The Plasma Speaker

Step 6: Test the prototype

After you had built it, go ahead and test it!
If it does not work, don't get all frustrated or anything like that, go back and check your circuit closely, make sure there are no missing connections, and check the components are properly connected to the circuit...

Mine works quite well, unfortunately, the MOSFET is wasting large amounts of energy into heat, so it is blazing hot... I have to make the heat sink bigger to try keep it cool longer. But it still goes blazing hot after three minutes of continuous operation.
Oh well, that is my efficient design so far...

If yours working well with out very much problem, thats great!

Comments

[lynchpman]

Why do you have to use a veroboard if the connections can just run through the breadboard?

[jj.inc]

Why is that yellow cord hooked to your speaker, I am not saying this doesn't work because I'm sure it does, but I just wondered

[Enoch23]

why not use more mosfets. I have seen a scematic that uses 3 or 4 i believe, and they all have little heatsinks on them...

[gobitz]

If you put a smaller heatsink on the mosfet and put it in mineral oil then the temperature should be quite lower, until it warms up the mineral oil.

[Gasburner]

You could make a crude water cooling loop with your idea. Simply gain a water cooling loop (a computer one), create a reservoir from something that iwll not melt, and have an input pipe and an output pipe. Then connect the fans and pump to a 12V DC supply and away you go. The pump may kill itself if you use mineral oil, but find something else. Anyway, the liquid is pumped past the MOSFET and then into a radiator, where fans dissipate the heat :D Should be really effective (note: SHOULD be, it may not work)(this is a disclaimer :])

[seabeepirate]

Good thinking gobitz. I had forgotten all about this until you mentioned it.

Using a large container with a thin wall, filled with mineral oil, the entire surface of the container could be used as the heatsink. Perhaps a popcorn tin? It might not need to be that big, I don't know. I'd still attach a small heatsink directly to the MOSFET as gobitz suggested. I think it would help distribute the heat to the oil for better cooling.

As an electrician in the Navy I was given a basic knowledge of transformers and most transformers that I dealt with used the oil and case as their heatsink. Usually the case was around 2-3 times the size of the actuall transformer if memory serves me. I seem to remember that most of what is actually in a "pole pig" is just oil to help cool the transformer.

I like Gasburner's idea too but I think the oil is a much simpler and probably safer idea. No pumps, the oil works as an insulator, and less chance that a leak will cause any major problems. Not to mention it's probably cheaper unless you happen to have the spare water cooler already.

Theoretically the oil could eventually evaporate and as the MOSFET heats the oil you could end with a fire on your hands, but you'd have to run this nonstop for quite a while before it became an issue I think. Periodically checking your oil level and temp could easily prevent this though. You could easily have too little oil for this but never too much, so don't be afraid to use a bigger container.

Great instructable! I was actually reading this hoping I might be able to use it with a tesla coil. What do you think?

[moshee]

hmmm. that heatsink you're using looks more like a giant piece of metal than a heatsink... could that be a problem?

[randomapps]

 im sure it disperses heat much better than the mosfet alone

[alexg50]

would i be able to use a voltage comparator as a mosfet driver?(like the LM311N) my mosfets are also getting hot!

[Tristian_Lyons22]

Hello everyone, I am currently using a computer power supply that i have adapted to a lab supply to power my speaker. I am having a problem with EM interference coming from the AC power grid, and tried running the speaker on some batteries. Like Plasmana, i used a 9V to power the TL494 side of the circuit, and am using a Yuasa NP7-12 (12V 7Ah) battery for the flyback. I can get the flyback and circuit running perfectly (with the exception of EM interference) when using the PSU, but absolutely nothing with the batteries. I think that the big battery needs to be charged, but i was wondering how you would check. It pushes less than one volt while running the flyback, but gives about 12 amps. If under no load at all and I test the battery leads with the Multimeter i get 12.3V and about 28A. Any suggestions? Thanks in Advance for any help you have to offer!

[guitarmaniac825]

Maybe try using a small fan to cool the MOSFET.

[girrrrrrr2]

That might actually work... or if that doesnt maybe get an ice pack or something similar...

[Cybot Rules]

Maybe a CPU fan, one of the larger ones for pentium 4 etc?

[girrrrrrr2]

get an old motherboard... some have heat sinks and fans on them already.

[elphreaker]

I did it already, im having big problems with the amps the flyback "sucks". Every time i connect batteries im scared they are going to blow to pieces ;)

[whiplash]

Heya, i would just like to ask, could you be more specific in what you will need. could you tell me the different voltages for all the components, there are a lot of different capacitors and resistors out there. thanks

[Callum Snowden]

Does anyone know how to make a bass plasma speaker because all the ones I've seen sound really tinny and don't have good bass responce? Thanks a lot Uberdum05

[Xellers]

Plasma speakers are only used as tweeters, I read on many sites. If you want to make a real audio system, you will need a woofer in addition to these.

[atarian]

i think that a plasma speaker with a much longer arc might make a better bass speaker, because if you think about it woofers + subwoofers move a lot of air, where as tweeters only move a little. A small arc moves a small amount of air and is a good speaker so that would suggest that a large arc moving a large amout of air would work better as a bass speaker. I am only theorizing so i could quite easily be wrong, please correct me if i am.

[Callum Snowden]

Oh thank you for your theory, this might help me when I build my plasma speaker. unless you could do it like this: you set up 2 plasma speakers, one with a small spark gap and the other has a larger spark gap.The inputs are both connected to a homemade crossover, so the frequencies are split up to the speakers.Thanks for your advice, Uberdum05

[zplizzi]

You don't really need two, one big one would work just fine. Tweeters are used because they have better high frequency response, but any size spark will have the same frequency response, so you don't need the tweeter.

[Callum Snowden]

That's if I ever get round to making a plasma speaker. lol

[froggyman]

can you say 5 meter plasma arc, omg that would be sucicidal and require an insane amount of input voltage and would probaly blow out a regular flyback, I guess you could build your own lol. *drooling in backround*

[atarian]

if you ran one flyback's into another i think it would be theoretically possible but would probably burn one out. That would be absalutely mad though.

[froggyman]

or you build a humungus one of your own!!! but if you have two flyback laying around that would pretty cool to see it blow(because the second one probaly wouldn't be able to handle that much voltage) <><

[Plasmana]

Well, I blew out one of my flyback transformers, but it did not physically 'blow'... It is just stop make arcs, just nothing... When I tried to hack it open to get the high voltage diode, I couldn't because the 'resin' stuff is really bloody hard, I really mean it is harder than a rock! I then tried bashing it with a hammer, but instead of breaking up the flyback, it dented the head of the steel hammer!! Really, how do you break up the 'resin' like stuff?

[emcelhannon]

The silicon carbide in a grinding wheel ought to cut through just about anything.

[Callum Snowden]

I think you can heat it up with something hot, like a screwdriver heated over a flame?

[froggyman]

hmmm.... maybe you could try one of those dremel bits designed to cut metal. you could probaly use a concrete/masonary bit and drill a bunch of holes in it and then try hitting it with a chesel or hammer. I have found that those bits drill through just about anything! have fun though trying to get it open! (dont forget to post results)

[atarian]

you could try a cold chisel ( a rock chisel) or try to heat it really hot with something like an oxytorch, have you tried a hack saw or metal bench saw? putting it in a big steel vice and tightening might work to? otherwise i'm stumped

[Arx]

Duty cycle shouldn't really be an issue. That fet has a nice low "Rds on" Either you're switching at too high a frequency for the fet (unlikely) or you're not switching it fast enough (taking too long between off and on) Perhaps the 494 doesn't put out enough current to drain the gate capacitance quickly enough? I'm just throwing out ideas, haven't really looked at the numbers. :)

[rocketgeek]

Gate charge (Qg) on the IRF540 is 71 nC, according to the International Rectifier datasheet. Current output of the TL494 is 200 mA... which implies a switching time of 355 ns... which means that the MOSFET is spending about 2.1% of the time partially on at a switching frequency of 30 kHz. Ouch! IR sells gate driver ICs capable of putting an amp or more into the gate for ~$1 on their site.

[The Lightning Stalker]

     BTW, that one does use a PAIR of IRF540s and they can get quite warm. It takes quite a lot of current because we're essentially shorting out the flyback transformer. The current has to be limited somehow. I've burned up lots flybacks, capacitors, and transistors due to crummy current limiting.

[The Lightning Stalker]

     If that is what's going on then this could benefit from using an SG3525. There's a flyback driver on my site that uses one http://kickme.to/lightningstalker It's the first circuit "How to Build a Transistorized Tesla Coil".

[Plasmana]

Your ideas might help with my plasma speaker, it is now beginning to have some problems...

^{I think it is the MOSFET's, I brought the cheap ones...}

[emcelhannon]

I've put this one and the 555 version mentioned on an earlier step, to no avail. I'm using a toy rail road variable transformer. I suspect I might have better luck with a car battery. I have gotten nice arcs with my cfl driver, and I'm wondering. Do you know a way to imput an audio signal into the cfl driver system?

[The Lightning Stalker]

     You have to limit the current by using a shorter duty cycle or else get a bigger transistor. If it's that hot I'd try getting a temperature reading. It could be really hot but still within the temperature rating.

[rocketgeek]

The fastest way to cut the heat is to switch the MOSFET harder, i.e. drive more current into and out of the gate.

[Plasmana]

It goes over 175^oC (350^oF) after about 4 minutes of operation with that large heatsink on.

[taoybb-TH]

Can I use a HeatSink CPU(Computer)? I don't know size to perforate