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

[Jim Houx <pha3zme@xxxxxxxxx>]

I got the problem fixed.  It was stupid.  The coil was bad.  I tried
everything under the sun and finally decided it must be the coil.  I
compared it to another coil and found that the second one had way stronger
sparks and more consistent sparking done by hand.  It worked perfect with
the circuit board.  The only reason I think the crap coil would spark when
I struck it by hand is because of vibration of me touching the contacts and
all the little harmonics and charge changes that were just enough to get an
arc out of it.

I was just too newbie to recognize a bad coil.

- Jim

On Thu, Feb 16, 2012 at 2:20 PM, Carl Noggle <cn@xxxxx> wrote:

> Hi, Jim,
>
> A 555 is pretty slow and doesn't have much current to suck charge out of a
> Mosfet gate.  You might need to use a driver.  There are many available for
> $2.00 or so.  Also, the Mosfet should have a pretty high voltage rating
> since the ratio of an ignition coil is not that high, so a big pulse
> appears on the primary of the coil, and your fet could be limiting the
> pulse.
>
> ---Carl
>
>
>
>
>
>
>  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<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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