Introduction: 2n3055 Flyback Transformer Driver for Beginners

Picture of 2n3055 Flyback Transformer Driver for Beginners


This instructable will show you how to make a cheap and simple driver circuit in order to get high voltage arcs out of a component called a flyback transformer.

A flyback transformer, sometimes called a line output transformer are used in older CRT TV's and computer monitors to produce the high voltage needed to power the CRT and electron gun. They also have other auxiliary windings built into them that the TV manufacturers use to power other parts of the TV, so they are usually customised by the manufacturers.

For the high voltage experimenter they are used to make high voltage arcs, which is what this instructable will show you how to do with just a few simple electronic components.

You can get flyback transformers out of older CRT monitors and TV's. They are the ones that have a big heavy chassis. There are also other instructables on this website showing how to remove them from the chassis and circuit board.


I am in no way responsible if you mess up with this circuit. If you mess up you have no one to blame but yourself.

What you will need:

1x Flyback transformer

1x 2n3055 transistor + heatsink

1x 220 ohm 5 watt resistor

1x 22 ohm 5 watt resistor
(Note: The resistor values do not have to be exact. Say if you had a 33 ohm and a 200 ohm resistor they would still work fine for this circuit).

Some enamelled magnet wire, single core bell wire also works well too for the primary and feedback coils.

A fast diode. Although this is not needed for the circuit to work, it protects the transistor from back emf spikes and can help prolong the life of the circuit. I just used the one I found on the TV board but the UF4007 is an easy one to get hold of in electronic stores if you need to buy one.

+Some way of connecting the components
such as alligator clipped cables or wire and solder.

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Step 1: Mount the Transistor Onto the Heat Sink

Picture of Mount the Transistor Onto the Heat Sink

Mount the transistor onto the heat sink. The heatsink is important as the transistor gets hot. I just bought the cheapest heatsink maplin sell. The 2n3055 is a TO-3 case style.

You can use an insulator pad if you want but I just used a small amount of old thermal grease I had lying around. To mount the transistor to the heatsink I just used some spare screws and nuts I had in the garage.

Make sure that the transistor pins do not physically touch the heatsink and it is screwed in securely.

Q: Can I use a different transistor?
A: Yes you can, as long as the transistor has similar specs to the 2n3055 or better.

Q: Can I use a PNP transistor?
A: Yes, but you will have to reverse the collector and emitter connections in order for it to work. It will also need to have similar or higher specs as the 2n3055 transistor.

Q: Is the heatsink really needed?
A: Yes, if you are wanting to use this circuit for more than a few seconds the heatsink is vital as the transistor will get hot fast.

Q: Can I use a MOSFET?
A: No, a MOSFET will not work for this circuit.

Step 2: Preparing the Flyback

Picture of Preparing the Flyback

Using some enamelled magnet wire wind two coils around the core of the transformer in the SAME DIRECTION.

11 turns primary and 7 turns feedback is a good starting point but you can try more or less windings to see what gives the best results.

Using a sharp knife carefully scrape away the enamel coating from the very ends of the magent wire.

Once you have wound the coils and removed the enamel at the ends of the wire check for continuity using a multimeter, doing this can save you lots of bother later on!

You do not need to worry about finding the HV return pin yet.

Step 3: Putting the Circuit Together

Picture of Putting the Circuit Together

Connect all of the components together as shown in the images above.

In the graphical diagram, the red coil is the primary coil with one end connecting to the positive "+" of the power supply/battery, the other end connects to the transistors collector which is actually the metal casing of the transistor itself.

The green coil is the feedback coil with one end connecting to the middle point of the two resistors, and the other to the transistors base (looking at the transistors underside this is the pin on the left).

If you have some alligator clipped wires then you can use these for temporary connections whilst you familiarise yourself with the circuit.

Step 4: Check Everything

Picture of Check Everything

Check to make sure that your circuit is connected up correctly.

You can use a multimeter set to measure continuity or resistance to make sure that everything is making good electrical contact.

Step 5: Safety First!

Picture of Safety First!
When drawing arcs...

I strongly urge you to make a "chicken stick", which is a 1 foot long minimum insulating stick of some sort. PVC pipe is very good for this. Wood is fine too but when damp it becomes a good conductor at high voltages.

Secure an electrode of some sort onto the end of it, sharp pointed nails work well and will give slightly larger arcs than rounded electrodes. You can then attach a wire of some sort to the chicken stick electrode the other end will be attached to the HV return pin on the flyback transformer.

Other safety concerns

Including the obvious risk of electric shock another thing to take note of is that the arc is VERY hot and can easily set to fire to anything that it touches. Even the cable insulation will burn if you draw the arc onto it.

So if you insist on burning pieces of paper or other objects take that into account and have some way of putting the fire out.
  • You should never touch the high voltage wire or any of the flyback base pins when the circuit is turned on.
  • Make sure that you can easily disconnect the power to the circuit.
  • Do not use this circuit on an unsuitable surface such as a metal table or flammable surface.
  • The transistor heat-sink can get hot so watch out not to burn your hand on it.
  • Keep any high voltage cables away from other parts of the circuit and low voltage cables.
  • Use common sense.
  • Keep pets away. As well as the risk of shocking your pet from the sparks many household pets like to chew things such as wires.
Following those basic safety steps you will be fine.


I am no way responsible if you mess up with this circuit.

Step 6: Powering the Circuit

Picture of Powering the Circuit

To power the circuit you can use any 12V source that can supply a minimum of 2 amps, as a rule.

AA battery's in series can be used but they will not last long and the arc length will get smaller and smaller as they drain.

x2 6v lantern battery's can be used and will power this circuit nicely for a decent amount of time before the arcs start getting smaller.

A 12v lead acid battery is a very good way of powering this circuit and what I personally use.

A 12V power supply can also be used providing that it can deliver 2 or more amps.

I do NOT recommended 9v /PP3 battery's as they will not last long at all and even when new are unable to provide the current needed for a decent sized arc.

Step 7: Finding the High Voltage Return

Picture of Finding the High Voltage Return
To find the high voltage return first attach your chicken stick to the high voltage out (the big thick red wire) and turn the circuit on. You should hear a high pitch noise. If you don't here this noise then go to the trouble shooting page at the end.

Bring the chicken stick close to the base pins on the flyback and go past each one individually. Some of them may give a slight spark but one of them should give a solid constant HV arc, this will be your HV return pin. You should now disconnect your chicken stick from the HV out and connect it to the HV return pin instead.

In the image's above are some arcs produced by my 2n3055 driver and some different flyback transformers, most flybacks will only give around a 1-2cm arc on 12V input and upping the input voltage only increases heating on the transistor in my experience.

Have fun and remember not to run this circuit for periods longer than 1 minute as the transistor gets hot fast.

Step 8: Going Further

Picture of Going Further

Now that you have your driver made and working you are probably thinking "what now?".

Well some things you can do include soldering your driver components onto a single piece of strip-board or making a high voltage capacitor and getting loud sparks.

You can also make a small Jacobs ladder by placing two vertical pieces of bare wire close to each other with a small gap at the bottom that gets wider at the top.

Step 9: So How Does It Operate?

Note: this is what I think is happening with this circuit, if someone with more knowledge could correct me in the comments I would be more than grateful to know!

When you first apply power to the circuit a small amount of current starts flowing through the voltage divider resistors and feedback coil and into the transistor base, as part of this current path is wound around the ferrite core (feedback coil) it stores some inductive energy in the core.

As current is now flowing through the base the transistor is now forward bias which turns it on.

Current then starts flowing through the primary coil and into the transistors collector and out of the emitter (conventional current flow BTW). Current will keep building up in the primary coil until core saturation occurs. This takes the voltage of the feedback coil down to almost zero and the transistor falls back into its linear region.

As the transistor turns off, the magnetic field in the feedback coil collapses which creates both a high voltage pulse in the secondary coil and a small voltage boost in the primary coil (this is why the transistor has to be a high voltage transistor).

As the induced current is in the opposite direction to the supply current i am thinking this serves a current limiting action to the circuit, which might explain why it only seems to draw 2 amps max. If this was a non-inductive load then the transistor turning on would effectively be shorting the power supply right now.

As the transistor turns off the magnetic energy stored in the core from the primary coil rapidly collapses giving an even higher voltage pulse on the high voltage secondary coil.

The process repeats its self thousands of times per second.

Please correct me in the comments if I got any of this wrong!

Step 10: Troubleshooting

Picture of Troubleshooting

Ok so you have made the circuit and it either does not work or it does not work very well.

  • If nothing happens and you cannot hear any high pitched noise from the flyback transformer then try reversing the connections to the primary and feedback coils, if you still get nothing try just changing the connections on one of the coils. Usually this resolves that issue.

  • If you have tried that and still nothing then you should check the circuit and make sure all connections are secure and nothing is shorting out. Sometimes people will forget to remove enough enamel on the magnet wire primary and feedback coils and there will be no electrical connection being made.

  • If it works but the arc is small try reversing both the primary and feedback coil connections. Remember that around 2cm is the maximum arc length you are going to get out of this driver, and 1cm may also be the maximum on some flybacks.


Alex1M6 (author)2011-09-23
Skip to 0:44 in this video to see some arcs.

AhmadM11 made it! (author)2015-05-31

I made it! I got the flyback from my old 14" CRT monitor.. Took some
time to build. But in the end, it's beyond my expectation. It was
powered 12VDC from a computer PSU and after a few adjustments I got an arc about 1,2cm long. And after playing around with my coil, curiosity comes to me.. What if I add more V? So I made a special simple-rectified 5A DC power supply with. It has 6, 12, 15, 18, 24 and 30VDC. So I try 15VDC as initial test with new PS. It works! But nothing significantly change. And then the unsatisfied me added more V to 18VDC. The start button pushed... And.. Nothing happens.. I found it that I had lost the 2N3055.. I couldn't understand.. 2N3055 is to sturdy to be fried by a 18VDC! But instead of learning what happen to the 2N3055, I just throw the dead 2N3055 and add 3 of it in parallel (I found it that adding more transistor helps a lot in keeping the transistor away from overheat).. Along with that replacement, I add a switch to bypass the 220 OHM and name it as the "FULL POWER" switch! After plenty of changes I decided to run a test to the circuit.. So I test it with 24VDC.. It runs perfectly with about 1,5cm or more (couldn't reach 2cm).. The only different (compared with 12VDC computer PSU) is the arc looks hotter.. It has brighter thicker yellowish arcs and even thicker in "FULL POWER".. But I don't see any different in length.. However, I am very satisfied with this project and decide to advance to build a medium sized tesla.. Thanks a lot to you, I got many instructables from yours.

L DushanF (author)AhmadM112017-12-31

can u give the curcuit diagram

bui anht (author)AhmadM112015-06-13

how did you adjust the psu?can you give me some information?i made it and ran by psu but only fan work,nothing else happen

L DushanF (author)2017-11-06

i tried using a some of flyback.but doent work can u tell me what type of flyback is suitable

Chinmaya Shyamaraj (author)2017-04-13

can i use the primary that is in the transformer?

Mehulk20 (author)2015-02-02

what happen if i use 2 or more transistor or greater then 2n3055 and more resistors of same value that you suggested us and a more powerful it sufficient to drive out 30kv. if not then can you please suggest us what to do for driving 30kv output from a fly back transformer of a monitor.

one more question ???

can i use transistors ,diodes ,capacitors ,resistors etc from my monitors circuit board.

GyurikaK (author)Mehulk202016-02-17

I didn't try more transistors but a dude said that he hooked up 3 in parallel and they worked but didn't make the spark longer by I said in the instructable that you can use the things from your TVs board :)

yogesh15889 (author)GyurikaK2016-10-19

Can you please suggest me what to do for driving 80kv output from a fly back transformer.

TheGreatResistor (author)2016-08-24

Hi thanks for the instructable i tried it was awesome i got 2.3cm sparks but it also gave off a weird smell i thought the transistor burned off but it didnt after research i found out it was OZONE. Is the ozone produced by this circuit dangeros

CJ4 (author)TheGreatResistor2016-09-26

Ozone is 3 oxygen atoms bonded together, and by itself is normally not dangerous. But ozone can be vulnerable to something called deflagration, where it can be lit on fire by a spark, resulting in a fireball, at worst. Make sure you have ventilation to get rid of the ozone.

Madpiper (author)2016-06-28

Rather than using an external diode, a damper-diode type HOT could be used.

atharva4rever (author)2015-06-23

Can anyone tell me what sort of power adapter should we use to drive it? In this it is written 12 volts 2 amps.... ?????

tiMRoni (author)atharva4rever2016-06-08

Get a lcd tv adapter which are 12v @ 5amp.

Tesladuke (author)2015-12-13

can I use a 2N 6292 transistor for this?

PlasmaGuy101 (author)Tesladuke2016-06-08

yes, just dont input above 7 amps

PlasmaGuy101 (author)2016-06-08

Can I use this circuit to drive a small solid state tesla coil? Also, can I use an IGBT ( insulated gate bipolar transistor ) in place of the 2n3055?

PlasmaGuy101 (author)2016-06-05

Thanx for the great instructable. I made mine with a darlington pair in parallel with a 2n3055, it makes a 1.5 inch arch at 13 volts. Also drives a sgtc very nicely.

multicaglar (author)2016-02-13

Do I use byt77 diode as ultra fast diode?

ConfederateKing made it! (author)2016-01-21

It works When Connected to 18V 4.3 amp arc look like Constant Dc i dont know if flyback have diode because i harvest the flyback in some plasma cutter also power Fluorecent CFL tube

ConfederateKing (author)2016-01-20

What about 7 turn primary and 3 turn feed back because my flyback is so small

JoshW44 (author)2016-01-16

Here is a video of it, too

JoshW44 made it! (author)2016-01-16

worked out great!!!

started with old donated CRT. Harvested flyback and the diode off the circuit board inside. made the circuit exactly as you have it. will use to power ES motor i 3D printed at here in Plano, TX.


ConfederateKing (author)2016-01-14

Can i use TIP Transistor NPN?

FacundoC3 (author)2015-11-29

Hey, great tutorial, I made one and is working, but the arc is intermittent, do you know what could it be? I swapped the cables of the primary and secondary to see if that helped but I only got a smaller arc? Thnaks!

Tesladuke (author)FacundoC32015-12-13

the resistors might have been overheated, try replacing them

gveselič (author)2015-06-21

After few seconds of working my transistor get really hot and i have a big heatsink and cooling fan. What to do? Please help.

PlasmaGuy101 (author)gveselič2015-09-16

put some thermal compound between the transistor and heatsink.

bui anht made it! (author)2015-06-21

i made it! but still a big problem,i use 5w creamic resistor,when run 10s,the transistor and resistor become too hot,any one got same problem?

ThomasF12 (author)2015-06-19

If you are interested in long sparks then buy yourself a 6 inch 12 volt DC powered plasma ball from Walmart for $17.

Presently I have harvested 140 DC volts from the OUTER SURFACE of the ball

in a way never done before. Tesla being the exception. That is true radiant energy collected and manifested into electricity just as Tesla might have done. Will post video on You Tube later.

bui anht (author)2015-06-13

can i power it by psu,with yellow and black wire?i made that circuit,ran it and nothing happenned.use psu,only the fan run,12v 3a accu,the resistor blown up... can any one explain me why?

AhmadM11 (author)bui anht2015-06-17

Hi bui.. I didn't adjust anything on the computer PSU.. The
adjustment is for the driver circuit.. So I didn't do anything to the

Anyway, have you exchange the primary and the feedback coil's connection? At my first trial I got nothing before I switch around the coils. And yes, for the computer PSU you can get the +12V from any yellow wire.. If your resistor blown up then try to double the wattage or the value of the resistor.. it works for me.. Currently I use 36V 5A with ZVS driver.. It can strike the ground from 5cm away and can stretch along 15cm..

bui anht (author)AhmadM112015-06-18

my friend told me that too,i did it and the transistor became too hot,then it blew up,why?use psu 12v.can you explain me why the psu case write 12v 18a,imax of transistor is 15a,why you still can run it?could you please send me some pic about your zvs driver.thank!

ThomasF12 (author)2015-04-26

what gauge wire is used for the feedback coil?

AhmadM11 (author)ThomasF122015-06-17

I use 1mm magnet wire and it works great.. Be free to experiment.. :)

hemant solanki (author)2014-08-22

please help me ! my arcs are smaller than 1 cm, I want to increase arc length

AhmadM11 (author) hemant solanki2015-06-17

Wow.. You may reconsider the distance from that thick red wire if you have a fix driver and coil..

Check and recheck your connection including the coils direction.. Make sure they have the same direction and sometimes you have to reverse the direction of the coil considering the direction of the secondary coil inside the flyback..

bhess2 (author) hemant solanki2015-05-10

make sure the winding are tight and straight are you sure that is the right ground and not the screen wires ???

Alex1M6 (author) hemant solanki2014-08-25

Have you tried reversing the connections to the primary and feedback coils? As this circuit will only give the best arcs when the coils are the right way around, this is caused by the internal diode built into the flybacks high voltage winding.

If swapping them around just makes the arcs smaller then experiment with the number of turns, I have a few flybacks that need lots of turns in order to give much of an arc.

On the driver reducing the 22 ohm resistor usually gives instant longer arcs, try something like 12-15 ohms there. A 33 ohm 2 watt in parallel with the current 22 ohm resistor will suffice.

What sort of power supply are you using to power the circuit? It should be able to supply 3 amps at 12 volts.

hemant solanki (author)Alex1M62014-08-27

I have tried reversing connection to the primary and feedback coil, but it reduces arc length.I an using a DC supply at around 9 volt and 1.5 amps.

enelson8 (author)2014-11-09

Hey! I love this and actually got it to work! But how much amps or volts would I need for a like 1.5 - 2 inch jump? This is using 9-12v with 2000mA

bhess2 (author)enelson82015-05-10

You would need about 40 -125kv depending on your elevation and humidity for a two inch arc and it doesn't matter how many amps you seed if you want it to spark at 2 inches not stretch to two inches but the more amps you have the more the arc "stretches"

If you have taken apart a microwave oven and used its transformer for high voltage arcs you would notice how you would almost need to touch the two wires together to spark then you could "stretch" the arc to about 4 inches this is because of the higher amps. (author)2015-05-06

WTF ,i have 5 flybacks and not one works ,, someone posted a schematics of quite a few flybacks ,i noticed that onsome of them they are over 10,000 to 18,000 volts , some are 250v 150,v 15 v 12v etc ,,when i measure the voltage its always cut in half, am i the lucky guy who has to combine certain terminals to get it to work.i even bought a zvs driver ive tried all the different ways on you tube.. the only thing that worked is the car coil but very small arcs..any ideas..

.. im so frustrated im ready to chuck it all out the window,,lol.

Doctor90250 (author)2015-04-09

great instructable! I'd like to add that after powering off, it's a good idea to short the hv output to each of the bottom pins of the flyback, because at high voltages, transformers with multiple coils can act as a capacitor and store a charge. while it's not enough to hurt you, it can startle the crap out of you, causing you to Yank your hand back, cutting it on a piece of sharp metal that happened to be on your work bench from another project....but of course that's never happened to me. (blushing ) lol

aryh (author)2015-04-04

help, I had previously tried this driver and it worked, after I run for a few minutes my transistor popping and I replaced it with the same transistor but it does not work, the transistor begins to heat up and no spark

thank you,sorry for bad english

GaryK5 (author)2015-02-06

i did this circuit a few times and failed. I did it sloppy the first time so i took my time and put it all on a wooden board just like in the diagram and it worked great. Thank you alex1m6. I always wanted a high power source and thanks to you it happened. I am just thrilled to see it work. It was worth building. Thanks a million my man.

PedroR8 (author)2015-01-18

Do I must use the resistors, or this circuit (2n3055 flyback driver) works without them?

PedroR8 (author)PedroR82015-01-18

What are the resistors for?

naga venu (author)2015-01-08

I have one flyback transformer which has only 3 bottom terminals and one output bulk red wire. How much voltage it can give ? I tired it with 9V and 12V DC but can't get output voltage.

Thanks in advance.

ann.bragonje (author)2014-12-31

I am trying to help my son with his science project which includes making the arc and then comparing different shaped electrodes. We are having a problem finding the flyback transformer. Is there another transformer that would work?

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