Picture of Building a Tesla Coil In 9 Easy Steps!

Over the past Summer I built two Tesla Coils. The first one didn't work, so I started building this one. This instructable will outline the steps I took.

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.

Materials :


-4' of 1.5" PVC
-8 pieces of 5"x5" plywood
-2 pieces of 3'x2' plywood
-4 caster wheels


-15kV 60ma transformer with no GFCI

Spark Gap:

-1' of 3" PVC
-2 brass bolts the same size, plus 2 nuts and 2 washers that fit the bolts
-2 1" brass balls
-1 Computer fan
-1 8 AA battery holder

Capacitor Array:

-40 Cornell-Dubillier capacitors, (Model# 942C20P15K-F)
-40 10MΩ resistors
-Material to mount your capacitors to (I mounted mine to sheets of lexan, with ceramic stand-offs as legs.)

Primary Coil:

-4 pieces of 10"x3" plywood
-50' roll of 1/4" copper tubing
-20' of 3/8" copper tubing

Secondary Coil:

-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
-Nylon nuts and bolts


-3 copper lug terminals
-High voltage wire
-Gorilla glue
-Drill press
-Table saw

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crashstudio11 days ago

I have a different model Franceformer 15kv 60ma. After removing the GFCI I had 2 whites, 1 black/line, 1 blue and 1 orange. I had to connect white to white and black/line to orange. Blue left disconnected.

TimothyG2 months ago

About 35 years ago as a teen I saw a Radio and Electronics type magazine that showed how to make a tesla coil. At 15 I built my first with no toroid, glass plate/foil capacitors, model T ford spark coil (later moved to a neon sign transformer), etc. and had sparks about a foot or so long. I showed it to my shop teacher in school and he told me about a city industrial arts contest. I made a base from wood with dowel rods for the primary coil and stained it. I took 1st place in the R&D category at the contest. I read all I could about Tesla and even wrote a term paper. I don't know what ever happened to my tesla coil but I'm now an Electrical Engineer and I would like to build a bigger one with a torroid this time using the neon sign transformer 15kv 60mA. I would like about 2-4 feet but nothing too big as this idea already scares my wife. I have done some internet research and purchased the $5 Tesla Map software online. It says this transformer at 100% efficiency will have the potential of over 50 inch sparks. I understand your never going to get 100% efficiency but I would like to know how to design one of these spark lengths. I read that the diameter of the secondary coil affects the length. However, the software just shows the max spark length based on the neon sign transfomer specifications and nothing else. I want to make sure I can get all of the parts and do reseach before I buy anything. Comments or suggestions about this? Thanks!

Beachley (author)  TimothyG26 days ago

In my experience with the Tesla Map software I have found it to be very accurate. If I were you I would definitely follow the software recommendations. Changing the shape and the length of the secondary will not provide noticeable power gains, the transformer size is the main factor of spark length and output. If you change the secondary coil then the primary coil and capacitor bank will need to be adjusted as well. IMO it's not worth it, it would be easier and more economical to follow the specs from my instructable

leo.mecham.72 months ago

I have some doorknob caps rated for 20,000 v . will they work?

Beachley (author)  leo.mecham.727 days ago

You should really try to stick to polypropylene capacitors

tzisis2 months ago

nice tutorial man ! I plan to build my own soon and I'll sure follow your instructable. And a question. If the secondary winding is more than 1100 turns then it will output more voltage right ? So it can produce bigger sparks (with a bigger toroid and all the adjustments) ?

Beachley (author)  tzisis27 days ago

Adding additional turns will change the frequency of the secondary coil. If you add additional turns to the secondary then the primary will need to be adjusted to match the frequency. I wouldn't recommend it.

The only way to get bigger sparks would be to use a larger size transformer.

THE INSIDE (glue side) of the aluminum does not conduct electricity!!! How to build that electrical path on the top of secondary using Al tape???

Beachley (author)  hao.truong.79674 months ago

I never inferred that the glue side of the tape was conducting electricity. The wire coming off of the top end of the secondary is resting on the aluminum side of a piece of aluminum foil tape. I then placed a second piece of aluminum foil tape over top of the wire, just to secure it and hold it in place.

zorcy5 months ago

I would love to see pictures of it running.

Beachley (author)  zorcy4 months ago

I'll post a link to my youtube video

Beachley (author)  Beachley4 months ago


Sorry about that. The video had been posted before, but I guess something happened to it.

Hi, Tesla peeps! Can I use ignition coils of cars instead of capacitors? Can someone help me build one that is in Solid State? I'll be helping my son build his (and mine, as well) first Tesla coil for his Science Project (one that could play .mp3 music from his iShuffle). After which, we could use this on New Year's day & 4th of July. This has to be done on or before December (2014).

Mickjohno10 months ago

Mate, you're a legend! I've been on a bit of a Tesla coil quest for months now, I've built it to the stage I can test it but nothing but a spark across the spark gap is all I have been able to get. I'm brand new to instructables so already had mine mostly built when I read this but your instructions are one of the better that I have seen that's for sure. to start with despite no lack of trying I had my spark gap & capacitors around the wrong way (so I'm guessing that wasn't helping!). Also my top rail was a full circle & u said not to do that. Plus the basic wiring up of the thing was poorly described in every other vid or write up I've seen so well done.
But unfortunately I still need some help if u can please. I'm running 2 MOTs with a voltage doubler off 240volts which I think is giving me close to 8kVAC, then I've got 2 MOCs in parallel & an assortment of capacitors in series I've been trying to get right. I don't have any like yours, those suckers are expensive. I have several small capacitor banks made up & soldered together in series but I have no idea how to work out what the total capacitance would be & can't follow how to do it. I understand when I put 2 together I just add the voltage & the capacitance halves etc. But what about when I combine 2 totally different capacitor values?
My primary is 3' x 3.5" wound with 24G magnet wire & the secondary is a 1/2" tube with about 7 wraps ( I used exactly half of the reel). The spark gap improved 10 fold once I removed the capacitors & ran just from the voltage doubler & MOCs.
I'm guessing once I get the capacitors close I'll be right..?
Any ideas or assistance would be much appreciated..
Thanks heaps!
Mick :)

My main drama/question I think is how do I add up my capacitance when I have 2 separate banks with totally different capacitors in each?
Cheers! :)

WHY would you want this deleted? It was featured, and it won a contest. Looks to me like it was a great ible' before you removed all the content.

milandin1 year ago
My son and I are getting started on this Instructable and I rolled the dice and ordered a Franceformer off eBay. It's a 15KV 60mA but it arrived packed terribly and two of the ceramic terminals are bashed up badly. Two questions: Are these replaceable and if so, where can one buy these parts? I've been looking online for a while but no good so far.

I'm sure you figured this out by now that sadly, the transformer is shot and most likely is not repairable. It might be possible to mold some new separators using epoxy putty. Could be worth a shot. Couldn't you get your money back?

sheydon1 year ago

Beachley is now selling this instructable for sale on Ebay in the form of a pfd document. I am really disappointed as well as I have numerous links to this site from my own tesla web site. - Anyone one is free to meet me there. I offer all of the information necessary to build a tesla coil. I will have to expand informationally in areas where I was relying on Beachley's instructable. This is mainly in regards to the design and construction of the base for the primary coil.

Beachley, what happened to your instructable? My son and I were using your instructions as a basis for his science project. Logged in today and *poof* it just says "Please Delete." Your instructions and images were some of the best available. Any chance of sending me a PDF? I can send you my email. Let me know.
Did you use any diode in your circuit ?
Beachley (author)  matthews martins1 year ago
Did you use any diode in your circuit ?
intead i use the same capacitor you use, can i use 146 capacitor with 2,2 uf and 250 v?
I forgot to say that they are electrolytic capacitors
or is better if i use polyester capacitors with 2,2 uf and 250v?
Beachley (author)  matthews martins1 year ago
(removed by author or community request)
I just have one more doubt, can I wire the primary coil with a AWG 12 wire?
Beachley (author)  matthews martins1 year ago
Using a conductor with a different width for the primary will change the primary inductance, which will change the required secondary inductance and the required capacitance of your capacitor array. If you plan to follow this instructable you cannot use 12 AWG, it will change a lot of the parameters I used.
I am now using 100 capacitors with 1,5 uF and 400v each made of polyester, that should work better, I couldn't find capacitors made of polypropylene here in Brazil
Beachley (author)  Beachley1 year ago
I really advise using polypropylene. 146 of these capacitors wired in series will give you a capacitance of 0.01506 uF and a max voltage rating of 36,500 V. That should work fine.
I am making a Tesla coil and I am only needing two parts the primary coil and plywood. But could I use adhesive to keep my toroid togethere? And what would be a good breakout point for the toroid?
Beachley (author)  Merlinthegreat1001 year ago
You can use adhesive to keep the toroid together, it doesn't really matter what you use as long as there aren't gaps anywhere. I like to use a piece of copper wire for my breakout point. Bend one end of the wire into a circle to make a base, then point the wire straight up into the air and lay it in the middle of your toroid. I also like to take a straight piece of copper wire and tape it to the side of the toroid, pointing outwards.
Beachley (author) 1 year ago
The first point you bring up, about the size of my primary, can easily be explained. As the size of the primary decreases, the size of the secondary must increase and vice versa. I chose to make my primary longer because it is easier to do that than to wind a longer secondary.

I can't explain the spark gap, I remember reading that you should close the gap until it first starts to fire. I started at 3" and nothing happened. I shut the coil off and adjusted the gap to 2.75", nothing happened. I repeated this process until the gap fired at 2.5".

The bottom of my secondary is laying flush on top of the plywood. The plywood is acting as the plexi-glass in your example. Underneath of where I have the secondary placed, I've drilled a very small hole in the plywood. The end of magnet wire coming off of the bottom of my secondary goes through this hole and attaches to a copper lug terminal, as you describe in your comment.

So I guess the only thing I can't explain is the spark gap!

Let me know if you have any other questions.
Beachley (author)  Beachley1 year ago
I just wanted to clarify that you were correct and my spark gap was not done correctly. I have since updated this instructable to reflect the corrections that I made. Thank you for pointing this out to me.
Hi Beachley,
Thanks for the update, and you can see on my TC, that I had to increase the size of my primary to 12 winds. I'm clipped onto the 11th wind for optimal performance.

I really like the look of your new Spark Gap with the ball electrodes. I'm currently looking into building a rotary spark gap. I hear the performance increase is incredible! Alan from sells a kit so one can put together one's own synchronous rotary spark gap. He also sells a pre-made high pass filter that he has had great success with and also the components to build one's own Terry Filter.
my coil 2.jpgmy coil.jpg
Beachley (author)  twotower1 year ago
I have heard similar things about using a rotary spark gap and I've been considering going that route in the future. In fact, it seems that most people that want to get serious with their Tesla Coils use a rotary gap. Static gaps like the one seen here are definitely in the minority. I would highly recommend purchasing parts from Alan, I've bought some items from him in the past and he is very helpful and ships fast.
Beachley (author)  Beachley1 year ago
I also wanted to say that your Tesla Coil looks great!
I would build one tesla coil just like yours, all the things are the same, but my transformer is a 15000 v with 30 mA only. It will work the same way? Because if don't work I would buy another one and put them in parallel, so I can get 15000 v and 60 mA (but it's more expensive).
Beachley (author)  matthews martins1 year ago
Since your transformer is only rated at 30 mA there will be some differences. The output you observe at the top load will be significantly less than what is seen in this instructable, your capacitor bank will also need to be slightly altered.

I would suggest you go ahead and buy another one to wire in parallel.
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