Plasma Jet Ignition

[Chris Conlon]

At 01:33 PM 2/21/99 -0500, Raymond C Drouillard wrote:

>On Sun, 21 Feb 1999 22:12:29 -0700 Marc Piccioni writes:
>>
>>Just a quick question, if you get the high current flowing how are you 
>>planning on terminating it?
>
>It'll go away when the capaciter discharges - the same as a xenon flash
>tube.

Ray is exactly right, of course. I did say it was like a flash lamp
driver. ;)

In this case though I'm looking at 2 possible ways to end the spark.

First, I'm planning to use a relatively high frequency step-up
transformer, and a relatively small capacitor. I can just turn off
the drive circuit, and the spark will die out in short order. (Yes,
this will put me in for a relatively inefficient circuit.)

This will probably be all the control I need - I *want* the spark to
last for 90-120 crank degrees, if possible!

Second, an idea stolen right from flashlamp stuff, you can have an
SCR or the like set up to "dump" the voltage when you want the spark
to end. Camera flashlamps use this as a way to abort the flash at a
desired instant and control exposure.

This stuff is still a bit uncertain because I simply don't know how
much voltage or current will be needed to sustain the spark after
it's begun, and the circuitry gets a lot trickier if you're talking
about 3000V vs. 300 or so.

   Chris C.