Re: [TCML] Ignition Coil Won't Spark from Mosfet but DOES spark By Hand??? HELP!?

[Grenadier <teravolt.org@xxxxxxxxx>]

Try an IGBT and snubber circuit in //. Maybe the mosfet you're using is
turning off too slowly, or is leaky at higher voltages.

On Thu, Feb 16, 2012 at 4:10 AM, Jim Houx <pha3zme@xxxxxxxxx> wrote:

> Hello everyone,
>
> I'm new to this list.  Please be gentle! :)  I came because I can't find
> the answer to my problem from googling.  And the problem is mind-numblingly
> simple.  I just can't see what is going wrong!  I thought maybe some
> experienced high voltage people could help.
>
> I'm trying to get an ignition coil to create sparks running it with a
> Mosfet powered by a 555 timer.   The Mosfet is definitely switching.  I
> checked it with resistor, ampmeter, and o-scope.  Everything is behaving
> predictably but when I use it to power a car Ignition Coil, I don't get any
> sparks.  I can tap the terminals of the Ignition coil by hand -- Even with
> it connected up to the mosfet circuit -- and get sparks.  But when I try to
> let the mosfet drive it, there are no sparks.  There is definitely current
> flowing.  And if I change the frequency to super low (like a pulse every
> second), the ampmeter is registering the pulses.  If I change the frequency
> to super high (like 100khz), I get averaged current flow on the ampmeter.
> But I don't get sparks!!!!!  I also switched out mosfet with other kinds
> (different ratings).  Didn't fix it.
>
> Anyone else ever run into this problem???
>
> Here's a schematic similar to my setup:
> http://www3.telus.net/chemelec/Projects/Car-Coil/Car-Coil-1.png
>
> Hope someone else has had this problem before and can help!!
>
> Thanks,
> Jim
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