From: firstname.lastname@example.org (Rich Grise)
Subject: Re: Ignition Coil Power Supply Final Question
Date: 14 Jan 2003 17:16:24 -0800
NNTP-Posting-Date: 15 Jan 2003 01:16:25 GMT
I disagree with M. Bachler, in that a diode to short out the
kickback will serioudly degrade your spark - most people use
them to protect their output transistors.
I wouldn't use 2N3055's, unless you have a bunch on hand -
they're not rated for anywhere near the voltage an ignition
transistor would have to withstand.
Thoremail@example.com (P!erCer) wrote in message
> In the coil, when the magnetic field collapses, is high voltage only
> produced at one end? I would think that high voltage would be
> produced at both ends and sent back through the ground wire too...but
> it isn't. Why?
Voltage is a difference between two points. The "high voltage" is
produced across the coil, which doesn't particularly care which end
is closer to ground potential.
> I can see no way this config is going to produce AC, but then again
> this project was basically the third electronics thing I've built. I
> appreciate the people on this forum who know what they are
> doing...this will be DC, right?
No, if it's done right, it will be pulses. Also known as "Pulsating
> And a last quick question:
> For the 2N3055s, I should connect the positive to the emitter,
> pulse from my signal generator to the base, and the output to the
> casing of the whole thing, which is the collector. Right? Why the
> hell did they make the CASE the collector instead of just a third pin?
Because the collector is where the majority of the power dissipation
happens, and the case conducts that heat to the heat sink.
> Couldn't that be dangerous, if you mount a metal heatsink on it and
> then somebody touches it to see if it is hot? I do things like that.
Learn not to. That's what insulators and heat grease are for.
> If more semiconductors are like this one, it worries me.
Almost ALL of them are like that.
> Thank you for your time,