555 Audio modulated flyback
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Read this document about safety! http://www.pupman.com/safety.htm
Introduction
This is one of the simplest kind of audio modulated arcs, its made with very few and common components.
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.
Considerations
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 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 datasheets.
How does the audio modulation work?
Pin 5 on the 555 timer is a direct access to the upper voltage comparator in the 555 timer. This allows us to pulse width modulate the output on pin 3 of the 555 timer.
Schematic
Construction
13. 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 heatsink with fan, the 555 timer circuit is also installed underneath this heatsink, its then all put on the side of the flyback transformer with wire strips.
The primary coil is 8-9 windings of 0,75mm² 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.
2. February 2009
Its time to improve the driver with a variable frequency control so the driver can be used with most conventional monitor flybacks 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.
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.
Conclusion
A quick and very rewarding little project, its fun to play music without conventional 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.
Demonstration
Posted October 22, 2009 by Mads Barnkob | Log in
Is it possible to use a 2n3055. if so how and what els would i need?
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
What does your arc look like? In order to have a good audio reproduction the arc needs to be thin, steady and silent.
my arc is purple and needle point thin
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
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.
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
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
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
Thank you very much, you have been very helpful.
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.
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.
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.
and a terrible screech.. sorry typo
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
im sorry im full of typos today.. Last line : “Again i have tested this again”
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.
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?
oh yah and in the pic just ignore the cap on the transformer
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?
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.
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.
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?
sounds like the same thing that happened to me when i blew my fet.
Ok i was wondering is it the amperage or the mosfet that gets you the silent arc?
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.
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
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?
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?
Does adding coils to the primary winding reduce or increase power?
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^
Hey i was wondering what gage wire should i use? is 16 ok?
wow thanks Joe Somebody i just tried 16 gage wire on my transformer and it doubled my spark gap.
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.
ya dude send me a msg with the link i can find ya a good one Dark_thero@yahoo.com
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?
a 555 can handle up to 16volts.. so 12 shouldnt be a problem i think?
)
just got one today
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
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
do u get a spark gap? describe it
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
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.
How dangerous is it to touch any cables or pots when you’re driving the arc?
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.
Error ** “it can give you a mild shock, *i have done this many times.**
anyone know how i can use 2 mosfets in this? N type
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
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.
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…
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 ???
please write me at badboy_matt2006@yahoo.com
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.
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!
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
Mads
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!
-Brandon
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!
http://www.futurlec.com/Linear/LM555CN.shtml
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
So virtually any flyback transformer works then, good to know. Thanks for the fast replies!
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
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)
PLEASE HELP ME GET THIS WORKING SO I DO NOT LOOK THE IDIOT THAT OBVIOUSLY I AM!
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
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
Mads
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
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
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….
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
Mads
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???
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?
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.
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??
AHAHAHAH!!!! IT WORKS!!!!!!!!!!! THIS IS THE BEST!!!!! I’M SO HAPPY!!!
thx for your help Mads Barnkob xD
IT WORKSSSSSS GREAT!!!
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!
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
Mads
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?!?!?
Matteo:
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
Mads
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?
Matteo: Yes its a dc blocking capacitor.
thx for the schematic and for all your help. now i understand all and it works great!
bye!
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).
Thanks!
edit- the arc is very needle point thin and constant- however it makes that sad noise- (like i’m strangling a pig! D:!)
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
Also, what volume do you get on this plasma speaker? Is there anyway to amplify it substantially?
Thanks again
*Bump*
Would an IRF520 MOSFET work in this circuit?