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

Step 1: The Transformer

Before you start this project, you may want to consider finding a good transformer. This will likely be the most expensive part of the project and the hardest thing to find. Most transformers today have a built in GFCI circuit, this circuit is designed to shut down the transformer if it senses any unusual fluctuations. These types of transformers are terrible for Tesla Coil use, due to the Coil's sporadic nature. Transformers with a GFCI circuit will have some sort of reset switch and an LED indicator light. There's a website called Info Unlimited that sells very nice ones with no GFCI, that's where I got mine but if you can find one cheaper then go for it.

For this instructable, I will be using a 15kv 60ma transformer from Info Unlimited.

Edit - 9/16/2013 

Since creating this instructable, I've figured out how to remove the GFCI circuitry from certain NST's. Since there seems to be a deficiency of online resources as to how this procedure is performed, I've decided to cover it here. The following process will only work with transformers that have the GFCI circuit exposed. In some transformers it is impossible to remove the GFCI because it is surrounded in tar and is inaccessible. As of this writing, I am aware of only two companies that leave the GFCI exposed, those being "Transco" and "France".

The following procedure is for "Transco" transformers, "France" transformers have a slightly different but similar procedure:

Safety Note
NEVER touch EITHER output terminal of the transformer while it is plugged in. 

1. Unplug your transformer.

Remove the access panel from the top of your transformer. "Transco" transformers have one screw and one rivet holding the access panel on, remove the screw and cut off the rivet with some pliers. For this step, please refer to pictures 3 - 6.

3. With the access panel removed, you should see two partitions on the inside of the transformer. The first partition will be completely filled in with tar and is inaccessible, the second partition will contain the GFCI circuitry. The blue box shown in the pictures is the GFCI. See pictures 7 - 8.

4.  Pull the GFCI box out of the transformer so you can get a better look at it. Notice that all of the wires coming from the transformer go through a terminal block to connect to the GFCI box. Use a screw driver to disconnect all of the transformer wires from the terminal block and set the GFCI box to the side, we are done with it. See pictures 9 - 12.

5. With the GFCI removed, we need to figure out which of the remaining wires are no longer needed and which of the remaining wires must be joined together. The remaining wires are green, brown, grey, blue, white and black. The green wire is ground for the components in the GFCI box. Since the GFCI box has been removed, we no longer need the green wire and it should be taped off to keep it insulated and out of the way. The brown wire is used to activate a relay in the GFCI box. Again, since the GFCI box has been removed, we no longer need the brown wire and it should be taped off to keep it insulated. The white wire and the black wire are the ends of the primary inductor within the tar-filled partition. In electrical terms, the white wire is neutral and the black wire is line voltage. The last two wires are blue and grey. The blue wire comes from the "line voltage" (L) terminal on the exterior of the transformer, where the power cord gets attached. The grey wire comes from the neutral (N) terminal on the exterior of the transformer. Connect the grey and white wires, since they both correspond to neutral. Solder them together and use tape to insulate everything. Connect the black and blue wires, since they both correspond to line voltage. Solder them together and use tape to insulate everything. See pictures 13 - 15.

6. Put the access plate back onto the transformer and get ready to give it a test run. Attach one electrode of your spark gap to each of the two output terminals on the transformer. If your spark gap fires when you plug in the transformer, you have successfully re-wired your transformer and removed the GFCI box.


When shopping for a transformer on online sites like eBay, transformers with no GFCI often cost significantly more money because of their increasing rarity. If you can, I would advise you to purchase a "France" or "Transco" transformer WITH a GFCI, then use the previous procedure to remove the circuitry. If you take my advice you could save upwards of $130 - $150.

The transformer I bought from Info Unlimited was $290 because it did not have a GFCI. Don't needlessly waste money like I did.


<p>how did you calculate the capacitance that would be best? I am using a 15kv 30ma transformer and my secondary coil is 3.5 in diameter and take little more than 2 ft tall. I tried using http://deepfriedneon.com/tesla_frame6.html to calculate my capacitance required, and it tells me I need 5.2 nano farads. Any advice? </p>
<p>I made this project, but I had to make some changes in order to make it adapt to Europe; I refer to International system of unit, and different voltage source. It's a very beautiful and functional project, thanks for havin' shared with us!</p>
<p>Glad it worked out!</p>
<p>I am making a school project so is it safe to present to a close proximity of people?</p>
<p>The arcs shouldn't exceed 6', so a 10' safety radius around the Tesla Coil would be adequate. However, if anyone in your audience has a pacemaker then they need to be much further away. It's not worth the risk of the Tesla Coil causing EM interference to the pacemaker.</p>
<p>okay thank you</p>
<p>What is the output of this Tesla Coil.I'm making it as my college project and want to know where can this be tested.</p>
<p>There are 3 equations. The first equation provides the secondary voltage, but you will first need to solve for the other 2 equations.</p><p>Vsecondary = Vprimary * sqrt( Cprimary/Csecondary)</p><p>Csecondary = the top load + parasitic C from the secondary winding</p><p>Cprimary = C from capacitor array</p>
<p>hi, great coil. yust on help with metrics what means 2' and what 2''. one is inch i think this with thease two dots above. can some one explain in centimeters, lenght or wide.</p><p>thanks becouse i canot find it on google. Thanks for help</p>
<br>So inch is any number with &quot; so in that case 2&quot; means 2 inch the other one I'm not sure about so I hope this helped a little :)
<p>&quot; means inches</p><p>' means feet</p>
<p>hi,</p><p>can you tell me or send bottom picture of your capacitors wiring. im not engineier so i dont wont make a mistake.</p>
<p>The Tesla Coil has been dismantled, so I can't provide any additional photos. The leads are just wired together in a straight line from end to end. The leads all have solder connections</p>
<p>Whats the cost of building one like you did?</p>
<p>This probably cost about $1000. </p>
Hello guys, <br> Can I know the maximum range of this project. Will it possible to make a range 2 meter.<br>Give mesuggestions, I need.
<p>2 meters would be pushing it with a 15kv 30mA transformer.</p>
hi yes you help. i think second one is lenght but im not sure
And Can U PlEASE tell How to remove the GFCI from the transformer of FRANCE ,-Franceformer....plzzz ( my is 7.5kv/30ma)
If ur skilled enough I wouldn't really recommend it but you open it up you could by pass it but I'm not sure how and also it's not 100% safe
<p>Will a 3kv 30ma transformer be powerful enough?</p>
<p>it would do something, but not much because that is only 90 watts of power, out of curiosity what kind of transformer is that? Like what did it come from I mean </p>
can the Tesla get connected to a computer out something that can make it play music?
<p>In order to get it to play music, you will need to do quite a lot more, if it interests you I suggest making a plasma speaker before trying to convert your tesla coil to be audio modulated </p>
<p>I'm making a 10&quot;x40&quot; DRSSTC that will hopefully do 10-12 feet. Only problem I foresee (other than cops to scare off) is having a lousy ground connection. For full power runs this will be ran in the park across the street on a 480v battery since I live in an apartment (only room for 4 feet indoors) so can't go around pounding pipes in the ground. Hopefully a 10-foot square of 1&quot; chicken netting will be enough.</p>
Hello friend <br>Could you please tell me what is the range of your project , because I also want to make this in my major project.<br>Give some advice to me how can I make this project .<br>My mail I'd - rkt.0072@gmail.comcom<br>Reply as soon as possibl .<br>Thanks
Google DRSSTC. There's a million websites explaining how it works and how to build one. I'd recommend building a spark gap version before converting it to IGBT's if you've never built a tesla coil before. And even then it's not easy without power electronics design experience (I built a big 16kW ZVS CCPS first for that experience). Steve Ward's HV website probably explains the details best. In short understanding his explanation of how his 12-foot one works is the prerequesite knowledge. Unlike some little Mazilli flyback driver you can't simply blindly copy some schematic from the internet and have it work perfectly, at least not without a lot of luck.
<p>chicken wire ground is very interesting though will have to try and compare</p>
<p>i have found that the heavier you make the ground the better the arcs like atleast 3 pieces of 1/2 copper pipe 3ft long driven into the ground and connected together with heavy wire all the way to the base of the secondary OH WHAT A DIFFERENCE!!!!</p>
<p>great tutorial ive never tried making caps this way and wonder if they are as robust as the old school roof flashing and polyethylene ones immersed in mineral;oil</p>
<p>i have built many of these and have always gotten the best results by hooking the cap in parallel with the tranny and placing spark gap before the tuning connection running to the primary will work in different configs though </p>
Hello, you by far have the best tutorial I've seen. I'm currently making a coil my self but In smaller scale, im using a transformer from an old microwave and im making a capacitor out of glass bottles, water, salt, and canola oil. I was wondering if you could perhaps break down the formula of primary cool to secondary coil length. Also for home made capacitors how much of each listed material would be appropriate.
And Can U PlEASE tell How to remove the GFCI from the transformer of FRANCE ,-Franceformer....plzzz ( my is 7.5kv/30ma)
Hey....I got every single part EXCEPT those Apple pie Cans.....I'm from India .....can someone plzzzzz help me??? With the can I can easily construct this Tesla!!!!!plzzzzzz!
<p>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. </p>
<p>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&amp;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!</p>
<p>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</p>
<p>I have some doorknob caps rated for 20,000 v . will they work?</p>
<p>You should really try to stick to polypropylene capacitors</p>
<p>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) ?</p>
<p>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.</p><p>The only way to get bigger sparks would be to use a larger size transformer.</p>
<p>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???</p>
<p>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.</p>
<p>I would love to see pictures of it running.</p>
<p>I'll post a link to my youtube video</p>
<p>Done! </p><p>Sorry about that. The video had been posted before, but I guess something happened to it.</p>

About This Instructable




More by Beachley:Building a Tesla Coil In 9 Easy Steps!
Add instructable to: