This Instructable will walk you through building a medium sized Tesla coil.
Step 1: DANGER
Unlike some other high voltage experiments, a Tesla coil's streamers can be very harmful. If you are shocked by the streamers, you will not feel pain, but your circulatory and nervous system can sustain severe damage. DO NOT TOUCH IT WHILE ON UNDER ANY CIRCUMSTANCES.Also, I don't take any responsibility for you hurting yourself.This isn't to say that you shouldn't get into high voltage though, its just that if you are planning for this to be your first HV project, its a little to involved. Instead, try out a nice microwave oven transformer, and be safe!
Step 2: Gather the Materials
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The total cost came to around $25, being that I already had the wood, Snapple bottles, PVC, and glue.
Step 3: Wind the Secondary
Put a small slot into the top of the pipe to wrap one end of the wire around. Slowly and carefully begin to wrap the coil, making sure that you don't overlap wires or have spaces. This step is the hardest and most tedious part, but taking a lot of time will yield a very nice coil. Every 20 or so turns, put a ring of masking tape around the coil to act as a barrier if the coil starts to unravel. Once finished, wrap a tight piece of tape around the top and bottom of the coil and spray it with 2 or 3 coats of enamel.Tips:
Step 4: Prepare the Bases and Wind the Primary
Align the metal stand in the center of the bottom board and drill holes for bolts to go through. attach the bolts tightly upside down. This will allow you to put a base for the primary on top of it. Then bolt the primary's base in. Take your pipe and wind it into a pretty upside down cone (not the flat spiral in the pictures). Then mount it on the supra-base.
Optional was the addition of 2 supports that I zip-tied the primary to.
Forgot to add how to make the spark gap! It is just two bolts in a open-air wooden box, and they are adjustable for tuning, etc. See the last image...
Step 5: Build the Capacitors
I decided to go the cheaper route and build a capacitor. The simplest way is to make a salt water capacitor, using salt water, oil and aluminum foil. Wrap the bottle in foil, and fill it with water. Try to get equal amounts of water in each bottle, as it helps to keep the power output stable. The maximum amount of salt you can put in the water is .359 g/mL, but this ends up being a lot of salt, so you can tone down the amount a lot (I used 5 grams). Just make sure that you use he same amounts on salt and water. Now put a few mL of oil slowly into the bottle. Punch a hole in the top of the cap and put a length of wire in it. You now have one fully functioning capacitor, go make 5 more.
Optional: to keep the bottles in order, make or find a metal crate for them
As Glenn781 pointed out below, 6 Snapple bottles with a 15kV 30mA NST can be deadly! If you are using a NST like his, use 8-12 bottles, not 6!
Step 6: Connect Everything
Wire up everything according to the schematic below. The secondary's ground CANNOT be put to mains ground, it will fry everything in your house.
My Coil's Specs
Step 7: Start it Up!
Bring it outside for it's first run, as it really isn't safe to run anything this potentially powerful indoors, there is a high risk of fire. Flip the switch and enjoy the light show. My NST, at 9Kv at 30mA, makes the coil give off 6 inch sparks. See it below:
Step 8: For the Future...There are a few things that I realize I should change in my next Tesla Coil, one of the main ones being the design of the primary coil. It needs to be both more tightly coiled and it needs more windings. Also, i want to make a better discharge terminal. But, I have a new Tesla Coil planned for when i find the time and money, and it will probably be 6-7ft tall!
But for now, I'd like to admire other coilers hard work!
(embedding seems broken, but links work)