problem which suggests
> to me that the fact that it does not *appear* to be ZVS may not really be
a
> problem. I cant explain it at all, but that phase shift has stayed with
me
> since the start and has never caused any trouble.
>
> >But without measurements?
>
> As i mentioned, i had the coil working without any measurements
> really. The only thing i always test is for either the tuning if im
> running a free running osc, or that feedback is taking over if running a
> feedback system.
> I usually get feedback to kick over at some 4vAC input.
>
> >I would like to stick a cap in the ground lead and derive the sync.
> >signal from there, as suggested by mr. Herrick, and it is the problems
> >associated with the ground lead that prompted this thread. I would like
> >to see that signal on the scope first, before piping it into the
> >comparator.
>
> Just make sure your clamping diodes (whether they be germanium or signal
> diodes) are in good shape!
>
>
> Also, consider a current transformer as a means of feedback. Ive tried
but
> was never successful. Basically use one of your gate driver transformer
> type ferrites and wind some 30-60 turns of wire on it (you will need to
> experiment) and pass the ground wire of the coil through the toroid. Now,
> on the output, you need diodes to clamp the voltage to a safe level.
> Usually, we use 2 sets of signal diodes. Put 2 diodes in series across
the
> output of the transformer, and then put another set going in the oppisite
> direction. This clamps the voltage to whatever the forward voltage of the
> diode is (i think i ended up with a 1.7V squarish wave after the diodes
> were there. Then find means of feeding this into the comparator via a
> capacitor to keep it strictly AC. Ive heard of others having some success
> with this using filtered DC as the supply, but with half-rectification the
> arcs to ground get thin and bad sounding (from something going wrong with
> the comparator). Good luck anyhow, its something to think about.
>
> Steve Ward
>
>
> >However, I`l probably try to see it on a cheap analog scope at low
> >power.
> >
> >There is a construction picture of the h-bridge with it`s piggyback
> >driver here:
> >
> >http://home5.inet.tele.dk/f-hammer/Resize-of-sstc1.jpg
> >
> >With 2 AMD K6 coolers it runs wonderfully. The gate resistors are not in
> >place on the pic.
> >
> >This is fun
> >
> >Cheers, Finn Hammer
>
> _
>
>