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Re: 250watt solid-state flybacks? (fwd)

Thanks everyone,
The answer is definitely in this last lot of info.
I will build up a HV full wave rectifier coupled to the primary cap, a test
spark gap and a lash up primary
to enable measurement of the number of bangs per second.

My guess is 24volt -at- 4amp may be enough. But if it isn't I'll then try the
auto-inverter idea.

I guess the Helmet mounted secondary will need fairly thin wire to get a
reasonable number
of turns.
Anyone had experience with making secondary coils say about 40mm diamx100mm
high?
Kind regards,
David Hosking
Pharmacist,Amateur scientist, Pyrotechnician & Tesla Coiler.

 "Be very careful what you put into your brain
  because you will never get it out!"

----- Original Message -----
From: Tesla List <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, October 14, 1999 10:14 AM
Subject: Re: 250watt solid-state flybacks? (fwd)


> Original Poster: Tesla List <mod1-at-pupman-dot-com>
>
>
>
> ---------- Forwarded message ----------
> Date: Wed, 13 Oct 1999 08:51:43 EDT
> From: Bobbaust-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: 250watt solid-state flybacks? (fwd)
>
>
> > Subject: Re: 250watt solid-state flybacks? (fwd)
> >
> >  Hi David,
> >               ditch the 2 lead acids for a start.  The power you can put
> into
> >
> >  most flybacks at 24V would be more like 50W or 100 if you were lucky.
I
> >  suspect I was the guy who said you can get 250W into a flyback.  For
this
> I
> >  used a 70V supply and put about 4A in but the FETs burnt at least
30-40W
> of
> >  that so cal it 250W.
> >  The basic system is fairly simple, a square wave oscillator, a a fet
> driver
> >  chip and a large FET or bipolar.  It is easier to use fets as they draw
a
> > lot
> >  less base current and make life easier for the driver.  If you use the
555
> > as
> >  your oscillator you can drive it straight into the FET as the 555 can
> >  sink/source 500ma, remember to put a snubber network in tp protect the
> 555,
> >  this isn't really necessary but it easier to take little peracutions
that
> >  cost almost nothing than keep blowing chips.
> >  I would question whether you need that much drive power as all that the
> >  higher power seems to do is heat up the flyback and make the sparks
more
> >  intense.  I have tried up to 2kW into a flyback and all it did was
shoot a
> >  huge arc then blow itself to bits leaving little more than a scorched
> core.
> >
> >  For your application I would say that you want about a 100W or so.
> > Therefore
> >  I would have thought you could get away with about 40-50V drive
depending
> on
> >
> >  your flyback.
> >
> >  Have (Head Mounted) Fun
> >  Nick Field
> >
> Sounds like Nick thinks you need more voltage input than your batteries
> alone.  Some options:
> 1) use 3 or 4 smaller lead acid batteries in series for 36-48 VDC as a
> source.
> 2) use the 12 V battery to feed a canniballized car stereo amp, they
usually
> have internal inverters that convert 12vdc to around plus & minus 20 to 30
> vdc supplies for a total of 40 to 60 vdc.
> 3) use the 12v battery to feed an inexpensive auto inverter.  You can get
> these for $30 - $40 rated at 100 to 140 watts.  They have inverters and
> generate a 170-180 vdc supply.  They also have high-V high-speed switching
> transistors (probably mosfets) to produce a nice square wave for the
> "modified sine wave" output they all put out
>
> If you get someting working let us know, this sound like something I would
> build (and wear).
>
> Bob Baust, newbie
>