On my last instructable about my mini Tesla Coil I did not do so well because I did not know much about them but since then I have learned much more and have batter plans.
How it works: First off the mains goes through a high voltage transformer and charges the capacitor bank. When the caps are done charging they will let the high voltage from the transformer "pass" through them. During that split second (much to fast for a human to detect) the arc will jump through the spark gap, which is automated with RSGTC's, the caps will discharge into the primary coil. This is where resonance comes in, the fast action of the caps and spark gap rapidly induces an electromagnetic field around the primary, what many dont know is it starts off as a low voltage that adds up each time the spark gap fires until it creates extra high voltage
-=This project deals with high voltage that could potentially be lethal, do not touch the streamers unless you know what your doing=-
-=never operate high voltage equipment before turning it off=-
-=I will be some information from my other instructable=-
Step 1: You Will Need
1' tall 1/2" diameter PVC pipe or other non conductive cylinder
about 5' of speaker wire, I didn't have enough of the thicker gauge wire
8" tall 1" diameter PVC pipe, you can use something a little wider but I couldn't find anything
10kV 23mA ignition transformer, you can get them on eBay for about $20-$40
15 1kV 0.01uF film capacitors
about 300ft of 32 awg mag wire
some 18 awg solid copper wire to connect everything
2 round headed bolts or "i" screws, try to keep them as smooth as possible
a 10"x4" piece of wood
copper connectors or some 1" bolts with nuts
a drill with various sized bits
a hot glue gun
a soldering iron, with solder
Step 2: Spark Gap
This is one of the most important part of the whole resonating thing, you could compare it to the heart in the brain, the brain cant control the hear without blood and the heart can't supply blood without the brain. with the heart being the spark gap and the brain being the capacitors: the capacitors charge up via the transformer, when they are charged the spark gap fires and releases its energy into the primary. without the spark gap you would have continuous input into the primary and without the capacitors all the power would just go straight through the spark gap. So lets make a spark gap.
If your using bolts:
Take two 2"x2" pieces of wood and drill a hole in the middle that can fit the bolts and put a nut on them to secure them or if the wood can hold them in place then dont worry about the nut. now glue these on the board in front of the inputs, the capacitors come after, then the primary, then the secondary.
If your using "i" screws:
First drill 2 holes at an angle where ever your going to position your gap, now screw them into the hole and adjust them until the are at an appropriate length apart .
Step 3: Capacitor Bank
The amount of capacitance is determined by the input current, I'm not entirely sure how to calculate this but I would be grateful for anyone who could post a comment on what the equation is. Now it just so happens that the amount of capacitance we need is exactly the capacitance of the capacitors so we dont need to worry about soldering them in parallel, we just need to do something about the voltage so we only have to solder them in series. Its best to have the overall voltage of the capacitor bank about 2 or 3 times the about of voltage going in, so-we are using a 10kV 23mA transformer to power it, our capacitors are 1kV 10nF. Solder all the capacitors in series to increase the voltage to 15kV and were not going to solder any in parallel because like I said, the capacitance is perfect. You may want to put a 10M ohm resistor across the leads to discharge the capacitors after use, you will also need to hot glue the capacitor lead to keep them from sparking over if you built yours like mine.
-=I did not get any pictures on how I made this because I built it for version 3 which I did not make an instructable on=-
Step 4: The Secondary and Primary
This will take a lot of time do do but is pretty easy. All you have to do is wrap the 32 awg wire around the PVC pipe until there is about an inch of space left on each side and hold in place with tape or do what most people do and cover it in gloss. The way I did mine: I put 3 nails into my desk, on one I put the role of wire, the other two I used to keep tension on the wire so I could use both hands to hold the pipe, it took me about 1/2 an hour to finish.
After you have cut your 1" diameter PVC to length grab your speaker wire and wrap it around he pipe. Strip the insulation off one end of the wire, and glue that to the bottom of the pipe. Put the other end in a vice and pull the wire tight (not to tight or the glue will come off), turn the pipe until you are all out of wire, the wire spacing should be about 1/2" apart. when you get to the end leave a bit of wire sticking out of the end and glue the insulated part to the pipe, now glue every turn to the pipe all the way down so it never comes loose.
Glue the secondary onto the end board, I drilled a 1" hole before i glued it on for support. now slide the primary over and glue it to the board after you have centered it.
In that last picture, the shine is the exposed wire but it looks like reflection on the insulation.
Step 5: Wire It All Up
Connect the HV transformer to the AC mains, connect the spark gap in parallel with the HV output, after that connect the capacitor bank series and close it off with the primary coil. Put the secondary coil inside the primary and hook the bottom wire to ground (I did nothing with it) and add a topload/toroid/torus to increase the voltage and effects of the sparks.