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

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.

Skip to 0:44 in this video to see some arcs.<br> <br> <div class="media_embed"> <iframe frameborder="0" height="315" src="http://www.youtube.com/embed/Bgcg4K5w4vU" width="560"></iframe></div>
<p>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!</p>
After few seconds of working my transistor get really hot and i have a big heatsink and cooling fan. What to do? Please help.
<p>put some thermal compound between the transistor and heatsink.</p>
<p>can i replace the flyback with a tesla coil?</p>
it doesnt work
Can anyone tell me what sort of power adapter should we use to drive it? In this it is written 12 volts 2 amps.... ?????
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?
<p>If you are interested in long sparks then buy yourself a 6 inch 12 volt DC powered plasma ball from Walmart for $17.</p><p>Presently I have harvested 140 DC volts from the OUTER SURFACE of the ball</p><p>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.</p>
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?
<p>Hi bui.. I didn't adjust anything on the computer PSU.. The <br>adjustment is for the driver circuit.. So I didn't do anything to the <br>PSU..</p><p>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..</p>
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!
<p>what gauge wire is used for the feedback coil?</p>
<p>I use 1mm magnet wire and it works great.. Be free to experiment.. :)</p>
please help me ! my arcs are smaller than 1 cm, I want to increase arc length
<p>Wow.. You may reconsider the distance from that thick red wire if you have a fix driver and coil..</p><p>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..</p>
<p>make sure the winding are tight and straight are you sure that is the right ground and not the screen wires ???</p>
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.<br><br>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.<br><br>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.<br><br>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.
<p>I made it! I got the flyback from my old 14&quot; CRT monitor.. Took some <br>time to build. But in the end, it's beyond my expectation. It was <br>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 &quot;FULL POWER&quot; 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 &quot;FULL POWER&quot;.. 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.</p>
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
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
<p>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 &quot;stretches&quot;</p><p>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 &quot;stretch&quot; the arc to about 4 inches this is because of the higher amps.</p>
<p>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..</p><p>.. im so frustrated im ready to chuck it all out the window,,lol.</p>
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
<p>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</p><p>thank you,sorry for bad english</p>
<p>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.</p>
<p>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.</p><p>one more question ???</p><p>can i use transistors ,diodes ,capacitors ,resistors etc from my monitors circuit board. </p>
<p>Do I must use the resistors, or this circuit (2n3055 flyback driver) works without them?</p>
<p>What are the resistors for?</p>
<p>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. </p><p>Thanks in advance.</p>
<p>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?</p>
<p>Cool! Simple and efficient</p>
<p>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?</p>
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
<p>help me i have to make a fly back driver circuit as teacher has given us this for project <br>teach me some thing as i realy dont even know the basics of this circuit<br>y we mAKE This <br>help me</p>
Which part of this circuit do you need help with?<br><br>Google for &quot;blocking oscillator&quot;, which is what this circuit is.<br><br>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.<br><br>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. <br><br>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.<br><br>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.<br><br>But now there is nothing to keep the transistor off so the cycle repeats itself over and over.<br><br>Hope I managed to explain that ok.
<p>My flyback had the HV return pin torn off on accident.any ideas?</p>
<p>Has the entire pin come all the way out or has it snapped right at the epoxy potting?</p><p>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.</p><p>I have attached an image to show you what I mean, click on it to get a full view.</p>
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?)
<p>1 year late I know...</p><p>Out of the flyback you will probably end up with around 10-15kV @ a milliamp or two.</p><p>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.</p>
<p>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.</p><p>Can you give the combination for some larger no. of turns and also tell me the cause for this.</p>
<p>Is <a href="http://www.electroncomponents.com/Mini-Components/Resistor/220k-ohm-preset-variable-resistor" rel="nofollow">http://www.electroncomponents.com/Mini-Components/...</a> resistor ok to make this driver</p>
Hi,<br><br>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.<br><br>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.
<p>Thanks for the reply</p><p>can i get one form this site <a href="http://www.onlinetps.com/shop/index.php?main_page=index&cPath=15_79" rel="nofollow">http://www.onlinetps.com/shop/index.php?main_page=...</a></p><p>and earlier i gave you the wrong link it was originally</p><p><a href="http://www.electroncomponents.com/220-ohm-preset-variable-resistor?filter_name=carbon%20resistor" rel="nofollow">http://www.electroncomponents.com/220-ohm-preset-v...</a></p>
<p>Hi Sarthak,</p><p>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.</p><p>I know its not neat but it will work.</p><p>Regarding the electroncomponentslink, that is an adjustable resistor (potentiometer) and will get hot and burn out if used with this circuit.</p>
<p>Thanks Man </p>
<p>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)</p>

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Bio: Me on YouTube youtube.com/Alex1M6
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