*Before I begin, I feel it is necessary to go over some safety guidelines. Please read each of these points thoroughly before starting this project.*
-Tesla Coils are potentially dangerous devices and precautions must be taken before every operation to help prevent possible damage to property, injury, or death. Prior knowledge of high voltage electrical safety is required, and assumed.
-The arcs from the Tesla Coil produce ozone and other gasses, which can build up to toxic levels in unventilated areas. Do not allow this to occur.
-Tesla Coils can damage or destroy hearing aids and cardiac pacemakers in the proximity of the unit. This means that Tesla Coils are capable of killing a person wearing a pacemaker. It is imperative to verify that anyone using one of these devices maintains a good distance from an operating Tesla Coil.
With that being said, here is what you're going to need for this project.
-4' of 1.5" PVC
-8 pieces of 5"x5" plywood
-2 pieces of 3'x2' plywood
-15kV 60ma transformer with no GFCI
-1' of 3" PVC
-2 bolts the same size, plus 2 nuts and 2 washers that fit the bolts
-1 Computer fan
-1 battery holder
-40 Cornell-Dubillier capacitors, (Model# 942C20P15K-F)
-40 6MΩ resistors
-Material to mount your capacitors to (I mounted mine to lexan, with ceramic stand-offs as legs.)
-4 pieces of 10"x3" plywood
-50' roll of 1/4" copper tubing
-20' of 3/8" copper tubing
-2' of 4" PVC
-1 piece of 4.5"x4.5" plywood
-~1200 ft. roll of magnet wire
-2 aluminum pie pans
-Aluminum dryer duct
-3 copper lug terminals
-High voltage wire
Step 1: The Transformer
For this instructable, I will be using a 15kv 60ma transformer from Info Unlimited.
Step 2: The base
Here's the way I did it:
Generally, you're going to want to have two layers. The bottom layer will consist of all of the delicate electrical components that are part of your primary circuit. The top layer will contain the primary coil, the secondary coil, and the toroid. Each of my two layers measure 2'x3'. I chose to use 4 pieces of 1.5" PVC as the legs of my base and they are each about a foot long. To hold the legs in place, I cut 8 square pieces of plywood measuring 5" by 5", and then drilled 1.5" holes in the middle of each of them to accept the PVC. As you can see, my capacitor array ended up being longer than the base of my coil, so I had to cut a separate longer piece of wood for that. To avoid using metal fasteners, I secured everything in place with gorilla glue. I also used 4 wheels from Home Depot to make the Tesla Coil easier to move around. Keep in mind that the components on the bottom layer should be evenly spaced apart, you do not want arcs forming down there.
This is the one part of the project that you can get creative with. There are plenty of designs that are better than mine so feel free to experiment with it.
Step 3: The spark gap
My spark gap is simply 2 long bolts, which are being used as the electrodes. I chose to enclose them in a piece of 3" diameter PVC. I simply drilled a hole the whole way through the PVC pipe, roughly the same size as the bolts I used, then threaded the bolts through. On each bolt I used 2 nuts and 2 washers to lock them in place, this way I know that the bolts will be secure but the gap can still be easily adjusted if need be. To keep my spark gap cool, I chose to drill a hole through the center of the base and mount a 12VDC computer fan. I glued the fan underneath of the hole, then glued my spark gap assembly over the hole, that way the air will blow up through my enclosure. I wired the leads from the computer fan to a battery holder and attached a switch to keep the fan from running all the time. The battery holder I used holds 8 AA batteries, creating a total of 12V. If you use a smaller fan, obviously you will need a smaller battery holder. AA batteries are 1.5V each, so make your adjustment accordingly. The final adjustment of my gap was ~2.25", but this measurement may vary depending on your specific Tesla Coil.
I'll go through how to wire it later, but hopefully you can begin to see how I have the spark gap wired from some of the pictures.
Step 4: The capacitor array
Step 5: The primary coil
1. Cut a 4.5"x4.5" piece of 3/4" plywood.
2. Drill a 4" hole exactly through the center of this piece.
3. Gorilla glue the piece exactly in the middle of the top layer of your base.
4. Drill a small 1/4" hole through the top layer of your base, right through the center of where you just glued the support for the secondary. This hole will be explained later.
Now, back to making the primary:
The primary coil generates the magnetic flux needed to allow all of your components to work together. As current is pushed through the primary coil, it will resonate at a certain frequency, coupling it to your secondary coil. It is necessary to be able to tune this resonance for the best results, so I took that into consideration when coming up with this design.
Your first step should be to acquire a 50' roll of 1/4" copper refrigeration tubing. This kind of tubing can be found at Home Depot or at online vendors like eBay, if you prefer. Be careful when working with the tubing, it can be easily kinked and I found myself wasting a large portion out of carelessness. When you purchase the tubing it will be wound into a circle, do not unwind it. Instead, use this shape to your advantage and gently start to spread the layers of copper tubing apart to form your coil.
Each turn of the coil is going to need to be separated by a 1/4" gap. In order to accomplish this I made 4 wooden braces measuring 3"x10" each. The wooden braces can be kind of hard to explain, so I drew a diagram and attached it to this step.
1. To start, I measured 1.5" up from the bottom of each piece and extended a center line down the entire length.
2. Next I numbered my pieces, 1, 2, 3 and 4. On piece 1, I made a vertical line .5" in from the end. I then continued to make vertical lines every 1/4" until I reached the opposite end.
3. Next, I made an "X" between the first two vertical lines I drew in the previous step. I then left a gap and made an "X" in between the next set of vertical lines, continuing this pattern until I reached the end.
4. Finally, I drilled 9/32" holes wherever there was an "X".
5. Pieces 2, 3 and 4 followed the same method, except the first vertical line that I made on these was not .5" in from the end. On piece 2, the first line was .625" in. On piece 3, the first line was .75" in. On piece 4, the first line was .875" in.
6. Unless you have an extremely steady hand, it is almost required that you use a drill press for this step. If you are not precise the copper tubing WILL NOT fit into the braces correctly.
7. If you notice, the first vertical line of each piece is offset 1/16". This way, as the copper tubing makes one complete turn, it will form a 1/4" gap between rows.
8. Now I went back to that original center line that I made in part 1 of this step. Using a table saw, I cut the brace in half along that line. This allows you to pop your copper tubing in from above, rather than trying to worm it through the holes.
9. The copper tubing fit nice and snug in the holes I drilled, but I occasionally used a dab of hot glue for extra support.
10. These braces will be under stress due to forces acting on them from the tubing. I found it necessary to use gorilla glue beforehand to hold them in place. Glue the braces perpendicular to the support you made for the secondary, one on each side.
Trying to force the copper tubing through the holes rather than dropping it in from above will be very frustrating and you'll probably kink it numerous times along the way. Because of this, I highly recommend you design your braces as I did in this step.
It is also important to note that the inner turn of the primary should have a diameter of approximately 5.5". If you follow the dimensions I used in this instructable you should get exactly that.
*The following step is optional but recommended*
If an arc from the Tesla Coil happens to extend down and strike the primary coil, a majority of your electrical components could be destroyed. In an effort to prevent this, it is common practice to utilize what is known as a "Strike Rail". The strike rail is a separate piece of 3/8" copper tubing that is placed approximately 2" above the primary and attached to ground. This way, any arcs aimed downwards will be directed at the strike rail.
When creating your strike rail, it is very important that your copper tubing does not form a complete circle. If it does, it could throw off the resonance of the primary.
Step 6: The secondary coil
For this step, you will need a 22" long piece of 4" PVC and roughly 1200' of 26 AWG magnet wire.
Make a mark roughly 1" from an end of your PVC, this is where you will start winding the magnet wire. Drill 3 small holes side by side on this mark, and wrap the magnet wire through them a couple of times, leaving at least 2"-3" of wire on the inside of the pipe. This will hold the wire in place as you wind the rest of the turns. This end will be the bottom of your secondary. Some people choose to use tape to hold their magnet wire in place, this works fine but it leaves the ends of the magnet wire on the outside of the PVC and, in my opinion, looks sloppy.
With an end of the magnet wire secured, you can now begin to wind the secondary. For this instructable, you are going to need approximately ~1150 turns. Go slow, this process will take lots of time and patience. Make sure you don't accidentally cross the wire anywhere and don't leave any gaps in between turns. Use painter's tape to hold the turns in place as you continue to wind, this way you can take breaks without having to worry about the wire coming undone.
Once you've counted roughly 1150 turns, temporarily tape the wire down. Drill 3 more holes on this end of the pipe, just as you did on the other end. Now wrap the end of the wire through the holes a couple of times to secure it in place. If done correctly, you should now have a few feet of extra magnet wire on the inside of the pipe. Bring this extra wire out through the top end of your pipe and cut it about 2" above where the pipe ends. Bend this extra 2" over the top of the pipe, this is where the wire will make contact with the toroid. (See picture 4 if you get confused.)
*You must cut the ends of the magnet wire to the specified lengths. Leaving the ends of the magnet wire too long will cause the Tesla Coil to not function properly and there is a very good chance you will fry some of your components.*
At this point it is a good idea to apply some type of protective enamel to your windings. Enamel will greatly help to hold the windings in place and prevent them from gradually coming undone. I used Dolph's AC-43 insulating varnish. Once 2 coats of enamel have been applied, you can safely remove the tape that was being used to hold everything in place. Now apply enamel again to cover the area where the tape was.
Once the enamel has dried, you can mount your secondary into the support structure that was made in the previous step. As you press the secondary into the support, guide the extra 2"-3" of magnet wire (that we left at the bottom of the secondary) through the small hole we drilled in the previous step.
Under the top layer of your base, where the magnet wire is now protruding through, I attached another copper lug terminal. I wrapped the loose piece of magnet wire around the lug terminal and bolted it in place. This terminal will provide a path to ground later on when we do the wiring.
Step 7: The toroid
The size of your toroid will make a difference in how the electricity is discharged. If you use a smaller toroid, electricity will be discharged more rapidly, but the arcs will not be as long. If you use a larger toroid, electricity will be discharged less rapidly, but the arcs will be much longer.
My toroid ended up being 3"x11" and it produces fairly long 3' arcs. To make it, I used two 8.5" aluminum pie pans that I found at Wal-Mart and a piece of aluminum dryer duct from Home Depot.
1. I bent my aluminum dryer duct into a circle around the bottom of one of my pie pans. You don't want to have any gaps between the dryer duct and the pie pans, so I bent it around the pan tight.
2. Once I formed the dryer duct into a shape I was happy with, I used aluminum tape to secure the two ends. I found that using glue and other adhesives will cause the toroid to underperform.
Place the dryer duct off to the side, we will come back to it later.
3. Bring the two pie pans together, bottom to bottom. While holding them in place with your hand, drill one hole through the center of the pans, and 5 other holes evenly spaced along the outer edge of the pans.
4. Place the dryer duct between the two pans and thread ceramic nuts and bolts through the six holes we just drilled.
5. Tighten the nuts until the lips of the two pans securely tighten up against the dryer duct.
6. Keep tightening the pans together until the dryer duct is firmly sandwiched between them.
The nuts should be tight, but not so tight that they crush the dryer duct.
Center the completed toroid on the top of the secondary. It should make contact with the magnet wire coming out of the pipe from the previous step.
Step 8: The wiring
In this instructable, I'm going to attempt to explain the entire process step-by-step. I uploaded numerous pictures and some of you can probably figure it out just by looking at them. If there's anything that you're unsure about just ask and I'll respond as soon as possible.
*You may be wondering why I have chicken wire rolled out underneath the base of my Tesla Coil. This chicken wire actually serves as my ground. If you don't have access to a good ground, or if you don't want to pound a grounding rod into your backyard, just use chicken wire. It works great, I never had a problem with it. If you use this type of ground, the chicken wire must be at least 10'x10'. I couldn't find a size that big so I ended up using two rolls of it side by side.*
*Please note that all wiring used in this step should be at LEAST 12GA.*
1. To power the transformer, use a long extension cord. This will keep you at a safe distance when you plug it in. I chose to wire my extension cord through a light switch, that is entirely up to you.
2. One wire will run from each output of the transformer to opposite ends of the spark gap.
3. From here, a wire from one side of the spark gap will go through the upper layer of your base, and wrap around the inner turn of the primary.
4. A wire from the other end of the spark gap will go to one end of the capacitor array.
5. A wire will come out of the other end of the capacitor array and attach to the outer turn of the primary. For my coil, I found that it performed best when attached to turn 14.
* This wire may have to be adjusted to properly tune the coil. In an effort to make the wire easily adjustable, I created a clip-like device that can be used to clamp the wire to the the primary. To create this device, I used a modified 30A fuse holder from Radioshack. I uploaded numerous pictures of this "clip" in an attempt to show how I did it.*
6. A wire will wrap around the strike rail and travel down to ground.
7. A wire will travel from the copper lug terminal underneath the secondary and go to ground.
Step 9: Fine tuning and operation
The Tesla Coil may need to be tuned before it will run properly.
1. Try clipping the wire onto different turns. For me turn 14 worked the best, for you it might be different. If you're having a problem, adjusting the primary in this fashion should take care of it.
DO NOT touch the primary coil or any component on the lower layer of your base while the Tesla Coil is running! The results could be fatal.
2. If your Tesla Coil still isn't performing very well, try adjusting your spark gap. The bolts should be spaced apart just enough so that they just barely fire.
* It pretty much goes without saying, but please do not attempt to make adjustments to the Tesla Coil while it is running!*
Thank you for taking the time to read my first instructable, I hope it was helpful to you. If you end up making a Tesla Coil please send me pictures/videos of it, I'd love to see them!