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Re: Help!

Subject:     Re: Help!
      Date:  Sun, 18 May 1997 17:01:52 GMT
      From:  jim.fosse-at-bjt-dot-net (Jim Fosse)
        To:  Tesla List <tesla-at-pupman-dot-com>
       CC:   theiber-at-lonet.ca
References:  1


On Sat, 17 May 1997 20:45:54 -0500, Tesla List <tesla-at-pupman-dot-com>, you
wrote:

>Subject:       Help!
>      Date:    Sat, 17 May 1997 15:17:25 -0400
>      From:    Tom Heiber <theiber-at-lonet.ca>
>        To:     Tesla List <tesla-at-pupman-dot-com>
>       CC:    tesla-at-poodle.pupman-dot-com
>References:    1
>
>
>Hi There. My name is Tom and I am new to "coiling" :)
>
Welcome aboard Tom,

>I have everything set up but I can't get it to work. As I have a wide
>electrical background. I am stumped by this.
>I am using a regular Auto Ignition Coil (which honestly i have no idea
>on what output it gives away) to produce a 1/2 inch spark (without
>caps). But as soon as i connect the Cap (Cera-mite 40KVDC, 3 in
>parallel, 570pf each) the spark dies out completely. No matter what I
>try I can't get it to work. I do not know whether it's the Cap or the
>AIC or something else. Like I said, I am quite new to this so I'd
>appreciate any help.
>
An Ignition Coil is operated in flyback mode where no current is drawn
from the secondary while current is flowing in the primary. When the
magnetic field collapses in the primary the secondary fliesback to
very high voltages.  The turns ratio is much smaller that the output
voltage would lead you to believe. With the capacitors across the
secondary of the ignition coil, the ignition transformer is operating
as a normal transformer - not a flyback.

I just measured one of my spark coils: I applied 1 volt ac to it's
primary and measured 75 volts out of the high voltage terminal. So,
it's turns ratio is 75:1.

Given your circuit with, say, 15 volts in: 15 * 75 = 1.13kV out. This
explains why you can't seem to get any output from it.

I looked up the schematic. Your 1710pF of capacitors is directly
across the high voltage output of the ignition transformer, then the
spark gap and finally the primary of your TC.  Reposition the 1710pF
of capacitors across the primary of the TC. This will allow the
ignition coil to once again operate in flyback mode - where it WILL
generate 15-30kV like you expect.

        Good luck,

        jim