Step 3: So, how does it actually work!?!?!?

Okay, you must be very curious how the plasma speaker works...

Note: This information is technical, skip this step if you don't understand...

The TL494 acts like an oscillator and a modulator, it generates a high frequency (5KHz to 45KHz) to drive the flyback transformer to make high voltage arcs. Then when you give it audio, the TL494 modulates the audio frequency into the main high frequency. Now the flyback transformer is being driven by the high frequency and the audio frequency, and when the arc is produced, the arc vibrates the air with both the audio and high frequency creating sounds.
If you tune up the 22K potentiometer, the high frequency increases, when it goes higher than 20KHz, we cannot hear it, but only the audio frequency...

I hope you can kinda understand this..
Just a little side note: the Smiths were a great music to test it out with!
<p>I gotta disagree...Morrisey's got a four, maybe five major-scale note-fixation, which I find grating at best, so probably not the best choice for a demo track. </p>
That is quite possibly one of the coolest things I've ever seen.
This is so cool!! How loud does it get? And what is the sound quality and frequency response like?
<p>That is good idea </p>
<p>Pretty lights, but don't look at them - plasma generates enough ultraviolet light to burn your retinas out...</p>
<p>Good point but what if the arc is enclosed in a traditional speaker box after removing the speakers themselves. Yes the fabric speaker grills will need to be retained. Perhaps doubled up too to prevent leakage of UV.</p>
My little knowledge of plasma speakers is they are higher frequency and might disappear in a box - think of them as tweeters (?)<br><br>Given that, maybe UV blocking glass? Flat black V with a plate in front, like <br><br> front<br> _______<br>\ /<br> \ X /<br> \ /<br><br>X is the plasma, the rest a sort of open, vertical horn.....<br><br>You've got a beautiful display potential, maybe make the front panel out of the UV glass? That'd probably be a lot cheaper and easier to find, too.<br><br>You'd want a fairly full spectrum blocker - I expect these things spray a LOT of RF, but don't know that for sure. Any AM radio will help you find that out.<br><br>I'll bet that plasma is hot enough to ignite most flammable material, so unless you can experiment, I'd avoid cloth!<br><br>Best of luck with this - I hope it works out for you!
<p>Agree with all that Kev13. Like the idea of the UV glass for the visual effects too. The RF spectrum could be contained in a Faraday Cage? Close woven 'chicken netting' stuff? lined on the inside like the acoustic wadding. Or metallised paint. Thanks for the vertical horn Idea Kev13.</p>
<p>why do you use 5 turns of wire instead of the primary pins on the transformer base ?</p>
<p>Nice project! I think one reason your MOSFET is running hot, and that some people might not be able to make this work is that there is nothing to actively drive the gate low during the off phase of the PWM so it takes a while to switch off, which makes it dissipate a bunch of power as the MOSFET (source to drain) resistance is between on and off.</p><p>You should be able fix this by using the second transistor (Q2) of the TL494 to pull the MOSFET gate low during the off part of the PWM. To do that, you'll need to connect C2 (pin 11) to the resistor that drives the MOSFET gate, and E2 (pin 10) to ground.</p><p>Also, be sure to wire OUTPUT CTL (Vi, pin 13) to Vref (+12v) so that you enable push-pull operation of the TL494's two transistors, Q1 and Q2. Otherwise they'll be exactly in sync (on at the same time) instead of exactly out of phase (one on when the other is off), and the circuit mods I suggest above would burn out your TL494!</p><p>To be sure, I'd like to put an oscilloscope on the gate of the MOSFET to see how quickly it turns off, but it sure looks like it would turn off slowly and run hot as-is.</p>
<p>Excellent stuff. Exactly the sort of project I follow Instructables for. Different, very interesting and do-able.</p>
<p>Pretty boring.....</p>
<p>Ok. So I tried to watch the last video but it is private...??? Can you make it public?</p><p>Cool project otherwise!</p>
<p>Cool! but what's the use of the diode in parallel with the mosfet? </p>
<p>in my opinion it isnt really needed as mosfets have diodes built into them anyways </p>
<p>Yes but reduces heating by externalizing that function, and somewhat better/faster at it. </p>
To help absorb emf puose in the oposite polarity, to protect misfet<br>
<p>Why is the last video that you posted &quot;private&quot;?</p>
<p>Cool project! Do you think we may be able to get more musical &quot;action&quot; out of the arc if we added a partial enclosure? - Enough to slow the escape of ionized air, but not block the audio? </p>
Heat = wasted energy. I would guess that a mosfet driver and a shottky diode to the power rail instead of ground would be an improvement. <br>Also the frequency should be matched against the inductance of the transformer and the duty cycle range of the pwm to the desired maximum/minimum current.<br><br>For those of you choosing a mosfet, the wattage of the fet is NOT the maximum power it can give to the load but the peak heat dissipation(wasted energy in the fet).<br>Example from the comments, irf3205 110A x 55V = 6050W max switched load.<br><br>In this design, poor switching of the mosfet may be the limiting factor for the current since there is no driver for the mosfet. But without matching the duty cycle to the current draw, it might burn up the psu, leads or the transformer! xD
Interesting stuff. I think I'm going to build one of these sometime soon. Looks like all kinds of fun to play around with.
<p>Is it possible to give specks for Xformer</p>
<p>Wow......................</p><p>where can I buy one ?</p><p>compliments</p><p>RAM51</p>
<p>Since the music is being modulated on top of an ultra-sound frequency be aware that any nearby dogs (and other animals) will be hearing a constant &quot;beeeeeep&quot; while you listen to music. Similar to what we hear at 0:52 in the video at the top but constantly playing over the music.</p>
<p>you'll get MUCH better sound if you introduce a DC bias in your secondary. You want everything offset so it doesn't reverse polarity.</p><p>Introducing ions into the arc will also help, as will using two sharp electrodes.</p>
<p>I can't watch the video ;(</p>
<p>Hey, how do you think we could go about the build if we replace some of these components with a CFL driver? Is it feasible? </p>
<p>Just curious, is it possible to modify an electric arc lighter to do this same thing?</p>
Hi, i have a problem. I also built this speaker, but when i start it, my mosfet instantly dies :) i tried to take a pulldown resistor, but it also doesnt work. Could anybody help me?
Dear Plasmana, <br> <br>I used my plasmaspeaker for over a year now but I have a problem. <br>I always used a laptop power supply (90 watt) for the flyback transformer and last week I bought a heavyduty power supply (50 volt/16 amps, 800VA) and now I killed my MOSFET (IRF640). My question is; wich MOSFET can I use for pulling a few hundred watts without killing it. The max the IRF640 took was 26 volts and about 3.80 amps (at 30 volt and 4 amps it blew up). I had a 2SK1082 MOSFET laying arround but that doesnt work very well. I got a very little arc from that one. <br> <br>Please help me, I really need a MOSFET that can handle much more current/voltage and still give a nice big fat arc from the flyback. <br> <br>Greetings, <br>Jochem
<p>irf3205 it has 110 amps of current handling and 55 volts</p>
I gave eight of those, they can make 7&quot; arcs when used in this circuit at 40 volts, 30 amps
<p>there made for car batteries</p>
It's not really about the MOSFET handling current but rather the switching. Get some IRF540's on Ebay for about a dollar a piece and they're 100V, 30A.
Thnx for the reply,<br> I got 2 irfb20n50k's now. 500V 20A and I guess they can handle 280 watt at 25 degrees celcius. Atleast that is what I read in the datasheet. :) This MOSFET works great at 35V and 3.4A but I don't want to blow it up, haha. Got a 50V 16A (800VA) toroidal transformer attached to it with a variac and a 100V 22000uF capacitor.<br> This MOSFET don't get that hot with a CPU cooler attached to it and I got a pretty long and loud arc. But I guess the MOSFET can handle even more! :)<br> Here is a movie of my power supply and plasma speaker (only on 25V) :p<br> <div> <iframe frameborder="0" height="360" src="http://www.youtube.com/embed/XtfuMuHwWTk?rel=0" width="640"></iframe></div>
Sweet setup and spark! =)<br>When ever I bother myself to make another of these I think I'm gonna add a 148watt Peltier cooler. Might help those poor MOSFETS from dying? =)
good idea about using a cooler but one side of them gets really hot so your just moving the problem. im probably wrong. will the cool side being heated by the MOSFET cancel out the other side from overheating.
<div> Hey Crimson-Deity,<br> Here is just another video of my plasma speaker at 34 volt this time.<br> The arc is now longer and louder! :)<br> I will probably crank the voltage up some more in the near future, but I really hope I don't pop the MOSFET. :P<iframe frameborder="0" height="315" src="http://www.youtube.com/embed/YvvjjsOXlFk" width="560"></iframe></div>
Thnx, I still need to build the variac, bridge rectifier and capacitor in a box :) <br>And maybe I will build a volt and amp meter in it aswell. Looks alot better then a separate volt and amp meter if u ask me! :) <br>I bought this stuff a week ago so that's why it lays all over the floor. :p <br> <br>About dying of MOSFETS, I guess if u stay in the voltage, amps and watt range of what they can handle, u will be fine and keep them cool as possible. :)
how much current requirement of FB transformer...?
how much current requirement of FB transformer?
Hi, 47nf capacitor or 47uf capacitor?
<p>i made it~ but it doesn't work.<br>i think that there isn't enough power to drive the flyback transformer.<br>how can i get the power to drive the flyback transformer?<br>can i use a switching power supply to provide enough power to the flyback transformer?</p>
<p>Wow. Completely impractical but completely awesome. I so wish I had the time to build one.</p>
<p>&quot;Here's a video of the arcs.&quot;</p><p>Click on play and get &quot;THIS VIDEO IS PRIVATE&quot; = B.S. </p><p>WHY even have this on the pages?? </p><p>https://www.youtube.com/watch?feature=player_embedded&amp;v=c9hkcDjotWk</p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/c9hkcDjotWk" width="500"></iframe></p><p> <iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/c9hkcDjotWk" width="500"></iframe></p>
<p>Wow, flashing back to 1968, high school chemistry class... my project was a &quot;Flame Speaker&quot; from an article in Popular Electronics, as I recall. Plasma created by wicking a potassium chloride (I'm pretty sure...) solution into a Bunsen burner flame, as high as it would go. Worked fine at home as a tweeter with my Fender guitar amp's speaker output to bare copper wire electrodes spaced above each other in the flame! Lugged the amp to class, set it up... and the flame wiggled and danced so much due to the room's A/C's fan blowing that it only squeaked once and blew the speaker fuse! Went back after school, turned the A/C off, and proved to the teacher that I wasn't &quot;blowing smoke.&quot; I imagined that a columnar flame of 24&quot; or more would lower the freq response range, but between music, girls, and cars, I never messed with it again. Thanks, Plasmana. :-)</p>
Reminds me of the OLD IONOVAC speaker...<br>Since nobody mentioned hazards except getting killed be high voltage here it goes..<br>OZONE GOOD. UV GOOD its all good.
<p>Gotta try to make one of these someday! nice 'ible!</p>
I cant get frequency modulation for lower frequency what shud I use I used 47nf 2kv capacitor

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