Here's one sure way to rig up a quick and easy spark coil to run old angine ignitions , keep dogs out of your trash or test the strength of one's continence. The best part is that it is made of ordinary junk car fodder - namely a coil and condensor (preferably one with internal resistor) and a NO/NC Bosch relay found in clusters under late model car hoods .! (If you like, you can add a 0.5 to 1 mfd capacitor in series with a 500 to 1000 ohm resistor across the breaking points of the relay (30 & 87a) and they will last much longer ).