How to Build a Tesla Coil





Introduction: How to Build a Tesla Coil

About: Devin is a cool guy, eh doesnt kill himself while doing stupid things, and doesnt afraid of anything.

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

The total cost came to around $25, being that I already had the wood, Snapple bottles, PVC, and glue.

Secondary Coil:
  • A length of 1.5" PVC (the longer the better)
  • About 300 feet of 24 AWG copper enameled wire
  • 1.5" PVC screw-thing (see picture)
  • 1.5" metal floor flange with threads
  • Spray on enamel
  • Circular, smooth metallic object for the discharge terminal
Base and Supra-base
  • Various pieces of wood
  • Long bolts, nuts, and washers
Primary Coil:
  • About 10 feet of thin copper tubing
  • 6 Glass bottles (Snapple bottles work really well)
  • Table Salt
  • Oil (I used canola. Mineral oil (horse laxative) it preferable as it doesn't mold, but I didn't have any.)
  • Lots of aluminum foil
And a HV power source such as a NST, OBIT, or other transformer that gives off at least 9 kV at around 30 mA.

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.

  • I built a rig for winding my coil that consisted of a microwave turntable motor (3 RPM) and a ball bearing.
  • Use a small block of wood with a notch in it to straighten the wire and tighten the coil.

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
  • 599 Wraps on secondary
  • 6.5 Wraps on primary

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)



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    10 Questions

    Why didn't you buy the capacitors instead of making them? Just saying it would have made this a bit easier. And what size would you use to make the Tesla if you did use store bought capacitors. Thanks

    Is it possible to run the coil with a 6.5kV 30mA NST? I'm considering purchasing one, and wanted to know if I could run the coil off of it. If not, do you have any suggestions for a better transformer? Thanks.

    Hey guys I have one question. I bought "400kV" transformer with 2-3 spark. I think that generator is around mabye 60 kV. (3 x spark(mm)) Is it OK for that teslacoil? Thanks

    Uhhhh.... That's not the greatest idea. 60kV is 60,000 Volts! You will need almost 40 Capacitors for it to run safely

    Hey, can someone link a 9Kv transformer? I can't find any for cheap.


    You can buy a 400kv generator from amazon


    What did you make the top load from?

    could not find one and 1/2 inch PVC, is it possible to use one and 1/4" PVC and if so what is the wraps of the secondary copper wire need to go around it and what size copper tubing? We are trying to make this for a science school project got the ok from the teacher, just need a little help.

    Can you tell me big is the Tesla . I mean what is the height and width of the Tesla .

    What is the expected capacitance of the capacitors?

    Hey! How did you connect your power supply to the capacitors.

    is it possible to connect a 400kv highvoltage generator to the coil?


    In my home, power supplied is 230 V, how can I make tesla coil.

    2 replies

    two things:

    1. buy a step-down transformer that steps the voltage down to 115 v but this would be alittle counter-intuitive

    2. just get a transformer with the same output specs that has an input of 230 v

    The good thing about this project is that it can be inprovised, really, any transformer would work in this project if the output is high enough.

    how much voltage would be the highest you can input??

    Is the diameter of the PVC pipe 1.5 inches or the radius?

    Don't forget it sparks generate ozone. If you can smell it, it's above the safe exposure limit.

    What tools you are using for bending those large copper tubbing???
    And what the function of oil in these capacitors??

    10 replies

    Actually the greater the resistance to the flow of electrons the greater the capacitance. Therefor pure water would be a better separation medium than saltwater and oil. Check out the basic physics of the difference on your favourite chemistry or physics website. It will not allow me to copy and paste from

    ?????????? The capacitance of the Leyden Jars (capacitors) is directly proportional to the surface area of the aluminium plates and inversely proportional to the distance between them (the thickness of the glass). It also depends on the type of dielectric (glass in this case). The reason a conductive liquid is used inside the jars, is simply to avoid the hassle of having to glue a layer of foil on the inside of the jars. Capacitance is not related to resistance. The resistance of a circuit matters only in calculating the rate of charge or discharge of a capacitor.

    I agree. And if the glass is very clean and dry there will be no surface leakage. I have used stacked perspex and Al foil to make a HV cap.

    You are right, I should have said capacitance. I was thinking about the capacitor I made for my pulse nitrogen laser. The pulse came from the build up of electrons on the bottom plate, that was insulated from the top plate by transformer oil soaked felt, The engineer that helped me build it referred to using the material with the highest 'resistance' to the break down current of the material. We had at one point discussed using pure water as the adjunct insulator to soak the felt in. the draw back of pure water was that since the whole capacitor was an open arrangement the water would evaporate too quickly. So I got stuck using transformer oil to increase the 'resistance' of the insulating material to breaking down under high voltage and current loads.


    Nomenclature is a funny thing, especially with engineering talk. I think what you probably meant to say is 'dielectric strength' instead of 'resistance' to breakdown. Using pure water as an insulator is problematic. It is difficult to get water pure enough to have a high resistance and to keep it pure when exposed to metal plates under high voltage conditions. How did the oi- soaked dielectric work out?

    I thank you for correcting me on that. Yeah, nomenclature is pretty rough for me to keep track of sometimes, since I dabble in a bit of everything. Trained in Electronics Tech, started in the engineering classes, went to LE, EMT, Fire, design and construction, emergency management, medical research including doing the cardiology surgeries... my Wife is a veterinarian. lol. Too many things to keep track of.

    I actually wound up using the felt, oil, and a Marlex sheet between the two plates we had trouble with the dielectric strength of just the felt and oil. We went up to 3 layers but were still getting burn through. My dad brought a sheet of the Marlex home from a friend at the Phillips 66 research center and that solved our problems. After that it was just keeping bolts around for the spark gap since they eroded pretty quick. we had a 36" square of 1/4 Al on the bottom and two sheets 17 x 36 on top. Silver soldered the copper sheet that led up to the lasing tube with low pressure N2 and a quartz lens. We put out enough power to burn through two sheets of notebook paper with each discharge. We had a minor IR burn around the goggles and hands after the first 5 pulses. and had to shield it. Entered it in our senior science fair, but they wouldn't let me fire it up, I just had to show pictures. OF course this was back in 1979.

    Hi KennethM45,

    You had quite an exciting experimenting career. My only experience with Tesla coils takes me back to the mid 60's. My high school science project was a Tesla coil with a 60" x 4" secondary with 2000 turns of magnet wire (24ga I think) - took forever to wind manually! The primary was 10 turns of high voltage test lead wire. I used a 20KV sign transformer and 1/4" diameter copper rods for the spark gap. I had nothing but trouble with the capacitor. I tried air dielectric, 1/4" plate glass, transformer oil, 1/2 acrylic - nothing lasted more than a few seconds - at least the oil would self-repair! Everything else became expensive garbage. But, when the Tesla coil did work for a few seconds, it was dramatic indeed! It drew arcs 3' and more. It lit up all of the flourescent tubes in the lab! It scared the hell out of everybody in the room. That was an additional bonus to a very exciting, but short-lived career as a mad scientist. I often dream of doing it again, but much bigger - going out in a fabulous light show! Keep up your curiosity and your experimenting - it's very liberating!

    You sound like you had fun too, Sir. Yeah, I always think of things I can keep doing, and since we live on 11 acres it can be pretty esoteric. lol. I was really privileged to work with some really great people over the years. I now pretty much concentrate on firearms instruction, my goal is to make people who carry safer than the law requires. Branching out into various methods of teaching, simulator, force on force, and standard classroom to get people to understand just how serious a matter it is to take up the responsibility of carrying a firearm daily. And then I see all the news reports and despair of ever getting enough people educated. It has been a great time talking with you, I hope we keep crossing paths here. :)

    A teaspoon of salt should be ample.

    oil as an impurity increases the capacitance. more the amount of impurities in between the plates more will be the capacitance. first study physics, then go on to make such things. >.<

    neon sign transformer,

    No one should be building this if they can not Extrapolate and Simplify V = I/R

    I mean come on I know Ohms law, but my maths is rubbish, and I only know basic algebra, but Tesla Coils can kill if you have; a Pace Maker, Epilepsy, history of a Stroke, history of DVT, history of blood clots and they can also cause Asphyxiation due to electrical interference in the respiratory nerves.

    I know enough about Darlington pairs, Brige Rectifiers and Decade Counters to know my way around Electronics, and this is not something anyone should build if they do not feel comfortable with over 200,000 units of IV.

    It is not something I would attempt to build, I already got a shock from installing a new fused circuit in my Mains Fuse Box, I do not care for another.

    2 replies

    I don't want to be THAT guy but Ohm's Law is not V=I/R; it's either I=V/R or V=IR