Picture of How to build a Tesla Coil
This Instructable will walk you through building a medium sized Tesla coil.
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Step 1: DANGER

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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!

Picture of 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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red_green8 days ago

Uhh, now that I look at this diagram again, wouldn't you want the capacitors in parallel with the NST and the spark gap in series?

have you tried lighting a fluorescent bulb? does it work

gencodeinc4 months ago

Finished my secondary winding, does the bottom of the secondary winding wire connect to anything or should I just cut it off flush to my pvc?

it connects to ground.

Thanks, I assume you mean a grounding rod outside or can I use a wire to the house ground?

derekiswise2 months ago
I am sorry for the stupid question but how do I physically connect the capacitors to the coil. Wouldn't using capacitors with alternating current cause this top cancel out? Could you very a close up picture of how it is connecting. Sorry about this, any help would be great, I am building one this summer
Glenn7815 years ago
 for the love of god do not use 6 snapple  jars with a 15kv 30ma nst you will get about 10 min of run time out b4 1 or more blow!!! all 6 were leaking badly. i think ill try a serise/parallel with 12 of them
HaykD Glenn7814 months ago

Why do they leak? Isn't there any way to prevent leakage. Or how you know that caps are leaking?

Glenn781 HaykD3 months ago

they would leak at the top of the foil with streamers moving to the lip of the bottle at 15kv

HaykD Glenn7813 months ago

But as i see from your picture that they are too far for arcing at 15kv if considering that you need 1kv per 1mm to break the air. Anyway is there a way to correct it?

Glenn781 HaykD3 months ago

there is far more then 1.5 cm gap! It was do to leaking. When it leaks you will see dim looking feelers bleed from the edges of the foil

how many volts will one of the snapple bottles produce?
lol!!! good thing you did cause I have 4 litle girls in my house, is it ok if i use 9 small mouth pint jars instead?

(i only would have done 3)

thanks alot for makeing these instructions.

ps i couldn' comment on the right one so this is for DevCoder
DevCoder (author)  electridanger4 years ago
DevCoder (author)  Glenn7815 years ago

I just fixed the Instructable!
gencodeinc5 months ago

Does the winding direction matter?

Cuanto tiene que medir el tubo de pvc y el de cobre

Also, what wire is used for connecting the NST, capacitors, spark gap, ect...

Also, how can I ground the primary and the secondary coil if they can't be grounded in the same area?

what is the "1.5" PVC screw-thing" used for?

ZariusI6 months ago

You should try to update your directions cause they are hard to understand and how long should are bolts, washers, nuts, wood and PVC pipe should be. Also what is a circular, smooth metallic object for the discharge terminal is what did you use ..maybe a metal bowl. But anyway thanks for making this and tell us were to go for the next Tesla Coil.

gencodeinc7 months ago

Is there an alternative to using Snapple for the capacitor.

gencodeinc7 months ago

Will this work for the secondary coil?


science mad7 months ago
i want to made this i dont have 9kv trans for mer
Luis967 months ago

Can someone please clarify me on this aspect of Tesla Coils: when building one, do we have to calculate anything, like how many windings, or the capacitor's capacitance, or can we just move on without doing any math?

Thank you!

you shouldn't have to calculate the windings, but you might want to find the capacitors capacitance.

How much oil did you use and what kind of wire is that?

I'm doing this for my science fair so I would very much appreciate a quick response please.

CCube5511 months ago
how many for a 3 kv nst? (snaple LEYDEN Jars) And what would happen if I did not have 6 jars...?
azvampyre12 months ago

Do we need a live cat, or can I scrape one off the road. The instructions werent clear on that point.

ChadC11 year ago

What does that cat have to do with a Tesla Coil?

Jknapp252 years ago
It looks like your capacitors are in series, why aren't they in parallel? Also deep should the wire go into the bottle? Does it even matter because the salt water mix is considered the inner plate, the salt is all at the bottom though. Lastly, if the foil is the outer plate, how do you connect a wire to it?

they prevent the coil from short circuiting... :)

current limiting capacitors, not smoothing
stevo-d4 years ago
Ummm, harmful amounts of UV light appears to be visible at your spark gap... I'm no expert here, but from what I've read, you really should have that enclosed for the safety of your eyes... Has been described elsewhere as like watching an arc welder, and use arc welding eye protection if you DO NEED to look at it for any reason.

I would care more about the radiation ;) but youre right, the UV light isnt very healthy for your eyes :P

does this just mean to wear sunglasses during use? If so, I am fine with that.

the current is only ~20mA, essentially the amount of power to drive an led
Your probabally going to get hurt anyway, so it doesent matter. I highly doubt that it is as bright as an arc welder, and will harm your eyes that much
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