Picture of 2n3055 flyback transformer driver for beginners
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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.

You may not, except with our express written permission, distribute or commercially exploit the content. Nor may you transmit it or store it in any other website or other form of electronic retrieval system.
Alex1M6 (author) 3 years ago
Skip to 0:44 in this video to see some arcs.

alirezaasadi2 months ago
it doesnt work
atharva4rever2 months ago
Can anyone tell me what sort of power adapter should we use to drive it? In this it is written 12 volts 2 amps.... ?????
bui anht made it!2 months ago
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?
gveselič2 months ago
After few seconds of working my transistor get really hot and i have a big heatsink and cooling fan. What to do? Please help.
ThomasF122 months ago

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 anht2 months ago
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 bui anht2 months ago

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 AhmadM112 months ago
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!
ThomasF124 months ago

what gauge wire is used for the feedback coil?

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

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

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..

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

Alex1M6 (author)   hemant solanki1 year ago
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.
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.
AhmadM11 made it!3 months ago

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.

bui anht AhmadM112 months ago
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
enelson89 months ago
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
14, 9:04 AM.jpg
bhess2 enelson83 months ago

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.

kel.moto.33 months ago

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 4 months ago
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
aryh5 months ago

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

GaryK56 months ago

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.

Mehulk207 months ago

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 diodes.is 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.

PedroR87 months ago

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

PedroR8 PedroR87 months ago

What are the resistors for?

naga venu7 months ago

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.bragonje8 months ago

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?

ualbuquerque10 months ago

Cool! Simple and efficient

JonS11 year ago

I tried this circuit and failed, probably because I am trying to locate the internal primary and feedback coils on the pins. Perhaps I have watched too many youtube vids on the subject and the ones who posted were lucky enough to have found them and hooked them up properly, and I am not so lucky. Why am I frying my transistors? Coils hooked up in reverse? Back HV? Is this all folly, and much easier done by making my own primary/feedback winds on the ferrite? Would dioding the circuit prevent all of this?

But doiding would stop hv feedback and that means you wont burn as many transistors just take a fast speed diode and conect it from the emitor to the collector make sure its going in that direction.
Srry about that
Well yes dioding would stop hv feedback to th

help me i have to make a fly back driver circuit as teacher has given us this for project
teach me some thing as i realy dont even know the basics of this circuit
y we mAKE This
help me

Alex1M6 (author)  sabah.malik.5601 year ago
Which part of this circuit do you need help with?

Google for "blocking oscillator", which is what this circuit is.

When power is first applied to the circuit the transistor is off. Current flows through the resistors which form a potential divider and into the base of the transistor via the feedback winding. This turns the transistor on.

The transistor turns on and current begins to flow through the primary coil, as this happens an EMF is induced into the secondary winding but no current can flow there since the flybacks internal diode blocks it.

As the current in the primary ramps up it also induces an EMF on the feedback winding which opposes the EMF from the potential divider, turning the transistor off.

When the transistor turns off the current in the primary coil is suddenly interrupted and large negative voltage spike appears across the primary, a stepped up voltage also appears on the output of the flybacks secondary coil.

But now there is nothing to keep the transistor off so the cycle repeats itself over and over.

Hope I managed to explain that ok.

My flyback had the HV return pin torn off on accident.any ideas?

Alex1M6 (author)  HighCurrent1 year ago

Has the entire pin come all the way out or has it snapped right at the epoxy potting?

If it is the latter you can chip away at the epoxy and solder a piece of wire into the remainder of the pin. If it has come all the way out then try putting some thick wire in there, if you get a good fit it should make decent contact with the end of the HV winding.

I have attached an image to show you what I mean, click on it to get a full view.

mopuccino2 years ago
hey alex ,just wondering ,do you know what is the voltage and amps of the output of this device?(using 12v input) does it work with 9v?(square battery?)
Alex1M6 (author)  mopuccino1 year ago

1 year late I know...

Out of the flyback you will probably end up with around 10-15kV @ a milliamp or two.

A fresh 9v battery will sort of work for a few minutes, but it will give very weak sparks on the output. A 12v power supply that can deliver a few amps will be much better.

Sarthak311 year ago

I made it with primary 7 turns and feedback 5 turns it was working fine but then i used 37 turns with 25 , 13 ,17 turns but they all gave very small arks and gave a high pitch sound whereas in the first case there were relatively larger arks with no noise.

Can you give the combination for some larger no. of turns and also tell me the cause for this.

Sarthak311 year ago
Alex1M6 (author)  Sarthak311 year ago

Sorry but that is not suitable for this application. It needs to be a 220 ohm and an additional 22 ohm power resistor of 2 watts and above, that is a 220k (kilo-ohm) potentiometer which is too high.

I had a look on that website for a suitable resistor but can't find any listed, are there any other electronics stores that you can purchase from? If so post a link and I'll find the appropriate resistors for you.

Thanks for the reply

can i get one form this site http://www.onlinetps.com/shop/index.php?main_page=...

and earlier i gave you the wrong link it was originally


Alex1M6 (author)  Sarthak311 year ago

Hi Sarthak,

I had a look on onlinetps and although they don't have the exact resistor values, you can use a combination of other values to get the correct one. I've attached an image to show you what I mean complete with part numbers.

I know its not neat but it will work.

Regarding the electroncomponentslink, that is an adjustable resistor (potentiometer) and will get hot and burn out if used with this circuit.


Thanks Man

I think that the diode is upside down as cathode of the diode is connected to positive terminal of the battery(I am not sure)

Alex1M6 (author)  Sarthak311 year ago


How the diode is shown in the diagram is correct (anode to ground, cathode to collector). It is only there to bypass any negative going voltages that may ring over the collector to emitter junction.

Are you not getting any output from the flyback transformer?

How can i check if my flyback transformer is broken

Great tutorial I made mine and it works great! I have a question though. How did you attach the collector wire to the transistor when the heat sink was on? I've tried it on mine but the circuit shorts out when connecting to the bolt and doesn't work. Any suggestions?

Alex1M6 (author)  candrewneal1 year ago

Thanks! That is a good question.

I used a small ring terminal that was threaded over one of the heatsink screws and connected to the circuit board with a small piece of wire. You can get these at any automotive store for pennies/cents.

Make sure that the transistors emitter and base legs are not touching the heatsink when you tighten it down. You can get little securing plates that attach to the back of the transistor and prevent shorts, but you could probably get away with using scrap piece's of wire insulation places over the base and emmiter legs near the transitors body.

There is a good articale on this here http://rimstar.org/equip/mount_transistor_heatsink...

Works great! Thanks for the reply! I'm highly considering building a ZVS driver for my next project. :D

Alex1M6 (author)  candrewneal1 year ago

Your welcome! ZVS drivers are great fun but require lots of current to work well lol.

tezza121 year ago

Regarding the Diode!

I have a 1N4007 Diode & a BY228 Diode would either of these work ok & if so which would be the best option.

Many thanks


Alex1M6 (author)  tezza121 year ago

Hi Tezza,

Anyone of those diodes would work, but a "fast recovery" diode is normally preferred here such as UF4007, BYV26 etc.

This is becuase diodes can actually conduct in reverse for a brief period of time when they suddenly go from forward bias to reverse bias. The switching frequencys and harmonics present in this flyback driver are right at the upper limit for a standard recovery diode (1N4007, BY228 etc).

But out of the two you already have I would just use the 1N4007 since the BY228 is way over rated in terms of breakdown voltage and current, save it for another circuit.

tezza121 year ago

Could someone please advise me where about to place the capacitor & what values it should be. I am new to electronics so any help what be great. Thanks. Tezza

Alex1M6 (author)  tezza121 year ago

Hi tezza,

Which capacitor are you referring to?

Magnetron1 year ago
I built this twise and it did not work why?? Tanx for upgrading the circuit
Alex1M6 (author)  Magnetron1 year ago

I would start with reversing the connections to one of the coils and listening for any sounds of oscillating, which will sound like a high pitch squeal. Did you scrape enough enamel off of the end of the coils to make a good solid connection?

What sort of power supply are you using?

yes i did scrap of enough enamel and i use a 12v alarm bat3 but i think the problem is my resistors i live in SA and they dont look like the ones you used but tnx for reply
todybog1 year ago

Does the wire have to be magnetic or can i use wire from one of the transformers on the circuit board i have. it seems to be the correct gauge.

Alex1M6 (author)  todybog1 year ago
Any wire will work fine.
ok thanks. also i set up a 50 ohm 10 w instead of 22ohm. the others i have lined up to form 200ohm. not 220. but 10 watts each. that okay too?
Alex1M6 (author)  todybog1 year ago

Substituting the 220 ohm resistor for a 200 ohm will be fine but at the expense of slightly more power being wasted as heat. But using 50 ohms in place of the 22 ohm resistor will reduce the final output voltage by quite a bit, worst case the circuit will fail to oscillate.

If you can get hold of another resistor of around 30 ohms 2 watts, place it in parallel with the your current 50 ohm it will work much better and still allow you to use the resistors you already have.

Like in the schematic below:

todybog1 year ago

can i put a 10W 1ohm resistor before the others resistors which are only 1/2 w but the correct amount of ohms?

Alex1M6 (author)  todybog1 year ago

That will not work sorry. The 1 ohm 10 watt resistors will stay cool whilst the 1/2 watt ones will burn up.

ya but it might fry

yea i know. i got two 100ohm 10 w and one 50ohm 10w instead
Cormaxzyz1 year ago
I just built this circuit and it works great. So far it only produces fairly short arcs, but I haven't fiddled with the number of turns in the primary at all yet. Thanks for posting this!
UPDATE: The problem was that the battery was almost dead, hence the short arcs. Interestingly enough, I found that the diode heats up a lot, warranting its own heatsink (and even that isn't always enough). Do you know why this might happen?
Alex1M6 (author)  Cormaxzyz1 year ago

Glad you got it working. The diode will get quite warm as it bypasses negative going spikes caused by the LC action of the primary coil and tank capacitor.

If it is heating too much you can use something like a UF5408 instead which is the 3 amp version and will stay much cooler.

Do you wonder to know at which frequency is the output of this circuit at? About 50Hz - 60Hz?
Alex1M6 (author)  shostakovichteddy1 year ago

The one I built oscillates at around 20kHz which drops when into the audible range when drawing an arc (below 17kHz). Any 50/60hz sound will be caused by ripple from an unregulated power supply, add a large smoothing capacitor of around 6800uF across the supply rails to reduce this.

millerair1 year ago
Yes Hailing,
I have an Viore TV with a faulty flyback, the flyback got misplaced can u help me with getting back that flyback number so i can purchase the flayback. Thanks

Model No.CFT27V20
Chassis No. CH-16CD
Hello Alex1M6,
I followed your instructable and made a great one :). One thing that I am wondering is the output of the driver. Is it AC or DC, what is it voltage, amp, frequency? Once I tried to measure it by a multimeter and the multimeter died :(
If I put more coils on the primary would it increase output voltage? What about the feedback?
Is thinner or thicker gauge wire better for bigger arcs?

~ Brad
Alex1M6 (author)  Bradster970072 years ago

I found different flyback transformers to react differently. Some worked better with more turns whilst others did not, so experimentation is needed here.

It is more than just turns ratio that determines the size of the arc in this driver, the frequency that this self oscillating driver oscillates at will play a part. There will be a "sweet spot" that produces the biggest arcs, but at the expense of more power draw and transistor heat (mostly, but that is a whole different issue).

Adding turns will increase the inductance of the winding and thus decrease the running frequency.

Generally thicker wire is preferable but anything larger than 20-18SWG is over kill for this.

Hi Alex,

As requested I have posted some pictures to help us both out :)

The cables aren't coloured right for the polarities and the wires with blue tape is the primary coil. I am using a 2n3055 and the same heatsink as you, coincidentally. No wires are shorting to the heatsink or others.
Any questions, ask me :)

Alex1M6 (author)  Bradster970072 years ago
Hi thanks for uploading the photos.

From the photos it looks like you have gotten the resistors mixed up. The 220 ohm should be installed where you currently have the 22 ohm, and the 22 ohm should be where you currently have the 220 ohm.

Try swapping them around and see if it works.
I also have a 12V lead acid battery that is 12Ah to use, thanks to my gramps, and my gokart starter motor hehe

breed152 years ago
I have built one of these but there is no high pitched noise. I have tried 2 transistors and swapped the primary and feedback coils' polarity and did everything on your troubleshooting page but nothing is making a noise or outputing any arcs. I am using a PP3 battery just temporerily until it works but do you think if I used a 18v cordless drill battery it will work?

leviterande2 years ago
mine only puts 0.8 inch or 2cm arcs.. what is the length of your arcs? at what voltage?
Alex1M6 (author)  leviterande2 years ago
Depends on the transformer used, my best one put out around 1 inch arc with 12v input (drawing just under 2 amps). Where as another one I have will only do around 1cm.

Try experimenting with using different numbers of primary and feedback turns.
aha I see so it depends on the transformers, I thought all pc crt were the same if they looked the same.. oh well... I have bought a 28" tv to butcher it anyways
Alex1M6 (author)  leviterande2 years ago
If you increased the value of the upper resistor to something like 470 ohm then you could increase the supply voltage to 18v and it might give you some extra grunt to the arc.
hmm gonna try that . I have found that 5 turns primary is what gives me the 1 inch sparks. I see most people use high prim turns.. like 10 and above, if I do that the sparks get very dwarfed, what was your prim turns?
Nico N.2 years ago
Hello. I did this the exact way you said. I am using a 33 ohm and a 220 ohm wirewound flame-proof resistor. I have wound 31 AWG magnet wire at 11 and 7 turns. I am using alligator clips temporarily. I am using a computer charger that supplies 15-24 volts (variable) at 70 watts (that equals 4.6 amps at 15 volts) I am getting nothing and no whistling. I have switched the coils in every possible combination too - nothing. I thought maybe the circuitry inside the charger was not letting the circuit work so I tried 8 AA batteries. Nothing. I am using a 2n3055 transistor temporarily while I wait tor my MJE13009 transistor to come. I am thinking it is the transistor, my coils or the flyback itself. Can you please help? I have made power sources before and I do no understand how this one is not working. Thanks so much. :)
Alex1M6 (author)  Nico N.2 years ago

Try checking for continuity between the coils and rest of the circuit as with magnet wire it is sometimes hard to get a good connection.
Nico N. Alex1M62 years ago
Thanks a lot. I just got my MJE13009 transistors today and it works great. Turns out it was just the 2n3055 transistor. Maybe I burnt it out it or maybe it just dosen't work with my circuit. Anyways thanks a lot for your support. I am so glad I finally got it working even though I don't use it for anything besides entertainment.
were did you get the coil does it have three plastic screws on the side if you are having trouble with striping the magnet wire do it with lighter or torch
dmytro5092 years ago
Are there any other resistors I can use for this driver?
Alex1M6 (author)  dmytro5092 years ago
Why what sort of resistors do you have?
I have the same value resistors that are required in this build. They're just rated at higher wattages. Like I have a 20 ohm 20 watt resistor.
Alex1M6 (author)  dmytro5092 years ago
That is fine. Using higher wattage resistors is fine, it just means they can handle more heat (20 watts of it in your case).

If you put a quarter watt resistor in there though it would be a different story (small resistor + lots of heat = flames lol).
dmytro5092 years ago
Are there any other resistors I can use for this driver?
vivabrdi2 years ago
Help! Thanks, your's is the best simple driver posting - but, I can't get it to work!
Tried 3 different flyback transformers, 2 transistors, two different windings (7 x 11 and 5 x 20), powered from both 2 x 6V dry cells in series and also a car battery, triple checked continuity and resistance on all parts, but.... no spark! Not only no spark, no heating of the transistor, no noise, nothing. Is this a hoax?

How does this circuit create a high frequency oscillation? Why does mine create neither sparks, no noise, no noticeable heating of any component? Components: radio shack 2n3055 transistors, 220 and 22 ohm 5 watt ceramic resistors, tried with and without the diode. Any ideas?
Alex1M6 (author)  vivabrdi2 years ago
Have you tried reversing the primary and feedback coils polarity? Do them one at a time as it will only work in a certain configuration.

No this is not a hoax, with it working when you first apply power to the circuit current flows through the potential dividers and into the base (which the potential dividers bias it to at around 0.8v). As the transistor begins to turn on current starts flowing through the primary coil (storing energy in the core) into the transistors collector, out of the emitter and then to ground.

But since there is the feedback winding sharing the same core current will be induced onto that too. This is why it needs to be connected in the correct polarity so that the current induced onto this winding turns the transistor off. When it does turn the transistor off the voltage across the primary coil will be now ring up to many times that of the original input voltage, and so will the secondary coil thus causing the HV.

This is also where the fast recovery diode and maybe a small capacitor help to protect the transistor.

Have you checked each individual component out of circuit? A good transistor should show about 0.7v drop between the Collector-Base and Base-Emitter junctions. If you used magnet wire for the coils then check for continuity there as sometimes not scraping enough enamel away makes for a bad connection. Also when winding the coils it can be easy to accidentally scrape of some of the enamel with the core edges and that can create shorts between windings.

Check the current draw too of the circuit and the voltage of your power sources when under load.

Hopefully you'll get it working ( :
Aj963 years ago
I am getting a high pitch noise from the flyback transformer, but i am not getting any arc from it, any advice on what to do?
mgingerich Aj962 years ago
Increase the input voltage and it should start to arc. Squealing means your driver is working, but it might not have the power it needs to make a satisfying arc. I found that at least 20 volts is needed with my 2N3055 driver.
hey man.I have the same prob.I can hear the high pitch sound but no arcs.When i touch ground out to pos out the pitch of the transformer changes. any ideas to whats happening?
Alex1M6 (author)  mkjunior2 years ago
What sort of power supply are you using, is it able to deliver enough current without its output voltage dropping?

Also have you tried reversing the primary and feedback connections?
a 9v battery plus 4v from usb. i shall give your suggestion a try and get back
Alex1M6 (author)  mkjunior2 years ago
That will be why then, the USB is probably going into over-current shutdown and a 9v battery can't really supply enough current. Try something like two 6v lantern battery's in series for 12v, they will be more than enough to power this circuit.
Alex1M6 (author)  Aj963 years ago
Try switching the coil connections until you get the right combination, a squealing noise means it is oscillating ok but you have the polarity wrong.
Why can you not just connect the batteries to the transformer? I'm new to this :P
Alex1M6 (author)  TheNickmaster212 years ago
The transformer needs high frequency pulsing DC to work, if you just connected batteries directly to the primary coil you will just short out the batteries and nothing will happen.

You could get some small sparks though by manually pulsing the battery through the primary coil (although they would be very small and hard to see).

This circuit self oscillates and gives the primary coil the high frequency pulsing DC it needs to function (plus the flyback "back emf", that is the real reason for the high voltage).
dmytro5092 years ago
Can I use a DC power supply from a wall outlet to power this?
Alex1M6 (author)  dmytro5092 years ago
Yes, as long as it can supply 12-18v @ 2 amps.
Thanks mate.
正安2 years ago
Why is my arcs shorter than your? I used the same electronic components as your ,
Alex1M6 (author)  正安2 years ago
Could be a number of reasons.
  • What power source are you using and are you sure it is strong enough for this application?
  • Have you tried switching the primary and feedback polarity around?
  • How many primary and feedback turns are you using and what gauge of wire are the coils?
  • Is your power sources voltage dropping much under load?
正安 Alex1M62 years ago
Thanks for your reply,that's quite important to me.
1.I used the same power source as your, 12V, 8 of AA battery

2.I don't know clearly what you mean in this point,I made the same polarity both of the primary and feedback and primary turns are more than feedback.

3.I used to make 20 and 12 turns of primary and feedback respectively and I used the enameled wire about 0.5 mm as the coil.

4.Yes,the voltage dropped quickly after few minutes when i switch on. But in the first, batteries just load,there is a shorter arcs than your.(suppose there is 12V when new batteries just load).

Thanks again for giving a direction
cprail2 years ago
If I used a 110VAC house main, and sent it through a bridge rectifier to change it into DC, could I use that instead of the 12VDC battery? Or would it blow the circuitry?
Or, could I send the 12VDC battery through an inverter, increase the voltage through a step-up transformer, rectify it back to DC, and then but it through the flyback circuit?
I've been considering a similar approach. Power straight from the wall would definitely fry the transistor, but a step-down transformer of the right kind would probably work fine. I've tried it with a transformer I had lying around that outputs 16 volts, and it worked, but the arc was wimpy. The inverter idea would probably work, but you might just end up killing your batteries. I would suggest getting your hans on a step-down transformer and using that. Does anyone know how much current a flyback's primary needs to function properly?
I've been considering a similar approach. Power straight from the wall would definitely fry the transistor, but a step-down transformer of the right kind would probably work fine. I've tried it with a transformer I had lying around that outputs 16 volts, and it worked, but the arc was wimpy. The inverter idea would probably work, but you might just end up killing your batteries. I would suggest getting your hans on a step-down transformer and using that. Does anyone know how much current a flyback's primary needs to function properly?
Will it kill you ? And if it won't how bad is the shock?
rliu53 years ago
Does this driver work with a Mini/Medium sized tesla coil ?
Alex1M6 (author)  rliu53 years ago
It will work for small tesla coils, however it will not be very efficient. See this page for more info http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sgtc-i/
Skarz883 years ago
Is this circuit ok to run with a modified pc power supply wired for 12v? The circuit works fine :-) jus had to reverse the connections on the feedback coil. Thanks for this instructable!
Alex1M6 (author)  Skarz883 years ago
An old PC ATX power supply is fine ( :

Might be a good idea to put a ceramic or film capacitor across the supply rails for decoupling (close to the driver) to help stop any protective features from kicking in if the LOPT/flyback transformer spits out lots of noise on the supply rails.
sleepyjz3 years ago
I really like the look of this arc you are getting with this circuit and your other projects are quality, and will attempt your plasma speaker next, but I'm going crazy trying to get this beginner one to work - there is no way it can be this hard. I have everything set up nicely, checked continuity at every-step until completion, and am using the uf4007 diode. I have 3 flybacks each a different brand. I have made primary + feedback coils on them with a variety of magnet wires of different gauges. I tried with the windings adjacent to each other on the ferrite and also with them center tapped. I tried to use the flybacks' internal coils (not entirely sure how to connect them, though). I'm using a 12v 7ah battery like yours. I get no oscillations/noise/arcs at all out of the thing. I tried reversing the coil connections in all sorts of combinations. I wound two flybacks with coils clockwise or counterclockwise (but primaries + feedback always in the same direction), neither worked. I think the transistor still works because I can hear the circuit amplifying the sound of the tiny scrapes made when I move the circuits lead around on the surface of the corresponding battery terminal . I would really appreciate your input on this and am eager to see some arcs, what could be wrong?

Many thanks,

- sleepyjz
Alex1M6 (author)  sleepyjz3 years ago
Could you try connecting a neon across the HV output and see if it lights up, also check how much current the circuit draws from the battery and report that back here.

Did you put the diode the correct way around?
R.A.T.M3 years ago
So i have a big problem i here a humming out of the coils and when it will not arc and if you look at the transistor theres a flash inside then transistor and the humming stops
nms223 years ago
I have made this circuit successfully and am running it off 12 V at 1.7 amps. I have a fairly large heat sink on the transistor, but it is still "frying". Is this because of it receiving an EMF pulse, or is the current simply too strong for it? Also, does anyone know the temperature limits of the transistor used?
Alex1M6 (author)  nms223 years ago
Hi, unfortunately this is normal in this circuit as the MOSFET is avalanching every cycle becuase of the back EMF pulses that appear on the primary coil every-time the MOSFET turns off. This is also what eventually destroys the MOSFET internally.

Have you got any spare computer or desk fans lying around? Using a fan on the heatsink will help.

One way of cutting down the back emf pulses is to use something called an "RCD snubber" across the primary coil, however they can be tricky to get right. And putting anything across the primary coil is going to cause a smaller arc since the back emf (this is where the word flyback comes from) is the only reason there is such a high voltage coming out of the flyback transformer.

Perhaps try putting a small film capacitor across the primary coil, anywhere around 0.47uF-1uF. You will get shorter but much hotter and thicker arcs and it should help reduce the MOSFET heating. You might have to play with the values and flyback frequency (adjust the pots) to get the best results.

As for MOSFET temperature, what MOSFET are you using? They can easily survive upto 150C, although that is with a large fan cooled heatsink.

One last thing, which circuit diagram version are you using? The first one I uploaded doesn't allow for fast MOSFET switching becuase of the resistor between the 555 timer and power supply.

Hope this helps.
nms22 Alex1M63 years ago
Thanks I'll have to try that! At the moment I'm using the 2N3055 NPN transistor according to the schematic on this website: http://www.angelfire.com/80s/sixmhz/flyback.html (Same as your design, I believe). I've wound my own coils, being that the ones already present were not working very well for some reason. And as for the frying transistor, perhaps I'm also not using a big enough heat sink, but its larger than the one you have in the pictures above. Another thing I've heard is using a diode on one of the transistor leads, but which one is it? Also, do you know if this actually helps? That seems that it would be the easiest fix, but I don't want to try it right away and blow another transistor unless it works. I'm looking to be able to run the flyback for more than just a few seconds at a time, so I definitely have to try one of these methods.
R.A.T.M3 years ago
that arc is loud ouch me ears
Alex1M6 (author)  R.A.T.M3 years ago
Everyone keeps saying that yet I can't see why everyone says it hurts their ears, what does it sound like to you? Which video are you referring to?
R.A.T.M Alex1M63 years ago
Umm the 1 titled simple 2n2005 flyback driver its screaming really loud height pitch
Alex1M6 (author)  R.A.T.M3 years ago
I personally cannot hear anything, just a faint squealing noise of about 16khz.
R.A.T.M Alex1M63 years ago
on the video or in real life the video camera may pick up more than humans can here and some people have a wider range of hearing so what i may here you may not
danton7213 years ago
This is plasma, right?
Alex1M6 (author)  danton7213 years ago
This plasma has power to cut some thing? (like a cnc plasma cutting)
-max- danton7213 years ago
poke holes in paper (and burn it) and thin rubber is about all.
Alex1M6 (author)  -max-3 years ago
With this driver maybe, but with another driver and a flyback transformer with a homemade secondary coil I made I can do some pretty good damage to objects, take this banana in the first picture and just drawing arcs in the second image.

I estimate there is no more than 900v-1kV here but there must be around 800mA-1amp in the arc.
moparman3 years ago
You rarely need to scrape the enamel off of magnet wire anymore. They have been putting "solder through" enamel on this kind of wire for many years now. You just need to hold the soldering iron on the wire for a few seconds longer than usual. This is particularly helpful when using very small guage enameled wire.

-max- moparman3 years ago
ioll try that, i found it works somtines so far, ill try holding it on longer
Alex1M6 (author)  moparman3 years ago
Thanks for the comment.

All the magnet wire I have purchased from my local electrical store has required me to scrape off the enamel before soldering. Even with my coil gun project where I was using voltages of around 300V with the magnet wire I still had to scrap off the enamel in order for any current to start flowing.
Dunharrow3 years ago
will u always get a plasma for the HV out or does it vary upon voltage input
ZygOhm3 years ago
When I combine the scheme 5 volts everything works fine, but when I connect a 12 volt, my transistor 2n3055 burns.
Maybe someone here knows what kind of trouble?

Thank you
Alex1M6 (author)  ZygOhm3 years ago
Are you using a heatsink for the transistor? if not then you really need to as the transistor can get very hot fast and quickly cook itself.
ZygOhm Alex1M63 years ago
Yes. I'm using a heatsink.
Alex1M6 (author)  ZygOhm3 years ago
Does it work on 12v even though it gets hot?
ZygOhm Alex1M63 years ago
it even not getting hot. When i connect 12v i'm just hearing some cracks from transistor (no arcs). And then i again conect 5V  - nothing happens.
Alex1M6 (author)  ZygOhm3 years ago
Have you tried making sure you got all of the joints connected securely with no resistance between them? If so then it might be the transistor that has died (Did you use the fast diode?), I would check the transistor using a multimeter's diode checking function to be sure.
pietzeekoe3 years ago
Will the MJ2955STM work (better/worst)?

Alex1M6 (author)  pietzeekoe3 years ago
Yes, actually it appears to be a PNP version of the 2n3055.

You would need to wire it up backwards though as it is PNP.
roberto1113 years ago
you MUST not....... never ever touch the life high voltage wire
I agree.
This can kill you if you don't know what surfaces you can/can't touch.
Even if the equipment is off and unplugged the charge stored can be lethal for a very long time. It's a big capacitor.
This step is attempting to describe how to drain this charge so you can work safely. You must connect the high voltage to ground THROUGH a small resistance to avoid welding your probe to the terminal.
Use Ohm's law to calculate how long it will take the voltage to drain through your resistor and how high a wattage rating your resistor needs to be.
If any of this confuses you.
This level of electronics is above your head.
Go back to the books to understand fully what you intend to do with electricity.
Alex1M6 (author)  sconner13 years ago
The flyback transformer holds little or no charge at all. This step is showing how to draw arcs (the fun stuff), not discharge anything.

You do not need a resistor, this is not a capacitor bank and it will not "weld" bits of metal together.

Have you actually made this circuit? It outputs very little current on the high voltage side, below 1mA.

I have done this many times for fun.
Correct, transformer's don't store charges.
The CRT's that one may be scavenging the flyback from certainly CAN hold a charge like a leyden jar.
Care needs to be taken on disassembly.
Why wouldn't you want to play it safe?
Alex1M6 (author)  sconner13 years ago
I do agree with you that people doing this for the first time should be careful.

To discharge it just use the alligator clip and chicken stick method to discharge any capacitive charge left between the CRT internal and external aquadag coating.
Bard3 years ago
Just want to WARN you guys crt picture tubes do store a charge even after the set is unplugged. the discharge could kill you.
So beware the suction cup.

basefilm3 years ago
It would be useful to state what the Instructable will be about at the start of the article. 'Getting started' doesn't even give a hint. Otherwise, nice pics and description.

An example of what else can you do with them. In a previous job we hooked up a flyback transformer to a solid-state flip-flop, and laid a piece of plexiglass over it. On the plexiglass we put magnets with different words on each side. They'd flip over every 30 seconds or so. We just made it as a product demo to try to get people to buy the flyback transformers and flip-flops (it was a surplus store).
Alex1M6 (author)  basefilm3 years ago
Done, although it might take a day or two for it to show up publicly.
rfmonaco3 years ago
Use needle points on electrodes for longer arcs.
Snerdguy3 years ago
I have many years of experience with TV repair and flyback transformers. When I was in high school I used one to make a Jacob's ladder where the arc climbs up between 2 conductors. Experimenters need to understand that flyback transformers can be dangerous if not used properly. There can be many thousands of volts at the high side and the current is not damped (limited) when not used in a TV. That is why most CRTs have warning labels on them.

Flyback transformers must be handled with great respect. I have been nailed a few times while servicing televisions and I know it can be quite painful. In some cases, it can stop your heart. Another thing to keep in mind is the size of the CRT as well as the age of the TV is good indicator of how powerful the transformer is. Larger CRTs require more power and older CRTs were less efficient requiring more current.

The other thing to remember is that these transformers with high voltages and high currents are not only an electrocution risk. If used inappropriately they can irradiate the operator with X-rays. (That's why the inside of CRTs are coated with a lead shield) The bottom line is, if you do not have experience working with these transformers, ask someone who is to help you. It beats getting a deep and painful burn.
snakerdlk3 years ago
What fast diode you recommend? One that is easily obtainable around the internet.
Alex1M6 (author)  snakerdlk3 years ago
Any that has a blocking voltage of 200V or more. If you took a flyback transformer from a TV board then have a look around in on there for one.

If you are in the UK then Maplin sell the 1N4937 fast diode in-store which is suitable.

The fast diode is not vital for the circuit to work but is there to help the transistor from being destroyed by back EMF created by the inductive load of the flyback transformer.
Will look for one. And ebay has the 1N4937 available.
Alex1M6 (author)  snakerdlk3 years ago
If you are in the USA then RadioShack will have them instore, if not then have a look at your local electrical component store (if you have one) as these diodes are quite common they may have them in stock much cheaper than ordering them online.

( :
Nope, I'm in Brazil, Rio de Janeiro. Getting to a good eletrical component shop here is not that easy. And I'm not so sure it will be much cheaper, considering the trip and all. Ebay will take a while but it's a more comfortable way.
bobwojo3 years ago
These transformers are going to become hard to find since noone makes CRT tv's anymore.
Alex1M6 (author)  bobwojo3 years ago
Yes unfortunately this is true but people are also throwing these things away so if you know where to look you can get them for free for the components inside.
bobwojo Alex1M63 years ago
True today but 10 or so years from now they will be very rare and much harder to find.

Same for Neon Sign Transformers, not as common as they once were and their use is rapidly declining. Although they will prob. always be available, i don't see Neon Signs being totally replaced by LED's anytime soon. But they will be harder to get and cost a lot more.
dragontirex3 years ago
Hey Alex i'm ciprianwiner from youtube, really nice guide step by step, wish I had such nice tutorials when I starded with flybacks :D
Alex1M6 (author)  dragontirex3 years ago
Hey Cip hows it going?

Thanks! When I first started I was always confused about connecting up the transistor more than anything and getting the primary and feedback coil's in the right polarity ( :
sitearm3 years ago
@Alex1m6; Hi! Excellent project. Excellent video and pictures and instructions. I especially liked the part about the "chicken stick." I think the question about what is a flyback transformer is more about, why is it called "flyback." Do the ends of the electrodes get red hot or is that just the plasma? Cheers! : ) Site
Alex1M6 (author)  sitearm3 years ago
Hi, the term "Flyback transformer" is more of an electrical engineers nickname for what was originally called a "line output transformer".

It is to do with how the primary current waveform looks on an oscilloscope and its effect on a picture tube. After each cycle (sweep) the electron beam that "draws" the picture onto the part of the screen that we watch will go from right to left of the screen to start drawing the next "sweep" (or picture frame).

Sorry if this is hard to understand, I am just not good at explaining this sort of thing ( :
haha totally thought it was the other kind of transformer
mcmahanly3 years ago
what is a flyback transformer and what are they used for?
Alex1M6 (author)  mcmahanly3 years ago
A flyback transformer or line output transformer are usually used in older CRT TV's and computer monitors to power the CRT and electron gun. They also have other auxiliary windings on them that the TV manufacturers use for to power other parts of the TV, so they are usually customised by the manufacturers.

For the high voltage experimenter though the are used to make high voltage arcs.

Hope that answers your question.
You should put that information in the introduction.

Also, just what it is you are showing people how or what to do with the flyback transformer.
I read the whole thing, so I am pretty sure this instructable is about taking a flyback transformer (that you get from somewhere) and putting it together with some other parts so it will do...something, for ...some reason. But where you get it and just what it is for, what the reason is for doing it escapes me.
Alex1M6 (author)  motleyjust3 years ago

I am showing people how to drive one of these flyback transformers externally with minimal parts.

The reason I am doing this is to make high voltage arcs/plasma.

If someone is wanting to get into this sort of thing (high voltage electronics) then this circuit is a great place to start and compared to something like a ZVS (zero volt switching) driver the arcs produced by this circuit are considered safe.
That explains it.
Is the arc coming off the wand lead or is it coming off what ever is sitting on the table?
I love the video you put together, nice touch as I am a kinetic and visual learner.
You could use this to make a Jacob's ladder. I made one for Halloween one year but used a neon sign transformer. Worked awesome
Nice instructable..
Alex1M6 (author)  illfixthatone3 years ago
The chicken stick/wand is connected to the flyback transformers high voltage out and it has a small piece of metal taped to the end of it (see step 5).

It is arcing to the high voltage return pin on the base of the flyback transformer completing the high voltage part of the circuit.

I have actually built a Jacobs ladder using a different driver that gives much more powerful arcs.

See it here

Unfortunately NST's are almost impossible to find where I live.