Re: The ignition coil driver circuit again!!!!

["Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

The problem is probably breakdown, not over current.  The 2N3055 can take
15 Amps all day long and, on a good heat sink, can dissipate 150W.

----------
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: The ignition coil driver circuit again!!!!
> Date: Saturday, September 02, 2000 4:20 PM
> 
> Original poster: "wsc1914" <wsc1914-at-hotmail-dot-com> 
> 
> Do you think it would take the strain off the2N3055 transistor if 2 of
them
> were put in parallel, then the current would the shared between them.
> 
> Oliver.
> 
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Saturday, September 02, 2000 10:22 PM
> Subject: Re: The ignition coil driver circuit again!!!!
> 
> 
> > Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
> >
> > 2N3055's should be $0.50 each. but they are a terrible choice to drive
> > anything with HV in it.  Why? because they have a 60Volt BVceo (thats
> > breakdown voltage Collector to emitter).  Sure, folks run them, mostly
> > because the breakdown is energy limited by other components so the
power
> > dissipated is low enough to prevent cooking them. However, they WILL
die
> > eventually.  A much better choice would be a Horizontal Output
Transistor
> > (radio shack used to have them, they may still), or a transistor made
for
> > electronic ignitions (450-700 V BVceo and 5-10 A Ic max)  that has a
> > several hundred volt BVceo. Both of these are made in enormous
(millions)
> > quantities so they should be cheap.
> >
> > However, if you insist on running a 3055.... Try putting a neon bulb
> across
> > the collector and emitter. It acts like a 60-70 volt limiter to clip
the
> > spikes.  If you blow up the neon bulb, you know you've got some other
> > problems.  Or, the solution used in electronic ignitions (a very
similar
> > application, if you think about it) is a 450Volt Zener. Take a look at
the
> > data sheet for the Motorola MC3335 (I think), automotive electronic
> > ignition IC for ideas.
> >
> > 2N3055's are ubiquitous, but they are basically a low voltage (60V) low
> > gain (hFE of 15!) low frequency (fT of a few hundred kHz)  part for
things
> > like linear DC regulators.  Lots of people have a box full of them that
> > they picked up somewhere (myself included), and so when they need a
power
> > transistor to try something out, they use it.  There are a lot of
better
> > parts that are just as cheap (surplus and new)...
> >
> > Think of applications that are mass, mass market:
> consumer/automotive/etc.,
> > and look for parts that would be used in that, and hunt those down.
> > .
> > ----------
> > > From: Tesla list <tesla-at-pupman-dot-com>
> > > To: tesla-at-pupman-dot-com
> > > Subject: The ignition coil driver circuit again!!!!
> > > Date: Saturday, September 02, 2000 12:25 PM
> > >
> > > Original poster: "wsc1914" <wsc1914-at-hotmail-dot-com>
> > >
> > > Well, I have just come across one other problem - the 2N3055
transistor
> > has
> > > just burned out. I'm not sure if this was the heat or it was a power
> > surge.
> > > Whenever I try to use it now it buzzes quietly (like normal), but it
> gets
> > VERY
> > > hot VERY quickly, and no power comes out of the coil.
> > >
> > > I thought about putting a cap over the transistor Collector and
Emitter
> > to
> > > supress surges. I have the following - could someone tell me what
would
> > be
> > > suitable, if any of them?
> > >
> > > 10000uF 16v Electrolytic
> > > 220uF 35V Electrolytic
> > > 0.1uF 50v Ceramic (I don't think so!)
> > >
> > > Any ideas?
> > > Please reply quickly if you have the time - as I want to get this
> working
> > > properly before I burn out any more! They are not cheap!
> > >
> > > Many thanks to all!
> > > Oliver.
> > >
> > >
> > >
> >
> >
> >
> >
> 
>