555 Audio modulated flyback


This is a audio modulated arc generator designed for simplicity rather than reliability, its made with very few and common components. There is however some serious trade offs described below in considerations.

WARNING: sensitive audio players might get damaged by this circuit. I bricked my iPod shuffle, seems that the controller chip for the mini jack got wasted as it could no longer detect charger, PC connection or play music as it could not detect headphones.


WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm


The arc have to be very short in order to limit the distortions of an unstable arc. The sound quality is low due to the way the audio modulation is implemented. If the distance between the elctrodes is too large, the high open loop potential of the high voltage transformer can generate some high transient voltages that through inductive kickback can destroy the MOSFET.

The 555 IC supplied by 12 VDC can not source much more than 140 mA before the voltage drop on the output gets very high. At 140 mA it is already 1,82 VDC. At 200 mA the voltage drop is at 2,5 VDC. The low output will affect MOSFET switching speed and result in higher losses. This graph shows the voltage drop vs. output current of the 555 IC.

In order to optimize the switching of the MOSFET, a small intermediate driver stage can be introduced with two transistors, a NPN and PNP. As illustrated in the red and green graph is the difference between running a MOSFET with proper switching and the other always in linear mode, where losses are very high. This is a future improvement and is not a part of this little project, but it is recommended to add this if you want reliability.

If the circuit can not produce a arc try to reverse the polarity of the primary coil on the flyback transformer.

There are basically 2 kinds of modern flybacks, television flybacks are driven near 15kHz and monitor flybacks are driven between 30-150Khz. Depending on which type we use, we have to adjust the frequency of the 555 timer to match the resonance of the flyback for maximum performance.


Choosing a MOSFET

There are some basic rules of thumb that I will just list here to start with, I will come with an explanation later on.

The voltage rating of the MOSFET (VDSS) needs to be 6 to 10 times higher than the supply voltage, reverse voltage spikes and EMF can be high enough to destroy the MOSFET if its too small. But we still need to use MOSFETs with a reasonable low on resistance (RDS(on)). Try to find a MOSFET with a RDS(on) value not much higher than 0.1 ohm, if you have problems try one with a lower RDS(on) value.

The gate resistor R3 is there to

  • Limit parasitic oscillations that could kill the MOSFET.
  • Limit the current that is needed from the driver stage, in this case our 555 timer.
  • Protect against surge voltages on the MOSFET gate, effectively this would require a much higher resistance, a high gate resistance would lower the operation speed significantly.
  • The values of a gate resistor could be anything between 10 ohm to 200 ohm, it all depends on the MOSFET, experimentation is needed. The alternative is complicated calculations involving data that is usually not available in standard data sheets.

How does the audio modulation work?

Pin 5 on the 555 timer is a direct access to the 2/3 voltage divider point of the upper voltage comparator in the 555 timer. This allows us to pulse width modulate the output on pin 3 of the 555 timer. By applying a voltage to this pin, it is possible to vary the timing of the chip independently of the RC network. When used in the astable mode, as we do with this circuit, the control voltage can be varied from 1,7 VDC to the full Vcc. Varying the voltage in the astable mode will produce a frequency modulated (FM) output.
If the control-voltage pin is not used, it should be bypassed to ground, with a 10n capacitor to prevent noise entering the chip


Both R1 and R2 can be 10K potentiometers.


13th November 2008

I wanted to do a audio modulated flyback arc with few components and a small form factor. I installed the MOSFET on a old CPU heat sink with fan, the 555 timer circuit is also installed underneath this heat sink, its then all put on the side of the flyback transformer with wire strips.

The primary coil is 8-9 windings of 0,75 mm² isolated wire. More windings will stress the MOSFET less but also output voltage will be lower.

The frequency output from the 555 timer is 26,7 kHz at 59,3% duty cycle. This is in the low end for a monitor flyback so further improvements will be adding a potentiometer to adjust frequency to match the resonant frequency of the flyback.

2nd February 2009

Its time to improve the driver with a variable frequency control so the driver can be used with most conventional monitor flyback transformers without changing any parts, but merely turn the potentiometer.

I installed a 9K potentiometer as R1 and a 10K potentiometer as R2, I adjusted the potentiometers till I had a nice silent thin arc at about 15 mm length. 10K potentiometers can be used for both R1 and R2, I just used what I had at hand.

Using a 555 calculator with the measured values of the potentiometers. R1 at 1K3 and R2 at 1K. Duty cycle is 69.7% and frequency is 43700 Hz. Very reasonable for a monitor flyback. Compared to the old frequency I now have a longer and more silent arc.



A quick and very rewarding little project, its fun to play music without conventional speakers. This was also known in the 1970’s as a plasma tweeter and could be found in special hi-fi speakers.

The arc is very very hot and I had to extend the copper wires where it is drawn between to avoid the heat being transferred far enough to start melting the flyback transformers casing.

The 555 IC is not able to supply enough output current to drive a IRFP250N MOSFET at a high duty cycle, so the MOSFET will at times still be in linear mode and this causes excessive heating, which is why the heat sink is necessary. So more notes under considerations about this.



209 Responses to 555 Audio modulated flyback

  1. Chris Ammons says:

    Is it possible to use a 2n3055. if so how and what els would i need?

  2. Chris Ammons says:

    OK nvm. i built this with the 2n3055. and it works i get a 1 in spark gap but. i cant get it to modulate sound. its just loud and buzzing

  3. Mads Barnkob says:

    What does your arc look like? In order to have a good audio reproduction the arc needs to be thin, steady and silent.

  4. Chris Ammons says:

    my arc is purple and needle point thin

  5. Chris Ammons says:

    Ok i suspect that my 555 is damaged or i should use a better substitute for the mosfet. .I have ordered a STB80NF10T4 N-Channel 100V 80A MOSFET and a IRF540 28A, 100V, 0.077 Ohm, N-Channel Power MOSFET. and more 555`s i hope this will solve my problems im having. Also my power source is 6-14v 300ma

  6. Mads Barnkob says:

    The IRF540 MOSFET will be good, but you will need a better power supply, I could only just power this from a 12VDC 2000mA supply.

  7. Chris Ammons says:

    ok i just found out that since my mosfet isnt rated a high enough amperage that i have to also tune my spark gap. i did this but the mosfet seemed to drift and i could only obtain the audio for half a sec

  8. Posnea says:

    I have some questions about the circuit.
    1. is it okey to use a rectified monitor flyback or is the old CRT essential?
    2. for the primary winding does it have to be solid core wire or is multi-strand okey?
    3.what gauge of wire is best for the primary winding?
    4. Is a mosfet with a built in diode essential (i.e. IRFP250N or the IR540) or is a straight MOSFET okey e.g. MJE13009
    5. how to you connect the audio signal to the cicuit, do you split the ground and combine the stereo sound, or is it done differently?

    Thank you

  9. Mads Barnkob says:

    Hey Posnea

    1: Almost all newer flyback transformers have a DC output

    2: Normal multistranded wire as f.ex. 20AWG is just fine for this purpose, its also easier to wind on the core, just be sure you can fit around 8 – 10 turns.

    3: I have used 18 to 22 AWG, the power levels in this primary circuit is not big enough for this to be an issue.

    4: You might have to add a external diode to protect the MOSFET from transients.

    5: Audio ground is connected to ground and one of the audio channels to pin 5 through C2, as written in the schematic, so it is only playing mono, build two of these for stereo 🙂

  10. Posnea says:

    Thank you very much, you have been very helpful.

  11. Posnea says:

    Hi again, I have constructed the cicuit on my test board and it seems to work. I hooked a speaker to the output of pin 3 and ground and could hear sound clearly. then I connectes the mosfet IR540, and tested with the speaker again in place of the coil, but it was incredibly faint. I wound a primary of reasonably thick wire ( aprox 22 AWG) and hooked it in but no sound or sparks. i have tried different polarities and 9, 10 and 11 turns. what could be my problem? please help.

  12. Mads Barnkob says:

    What is your input voltage?
    Have you tried to adjust frequency / duty cycle in order to get a spark from your flyback?

    This circuit does run on the edge of what is possible, the 555 is having a hard time supplying the drive current to the MOSFET, you could try to add a transistor in between the 555 and MOSFET to solve this problem.

  13. Chris Ammons says:

    i think i know what you did lol i had to do exactly what you did..after you connect your mosfet. take one lead from the speaker to your drain on the mosfet and the other to Positive not ground.. Mine i heard music a a terrible screech.

  14. Chris Ammons says:

    and a terrible screech.. sorry typo

  15. Chris Ammons says:

    oh are u using a flyback transformer or ignition coil? if your not otherwise it may not work with regular transformer. again u have tested this too

  16. Chris Ammons says:

    im sorry im full of typos today.. Last line : “Again i have tested this again”

  17. Posnea says:

    Yes it is a flyback transformer i have been using. I have tested it before with another circuit so I know it works. I think I have found the problem. I am using the IRF540 MOSFET and it has a threshold voltage max of around 4v, I think the output from the 555 is > 4v so it is overloading the FET. Any suggestions to fix this? or should I just buy the transistor suggested?

    p.s. If I do get the circuit working how would increase the length of the plasma arc? with a similar circuit i have used i could just increase the voltage, but with this one it would blow the IC.

  18. Chris Ammons says:

    Ummm.. here us a schematic my teacher helped me with. its currently what im using. http://img22.imageshack.us/img22/1871/plasmaspeakerv1.gif this way you can increase and limit the voltage to your 555 and mosfet. Posnea you should get Email me at Dark_thero@yahoo.com also dose anyone know if it will be safe to power my circuit with 26 amps?

  19. Chris Ammons says:

    oh yah and in the pic just ignore the cap on the transformer

  20. Posnea says:

    I have found this guide to flybacks on this website http://www.volny.cz/jmartis/flybacks.htm I have the 3rd type of flyback described could this be my problem?

  21. Chris Ammons says:

    TY Mads Barnkob i also have the same transformer. dose the amount of turns matter? because id like to use 5 turns. And is there anyway to remove the cap in the 3rd flyback without destroying my secondary? and about the 26 amps i got to make a controller for my Power supply to reduce amperage.

  22. Mads Barnkob says:

    Chris Ammons: You limit the the current draw by adjusting the frequency en duty cycle on R1 and R2, but this circuit should never get anywhere near 26A at 30 or even 12VDC.

    Posnea: Arclength is dependant on finding a frequency that works for your flyback transformer, and then adjust the duty cycle for a higher output current to draw a longer spark.

    You flyback transformer is perfect for the job, remember to turn screen and focus potentiometers on it way down.

  23. Posnea says:

    Hi once again, after hooking the cicuit up to a 12v power supply, there are only minute sparks forming, less than 1mm. is it possible that i have broken the flyback?

  24. Chris Ammons says:

    sounds like the same thing that happened to me when i blew my fet.

  25. Chris Ammons says:

    Ok i was wondering is it the amperage or the mosfet that gets you the silent arc?

  26. Eddie Nolan says:

    2 questions:
    How do you prevent the whole circuit from short-circuiting when you connect the flyback coil to the MOSFET?
    What program do you use to make your schematics? They’re nice.

  27. Posnea says:

    Hi again, I have got the thing working, finally, (the problem was the flyback and went and bought a 60kv and got the plasma after tuning, as opposed to sparks on my old one) but I have a problem, the volume is very quite, i have to strain to hear it. i have tried using less turns on the primary coil to increase power put it doesn’t work. how do you inrease the volume, or should i just use Chris’s 30v design, i have an adequate power supply?

  28. Posnea says:

    Also with the 30v cicuit is the 4700uf AC or DC beacuse it is not clear, and if it is DC why does the posotive go to the ground?

  29. Mads Barnkob says:

    Chris Ammons:
    A silent arc is obtained by adjusting the frequency and duty cycle of the driver circuit to your flyback transformer, there are no golden rule that fits all flyback transformers, my best advice is to experiment till you get a stable arc. Obviously this is easier in a room with draft or if you shield the arc from wind.

    The MOSFET have nothing to do with the arcs appearance if you choose it from my advice in the article.

    Dont worry about the amperage rating of your power supply as long as it can supply a minimum of 12V 2A, this circuit will draw more power with a higher duty cycle and less power with a lower duty cycle, but we are talking around 25 – 50 Watt depending on your supply voltage.

    Eddie Nolan:
    The flyback transformer is only connected to the circuit through the new primary coil that we wind on the open ferrite core, the MOSFET pulses the driver signal through this primary coil to drive the flyback transformer.

    I use ExpressPCB, its a free program that comes with both schematic and PCB layout programs, you can get it here: http://www.expresspcb.com

  30. Posnea says:

    Does adding coils to the primary winding reduce or increase power?

  31. Chris Ammons says:

    DONT try to use my design i messed up on it. and i put that cap there by accident. and the less turns you have the higher the voltage , and more turns is lower voltage and less strain on the mosfet ( got info from text in Construction ^Above^

  32. Joe Somebody says:

    Hey i was wondering what gage wire should i use? is 16 ok?

  33. Chris Ammons says:

    wow thanks Joe Somebody i just tried 16 gage wire on my transformer and it doubled my spark gap.

  34. Posnea says:

    Hi again, the electronics center where i get my parts has a store that sells many flybcak transformers, but they don’t know aboyt different types only manufactureres. Could anybody recomend a flyback manufacturer or even better a model number of one that works well for this project.

  35. Chris Ammons says:

    ya dude send me a msg with the link i can find ya a good one Dark_thero@yahoo.com

  36. Chris Ammons says:

    i think this is my last question. What is the best DC power source to use for this circuit? Because i have tried to use a 12v 1 amp transformer and it runs. but i think it keeps making my 555 die on me.Also other people reading this, What did you use to power this? or, what would you use?

  37. voraz says:

    a 555 can handle up to 16volts.. so 12 shouldnt be a problem i think?
    just got one today :))

  38. Chris Ammons says:

    ok i run this at about 2 amps and i get noise and a small arc but then i run it at 5amps i get the perfect arc

  39. jules says:

    we build the circuit exactly as you draw in you schematics, but we do not get any sound at all…..
    do you know whats could be wrong?
    many thanks

  40. Chris Ammons says:

    do u get a spark gap? describe it

  41. Jules says:

    Well here is an update ^^
    we do get a spark gap, and, we managed to create sound 😀
    but, we couldn’t use music from a normal mp3 player, we had to use the disconected wires of a 50 W stereo:P
    and, we had to use a different Flyback.

    The only problem is, the sound quality is Really really bad. You can hear the music, but you cannot understand a thing. Could it be that is accidentally changend de 100 nF and the 10 nF caps? because, I just think the largest one is the 100 nF, and the smallest cap, which is no bigger than a match-head, is the 10 nF…
    How can we increase sound quality?

    Many thanks, you are really helpfull 😀

  42. Chris Ammons says:

    ok i think i had the same problem. heres how i fixed that. Put a .01uf cap from pin 5 to ground this will stabilize the chip.

  43. Bane says:

    How dangerous is it to touch any cables or pots when you’re driving the arc?

  44. Chris Ammons says:

    when i have it running i sometimes adjust the pots, and move around the wires. but if u separate your spark gap too much it can give u a mild shock. i don’t this many times. i don’t believe its too lethal but it doesn’t feel good. I haven’t yet touched the spark, and i hope i wont.

  45. Chris Ammons says:

    Error ** “it can give you a mild shock, *i have done this many times.**

  46. Chris Ammons says:

    anyone know how i can use 2 mosfets in this? N type

  47. Shelby says:

    Hi I am currently looking into making a “singing arc” and this page interested me. I have 1 question though. I notice you are using a flyback but is it possible to use an automotive ignition coil in place of the Flyback? Thanks A lot

  48. Mads Barnkob says:

    Hey Shelby

    A ignition coil would work, not from personal experience, but from what I have heard. Though it will be very distorted and have more noise than a flyback transformer.

  49. Matt says:

    its a dumb question but i guess it could mess alot of people up?, when you hook the audio up to pin 5 of the NE555 there is three wires a red, white, GND, from the audio jack thing, now the red (+) and the whites (-) and the GND?? do i hook that up to red? white, or is it by itself?? please help >>>urgent…

  50. Matt says:

    how i figured was since the audio output is (+) and that goes in the 555 as a input and the GND hook up on the red makes it louder, but if you put it on the white it also makes it loud but i dont know if i can put the GND on the white ?? hook up to the negative on the circuit would it work or would it? or ???

  51. Matt says:

    please write me at badboy_matt2006@yahoo.com

  52. Mads Barnkob says:

    Hey Matt

    I used one of the channels + the ground wire from the audio source, as if I was feeding a mono signal to the circuit.

  53. Brandon says:

    Hi, is there anywhere to get a parts list for this and websites to buy/ship the 555 and IRFP250 mosfet to canada. by looking it looks like the rest of the parts are easy to obtain?

    Thanks alot!

  54. Mads Barnkob says:

    Hey Brandon

    Find a local store if you just want single pieces of electronics, but if you are getting into power electronics then it is not a bad idea to invest in a load of 555 timers and some mosfets from hong kong ebayers, here is a seller that I have used a couple of times, good prices and service.

    He is no longer selling the IRFP250N mosfets, but instead some IRFP264 that are almost identical but have higher current rating, should be fine!

    Thaishopetc shop on ebay: http://stores.shop.ebay.co.uk/Thai-Shop-Etc__W0QQ_armrsZ1

    555 timers: http://cgi.ebay.co.uk/50-pcs-NE555-IC-555-SGS-THOMSON-DIP8-Timer-Kit-HAM_W0QQitemZ350272904187QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item518de45bfb
    IRFP264 mosfets: http://cgi.ebay.co.uk/IRFP264-IR-MOSFET-N-CHANNEL-250V-38A_W0QQitemZ400074322526QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5d2649b25e

    if you want to venture into solid state tesla coils, get some IRFP460 mosfets while you are already ordering: http://cgi.ebay.co.uk/10-pcs-IRFP460-IR-Power-MOSFET-N-Channel-20A-500V_W0QQitemZ400089677998QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5d273400ae

    For the part lists you will have to look at the schematics.

    Kind regards

  55. Brandon says:

    Hey thanks so much for the info, I ordered about 5-7 of each the 555chip and the 264 Mofets for now. I hope this is enough to complete this?

    Im really having a hard time tracking down a Flyback that will work. Unfortunately flybacks are new to me and im not 100% sure to which one(models) will work for this. Any links for a website/model to buy? (ebay, online retailers ect..)

    This is going to be for a year end physics project for now as I am new into this venture. Any help would be amazing.

    Thanks again!


  56. Brandon says:

    Also looking at the 555’s you bookmarked to ebay, the ones i ordered online look different in the pdf. These are the ones i ordered, hopefully they are right!


  57. Brandon says:

    So virtually any flyback transformer works then, good to know. Thanks for the fast replies!

  58. Mads Barnkob says:

    You can salvage flyback transformers from old computer CRT monitors, virtually free!

    Those 555 timer ICs are all the same, differences are sometimes the current output capabilities, nothing you have to worry about at this point 🙂

  59. Suhel Chakraborty says:

    Hey, I tell you one thing. Just put a 100K to ground from Gate of MOSFET. It will reduce the chance of capacitive feedback inside the MOSFET. Or else as it switches on, the first cycle(due to inductive property of primary) will tend to have no work and in turn charge the Gate of MOSFET which will donate excess electrons while the positive is at the source. Then it will go off. IF ANYONE’S CIRCUIT DOES NOT WORK, TRY REVERSING THE PRIMARY POLARITY AND CHECK THE ISOLATED RESISTANCE BETWEEN THE Gate AND Drain OF MOSFET.

    Thank You

  60. James Howells - Tou Tue sparkfishes says:

    HELP- I am supposed to demonstrate this this week end and I can not get it working again
    I have made it up several times, and even got it working several times but now I want it Tidy I can not get the MOst fets from passing a current even when there is no signal to the gate
    I am using( To-30 I have two IRF250 x 2 ,parallel, heat, sinked etc and I have checked the connections GSD Main power is a SLA battery 12v 8Ahr
    I have tried shorting the G- D before I start BUT no matter what I do the Mosfets coduct as soon as I put te power to tem and get hot – weven with the NE555 circuitdisconnected
    Even when I did get the Circuit working with 4 X IRFZ46N they would not work for more than a few minutes
    No matter what I do The Mosfets over heat – I do have massive heat sinks on them
    I have taken the IRF250 out and done the SIMPLE tested them with a multi meter and the work fine
    I have some IRF530 left and TWO IRF250 in the plastic packaging ( don’t Know what that package is called – can’t remember)


  61. James Howells - You TuBe sparkfishes says:

    Oh! additional information
    I am using the method where the primary is a winding around the Ferrit Former – Viz not the original pins
    I have made Fly backs work Lots of times with lots of different methods ( and 2n3055 transistors) but the Mosfet circuits ALWAYS fail on me

  62. Mads Barnkob says:

    Hey James

    It sounds like you are burning up all your MOSFETs, what is happening is that this circuit is somewhat weak to drive a MOSFET so the MOSFET conducts a large time in linear mode, this generates a lot of heat and eventually kills your MOSFET.

    You could add a transistor to drive the gate of the MOSFET to avoid this issue.

    Kind regards

  63. squagin says:

    Hey Mads,

    A friend and I just put together the circuit (hopefully) exactly as it was depicted in your schematic. We’re powering it off of the 12v rail of an ATX computer power supply (corsair TX750, so no power quality issues); but we’ve yet to get even a spark from the flyback. The MOSFET heats up a lot (yes, we’re using a heatsink), but that’s about it. Power is being drawn as the input wires spark a bit when disconnected – We don’t have an ammeter on hand.

    Thanks 🙂

  64. Matteo says:

    i made this schematic but it doesnt works (12V 2A power supply) i can’t see any spark…
    with a normal driver (with one 2n3055 the flyback works but with this schematic nothing work grrr

    i have a question: if i dont put any audio source i must see a spark or not? with audio and with not it doesnt work 🙁

  65. Matteo says:

    other question if i put an audio source and i dont use the flyback but a normal spearker what i must hear? music/bzzzz/nothing….

  66. Mads Barnkob says:

    This circuit produces a arc no matter if there is a audio source or not. connecting a speaker, I do not know what you would hear there, maybe except a speaker dying…

    I got a feeling I will have to make a new schematic as some have misunderstood it earlier, it might not be drawn too good 🙂

    Kind regards

  67. Matteo says:

    hx for the answer Mads Barnkob anyway this moning i see that the capacitor 10nF doesnt work i think i destroyed it now i replaced with 8nF and on the pin 3 (out) of ne555 i can hear bzzzz and flyback produce a spark (very very short) but audio doesnt work.

    i tryied remove the 100nF capacitor (audio is direct connected to the pin 5) and if i do this i can hear the music on the pin 3 (out) but not on the flyback. i must try to replace both capacitors i think they are destroyed.

    how much is long your sparks? my is about 1mm (very short) but with a normal driver (with 2n3055) i can do longer sparks. is a problem of the mosfet???

  68. Matteo says:

    some news: im not sure but capacitors can be wrong (i hope because if not i have no idea of what can be the problem) in a old circuit i used 10nF and 100nF capacitors and they were “white square” with a label that say 10n… this is an orange circle with a 10 so i think that the shop sold me a 10pF capacitor and not 10nF. this evening i try buy them again and replace.
    i think also that while i was putting them on the board i make them too hot and they are destroyed (sorry for bad english)

    what if i replace the mosfet (IRFP250N) with the transistor (2n3055)??? or add a tansistor between ne555 out and the gate of mosfet?

  69. Daryl says:

    I was wondering. Could i use an IRFP450 Mosfet for this project? I have used one of those in a different 555 based LOPT driver and it worked fine. Just wondering if you modulate with that.

  70. Matteo says:

    i changed capacitors (old was destroyed or something)
    both trimmers are at 2k so is 24,1kHz and 67% duty cicle the arc is about 3-4mm and is silent BUT! if i touch the wire of audio+ the arc stop (also if i put the wire in the radio headphone the arc stop)

    so what to do??

  71. Matteo says:

    AHAHAHAH!!!! IT WORKS!!!!!!!!!!! THIS IS THE BEST!!!!! I’M SO HAPPY!!!
    thx for your help Mads Barnkob xD


    i dont want to use my ipod so i attached the ipod to a fm transmitter and i used a normal radio to recive the fm signal this circuit is attached on the headphone of the radio anyway IT WORKS! 😛

  72. Mads Barnkob says:

    Hey Matteo

    I am happy to hear that it works!

    I suspected my ipod dying was due to the multipurpose jack in the ipod shuffle, the controller IC handling it died, in something as sturdy as a normal radio headphones output I do not expect to find such new exotic ICs that doesn’t handle EMI too well 🙂

    Kind regards

  73. Matteo says:

    i have an important info for who want to try to make this!!!
    if you can’t see any spark try use a wire that go from the source of mosfet to the 0Vdc of your power supply and another wire for all other components that must go to the 0Vdc

    i don’t know why i must use 2 gnd wires 1 for mosfet and 1 for all other but if i don’t do this i can’t see any spark.
    Mads you know why? it is because of interferences of something?!?!?

  74. Mads Barnkob says:


    What power supply did you use for this circuit? I used a 12VDC 2000mA, and it was also connected as you say it should, if you look at the bottom picture of my assembly you can see that the 0VDC is looped into a separate wire going to the source pin. It could be the MOSFET that pulls the voltage down hard enough to cut off the 555 timer and it stop oscillating… I am not sure though.

    Kind regards

  75. Matteo says:

    I use 12V 2A power supply (i added 4000uF capacitor at the power supply).
    it works great but i saw that my flyback works good at 60 / 70 kHz but is a tv flyback not monitor.
    now i must change the heatsink of the mosfet because is not good.
    i used my ipod and it isn’t destroyed ^_^

    i have a question: i know how this circuit works because i know 555 (but i never used the pin 5) anyway i don’t get why there is the 100nF capacitor at the audio+
    is for remove dc component of the audio signal?

  76. Mads Barnkob says:

    Matteo: Yes its a dc blocking capacitor.

  77. Matteo says:

    thx for the schematic and for all your help. now i understand all and it works great!

  78. Rob says:

    So I have wired the circuit together. I needed to add a transistor to the gate in order to supply more amperage to the mosfet (this now makes it possible for me to run a nice 32 cm arc at an impressive .21 amps. However, i notice im supposed to get a silent arc? i cannot manage to get one- i have tried four different flybacks too. I hear a very high pitched whine composed of very rapid pulses, and they can go slower with the change in the tuning potentiometer. Is there something i’m doing wrong? im using an irfp264, 25k and 10 k pots (tried other ones as well).

  79. Rob says:

    edit- the arc is very needle point thin and constant- however it makes that sad noise- (like i’m strangling a pig! D:!)

  80. Steel Banana says:

    Hey, awesome design btw. Clean, compact and tidy 😉 Would you know how to replace the spark gap with an SSTC Tesla Coil? Forgive me if it’s obvious…

    Thanks 🙂

  81. Steel Banana says:

    Also, what volume do you get on this plasma speaker? Is there anyway to amplify it substantially?

    Thanks again 🙂

  82. Steel Banana says:


  83. Caleb says:

    Would an IRF520 MOSFET work in this circuit?

  84. Peter.sz says:

    Hi! i will using LMC 555 CN and IRF 540 N mosfet, it will be all right?

  85. Mads Barnkob says:

    The MOSFET looks fine for this project, but remember that difference between 555 timers from difference companies is their output current ability.

    Find out how much current it can output and calculate if its sufficient to drive the IRF540Ns gate at the frequency you want to.

    If the MOSFET heats up a lot, it might be running in linear mode and thus the 555 is not supplying enough drive current.

    Kind regards

  86. Peter.sz says:

    hi! thanx

    i build it… but i havent got arc, the transistor doesnt heats up, but in the sluppy current is 1,2A.

  87. Bear says:

    Hi! =D I am building this device as a school project and this guide has really helped me, thanks a lot!
    I just have a couple of doubts… would it be possible to use a 1A power supply to make this work? And what would I need to do to increase the volume of the music provided by this device?

    Thanks in advance =)

  88. Mads Barnkob says:

    Hello Bear

    I think the 12V 2A supply is just about minimum at maximum duty cycle, I could make pull down the supply at certain points.. it is afterall only 24W.

    To increase the volumen use a small amplifier on the audio input, a simple single transistor amplifier would be okay, if you would like to protect your playback device from high voltage spikes running backwards in the circuit add some opto isolation to the audio input.

    Good luck with your school project!

  89. Garrett says:

    So I have made this circuit and it worked just fine to produce an arc when connected to 3 9v batteries or a 20v .25 A power supply. Then I tried to connect it to a 16v 1A power supply and the power supply somehow managed to short internally (lots of smoke and it heated up.) Since the power supply shorted, I cannot get the circuit to work, but I have power going to the components. The other thing I have noticed is that the circuit now very quickly kills the voltage coming from the 20v power supply, it will go from 20 to less than 10v very quickly. I am at a loss for what to do since I am building this as a hobby and have limited experience with electronics in general.

    I have also tried to incorporate the audio portion of the circuit, but with no luck since the arc just produces a high pitched hum/squeal, also like nails on a chalk board. Any help with these problems would be appreciated.

    Thanks in advance!

  90. Mads Barnkob says:

    Hello Garrett

    With a multimeter try to measure between the gate, collector and emitter and see if its shorted, the MOSFET might be destroyed. Which components did you use?

    Kind regards

  91. Aiden Gibson says:

    Can you please tell me where you got the parts. Im doing something related to this for a school science fair project and cannot find some of the parts. It would be greatly appreciated if you could give a link to the company or some info on where to get the parts. I already have most of them but still need both of the capacitors and the 9K potentiometer. Like I said before any help would be greatly appreciated!

  92. Mads Barnkob says:

    Hello Aiden

    You should just get some metallised film capacitors and for the 9K potentiometer, just use a 10K if that is easier to get hold off…
    There is really no point in telling you where to buy components, other than ebay, mostly hong kong sellers are cheap.
    Good luck with your project 🙂

    Kind regards

  93. Aiden Gibson says:

    Thank you so much

  94. Giorulesall says:

    Just build it! Works great so far, haven’t added the audio modulation aspect yet, but it runs great! =D At one point I got ~3in wild arcs and ~1.5in smooth, but i moved it around and im down to ~1.5cm smooth =/… Also my mostfet “sings” quite loudly, as in it makes a relatively high pitch noise… Any ideas?

  95. Giorulesall says:

    I should note that the high pitch noise on the mosfet is only when im not producing any sparks (Too large of a spark gap), whereas once i begin arcing, the high pitch noise is heard from the flyback… Im not sure if the two are exclusive as the noise from the flyback as much too loud!

  96. Mads Barnkob says:

    Hey Giorulesall

    I am not sure, but when the circuit runs open loop there could be transients going backwards in the circuit and other stress factors that could make the MOSFET squelch. If the MOSFET is running at a decent temperature I would not worry too much about it. This circuit is hard on the MOSFET as there is very little protection of it.

    Kind regards

  97. Giorulesall says:

    Hey everyone!(Again) My stoopid parents kicked my circuit while it was on the breadboard and its stopped working…. Ive basically rebuilt it BUT it doesnt work anymore… Ive switched out 555s mosftets and flybacks to no avail…. My mosftet no longer makes the squeeky noise, i assume this is a sign of the problem… Im relatively sure its NOT the flyback, and i tried with another psu with no luck…. My mosfet still heats up though…. Any ideas?

  98. Jose says:

    create a fast mosfet driver with a BS250 and BS170 (p-ch, n-ch pair) for feeding the mosfet.
    They are cheap, really fast (10ns) and enough for controlling a IRFZ44E withouth heating, no need of limiting resistors because input capacitances of BS’s are 15pF. The main heat mosfet comes from the bad absorbed spike from the primary and the low rising and falling time of the 555 but if you use a good driver like I said, mosfet will not heat anymore.
    If you use the mosfet driver, the output duty cycle is inverted. My advice to use a frequency around 50kHz and a duty cycle around 5% and 60% (lowest sound distortion range).
    And a very good power supply of 12V 250W if you use the IRFZ44E (the one I use).

    I hope it will help.

  99. Jose says:

    AAhhhh and put a switch in the main mosfet gate for activate it after the 555 is stabiliced and running, why? because if not, the mosfet could make fire.

  100. Jose says:

    5% to 60% means 95% to 40% in the 555 output.
    Mosfet driver means you must create a driver to drive the main mosfet, like this:

    [555 (out)]—[(gates)mosfet driver(drains)]—[(gate)mosfet(drain)]—[primary coil]—[Vcc]

    no need of limiting resistors 😉 good luck

  101. Jose says:

    Sorry, I forgot one thing more, that 555 configuration of the schematic it is not a pure pwm because the frequency is modified too in the control voltage pin of the 555 (number 5)

    Use a pure pwm configutarion, why? because if the working frequency goes high enough (not much :D) you will scream:

    Fire in the hole!

  102. Mads Barnkob says:

    Hi Jose

    Thanks for the advice on improving the circuit, though it is already mentioned in the conclusion that this circuit is self destructive, but very simple and contains almost no components.

    A better quality driver, power stage and self conserving audio modulated flyback is on my to-do list and will be a separate project. I feel this will have to stand alone with its limitations and it provides a good learning experience in why we must drive and protect our MOSFETs properly.

    Kind regards

  103. Aiden Gibson says:

    Hi again, I have started construction on the audio modulation circuit. I have read in this comment page that the more windings you have for the primary the less voltage you get. I have an old open core ( 50’s television or something ) flyback and my question is, Can I use the original primary windings on the transformer instead of winding new ones? Thanks for the support


    Aiden Gibson

  104. Mads Barnkob says:

    Hello Aiden

    Using the original primary windings would require that you do not exceed the driving specifications of the primary coil, you will risc internal arcing that will lead to the destruction of your old and precious flyback transformer.

    I would only ever advise on winding a new primary coil when you have no knowledge of the original.

    Kind regards

  105. EviL_LaugH says:

    Hi, Mads 🙂

    So I’ve constructed this nice device. I’m using a NE555&IRFP250M with a TV FBT. I’ve read the docs about it and they say its main frequency is 15 kHz. So I’ve connected my circuit to a frequency meter (without an FBT) and tuned it to 15062 Hz, and my oscilloscope showed about 60-70% duty cycle. My voltage source is 13 V, 10 A (self-winded transformer). No audio modulation is applied yet.

    The main thing I get is a buzzing arc, however, it lengthens up to 4-5 cm. I tried tuning the sound – no effect, the arc still buzzes. Should it be completely silent?..

  106. EviL_LaugH says:

    Oh, and I forgot to add…. The current is approx. 4.5 A. This is what my multimeter says. Howewer, when I tune the potentiometers, it can raise up to 6-8 A (wires on the PCB start smoking :D). The transistor heats up like hellfire, i placed it on a huge CPU heatsink with a fan 😀

    So, what can be the problem here?… Some kind of inductive currents in the PCB wires? I tried to place them in such a way so they wouldn’t get close to high-current or high-voltage ones.

  107. Mads Barnkob says:

    Hey Evil_laugh

    Its hard to give a general troubleshooting of a buzzing arc, but try to vary the frequency till you find one that is silent. In my oppponion its better to have a shorter silent arc than a long buzzing one. It could also be that the arc is too long, they are very sensitive to air movement when too long.

    Its hardly induced voltages in your PCB.

    Kind regards

  108. EviL_LaugH says:

    Thanx Mads. I finally made it work. Just connected an audio player to 5 pin of NE555 and tuned the arc to be almost completely silent 🙂 I don’t know why it wasn’t without any player. So the arc is now silent and extremely thin 🙂 however, my PDA didn’t produce enough power to make the arc sound. I had to pass the audio through an LM386 audio amplifier, and it started singing some Falkenbach xD but not so loud yet 🙂

  109. Hubble says:

    Hey I was wondering if you know whether anyone has manged to get this working with the IRF540 mosfet. I can get a spark approx 1.4 cm but no music. I am using a 9v 500 mA adapter but im not sure if that should be an issue, because i’m getting a spark anyway?

  110. Bryan says:

    I have just a little trouble reading your schematic. It seems one end of the primary is connected to the fets drain, is the other end connect to pin 4 of the 555 chip? Pin 4 and 8 are connected while pin 4 receives 12v. Then pin 8 is connected to R1 to pin 7? So pin 4 and 8 are getting 12v? sorry but im learning how to read schematics, and yours is really nice. Any help would be great! Thanks

  111. Hubble says:

    Pin 4, 8 and R1 are connected to v+ the other end to your primary coil should also be connected to v+, so Pin 7 to v+, as for the voltage on each pin i’m not sure but it should vary on the setting on your variable resistors due to V = IR.

  112. Mads Barnkob says:

    Hi Bryan

    Hubble covered the most, a tip on reading the schematic, black dots on the lines indicate that the lines are connected, all other lines crossing without a dot means there is no connection.

    Kind regards

  113. Matteo says:

    if the arc makes noise try remove the wire of audio or attach it to a player because if you use a long wire attached to nothing it works like an antenna and makes noise 😛
    i had the same problem xD

    after this schematic (that works great) i made another one + power supply schematic and circuit it works great ^_^

  114. Hubble says:

    Hey has anyone tried using this with amplifier circuit, I got my arc 3/4 done I get nice long arc and can make short steady ones but i’m not sure if its steady enough.
    I connect audio and can only hear it when the adjust the variable resistors to a point where there is no spark. (theres a humming coming from the flyback transformer and i can pick out some audio if i listen carefully)
    So im thinking maybe a stronger audio signal (the amplifier i mentioned.) and maybe use my R2 as 2 20k’s in parrallel to obtain greater accuracy on resistance, an the same with R1. I am using the exact same setup except with a IRF540 mosfet instead of the one listed. Any opinions or suggestions please?

  115. Alex says:

    Can I use two 10k pots instead as I can not find any places to get 9k pots close to where I live and ordering online could be expensive for just one 9k pot.


  116. Mads Barnkob says:


    Not to be rude, but ask yourself if a 10K potentimeter set at 9K would equal a 9K potentiometer…. it will.

    I just used parts I had lying around 🙂

    Kind regards

  117. Alex says:

    @Mads Barnkob , Sorry I was having a dumb moment and I can see my mistake looking back now!

    I have made this now and it works nicely, see it here http://www.youtube.com/watch?v=n97QQkqcIss

    One question though, should I use a higher wattage resistor for R3 as at the moment I am using 2 1/4 watt 100 ohm resistors in parallel and they get moderately warm.

  118. Mads Barnkob says:

    If the resistors get so hot that you can not touch them without getting burns, it might be a good idea to change for a higher wattage 🙂

    Remember that such amateur projects like these are not meant to run 24/7 for many many years, so we can push the boundaries on the ratings.

  119. Marissa says:

    I’m building a speaker for a class project and I must have horrible luck because this is the second speaker that I have built that I cannot get to function.

    When I apply power (13v and ~4.5A) all it does is make the winding around the coil smoke. I have 8 windings around it. Is that took many? I’m not sure if I wired the mosfet correctly. I have the gate soldered to the resistor and then to pin 3. The drain is connected to the wire that wraps around the flyback, and the source is connected to the negative power supply. Is that all I needed to do?

    Thanks a lot for this! 🙂 I hope I can get it working with your help!

  120. Mads Barnkob says:

    Hi Marissa

    What MOSFET did you use?

    If you follewed the schematics to the point it should work, remember crossing wires in the schematic are only connected if there is a dot.

    Kind regards

  121. Marissa says:

    I used an irfp250n mosfet.

    Yea I followed the schmatic and connected everything that should be connected keeping in mind the dots. I got an arc actually!! but only for about a second. I think it might be that I need to adjust the potentiometers so the wires don’t overheat again, and put the mosfet in oil to cool it. (sorry just thinking out loud)

    Currently your wonderful schmatic almost saved 50% of my grade. So thanks!!

  122. Marissa says:

    I got it to work! The ic seemed to have blown so I replaced it and got an arc 🙂 I’m just having trouble with the audio now :/ Whenever I apply audio the arc turns into a baby arc (or just dies) and there is no sound. But on the bright side I got an arc!!!! I can do experiments with an arc! Thanks so much!! 😀

  123. Mads Barnkob says:

    Try to amplify the input audio signal and its good to hear you got it working 🙂

  124. Alex says:

    @Marissa Try turning your duty cycle pot resistance all the way up and your frequency pot down to the lower ranges, in my case this gave me a much clearer arc when playing audio through it.

    Another thing is that for the mobile/cell phone I was using as an audio source, I had to have the headphone volume level all the way up in order to get a decent level of audio from the arc.

    One more thing is to only use one channel from the audio source as in my experience my mobile/cell phone did not like having both L and R audio channels mixed together. I guess this could be something to do with one channel being positive and the other being a negative voltage with respect to the audio return pin.


  125. Dustin says:

    Thanks for all the info everyone. My “singing arc” is in the process of being made now. I might have questions later on, but at this moment I’m okay. This page has been very helpful.

  126. Dustin says:

    Is 50r a pot?

  127. Dustin says:

    Okay I think that the 10k and 9k are potentiometers. What is the 50r?

  128. Dustin says:

    Where can I get the 9k?

  129. Dustin says:

    And a 50r?

  130. Alex says:

    @Dustin the 50R is just a normal resistor and the 9K and 10K are potentiometers (POTS) which you can get at places like RadioShack and Maplin.

  131. Dustin says:

    @ Alex thanks so much. And that would be a 50 ohm right?

  132. Mads Barnkob says:

    You can just use two 10K potentiometers.

    50R = 50 Ohm, 10K = 10000 Ohm

    Ex. 4R7 = 4,7 Ohm

  133. Dustin says:

    @ Mads thanks. You guys are awesome for helpin me out

  134. Dustin says:

    What wattage should the pots be rated? Would a 10k 15 turn pot that is rated 3/4 watts with a max of 1.25 work?

  135. Dustin says:

    How many volt should this be ran from?

  136. Mads Barnkob says:

    The potentiometers are only for setting the frequency and pulse width of the 555 timer, they do not need to meet any specific requirements, I recommend you just get some regular linear potmeters, they are cheap and works fine for this application.

    As this circuit has the 555 timer supplied from the same source as the primary circuit you can not supply it with more than the maximum ratings for the specific 555 timer type you use, look it up in the datasheet.

    Dustin, I suggest you get hold of a book on basic electronics or find some websites, you lack a great deal of common knowledge regarding basic electronic components, take care when working with high voltage!

  137. Dustin says:

    Well thanks. And I’ve only been “into” electronics for around 3 months. I’m not sure which books or websites you are referring to but if you will give me a couple names or URLs I’ll gladly check them out. Oh and I realized that I think to hard on stuff and tend to over think the subject. Hence the stupid questions above. I need to relax and think before I speak. I knew the answer about the pots but I got ahead of myself. And I’m not familiar with reading schematics.

  138. Mads Barnkob says:

    Scroll down to “beginners luck” on this site: http://sound.westhost.com/articles.htm

    There are too many good books on too many different subjects, but “Art of electronics” is a worldwide classic.

  139. Dustin says:


  140. b shaw says:

    hello, I get the circuit working fine on and off. when it turns off there is a transient discharge between the electrodes.today i was planning on winding my own primary on the flyback, but when i turn it on before winding the new primary I get nothing. This keeps happening, the only solution that worked before was to just rebuild the circuit. I dont know if its the power supply im using. its emco variable supply and fixed. I run it slowly on the variable supply around 12V 3amps. Also when I get now discharge there is a high pitch coming from the flyback but no discharge. I redid the flyback test so I know that its working fine. Also the beam and focus should be turn down is that a clockwise or counter clockwise turn. any help would be nice. also the circuit when it was working was running cold. the mosfet used was irf630A, i do have irfp250. what about magnetic sheliding from the flyback. thanks for all your help.

  141. Alex says:

    @b shaw The most likely problem is that you got the polarity of your primary coil wrong, which all you have to do is swap the polarity of the connections going to it.

    Also try adjusting your POTS until you get the best output, in my case I had to to put the electrodes close to each other to start the arc and then draw it out after. Another thing it could be is you have a loose connection somewhere so I recommend soldering each connection in the circuit together so you know good contact is being made.

    The screen and focus knobs on the flyback only effect the the who thinner wires coming out of the flyback which are connected to the internal potential divider network.

    Also in my case using an internal primary coil with a resistance of around 1 ohm gave me the hottest arcs and using a primary wound around the core with a lower resistance gave me higher voltage but thinner arcs.

    Hope I helped,


  142. bryan says:

    @alex, thanks, i must have a short somewhere because on my power supply, when i slowly adjust the voltage at some point the amperage gauge goes very high. Does anyone know what could cause this?

    anyone try using irf630A seems to stay cool during operation. I have had no problems with overheating it.

    Also since im using a crt flyback i need an oscillation frequency in the range 50khz-100khz. do you play with both pots or possible the 10nf cap? when i used a 555 calculator if i recall right r1 and r2 were about 1k and 2k?

    Does anyone know of any designs where one could use this plasma speaker as a tweeter. That is part of a typical stereo system, where we have a high pass filter sending signal to the plasma speaker? i have to think about impedance problems if we would like to do this.

    thanks for all your help

  143. bryan says:

    sorry one more thing in modifying this design, how where and what purpose would adding a diode to the circuit improve and or protect it. thanks friends.

  144. Mads Barnkob says:

    Bryan: If your power supply is shorted, it is most likely a MOSFET failure, short circuit measure across the legs of it, my guess is it is gone open circuit from conducting too much current while in the liniar region, this circuit is really hard on the MOSFET.

    If you want this as a speaker system you will have to upgrade to a better circuit, for now this is still in the planning and queue of work to do for me, the circuit presented on this page is merely a proof of concept work, its not very good quality or reliable 🙂

  145. bshaw says:

    @mads, thanks for the reply. I did manage to salvage the mosfet you use in the schematic, the irfp250N. Do you think ill have btter luck with this rather then the one i was using irf630A. Well theres one way to find out.

    I know this circuit would be a no go for integrating as a tweeter, but it is possible. Think about mainly a massless driver (the discharge) and the transients in music, some day that will make a lot of people happy. thanks for your time

  146. Alex says:

    @bshaw I have not tried the IRFp250N myself, but I have had success using both the IRF634A and IRF644A which were both salvaged from an old CRT TV board, I also tried the IRF540 and found that I got smaller but slightly hotter arcs.

    Also make sure you use a heatsink with any MOSFET!

  147. Alex says:

    @Mads Just wondering, have you tried running this off of a higher voltage? Say 18-24V.

    Or perhaps running the 555 driver off of a 9V battery and give the flyback a separate power supply so as not to damage the 555 chip.


    BTW here is a video of me running it off of a 12 7AH lead acid battery http://www.youtube.com/watch?v=fpc2n4dsoIw

  148. Mads Barnkob says:

    I haven’t done it myself, but I have seen my schematic modified to run with a seperate supply for the 555 and 30VDC to the primary circuit.

  149. Alex says:

    Oh, ok.

    I just tried winding my own coils on the flyback core and after about 30 seconds a burning smell started coming from the MOSFET. So I turned the circuit off and went to inspect the MOSFET (which is mounted on a heatsink) and the heatsink was RED HOT! (I also burned my finger!) I did a quick current draw test and found that I was drawing around 4-5A from a 12V source using my wound primary coil but when using the internal winding with a resistance of 1 OHM it was drawing around 2.5A.

    How on earth did you get away with winding your own primary coil and not cook the MOSFET?

  150. robin says:

    hi i whas wondering why exactly is it that the mosfet heats so fast? the 555 output voltage is to low? or what is causing it?

  151. Mads Barnkob says:

    Hi Robin

    The 555s output stage is not powerful enough to drive the MOSFET gate, it is not capable of supplying enough current to charge the gate and thus the MOSFET stays most of the time in linear mode which dissipates a lot of power as heat.

    Kind regards

  152. coil winder says:

    I?ll immediately clutch your rss feed as I can not in finding your email subscription hyperlink or newsletter service. Do you’ve any? Please allow me recognise in order that I may subscribe. Thanks.

  153. Alex says:

    Mads what about using some sort of transistor in a Darlington configuration with the MOSFET, wouldn’t that help drive the gate more efficiently?

  154. Mads Barnkob says:

    Hey Alex

    It would indeed, but as I wrote in the article, this is a very very simple and ineffecient design 🙂

    Kind regards

  155. Alex says:

    Oh ok, the reason I ask is becuase I have recently started playing around with this circuit and after managing to get some pretty decent arcs though I would set it up for Halloween but the MOSFET is just getting too hot and dies easily for a reliable center piece.

    Do you have any tips on stopping the MOSFET from getting destroyed?

    As you can see here

    [youtube http://www.youtube.com/watch?v=ZdrLaPi6rx4&w=560&h=315%5D

    the arcs are pretty decent for just 12V input, but the MOSFET died.

  156. High voltage says:

    Hi i built this using a IRF644 MOSFET and the only mod is a switch between the 555 and the FET. It works great so thanks Mads.I used a 12V 15A power supply from an old PC and a cpu heat sink and fan to cool the FET i ran it for about 60/90 mins with no prob,but the heatsink was burning hot so be careful peeps i mean HOT .Thanks again mads great project .. here is a link to a vid of it working and zapping myself by accident …..http://youtu.be/kIVdGe3KtsI

  157. High voltage says:

    One last thing it really makes a big difference to tuning ,arc stability and sound quality just by changing the 555 ic .I have loads of them and if you use one that costs like 20p this circuit is not good, but put one in that costs 40/50p and it works great ,this is probably an obvious thing to be saying but it makes so much difference it really is a matter of this working and not working .LMC555cn works good for me but the TLC555CP is bad .hope this helps

  158. Mads Barnkob says:

    Hey High voltage

    I suggest that you use a chicken stick next time, that is something not able to conduct current 😉

    You are right about the difference in 555 timers, as I mention in the conclusion, the 555 is not able to supply enough current to drive the MOSFET properly, but it should be known that cheaper chips comes with a down side, in this case, its lower output current driving abilities. Check the datasheets.

    Kind regards

  159. Alex says:

    @High voltage you had it running for more than an hour? wow, I could barely get this thing to last for 10 minutes with out the MOSFET dieing from back EMF.

  160. High voltage says:

    @ Alex ..I thought that was good too but there is 2 cpu heat sinks 1 either side of the FET and siver nano cpu grease with a cpu fan keeping it cool .having said this the next day i tryed it ,it didn’t work ! The 555 had blown ,easy fix i here you say ,well it was for about 2 mins coz then the FET blew !!! easy fix again !!!! well it worked for about 30 seconds .So i have completely rebuilt the whole thing using all new but identical parts and nothing ! iv tested the flyback and checked capacitance and resistance of parts all of which seem to be fine, tried 2 new FETS and a load of 555s . Nothing 🙁 Im just glad to have had it working and it is still a fun build .But i think ill stick with the tesla coils it seems that im growing a hatred for FETS lol.

  161. Alex says:

    @High voltage Strangely, when I first made my circuit it worked fine for a long while but now it is basically a MOSFET and 555 chip killer and doesn’t last long at all before something goes pop.

    Like you I also checked the capacitors and resistors/pots and they all checked fine and there are no shorts anywhere. I am going to try making a more advanced version soon using the SG3525AN chip.

  162. Mads Barnkob says:

    Alex, you are on the right track.

    This is really only a simple beginners circuit, moving on and designing from scratch when you have learned the basics from this circuit is something that warms my heart 🙂

    Kind regards

  163. Josiah says:

    I have constructed the circuit though my 555 timer is heating up, I am using a 12v 400 mA supply, I am hesitant of hooking it up to a 2 amp supply if it is already heating up the 555 timer. Now does the MOSFET need a 2 amp power supply, And I can’t see why the 555 timer is heating up.

  164. Mads Barnkob says:

    Hey Josiah

    Its highest likely because the 555 can not supply enough current to drive the MOSFET, so it is outputting all the current it can, thus it heats up.

    Look into using the 555 to drive a transistor stage that drives the MOSFET, this will ease on the stress and have the 555 and MOSFET run much cooler.

    Kind regards

  165. Alex says:

    Hi Josiah,

    What MOSFET are you using?

  166. Alex says:

    @Mads in reply to the comment you posted to me, I agree. This circuit is a great way to learn the basics of the 555 timer and pulse width modulation, I certainly did learn allot from this circuit and your website in particular has been a great help for me in learning how these circuits operate.

    It doesn’t matter if this circuit breaks easily as I think the knowledge learnt by building and learning how to tweak it is worth allot more! (The high voltage is a plus lol).

    But anyhow I will be sure to post my results with the SG3525AN MOSFET driver once I find a cheap place to source it (probably ebay) and finish my current projects (Motors).


  167. ebenvios says:

    I do trust all of the ideas you have offered on your post. They are very convincing and can definitely work. Still, the posts are very quick for beginners. May you please extend them a bit from next time? Thank you for the post.

  168. Mads Barnkob says:

    Hey ebenvios

    Would you like to tell me what to describe in more details? I do not see the same missing as you do, so it would be nice if you could tell me what to improve 🙂

    Kind regards

  169. high1voltage1rules says:

    Awsome circuit. Thanx for sharing. Will build and enjoy!

  170. Круто конечно но с динамиками не сравнится. По сей день круче их ничего ещё не видел и не слышал.

  171. ragatinto says:

    good morning

    Mads Barnkob

    I’m doing thesis on the plaza speakers, is there a formula about the relationship of sound, plasma, and the force or energy.?? I am confused to find the reference ..
    Please Explain ..

    thanks before ..

  172. Chris says:

    Thank you for this. i have been building a circuit to drive an ignition coil for a tesla coil. But I have a flyback I am going to try instead now as i ultimately want my tesla coil to play music. I hope driving the flyback this way will also translate into music on the output of my tesla coil. Do you believe it will? When you say the sound input modulates the pulse width, does it actually turn the arc on and off or just control the intensity?

  173. Mads Barnkob says:

    Hi Christ

    If you use the flyback transformer to power a small SGTC, then the audio modulation will not get through and if it does, it will only be very short burst and nowhere near audio modulation quality.

    on/off or control the intensity, as the audio input is a analogue varying voltage, you can say its both, intensity can also be zero volts which would be off.

    The SGTC works about the same, the coil itself have a resonant frequency and the modulation would be the spark gap that turn the coil on/off. Hence why you can not further modulate this topology by just modulating the power supply.

    Kind regards

  174. Chris says:

    Ok I appreciate the quick answer. So then let me run this by you. Starting with the assumption that if i turned the tesla coil on and off fast enough, would that on and off pulse of the 200 khz resonant circuit create my sound if it was in audible frequencies. In other words turn that 200 khz arc on and off say 2000 times a second so as to simulate a lower frequency arc? Cause i know musical tesla coils exist and if this is one way to do it I would like to use a sound signal driving a zener diode in reverse bias to make the wave closer to square on the gate of a mosfet that turns my whole 555 circuit on and off at the desired frequency. Do you think that is something that would work and translate all the way to the final tesla output? Essentially turning th whole coil on and off really fast? Thank you and i await your input.

  175. Mads Barnkob says:

    You example of turning it on/off 2000 times a second would give you a 2KHz sound.

    You need a SSTC or DRSSTC in order to obtain the control over the switching transistors to audio modulate a Tesla coil.

  176. Chris says:

    Ok thank you

  177. Evan says:

    Thank you for sharing your project online like this. It was so fun to build and play around with that I actually used a very similar circuit as my senior project this year for highschool! I passed with flying colors and am still enjoying this unique device in its own neat case. I got so much help from this site. Stuff like this is what can get people interested in electronics and wondering how it can work. Thanks again!

  178. Mads Barnkob says:

    Hey Evan

    Thanks for the kind word, I will keep on it and add more content, though it will be in the high power end of the hobby 🙂

    Kind regards

  179. stephen says:

    can i use a 13.5v 1.3A power supply? 13.5 volts wont fry it will it?

  180. stephen says:

    how to you get this circuit to work with a 2n3055? how do you wire it up? also what would the potentiometers have to be set to, to make this circuit work with an ignition coil? what would the 9k pot need to be on and what would the 10k pot need to be on? and my ignition coil primary coil has 1 ohm of resistance

  181. stephen says:

    im trying to use a sup60n10 16-l mosfet rightnow. i was running the circuit(trying to) on 13.5v at 2.15 amps it only made a spark when i turned the power on and of so i decided to leave the power on and adjust the potentiometers and nothing happen, then i turned it off, and waited a few minutes because the power supply was getting a little to warm and after i let it cool i turned it back on and 5 seconds later my 555 timer blew so now i have to buy another. why isnt it working right? i follow your schematic right down to the bone. was it because of the ignition coil or maybe did i adjust the pots wrong? i neep help really really bad with this

  182. Mads Barnkob says:

    Hey Stephen

    The primary coil of a ignition coil could have too many windings compared to the few you could wind yourself on a flyback transformer. The ignition coil also returns much more EMF that will destroy your circuit.
    I advice that you only use this relatively weak circiut on a flyback transformer.

    Kind regards

  183. DarkMein says:

    Umm, you should put a 1K resistor after or before the R1 (9K) variable resistor to avoid a shortcircuit if you put the resistor accidentally to 0 ohms…
    This is because the pin 7 is grounded while the device is working.

    Im testing the device and it works very well but it drains a lot of amps… more than 15A at 12volts. Im using a ATX 300W power supply with a max of 20A on 12v channel, if the device works with 5 primary windings (to obtain a large arc) it works perfect but if i reduct the windings to 4 the ATX shuts down xD… excesive amps drain. Thanks for your schematic, its very simple to build, but you should put that 1K resistor to avoid destroy the NE555.

  184. david Ahlers says:

    I have built this circuit and once got a good arc but cant seem
    To repoduce it again. My timer chips seem to get fried quite easily.. i am using the 250n mosfet. I also built it on a test board.
    How do i keep parts from frying so easily. I have heat sinked the
    mosfet but not the timer chip. I also am using a garden lead acid
    Baterry. To much amps? I will continue trying but any help would be great. Thanks dave

  185. stephen says:

    the mosfet and the chip have to run on seprate power supplies. what you do is get your 555 oscilator and hook up the pin 3 output to the mosfet just like you normally would. then you take the source of the mosfet and ground it to the 555’s ground(seprate power supplies but they share common ground) the drain of the mosfet goes to the negitive terminal of the primary transformer/flyback coil. the positive terminal of the primary goes to the secondary power supply’s positive terminal. the secondary powersupply’s negative terminal is conected to the common ground where everything is grounded. for the seconday power supply (this is the one that will power the coil) you will need atleast 12volts and no less than 3 amps for a good spark, depending on your mosfet and heatsink(always use a very large heatsink). i run mine on a 12v 6 amp battery charger. and for the primary powersupply (the one that powers the 555 circuit) should be about 5v at a few mA. actually 3 AA batteries works perfect. i hope this helps. i have a schematic i can send you a schematic to make things simpler just leave me an email adress and i can send it right away. but good luck! i know those chips and mosfets are expensive haha my schematic also shows how to audio modulate it, but a high amp output power supply is needed to draw a big enough arc from the coil to make audio loud enough to hear clearly. and doing this mean you need a beefier mosfet to handle the amps also meaning your going to need a bigger heat sink and possible some kinda of cooling source for it. from my experience royer and the zvs drivers produce very nice acrs and dont require as much cooling as they seem to run more efficient. but i have not yet experimented with audio modulating those

  186. Have you tried using a dead time circuit after the NE555 before the IRF MOS.

  187. picka says:

    I would like to ask whether to use the ZVS driver?

  188. Mads Barnkob says:

    If you want to audio modulate with a ZVS driver, you will have to build a way more complicated amplifier to modulate the supply voltage as the ZVS driver is self oscillating.

  189. Lucio says:

    Hi, can I use the 2N3055 instead the MOSFET? I mean, make the same circuit but changing the MOSFET for the 2N3055, or I need another thing?


  190. teslafan says:


    I am trying to run this circuit on a aircoil. i hava a 350 turns (.15mm wire)on 7cm tube secondary and about 20 turns (speaker cable) 12v 2A power. Im getting a 5mm spark but no sound, it keeps sparking even when audio source is disconnected

    anyone tried this please let me know what

  191. frejatet says:

    Hey hello,

    i have been trying to follow your steps from

    everything looks good to me but i have no spark coming ((
    i hear the flyback whistling tho …

    the Mosfet doesn’t feel hot at all .. and the current consumation doesn’t go more than 0.35A for 12v

    i tried by finding the primary coil and also by doing windings like you advised .

    any idea where i could look to try to make this work ?


  192. Mads Barnkob says:

    Hey frejatet

    If the circuit is pulling current and you have a whistling sound from the flyback transformer, I will assume that the circuit actually works.

    I would first measure the resistors and capacitors used in the frequency and duty cycle setup network for their exact values and calculate the frequency and duty cycle.

    I think it could just be a too low duty cycle and secondary maybe some odd frequency where this transformer does not work very well, but first check the duty cycle.

    Do you have a oscilloscope at hand to check the gate signal on the MOSFET? It could also be that the MOSFET hardly is turning on if it is a too heavy load for the 555. Which MOSFET do you use?

    Kind regards

  193. frejatet says:

    thank you. unfortunately i don’t have oscilloscope. i use the IRFP250N. he is staying dead cold tho. i checked with a voltmeter and it looks like he is running like expected tho..
    i gonna check the duty cycle!

  194. Teslafan says:


    after some modifications got it to work on my own aircoil . sparks are not that big and only works if i connect input signal is amplified.

    But still its a great circuit


  195. Mads Barnkob says:

    Hi Teslafan

    I am wondering about the iron core E iron there is inside the primary coil and secondary coil, this will absorb a lot of the energy.

    To get a higher output, remember that this circuit runs on a fixed frequency and does not lock onto the resonant frequency of the secondary as most SSTC does f.ex. through an antenna.

    Try to calculate the resonant frequency of your secondary with the aluminium topload, then see if you can modify the 555 circuit to be in range of that same frequency.

    Kind regards

  196. Teslafan says:

    Hi Mads

    At first test i got best sparks with the iron core but did not try without after the mod.
    Thx for the info , i will try this soon

  197. Mads Barnkob says:

    Hey Teslafan

    It is no longer a air cored transformer if you add a core 🙂

    The iron core will absorb the power as it is not very good at conducting power at high frequencies, you should try to use a ferrite core instead, and then you have basically made your own flyback/high voltage transformer.

    Kind regards

  198. Matthew says:

    Hello Mads,

    I built this circuit with a 12v 6 amp power supply. I also used a IRFP460 MOSFET. Everything else it the same as your schematic. I’ve played around with the 2 pots and spark gap but can’t seem to get good quality sound out. My heat sink will get very hot a little after a minute of turning it on. Any ideas for better sound quality?

  199. Matthew says:

    Nevermind!!! some how i didn’t see your sweet spot on the resistor value. sorry.

  200. Markus says:

    Hey, by adding a diode to the 555 circuit you could get duty cycles o 50% or lower. That could help to destress the MOSFET, couldn’t it?

  201. Mads Barnkob says:

    Hi Markus

    What is needed is more drive power to turn the MOSFET on faster, a MOSFET driver IC or a couple of small transistors between the 555 and MOSFET would be enough. Lower duty cycle on the 555 will not provide that, infact the opposit.

    Kind regards

  202. KhaSieu says:

    Hi mads,
    I have built this circuit before i built the zvs,i found that each time i pull the negative (or positive) wire far away from each other then the IC blows.Sometimes takes the MOSFET along with it,too.So i recommend to make sure the spark jump before apply power.
    I want to add to your circuit, your circuit (and many other) needs an driver circuit, by adding a pair of similar pnp npn transistor. Their bases to the 555 and their emitters to the gate resistor( remove gate resistor?) And npn collector to 12v supply, pnp collector to 0v.
    I live in a very rural area so online shopping is not available, the electronic shop takes a month or so to restock their parts.

  203. Mads Barnkob says:

    Hey KhaSieu

    I was convinced that I had it mentioned in the start of the article that this is a very simple circuit that has some trade offs in reliability to gain simplicity.

    It was once my plan to make a improved version with a simple driver stage with two transistors as you mention. I just moved on to bigger projects before I got to do it. I believe it is discussed in some earlier comments.

    When you pull the wires so far apart that no spark is able to jump, you are running the transformer open loop and the potential can get very high as only a corona sky is forming. The inductive kickback properly has some high voltage transients in this scenario that could kill the MOSFET.

    I added some more information to the article 🙂

    Kind regards

  204. Eldhose says:

    What type of capacitors are they

  205. Mads Barnkob says:

    Hi Eldhose

    They are metallized film/foil capacitors, but you can use both ceramic, MKT or MKP capacitors for the timing circuit.

    Kind regards

  206. Eldhose says:

    What are the use of the potentiometers


  207. Mads Barnkob says:

    Hi Eldhose

    One is for adjusting the frequency at which the MOSDET is switched on and off, to be able to adjust for the best possible output of different flyback transformers. The other adjusts the duty cycle and makes it possible to adjust how much power is put into the arc, low power gives thinner arc and high power gives thicker and hotter arcs. For music modulation the thin arcs work the best.

    Kind regards

  208. carlos says:

    I did the project, and the spark was hiting. half in half a second. Could not make a sound, is my radio too weak? and my ci555 broke in five minutes, two of them. please hep me 🙁

  209. Mads Barnkob says:

    Hi Carlos

    You need audio source that is powerful enough to drive the pin 5 of the 555 timer, maybe you just need to turn up the volume for the output of the radio, using the line output will properly not be enough!

    You might be drawing too much current from the 555, to drive the MOSFET, try a higher value gate resistor or implement a couple of transistors to drive the gate with instead of using the 555 output. It is already grossly underrated for this task 🙂

    Kind regards

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