555 timer help

I am new to this newsgroup, I am typically a poster on rec. pyro or metalworking, but I have been working on a new project. I am trying to make an ignition coil for my new turbing engine, and I am quite terrible at reading electronic designs. I know that I will be needing a 555 timer, and an ignition coil. The input into the coil should be

12 volts. I have built a neef type vibrator switch, which made quite a nice spark when used as a relay to put the 12 volts into the ignition coil. But it was very unreliable, and I believe that a 555 timer should be the best route to go, but I am quite new to electronics and have become lost with all the complicated 555 timer circuits shown online. I just need something simple that will trigger a pulse of 12 volts to the ignition coil.

Can aybody help me out?

Thank you, Bob

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See the current issue of Nuts & Volts magazine. Stuart.

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I've used this for various Ign. coil experiments..

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I can help you in designing the 555 timer ckt. Please mention about the duration or frequency of the output pulse you want to give to the ignition coil. If you want the ckt diagram please mail me to snipped-for-privacy@rediffmail.com.

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2N3055 not very good for this. Rated what, 60 volts? Coil flyback voltage likely a couple hundred volts. Use a high voltage transistor, better yet a mosfet or IGBT. You can get a coil driver IGBT designed expressly for use with automotive ignition coils, rated 350 or 400 volts. One example:
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You can find others by using Digikey's parametric search. Go to the

--site map

--parts search


--insulated gate bipolar transistors

narrow the parameters down to

--voltage between 350 to 410 volts

--current less than about 25 or 30 amps

you will get a few dozen IGBT's to look at, quite manageable.

A coil driver IGBT costs a buck or two and will last forever in this punishing application. It's also much easier to drive than a bipolar transistor.

I've built a few custom ignitions and sold them to some motorcycle enthusiasts that wanted to upgrade their old points systems. I used the coil driver IGBT's because I know they will work; they are installed cars out on the road now and have done service for millions of miles with minuscule failure rate. Don't botch things by using a


The original post has a glaring omission: What timing do you require of the spark? We can advise you about the circuit but we need more information.

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