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

["wsc1914" <wsc1914-at-hotmail-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

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.
> >
> >
> >
>
>
>
>