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Needing timed spark (Noob)

a062549

May 3, 2016
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May 3, 2016
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I have a need to build a reliable spark generated from a 12 volt automotive coil.

I need it to spark every 4-5 mostly consistently. It'll be driving a single spark plug

I have looked and thinking a MOSFET using a 555, but about as far as I am capable of in my learning.

Thanks!
 

a062549

May 3, 2016
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May 3, 2016
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Whoops! I need it to fire every 4-5 minutes.
Fingers significantly slower than my thinking, which is pretty slow too!
 

Bluejets

Oct 5, 2014
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Do you know the basics behind how an automotive ignition coil works?
I assume for simplicity you are referring to a Kettering system and not CDI.
A 555 timer on it's own may not deliver accurate timing over 4 to 5 minutes.
How accurate are you talking here?
 

a062549

May 3, 2016
4
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May 3, 2016
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Yes Kettering is my plan. As for the timing just close is fine, a minute or two either way is workable.
ive looked at the other posts concerning using an ignition coils but they tend to want giant spark for a Jacob’s Ladder type projects. I just need a single spark with some repeatability. thanks for helping
 

Bluejets

Oct 5, 2014
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555 circuits in astable are simply not suitable.
There may be an exception circuit out there somewhere but not known to me.
Below is an example what you will be required to reproduce.
Pulse.jpg

The time "T" will be your 4 to 5 minutes.

The time "t" is the time your coils is energised and then turned off to produce the spark.
This time will only need to be very short, long enough to saturate the coil, and that's it, maybe less than 1/2 second would be plenty.
Remembering these coils normally operate in multicylinder engines at many thousands of revs per minute.

A basic solution would be a monostable 555 and have it's "push button start" operated via a small dc motor/gearbox with a cam and microswitch, set so the micro is only on for a second or so. Mechanics could get complex though.

An Arduino promini with a simple timing sketch would be the easist I can think of.
Drive the mosfet via Arduino pin but I would use separate opto isolated supplies for the Arduino and the coil.
 
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