A Tesla coil, named for its inventor Nikola Tesla, is a high-voltage resonant transformer that can be used to produce long electrical discharges. They are relatively simple to construct from easily obtainable materials, and the light shows they produce are fascinating to watch. To make a very simple Tesla coil, follow these steps.
Make the Parts
Find a transformer rated at 9,000 volts or better and 30 milliamps. Many people opt for neon sign transformers, which are relatively easy to find. Others use oil furnace ignition transformers or automotive coil transformers, which produce much more subtle effects.
Make a capacitor by layering the five sheets of polystyrene alternating with the four metal plates. The plates can be copper or aluminum foil or just very thin aluminum plates.
Make the spark gaps with the four L brackets and the bolts. Put the round end caps on the ends of the bolts.
Wrap a heavy-gauge bare wire six or seven times around a cylinder form at least eight inches in diameter. Poke holes in four pieces of PVC pipe and thread the wire through to form your primary coil. The holes in the PVC should be about 1/8 inch apart.
Wind the enameled wire tightly around the three-inch PVC form for your secondary coil. This one should have about 500 turns. Varnish the coil with several heavy coats and make sure it dries evenly.
Wrap 20 turns of enameled wire on two separate 1½ inch diameter PVC pipes for your radio-frequency chokes (RFCs).
Assemble the Parts
Mount the doorknob on top of the secondary coil. This acts as the top discharge terminal. Set the secondary coil inside the primary coil and attach both at the center of the piece of wood.
Attach the four remaining PVC pipes to the underside of the board. Attach the spark gaps, radio frequency chokes, to the top of the board. Slip the transformer underneath, and put the capacitor on top of the transformer.
Attach a ground rod to the wire leading from RFC 2 to the primary coil.