How to Build a Tesla Coil

Intro: 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

[cevigmotad]

typo in 5

[poseidon106]

Where does the PVC reducer come into play? it's never mentioned in the instructions. It appears like it's used for the base of the coil, but if all it's doing is acting as a base, I see no point in including it.

[shigginswi]

Just scanned through the comments didn't see if anyone already mentioned this but the pvc screwy thingy is a PVC male adapter.

[poseidon106]

Can you tell me where it's used in the build? it's only mentioned at the beginning then I don't see it used or mentioned in the instructions at all

[Nikola TeSlaa]

hello so my teacher said to bulid a tesla coil and i did it worked perfectly un till it made a hole on the wall can u tell me what i just did?

[dmdobratz]

Just test it outside thats what I do

[Kadde]

How do you make the top part, is it just tinfoil?

[m73humphrey]

What sizes to wrap my coil then. I was thinking thicker then0.5 10 I was thinking what’s best as per pic yes

[Engrumpled Curmudgeon]

The construction shown in this project is pretty typical but not especially optimal due to a number of factors that the builder fortunately has some control over.
For example, the secondary winding (the tall one) is wound with 24 AWG (0.5106 mm diameter) wire and the windings are closely spaced. Convenient for construction but not optimal for operation. This can be improved upon

Some of these factors are:
1) the intrinsic (DC) resistance of the wire in the context of #2,
2) the AC resistance of the wire which increases with frequency and is always greater but never less than than the DC resistance,
3) the proximity of each winding to adjacent windings, which also increases the AC resistance with frequency and,
4) dielectric losses in the coil-form (here, the PVC pipe) and in any coatings applied to the wire.

#1 Not really a limitation in and of itself, but does set the lower bound on the secondary coil resistance, and so you want this resistance value as small as possible. See also #5.

#2 is a biggie. Skin Effect: AC currents tend to flow only near the surface of a conductor with very little flowing inside, considerably increasing the conductor's effective resistance. This layer becomes thinner with increasing frequency, causing the resistance to likewise increase. The result is that much of the energy in the coil is wasted as heat rather than in producing the much-coveted ginormous sparks that are the Holy Grail of every Tesla-coil builder ever. The way to mitigate this is to *increase the wire's surface area,* ie, use a larger diameter wire. This is also why copper tubing is used for the primary winding; there is no point in using a solid conductor when most of the current is flowing within only a few hundred microns of the surface, no? It is not called for in the secondary mainly because of cost.

#3 is also a biggie: Proximity Effect: When two conductors carrying high-frequency AC current are next to each other, the magnetic field from each conductor tends to push the current in the other conductor off to one side. In conductors already suffering from skin effect, this can double the effective AC resistance. Not good.
The cure? Space the wires some distance apart. Just a spacing of one wire diameter can make a big difference. The easiest way to do this is to carefully wind two wires in parallel, then remove one of the windings after anchoring the other.

#4 is probably not a big deal for a coil this size and power, but it can be for high-power (kilowatts) Tesla coils operating above 30 MHz, as the dielectric losses can become so large that the resulting heat can melt the pipe, and there goes your project down the bog.

#5 Ideally, the secondary uses the least amount of wire for a given inductance when the coil's height is approximately the same as its diameter. Look at old photos of Tesla's biggest coils: almost as wide as they are tall; big fat conductors spaced several thicknesses apart, the coil-form made from vertical rods spaced in a circle rather than using a solid cylinder. He knew what he was doing.

[victorkerryotieno]

I don't understand the circuit may you please explain it in more detail

[RayRay1132Gaming]

Its an air core transformer, when the spark gap fires it dumps the energy from the caps into the primary coil inducing a huge voltage in the secondary

[Engrumpled Curmudgeon]

Transformer action couples the primary and secondary, but it is not the basis of a Tesla coil's operation, only a component of it.

A Tesla coil is a tuned, series LC (inductive-capacitive) resonator. A circuit functionally no different than what you would find in a radio receiver or transmitter. Closest in form and function are the antenna tuners used in AM, shortwave, longwave, and VLF transmitters. Those used in VLF transmitters can literally be several storeys high and handle megawatts of power, but electrically they are nearly identical to Tesla coils in every way.

The primary induces current in the secondary in bursts due to the spark gap discharging the capacitor bank through the primary. As the pulse is very short, it contains a wide range of radio frequencies, one of which is at the resonant frequency of the secondary inductance and its 'top-hat' HV-terminal capacitance. This RF pulse causes the secondary LC circuit to 'ring' at its resonant frequency. As it has nowhere to go, the voltage builds up to very high values. However, losses due to the AC resisistance of the secondary windings causes the circuit to lose energy (called 'dampening') and the oscillations eventually die out. They also die out if there is a spark from the HV terminal, as this also removes energy from the circuit. They are regenerated during the next spark-gap discharge and the cycle repeats.

[bryanbantugan7]

Can i use a 220v transformer?

[Engrumpled Curmudgeon]

You can use a 220V (primary) neon sign transformer on a 110V circuit, but NOT the other way around.
Also, 220V-input transformers are often also rated for 50 Hz operation. It will say so on the nameplate. If you try to use a 50 Hz transformer with 60 Hz mains, it can overheat, eventually causing insulation failure. DO NOT use 50 Hz transformers on 60 Hz circuits and vice versa. Use them at the frequency they were designed for.

[Engrumpled Curmudgeon]

If you use a neon sign transformer (NST), note that these have a ground terminal bonded to the metal case. It is important that you ground this via the power cord. The reason is that NSTs are *center tapped,* and that center tap is brought out to that ground terminal. IT MUST BE GROUNDED. The reason is safety:
1) the voltage between either HV terminal and the case is (ideally) half the voltage between the two HV terminals. This can make a difference between life and death should you contact one of the HV terminals accidentally while the transformer is live and
2) the windings may not be symmetric about the center tap, possibly putting a floating (ungrounded) case at a high potential with respect to ground and even the primary.
3) GROUND THE CASE.

[Junaid29]

How shall I ground the secondary coil?

[Engrumpled Curmudgeon]

You don't ground it.

[JackeyC1]

you can use a machine

[ZackG16]

Can you hook it up to a converter and run electronics?

[Engrumpled Curmudgeon]

Find out what the electronics need in terms of voltage and current and find a supply which provides that. Electronics don't like high voltages, even if it's not directly connected. This particular Tesla coil design is also inefficient. Most of the power you pump into it would be wasted. Lastly, why raise the voltage only to bring it back down using a 'converter' to a value the electronics could actually use?