Here is probably the best ignition coil driver circuit that I have seen. As far as I know it was designed by Jochen Kronjaeger. You can find the original at Jochen's High Voltage Page This circuit is designed to run from 230V, but I have came up with a circuit that will run from 120V about just as well. You will need to find two ignition coils (preferably of the same type), a 100uF with at least a 200VDC rating, a full-wave bridge rectifer with a rating of about 5A at 200VDC. A large power resistor with at about 150-200ohms resistance and a power capability of at least 100W, or you can use an aquarium immersion heater. The next two things are optional, but they will make the project a lot more interesting. You might want to get about three 6A 200VDC SCRs. You can get these from Radio Shack. You might also want a simple square wave pulse generator. This can be just a simple 555 timer circuit. Make sure you can vary the frequency on it.

Ok, here is a simple schematic showing my project:

This circuit is fairly easy to build. If you can't get an SCR, you may also use a TRIAC as a substitute. If you can't get either then you can use a relay, switch, or just two pieces of wire to trigger it. The contacts will probably be burned out soon though. The resistor or heater is used so that the power doesn't need to be cut when you discharge the capacitor. It limits the current to a safe value when discharging the capacitor. If you choose not to use the current limiter, the power will have to be unplugged every time you discharge the capacitor. If you cannot find a heater or power resistor you can also use a common household lightbulb. This will also give you a visual indication when the capacitor is charged. The bulb will go out when the capacitor is fully charged.

See Automobiles for ignition coils.

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