# Simple Tesla Coil

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## Introduction: 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

There is a

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

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

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

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

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

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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## 43 Discussions

Exactly how many volts and amps needed for the power supply ??

It starts working with a 9V battery which provides just enough current for it to work. You can ramp up the power if your components can take it.

Does it matter how even the coil is? Does any NPN transistor work?

Different transistors have different parameters, which are for example how much voltage & current they can take, how fast they switch or how much voltage & current on the base they require to turn on, NPN or PNP, ... So .. not every transistor will work fine.

The higher quality the secondary is, the better it's going to work, but when I was testing my circuit, I didn't really care about winding an even coil with more than a thousand turns. I just wrapped tons of wire around a pipe. Allthough it worked to some point you want to avoid overlaping wires, as the high voltage can break through and burn the windings.

Hello,

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?

The problem could be the transistor heating up. Try mounting a heatsink. You might also want to try the TIP31C NPN transistor instead.

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?

Yes, it does. The primary should be wound oposite way as the secondary.

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

The way this works is, that when you first power it up, a DC current is sent through the primary coil which creates a magnetic field and so induces voltage to the secondary coil. At the bottom of the secondary coil, which is connected to the base of the transistor, there exists a negative voltage which turns off the transistor. Since the current through the primary is DC, the voltage on the secondary only exists for a short period of time, so when the transistor turns off due to the negative voltage, it almost instantly gets turned on again, letting current flow through the primary. This cycle continues many times per second. I hope that helps ..

As for the heatsink, it deepends on how much your transistor is heating up. If it gets quite hot, you should probably mount a heatsink to avoid damaging it.

As you choose the power supply for your coil, be aware of the maximum voltage and current you can put across the transistor Collector/Emitter junction For this particular transistor (2n2222A) you can put max. 40V across the Collector/Emitter junction and a max. Collector current of 0.8A. See the datasheet for more details. Have fun building it.

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

THE PROBLEMS IS THAT 9 VOLTS DC BATTERY DOES NOT DELIVER ENOUGH CURRENT AND VOLTAGE TO THE CIRCUIT.... THAT'S IT!!!!

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.

The secondary coil has to be connected to the base of the transistor to make the circuit oscillate based on the feedback from the HV coil. This way it adjusts the primary frequency to the resonance frequency of the secondary.

The schematic is totally perfect dude connect in that way and circuit gonna work.

TIP31C transistor work?sorry by my not good english

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.

I feel you. I learned about circuits just to understand how to do this. And now I want a soldering iron for Christmas.

These comments are longer than the Instructable. XD