Flyback Plasma Speaker With 555

so i thought i would set out to make a plasma speaker! SO one chip i know well is a LM555 so this is my base! one pin most often skiped on this chip is pin5 it s the voltage control oscillator. all that is needed is an audio signal to this pin to get pwm

                                  This Is A High Voltage Project
                                        YOU HAVE BIN WARNED

                            CLICK HERE IF YOU CANT BOIL AN EGG


Step 1: Parts List

99% of the parts can be obtained from




1   Heatsink

1   Lm555

1  8pin socket for the 555

2   20k pots

1   10k trim pot

1   100ohm pot

2 1n4148 diode

2   1k 1/2 watt risistor

1   ADJ. POS. REG.

1   2n3055

1   .001uf cap

1   .03uf cap

1   Gi2404 diode

othere parts needed 

2   9v batteries

1   16v 3 amp DC power supply


1   audio signal you may need some type of amplifier  if you use a          weak signal like a cell phone or weak mp3(im using an old              raidoshack amp)

Step 2: Schematic

note the batts ground and the power supply ground are hooked together

Step 3: Heatsinking

mount 2n3055 and gi2404 diode to a large heat sink

Step 4: Find the Flyback Pin Outs

this set shows you how to find you flybacks pin outs

Step 5: Last Chance to Rechk Everything

ok so now that your allset start with the 0v and hv out about 1/4inch apart then slow move back till you get a longer soft spark if it go wild move it closer




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    30 Discussions


    2 years ago

    Do we have to stop after a few minutes because of the heat ? I read in another plasma speaker instructable that used 2 FETs and a flipflop device that with one transistor it was difficult to use it continuously.


    5 years ago

    hey dude. so i got it all toghether but it doesn't work for me. there is no arc or anything. the trani is heating big time. and i'm using a cell phone for an audio supply. any recomendations or solutions?


    5 years ago on Introduction

    Hey Glenn781 i have a new Q
    The power source for the flyback is 16V and the diode starts to lead and give the output signal at 20V so how is that posible to work???
    BTW in my country vishay who is the manufacturer of the Gi2404 isn't availble so i've found a replacement, the BYV42/200 and it might be even better for the role.

    I must be finished by friday so i have 2 days and please be quick with the answer.

    sorry for my bad english


    5 years ago on Introduction

    Hey Glenn781 could you please help me out.
    I'm in the process of building this project and i couldn't get my hands on 2n3055 but i got a replacement the BDY90 and now i can't find the collector.
    The datasheet says it is "tab" but i don't know what that should be. Could you help.

    BTW i'm doing this as a school project and a fast reply would be very very apreciated.

    4 replies

    Reply 5 years ago on Introduction

    yes plz let me know if you have any problems i would be more then happy to hlp you out


    5 years ago on Introduction

    I got it working on the computer power supply! It works pretty well on 12V without any major problems with heating unless I really crank it up. Just out of curiosity I also tried 5V but the arc is less than 1/8" and it's super quiet and that just doesn't quite cut it.

    I'm not using the rectifier(GI2404) at all, initially I used a set of heavy high speed diodes but it's been running fine without them.

    Typically I keep the arc as fine as possible, it's quieter when it's turned down but the audio quality is better and the arc is more stable/cooler so I don't have to "relight" it.

    I didn't have any 20K pots on hand for the pulse width adjustment so I experimented with 10k and 50k. It seems to run better on the 50K pots. I'm going to try a pair of 10k pots in series in place of the 20k pot next.

    Another pot I'm experimenting with is the 10k on the voltage adjustment. For the LM317 by replacing the 10k pot with a 3k resistor and a 7k pot, I limit my voltage to a range of 5V-13.75V, keeping me in a safe range for the 555.

    Thanks for all the help! I assembled my circuit (with a few minor modifications) according to your diagram and it worked right the first try. A little fine tuning and it was audible from across the basement workshop.


    5 years ago on Introduction

    hi seabeepirate as for your LM317 it will work gr8 but if you put the driver on the same power supply as the coil i would use the : Voltage Regulator with Protection Diodes how to hook that up should be in the datasheet

    a 12v comp power supply is the way to go as for the noise using : Voltage Regulator with Protection Diodes and some filter caps around that should cut this down if there is any at all. now for the max input of the 555 you never wannt run a chip at the max anything once you reach the max the chip will get hot and the burn!!!!

    NTE6240 looks good

    brushless computer fans have little to no noise you are gonna need on hell of a heat sink mine is sitting on a peltier device

    the 555 is just an oscillator each pot just sets how long its on and off one pot set the high time the othere sets the low time if you need more info on the 555 i got a killer PDF on 555's and lots of there chips i can email you

    if you have anymore questions please hit me up i wanna see your finshed build
    and if you need more infor on the 555 i can help with that too

    2 replies

    Reply 5 years ago on Introduction

    That all sounds good. Should I use the comp power supply for the flyback driver also or should I stick to the 19V power supply for the flyback? I would imagine running the flyback on the lower voltage will help keep the transistor temp down, but my concern is that I won't get a good arc.


    5 years ago on Introduction

    Awesome project, I'm actually using your design for a class project this semester (Most of the other guys are using kits from Radio Shack that blink LEDs but that was a little on the boring side for me) I'm gathering the parts to build it now, but I have a few questions.

    Does it matter if you use linear or log/audio pots?

    Does the LM317 look OK for the voltage regulator?

    Can I replace the 9V batteries with a 12V computer power supply and will the power supply add noise to the audio? I want to make it a more permanent rig. I understand the 12V power supply doesn't reach the max input for the 555, but do I want it to be able to?

    If I've read the datasheet for the 2n3055 correctly, my 19.5V/6.7A power supply will be OK to power the flyback. Does this sound reasonable? Here's the datasheet:

    Could I run both the timer and the flyback on the same supply? Say,  using 7812 or 7815 to drop the 19.5V to a safe 12V-15V, or is the variable voltage supply crucial? Maybe use a 7815 to give me a safe 15V and and then the LM317 to adjust the level?

    I'm having trouble locating the GI2404 locally, is the NTE6240 OK? I think I read that they're equivalent and the figures look the same, but I'd like a second opinion if you don't mind. Here's datasheets for both:     -GI2404   -NTE6240

    If I run a fan mounted to the back side of the heat-sink will it add noise to the audio? My thinking is that I could run a CPU cooler(if the computer power supply is ok) as my heat sink since I have half a dozen extras sitting in my junk parts pile. My junk pile is where I get a lot of things like heat sinks, power supplies, and sometimes hard to find parts.

    I really like your Instructable. My only suggestions are to explain a little bit about how you use the 555 to produce PWM, what the individual pots do, maybe add a section on how you built your enclosure(not really important I guess), and maybe add more pictures. I'm very partial to lots of pictures.

    I have to stop now, the more I think about it the more questions I have. Any help is much appreciated, if I get it working maybe I'll make an Instructable of my own.

    2 replies

    Reply 5 years ago on Introduction

    oh as for linear vs audio pots you can use both but the audio pots will be touchy on the highend


    6 years ago on Introduction

    This is looking sweet.
    I have to ask, you didn't wind any additional wires around the FBT core as I have seen in other instructables. Those are just for longer arcs, right? Or do they serve any other purpose?
    Thanks for a great 'ible. Now that I got my hands on 2 FBT's I'm gonna try this one out :-)

    3 replies

    Reply 6 years ago on Introduction

    To be honest I have never had to much luck with winding my own primary.i always seem to burn up a tran or something. this is one of the reasons I made this


    Reply 6 years ago on Introduction

    Gotcha. I suppose since I have 2 FBTs I'll use the one I know that works with your schematics.
    The other one I don't know if it's any good, so I'll try winding some wire on it and hope it doesn't catch fire :)


    7 years ago on Step 5

    Well done on getting this working.
    A question though, what is D5 there for?
    Also, do you need to take into account that most LOPTs these days have a rectifier in its output? Will it work regardless?