How to build a Tesla Coil

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

Capacitors:

• 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.

Tips:

• 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)
http://www.youtube.com/watch?v=iVmX2Ik4ylg

Comments

[The Asian Cow]

Do the saltwater capacitors do well with time? I will be leaving my tesla coil at my school and it would be sitting for months at a time. If that is not good for the salt water capacitors then if I were to get an actual capacitor, what voltage and capicitance should I look for? Also do the direction, spacing, and shape of the primary coil matter? It sounds like you can "tune" it for maximum spark length but if I just set it up in a coil or helix with no measurements will it still produce something?

[saksham bhadani]

from where have you bought thin copper tubing?

[Liam.great98]

OBIT stands for Oil Burner Ignition Transformer

[rocketfire4]

just wondering where would you get the neon sign transformer for cheep or free because i was looking online for them and they were pretey expansive like 75-150 dollers idk what BOIT stands for

[Morzie...!]

would you be able to use capacitors from a microwave, as im guessing you got the slow engine for the secondary from one?

[Jknapp25]

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?

[The_Tech_Man]

I wanna see him connect it to a nuclear reactor and make someone touch it. >:D

[Credible Halter]

would a solid state transformer work, and if so would what efect would it have on it?
and i am not new with electricity.

[Credible Halter]

just new to tesla coils!

[sarithallen]

Why can't the primary by completley horizontal instead of your final upside down spring design?

[dming98]

Does any body know somewhere cheap to get all the materials

[fun bags]

What type of transformer do i need i already know that its a 9kv and all but i ordered one for about 45 dollars and it wont power my tesla coil because it is a solid state transformer. Can someone help me please?

[funwithpower4242]

there is a good webste www.pupman.com and it has an active mailing list - someone there can probably tell you how to use that to make a solid state tesla coil

[smoothisfast1]

I still can't make sparks come out of my toroid. I am using a 20kw transformer and ten 20 amp capacitors. Should I increase my capacitor bank?

[smoothisfast1]

I mean 20kv capacitors.

[Evisela]

3 Things. 1. Can I use a computer power supply instead of an nst? 2. Can you write out what to connect everything to plz because I don't really understand the diagram. 3. Can you use beer bottles for the capacitors? Thanks!

[funwithpower4242]

beer bottles can indeed work for the capacitor if they are glass. clear beer bottles like from Corona are prefered since the colored glass (green, brown etc) may cause a bit of dielectric weakness. but it should still work and get you started. Tesla himself used wine bottles in a big metal vat.

[smoothisfast1]

I found that salt water capacitors are unreliable and don't last long. Better to bite the bullet and buy commercial capacitors.

[crazy-blender]

no you cannot use a computer power supply it has to be high voltage

[RobandStephenCUBED]

me and my friend are doing this for the BASEF science faire, then converting it to play music. Thank you for the design

[stevo-d]

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.

[sam48415]

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

[stevo-d]

Well you're right that it would not be as bad as an arc welder because if it was, it would probably melt the terminals!
My point is however that high voltage arcs do indeed produce harmful ultra violet light and just letting anyone intending to do this know to take caution.
As for "getting hurt anyway", I will disagree... Again, we should take caution... Make some pretty sparks, but DON'T make yourself part of the circuit!!!

[sam48415]

Yeh i agree, dont be a conducter of that circuit, it will mess u up. Now that i look at the bottom, where the spark gap is, it looks kinda bright, take caution

[red_green]

so what would happen if i used a semi-silvered mirror to protect the spark gap, but still let u see the spark?

[eichermacher]

Semi-silvered mirror might work, but a few filters to filter out most of the light would work just as well. Rosco has UV filters you can buy, as well as good filters you could use to filter out most of the visible spectrum. That way you'd be able to see the spark but wouldn't have to worry about the intense light.

[sam48415]

I wouldent bother...

[stevo-d]

I'm not an expert in light radiation, but I would bet you would still get UV reflecting off such a mirror.
I used to work with high intensity UV light equipment for curing acrylics and we needed to be able to watch it... We worked with the work-piece and light source behind a thick (5-8mm) piece of orange transparent perspex - you could still see the light shining, but it no longer appeared blue and no UV would get through.

I would also like to mention that the equipment I worked with was an arc lamp that sent the UV through an optic-fibre cable - the light coming from the end of the cable would easily set tissue paper on fire, and a few careless co-workers got some nasty burns.

UV LIGHT IS DANGEROUS - Be careful.

[red_green]

if i eliminated the ground on the secondary, would it create a better display?
i ask this as i don't want to have to ground it directly into the ground.
also, i wonder why you couldn't connect the three grounds together to eliminate any more grounds to condense it into one outlet.

[red_green]

i have been thinking, and i think that the electricity would take the path of least resistance (down into the ground), or are all you talking about it like high pressure water in a pipe with holes in it???

[eichermacher]

Without a grounding wire, going all the way to the ground is not the path of least resistance. If you let the coil run without providing any specific place for the secondary coil to ground, the electrical arc will hit the primary coil.

[eichermacher]

If I wanted to buy capacitors instead of making salt capacitors, what kind of capacitors should I purchase?

[geofisiks]

How do you test a salt water capacitor? I have a multimeter but it doesn't read any capacitance when i connect the two leads. This MM has micro and nano capacitance readings.

Thanks.

[funwithpower4242]

i have a video on my youtube channel technow1zard where i make a saltwater cap and test it out

[smoothisfast1]

You have to charge them first with a power source. As soon as you connect your multimeter, the capacitors will quickly lose their charge, so your first reading will be the capacitance.

[MRBADASS]

i have a question, how did u ground the secondary coil??

[fun bags]

hook it up to the capiciters

[funwithpower4242]

Actually it's the primary coil (the big spiral cone of copper pipe) that is hooked to the capacitors. The secondary coil - the one around the PVC with lots of turns of the thin copper wire - is best grounded to a rod that is literally pounded into the dirt outside. Otherwise have it go to some flat piece of metal laying on the table on the side or on the ground (look up 'ground plane) or for a small coil it won't hurt to just make sure it does not arc out to the primary coil. Cover with electrical tape, a few layers, to prevent lower arcs from the bottom of the secondary from leaking out. DO NOT connect the secondary to the capacitors - or you may have to spend all that time winding another secondary again!

[prussell3]

Couldn't using salt water in the capacitor have the potential to cause a build up of explosive hydrogen gas? With high voltage sparks flying around, explosive gases would not be a good thing.

Thanks for hearing my worry

[funwithpower4242]

yes it can be a concern, where you have the wire going in through the bottle cap leave a gap of space at least a couple to few mm around most of the circumfrence. keep your runs of the coil to 5 or maybe 10 minutes at most to reduce risk.