Let’s listen to a plasma speaker.
If you want to see how this circuit works,
the other circuits we have for this, the use of a flyback transformer and more examples,
stick around till the end. I will show you everything you need to know about this circuit,
then we assemble it on a prototyping PCB for one circuit and on a PCB kit for the other
circuit and make some tests in order to see which one will get best results with music
plasma arcs. So, let’s get started.
What’s up my friends, welcome back.
This is called flyback plasma speaker circuit. This is also a flyback speaker circuit but
is homemade, more power and with a different implementation. We’ve seen how to create
plasma in a previous tutorial using a small tesla coil circuit. High voltage with high
frequency will create these plasma arcs that will ionize the air around and that’s why
we can see this purple glow and also we can hear the air snapping. But that project was
very low power and not that cool. The difference between that previous circuit with the tesla
coil and the one we will see today, is that this new one is using a flyback transformer
to elevate the voltage. Remember that a few months ago I’ve made a teardown of an old
black and white TV and I found this nice flyback transformer. Using the multimeter, we search
for low resistance connections and like that we can find the secondary and flyback pins,
and then we can use it. Another difference between the last tesla coil project and this
circuit, is that today we are working with a lot more power. You will see that at 24V
we use around 5 or 6 amps, so that is around 130W. Please, make sure you stay safe, never
touch the high voltage side and use proper tools. There are a lot of circuits online
for such project. In my case I have this one that also has a PCB that we will assemble
later and test it out, but then I found a better circuit made by Franzoli electronics,
and you will have the links to his work below. The difference is that this is an interrupted
plasma speaker. What that means? Well, it means that when we play some music, with the
interrupted circuit, the plasma arc should stop on low peaks of the music and the arc
will be created on high peaks of the music. I didn’t really get those results, but this
second circuit had a lot more power. With the other circuit and the PCB kit, we have
a constant plasma arc and the music is modulated on top of those high frequency arcs. We will
take a look at both circuits today, but let’s start with this first circuit kit that I’ve
bought online and you will find the links for this below if you want to buy it as well.
You can also find the GERBER files for my PCB and the full schematic below. With this
kit from the internet, you receive the PCB, the flyback transformer, wires and all the
components and following the schematic you can assemble the module. Once assembled, you
can connect a 3.5mm jack for music, supply the module at 12V from a powerful supply with
around 5 amps of current, and then connect the flyback transformer at the output. For
the transformer, to make the primary we need to make between 6 and 8 loops with a thick
wire around the ferrite core. Then we connect it to the module and the secondary output
will be between the main thick wire and one of the pins below which in my case is marked
with a red line. I supply the module and connect the secondary output to this ceramic support
with two electrodes. Ceramic is a good insulator so the sparks will jump only at the tip of
the electrodes where the distance is smaller. I power it on and apply music from my smartphone.
To start the plasma arc you must flip the small switch to off and then back to on, and
the circuit will start oscillate and create plasma.
The results are quite awesome, we can create arcs of a few cm. The music is not that laud and
we can also hear the high frequency hiss of the arcs instead of the actual music. Let’s
analyze the circuit a bit. The magic is created between the primary coil of the flyback and
this high voltage capacitor. A coil together with a capacitor is a so-called LC tank and
this will resonate. The coil is connected on one site to positive 12V. The other side
is connected to a MSOFET which is connected to GND through a second MOSFET. So by modulating
the signal applied to the MSOFET gate, we modulate when the circuit is closed and power
applied to the flyback coil. Music signal is also connected to the base of a two BJT
transistors that create an inverter. Then we connect the output to some other BJT transistors
in cascade and with that we amplify that signal, because the music voltage from a smartphone
if very, very, low. That output is used to apply pulses at the LC tank and make it resonate.
On top of the resonance frequency which is given by the used components such as the 330nF
capacitor and the inductance of the primary coil from the flyback, on top of that, we
insert the music signal as well and that’s how we get the music on top of the plasma
arcs. The second MSOFET here is connected to GND and is activated with the sliding switch,
and that turns the oscillation on and off. Is a pretty easy circuit. So follow the schematic
and mount the PCB. I add the audio input jack connector, the switch, the MOSFET, which by
the way, it must have a heat dissipator otherwise it will burn out very fast, the capacitors
and all the small SMD components on the back. Check all the links for this circuit and the
PCB below. Is quite amazing to see the plasma arca forming and hearing the music getting out of them.
Let’s take a look at the second schematic
and this homemade PCB that I’ve made. First of all, as you can see I’m now using a huge
IGBT and I’ve place it over a big heat dissipator. At such power, the transistor was getting
hot in a couple of seconds, very hot, probably more than 100 degrees. We have again a big
capacitor of 330nF to oscillate together with the primary coil of the flyback transformer.
The main difference for this circuit, is that the music modulation is made with a 555 timer.
As you know, this IC will create a square wave and we can change the frequency of that
signal using this potentiometer. On top of that, we connect the audio signal to a BJT
transistor to invert it and then we control the reset pin of the 555 time, and by that
we tell the IC when to enable the high frequency output or not. By that, the output signal
will be with the rhythm of the music. The rest of the circuit is just a regulation IC
to get 12V from 24V because this circuit works at 24V but we supply the 555 timer with only
12V. Again, the flyback primary coil is connected between VCC and a MOSFET connected to ground,
and the gate of this MOSFET, which in my case is an IGBT, is controller with the square
wave from the 555 timer. Between the drain and source of the transistor we have the 330nF
capacitor and that’s it. You can get this and the rest of the schematics from below.
I first solder the voltage regulation part with a huge capacitor at the input, since
this circuit will create a lot of noise. With the multimeter and the potentiometer, I set
the output at 12V. Then I solder the rest of the components and I place the IGBT external
to the PCB and fix in place on the heat dissipator, this is very important since the circuit will
waste a lot of power and transform that into heat. I connect the flyback at the output
and the secondary is connected on one side to a metal case to increase the area and on
the other side just a simple wire. We supply this at 24V and make sure your supply could
give out 5 or 6 amps, otherwise the voltage will drop. This circuit needs more than just
a few mV at the base of this transistor in order to control it with the music. Since
the music signal from the smartphone is very low, we need to amplify that signal. Franzoli
electronics has a circuit for that with an operational amplifier but that didn’t quite
work form me, maybe I had some connections errors. That’s why for this test I will
increase the audio signal using another high voltage transformer that I have laying around.
The output from this transformer is connected to the audio input of my circuit and now we
can test it. I play some music and power on the circuit and there you go.
We can get huge arcs, of a few cm and that’s amazing. The music is louder and the sparks
are powerful. The circuit is using around 150W. The IGBT is getting quite hot. If we
make the gap to big, the spark will die and new sparks will appear at the base of the
flyback transformer so watch out with that because we could damage the transformer. Here’s
another cool example. We connect the output to these wires and as you can see, we make
the gab larger and larger while going up. The arc will start where the gap is smaller
but since the plasma will heat the air around, this arc will start rising. It will do that
till the gap is too big that the arc can’t be created anymore so is easier to just start
a new arc at the bottom. This process will repeat on an on. This is cool, right? So guys
these were my tests for a plasma speaker and a so called interrupted plasma speaker. The
results are sparky and awesome, right? Check the description and electronoobs.com for more
and thanks again to Franzoli electronics for his work. If you like this video and learned
something new, give me a like or comment below.
Thanks again and see you later guys.