Mini Spark Gap Tesla Coil

About: I have 3 associates degrees in Electrical Tech/Engineering.

Right after I got done making the Plasma speaker I wanted to work on something else that had to do with a high voltage flyback transformer. I searched on the internet, looked at videos on you tube on how to make them. I am going to show you how I made a decent SSTC that makes about 4 inch arcs. This is a good way to have both a working plasma speaker and a mini tesla coil just by adding a few extra parts!

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Step 1: Items You Will Need

Flyback driver:

TL494 chip
200uF (or 220uF) electrolytic capacitor
47nF 250v capacitor
100nF capacitor
10nF capacitor
2.2K resistor
10 ohm resistor
UF4007 diode
10K potentiometer
22K potentiometer
Large heatsink
Flyback transformer (you can get one from an old CRT.)
12v power source for TL494 oscillator
12v to 40v power source for the flyback transformer
*All the parts (Excluding the fly back, heatsink, and the power supplys, ) I got off of mouser for 12 bucks.*

Tank capacitor & Spark Gap:

8 -- 3000V .047uf CDE HV Meallized Polypropylene Film Capacitors
8 -- 10 Mohms 5% Carbon Film resistors
2 -- Screws for spark gap
*Pricy, caps was 2.22 each on mouser*

Primary Coil:

10 ft soft copper tubing � OD ( 7 bucks at lowes or you can get 12awg solid wire, it will also work!)

Secondary coil:

PVC 1.5 d x 4 w pipe (2 bucks at lowes)
27AWG enamel-covered solid-conductor copper wire ( Got from radioshack comes in a pack of 22, 27, and 30. Get three of them! Or if you can find them cheaper somewhere else get em! They are 6.59 each


1 Ft 2.5 in drain pipe (lowes 2.15 a foot)
Aluminum plated tape (7 bucks at lowes)
Wood or cardboard
Nylon bolt and nut

Step 2: Flyback Driver

Earlier I told you I got done building a plasma speaker, well I had some spare parts left over so I decided to use the them. In NO way I am taking credit for the design of this circuit a boy by the name of Plasmana designed it! I will give the schematic and the link to his page

Hook everything up like it says, to test and see if the tl494 is oscillating put a speaker where the fly back is and change the voltage to 12V, you should hear a loud screech, if nothing play with the pots or look over your circuit. One other reason I wanted to use the Tl494 as a driver is because I thought it would also produce music from the arc. I was soon let down when the sound was coming out of the fly back and the arc from the tesla coil was the sound of the spark gap. If anyone knows how to audio mod this I would love to know! The flybacks secondary from the plasma speaker schematic is the HV DC from the tesla coil schematic.

The cam didnt pick up the screeching you can barly hear it

Also there is another driver that works well to but im not going to go into it. ill give the schematic its called ZVS driver.

Step 3: Tank Capacitor & Spark Gap

For the tank cap I made a MMC (Multi-Mini Capacitors) I used 8 3000V .047uf CDE HV Meallized Polypropylene Film Capacitors. The reason we need to use eight is because we need to raise the voltage rating of the caps because the fly back will give off a massive amount of voltage! So we need to put the caps in series! So lets do some math 3000v x 8 = 24000v this should be good! Once you put them in series the capacitance will go down so .047uf / 8 = .0058uf or 5.8nF. Once you have them in series we need to put the 10Mohm resistors across each of the capacitors to drain the voltage out of the capacitors. A good website to visit is

VERY HELPFUL! The spark gap is two screws put threw a box, the closer they are the more the arcs going into the air are ( The lightbulb I put on top move the arcs close together to get it) the long apart they are the longer the arcs will be in the air! Play around with them to get it the way you like it! Also the transformer I am supplying power to the flyback, I put a meter to it and it says 32 V dc but when I take another reading when its turned on it reads 8 v dc. Its out of a TV, i need a bigger transformer.


Step 4: Primary Coil

The Primary coil is the that goes around the outside of the secondary coil. I am using 10 FT 1/4 OD copper tubing made in a cone shape. Before I got the tubing I was using 12AWG solid copper wire wrapped around a 2.5 piece of PVC. If this is all that you can get then that will be fine. I find the arcs are bigger at the third or fourth turn of the primary coil. Its best to use alligator clips on the wires to adjust the turns. The primary coil will be hooked up at one side on the tank capacitor and to the other side of the spark gap.

Step 5: Secondary Coil

The secondary coil is the long vertical coil rising from the primary coil. This is where you spend a good chunk of time winding the coil. The secondary coil should be 5 times bigger than the diameter pipe you are using so I am using 1.5 in diameter then the length of the coil should be 7.5 in. I got my magnetic wire from radio shack remember it comes with 22, 27, and 30 gage wire. You are only going to use the 27 awg wire, it should be green. You are going to use all three of the rolls of wire! This will make the coil to turn out at 8 in which will be fine! I drilled 4 small holes at the bottom of the pvc pipe. Run the wire in then out, in the out and back in. There should be a little bit of wire sticking out the bottom of the pvc pipe. This will be connected to earth ground! After you have done that then start to roll! When your rolling the coil and run out of the first roll, put a piece of tape holding the wire to the pvc pipe, get the second roll that you have and solder the two leads together (make sure you scrape off some of the enamel). Get as little solder on them as possible, and just keep on rolling! You can check and see if you have a connection with a meter. If you find wire somewhere else and have enough then you can just skip this. After you are done rolling I drilled three holes where the coil ends and ran the wire in then out and back in and up the tube. This will hold the wire so it dont come unwound! Cut off the remaining pvc pipe but leave about 1 to 2 inches above the coil!

I made another coil out of the 30 awg wire. You will have to add more turns on the primary

Step 6: Toroid

I thought about buying a toroid to put on the top of it but im not going to pay 1 to 2 hundred dollars for one so I made my own! So your going to take the 1 Ft 2.5 inch drain pipe and curl it in on itself so it should be in a circle. Stretching it out a little bit will help it some. Measure the inside diameter of the circle and cut a piece of wood or cardboard and place it in the center of the tube. It will look like a space ship when your done! Take the Aluminum plated tape and start taping from the bottom of the cardboard, around the tube, to the top of the cardboard (it is extremely sticky!). Get the tape as smooth as possible! Its easier said than done but get is as best as you can! Once you got it covered with aluminum tape, Drill a hole in the center, put your nylon bolt threw the hole, place the washer and nut on the other side. Be sure to scrape the enamel off the wire to make a good connection with the toroid!

Step 7: Hook It Up and Make It Happen!

After that then your done! Hook it all up and play with it! You can see the arcs better in the dark than in the light I wish my cam could pick up the little arcs. Im sure if I had a better power supply to the flyback they will be more impressive! If theres any I left out or could make this better please give your input!

Sorry about the dark shot you cant see crap! my cam sucks!

The lightbulb is cool!



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    62 Discussions

    Jimmy Proton

    8 years ago on Introduction

    Just a comment on the name, all Tesla Coils are spark gap (except solid state), it suppose to be the kind of gap.

    5 replies

    not all tesla coils are spark gap/solid state! You kids have no idea what vacuum tubes are these days, do you? :D

    pdub77spark light

    Reply 8 years ago on Introduction

    HA! Hey, at least they're trying, right? How many kids out there are making Tesla coils? How many kids know who Tesla even is?


    Reply 2 years ago

    bruh we had an entire day at school dedicated to tesla coils and im 14


    4 years ago on Introduction

    I'm 11 and I can't find a material the can magnify the plasma sparks from 0.5 inch to around 30 inch if anyone knows then tell me at thx


    10 years ago on Step 2

    If you want if to sing try replacing the spark gap with some xenon flash tubes from camera flash circuits. Hope it works

    12 replies

    Reply 9 years ago on Introduction

    How would that work? Modulation is only possible on solid state and vacuum tube Tesla Coils.


    Reply 5 years ago on Introduction

    What if you used solenoids or servo's to adjust the spark length, so different notes can be played. Maybe use an arduino plugged into a MiDi source to modulate the spark gap. It wont be easy, but a fun challenge!


    Reply 9 years ago on Introduction

    You would need to have a bps of 20000 and vary the current with IGBTs. Also I have learned a lot more since I posted that comment. And some (like me) have a low budget so MOTs are the only option. MOTs can be ballasted resistively with a 150W light.


    Reply 9 years ago on Introduction

    Changing the BPS rate does change the frequency that you hear coming from the sparks, but the reason that it is not done with SGTCs is that as you increase the BPS, the energy stored in the tank capacitor in each cycle is lower and lower, and the capacitor is usually matched to the frequency of the transformer and its voltage and current, so on some cycles, the transformer will charge the capacitor and then reverse polarity, and discharge it. It might work, but at each frequency, the sparks would take a different appearance, even though the total energy in the circuit would remain the same. Also, IGBTs are not practical with a SGTC due to the VERY high voltages and currents involved. You might be able to try this with an OLTC, but I wouldn't expect good results. Also, MOTs are usually better ballasted using an inductive ballast, such as another MOT with shorted secondary windings.

    Im trying to put together another circuit for this. I ordered the parts for it a couple days ago so it should be coming in soon, Im going to make a solid state and improve the spark gap, I have a couple of microwave transformers around here somewhere, Know anything that i can do with them???

    Don't use microwave oven transformers, yet. You should only do this when you are very confident in your constructions skills (verify this by building a few smaller neon sign transformer or OBIT powered Tesla Coils first), when you fully understand the physics of the circuit (be comfortable with LC circuits and using calculators, understand quenching and damping effects within the circuit, and be able to understand the current flow within the circuit), and when you have a large, clean area to work in. Even a ballasted microwave oven transformer is lethal. Also, you should collect more transformers, at least 3 for a ballasted antiparallel setup that should provide 4kV. You may also consider using a voltage multiplier, to make the voltages easier to work with. A Tesla Coil built using microwave oven transformers is a big commitment, and will take a lots of time and effort. I recommend that you set those transformers aside for the time being.

    well ill just work with what i got now. ill put what I got together and throw it on here and see what you all think! just gotta find the time with school and all.....


    Reply 9 years ago on Introduction

    Before I build this and attempt to also modify it to "sing", there is one thing I am unsure of... After modifying the coil to sing, would the current be higher than in the unmodified version?

    I dont know I didnt test it with a meter, I really dont think you can make it sing unless you get rid of the spark gap and make it a solid state. I tryed the spark gap and you can only hear the music inside the flyback, Im trying a new circuit and got the parts in today so im gonna try it out.