Introduction: Simple Tesla Coil

Picture of Simple Tesla Coil

Hello! Today I’m going to show you how I build a Tesla coil! Probably you may know this device from computer games, movies or some “music tesla show” whatever they call it. If we ignore the mystique around the Tesla coils, it's just a high-voltage resonance transformer working without a core. So as not to get bored from theory let’s jump to practice.

Step 1: Circuit

Picture of Circuit

There is a

circuit of coil, as you can see it’s very simple and we need only few components.

- power supply, 9-21V, also it’s gonna work from batteries with same voltage

- little heatsink

- Transistor 13009 or 13007, or almost any NPN transistors with similar parameters

- variable 50kohm resistor

- 180Ohm resistor

- cooper winding wire 0.1-0.3mm, I used 0.19mm which is 36 American wire gauge, about 200 meters.

Also we need a frame for secondary coil, it’s could be any dielectric cylinder diameter of approximately 5cm and length of 20cm. In my case it’s piece of 1-1/2 inch pvc pipe from home depot.

Step 2: Coils

Picture of Coils

Let’s begin from the most complicated part – secondary coil. It has 500-1500 turns turn to turn, my is about 1000 turns. Fix the beginning of wire and wind, actually you don’t need to count every turns, simply multiply diameter of wire to number of turns you planning to make - it’s going to be your winding length. When you done fix wire with some tape or better by couple layers of varnish.

Primary coil is much easier I put paper tape sticky side out, in case to save the ability to move it, and wind on it 10 turns of regular wire in pvc insolation.

Step 3: Soldering

Picture of Soldering

Next is soldering, all under the circuit, PCB is not necessary. Be careful when soldering variable resistor! 9/10 coils didn’t work because of wrong soldered resistor. Connect primary and secondary coils, latter has a special insulation which must be scraped off before soldering.

Step 4: Turn On

Picture of Turn On

So we done. Before you turn on the power at first time, place the variable resistor in middle position and put light bulb near to the coil, because usually you’ll not see high voltage sparks immediately and only thing notice that it's working is light bulb. Turn on power, and slowly turn the variable resistor. It's quite weak coil, and you can not get electrical shock because of skin-effect, but any way be careful and don’t place any electronic devices such as cellphones, computers etc. near to the working coil and notice that high voltage sparks is made of plasma and it's actually very hot, be careful when touch it. If Tesla coil doesn’t work, try to flip wires from primary coil, usually it helps, also you can try add or subtract a couple of turns from it.

Step 5: Final

Picture of Final

Now lets talk about improving results, first you can do is rise voltage, but I don’t recommend go over 25V at this circuit. Second is playing with primary coil, logic is simple, fewer turns – more current equal more power and more hitting, I stopped at 5 turns, also try to move it around secondary.

But to be honest this circuit is so-so and can run only like simple model for beginners, next time I’ll show how to built real device. If like this instructable don't forget to check out my YouTube Channel :)

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SaumyaM2 (author)2016-10-28

I am trying to make it for my science project, i have already tried the following method -

(by roman ursu hack)

but it DID NOT work.

can you please help me understand how this works in simple english and guess probably why this didnt work.

and CAN I USE 2 dc batteries of 9v used in remote controls?

and not use the heat sink

steinc1 (author)SaumyaM22017-09-02

I made a little tesla coil and powerd it with a "small" wimshurst generator we had in school.


jsdir made it! (author)2016-12-04

Nice project.

I did it with my almost 12yo son during the last 4 weekends.

We winded an undefined, but high, number of turns of thin copper wire from the primary winding of an old 12v psu transformer on a carton scottex tube.

Mounted the circuit, with a fixed 5600 ohm resistor instead of the trimmer, the value found experimentally in conjuction with the 2N3055 transistor, the only one in my old-stuff-stockpile.

Used a simple psu (transformer, rectifier bridge, 2200uF electrolitic) in the white box for a continuous fun, instead of the battery.

The result isn't really exciting, sparks are short and didn't appear by itself, but is acceptable considering the raw materials we used.

At the bottom of the coil I placed a couple of blue led (with a 100ohm limiter resistor) soldered in anti-parallel on about 10 turns of insulated copper wire.

When the tesla coil works some of the energy is catched by the led circuit and a shiny funny blue light emerge from the top. Of course it turn off when the neon lamp light on or when there are sparks.

Thanks for the fun :D

Here are some photos, sparks are produced with a screwdriver and a pencil.

jmhar0520 (author)2016-12-03

I have just tried to build this project myself and have run into a problem. Does it matter which way the primary and secondary coil are wound? should they be oposite?

baburas (author)2016-12-02


I finished the coil using almost the same steps.

I used a BD135 transistor, one Resistor - 47k 1/2w, 9V battery, 6 turns primary coil, 2400 turns secondary.

There is no spark, but it successfully lights lamps. There is though a small problem. When I approach a lamp to the coil, the lamp lights but if I leave it there
the lighting lasts only for 80-90 seconds and then fades away.

I have to close the circuit for some time and open it again to make it light again.

Could this be a heating problem? Can you help me with this?

Thanks for your help

loki2012 (author)2016-10-27

Is the schematic correct? The HV coil goes to the base of the transistor? I would think it would go to Battery Ground. But I looked online and that is how others show the schematic. And this one seems to work. Huh.

Leonardo2016 (author)2016-10-20

Being pedantic, this isn't a Tesla coil at all, it is a simple Induction Coil.

A Tesla coil works on a totally different principle and generates far more spectacular results and is well worth taking the extra effort to make. Just Google Tesla Coils and you will find dozens of sites telling you how to make one.

bpark1000 (author)Leonardo20162016-10-20

It is a Tesla coil if the secondary's coupling to the primary is low, and the secondary is resonant. When a relatively large secondary is made, the capacitance to ground tends to dominate, making this a Tesla coil if the primary is driven at that resonance. That is forced as he is using current feedback to the transistor's base.

What I would do is add an "anti-parallel" diode (most likely a 1N4148 or 1N914) across the BE junction (cathode banded end to B, anode to E) to carry reverse cycle of AC safely around transistor's BE junction, otherwise transistor could fry. Also a smooth metal toroid or ball on top would improve voltage output, and the E lead/battery minus lead should be grounded.

How long of a spark do you get?

tgriner1 (author)bpark10002016-10-24

I think your Idea is interesting, Could you edit the circuit diagram to show where you would add the diode?

bpark1000 (author)tgriner12016-10-25

The unmarked capacitor is selected to tune the primary's resonance to match that of the secondary. Diode, earth ground, and sphere on top are shown. What you do is: wind secondary, and put sphere on top. Drive bottom end of primary with signal generator (or kludged-together oscillator) connected through a 1K resistor. Ground other terminal of generator. Do not make any other connections. Put meter from ground to the 1K/secondary node. Turn on generator to a couple of volts. When you are out of resonance, meter will read generator's voltage (as expected, you have no circuit "connection"). Sweep the generator. When you hit resonance, the meter will show a dip in voltage. (This should happen at about 1 MHz). You know you have it when waving hands around secondary disturbs meter reading.

Wind the primary over the secondary, tape it, and then slip it off the secondary, but keep the form intact. Connect cap in series with primary, and sweep with generator as for secondary, except "far end" of primary is grounded. Adjust cap value until primary resonates at same freq as secondary.

Slip primary back on secondary, connect cap in parallel with primary, and proceed with Tesla coil assembly/test.

tgriner1 (author)bpark10002016-10-27

Makes sense, thanks!

JankoJ (author)bpark10002016-10-26

What is capacity of that "unmarked capacitor"???

bpark1000 (author)JankoJ2016-10-26

That is explained in detail in my previous comment. My guess it will be in the 0.01 uF range. It is selected to resonate with the primary alone, at the same frequency that the secondary resonates with its top loading sphere only, with the bottom grounded. I can't give value, as that depends upon the diameter of the secondary, number and spacing of turns, and the loading capacitance of the sphere you choose. I would have to build an exact "carbon copy" of the coil to determine that. That's why I included the long-winded explanation of how to determine the value in the previous comment.

If you don't have test equipment, you can build an oscillator from a CMOS chip, a capacitor, a resistor, and a pot. Wave shape is not important, but stable amplitude is, which a CMOS oscillator will give you. The important thing is that you can "make the same frequency twice" by marking the pot position when you test the secondary, and tuning the primary to "dip" at the same pot setting.

Udon (author)Leonardo20162016-10-24

Not pedantic.

I also clicked through thinking this was a tesla coil, when in fact it was not.

That is not to say its not well-executed, well-photographed, and very interesting.

Apart from maybe the start of a very dangerous electric fence energizer, what else could this be used for? Could the spark be used for some interesting process?

NSX7342 (author)Leonardo20162016-10-22

Thank you

soumitraseth (author)2016-10-25

I`ts Great

Udon (author)2016-10-24

I realized after a few seconds that the red was a coil, and I wept for you.

That must have been an absolute bi-yatch to wind.

Dr.M3 (author)2016-10-20

hey you can increase results with metal topload, an aluminum foil ball can work too, if you dont want to spend money on something fancy, it increases capacitance and such

blackhol1 (author)2016-10-20

This is actually a low powered Tesla coil. The main factor is that a Tesla coil is an air core resonant transformer ( exactly what is shown here ). There is no iron core in this unit, it is also tuned to its own resonant frequency, hence the need to have a proper amount of turns on the primary and location of it as well. Also the DRSSTC is a solid state Tesla coil. A Tesla coil does not need to be spark gap driven to be classified as a Tesla coil.

LeeM84 (author)2016-10-20

so annoying when you get know it all's criticising this . Let's see your version then if you know so much . Anyone can copy and paste . This is for fun so stop bickering as to weather it's Tesla or not make it cos it's fun to make .... Great project btw

JankoJ (author)2016-10-20

What is the frequency of output current??? Have you measure it???

How-ToDo (author)JankoJ2016-10-20

I didn't measure this coil, but usually it is about 300 kHz
You measure it with oscilloscope, frequency counter/meter, or you can google something like "Tesla calculator" it gives approximate results

logical (author)2016-10-20

Circuit wise, this isn't really that complicated but I'd hardly call it a Tesla coil either. What you have here is basically a step up transformer and no more and with a ratio of 1:100 (10 primary / 100 secondary) and a 25V input, you'd get around 25,000 out but that alone doesn't make it a Tesla Coil, it simply makes a transformer. A genuine Tesla Coil while still relatively simply to make, does a little by achieving a higher than expect output for a given turns ratio.

A genuine Tesla Coil takes a simple tuned, resonant circuit driven by an already high voltage such as a neon sign transformer or (or even better, a Pole Pig) to drive a 'tuned' primary via an LC (tank) circuit. This is a little more than just pumping AC into the primary. Both the primary/secondary and the tank circuit are all carefully tuned to hit resonance at which point, this no longer behaves like a classic transformer and suddenly this is generating much higher voltages than you'd expect for the chosen turns ratio. This circuit may well be self-oscillating but without a capacitor in sight, we no longer have the all important LC (tank circuit) so it's not a Tesla Coil.

That btw, is probably a good thing as a good Tesla Coil can be rather dangerous if you don't know how to operate it safely ;-)

How-ToDo (author)logical2016-10-20

Okay, I will not argue. As I see it, in fact there is one task - to apply a powerful signal with resonance frequency of the secondary coil to the primary coil, and no matter where it came from, from tuned LC charged from HV or simple transistor generator with feedback.
Can we call this circuit Tesla coil?

JankoJ (author)2016-10-20

And to all of you who says that this isn't a Tesla coil, IT IS!!!! Tesla coil meaning the two separate circuits that are with same weight but different diameters of the wire, and no iron core inside!! That is the basic meaning of Tesla coil, and where ever you have this kind of circuits, you can call it a Tesla coil!!! No matter of output voltage, current or frequency!!

tina.gallagher.125 (author)2016-10-20

I would love to make this device, as it looks very useful. Unfortunately, I am not an electrician and don't understand all the highly technical language.

Chrome98 (author)2016-10-19

Too much information/instructions left out for novice to make.

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