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Simple singing flyback/LOPT

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Mark-H

Wed Apr 09 2008, 02:42PM

Registered Member #607 Joined: Tue Mar 27 2007, 10:39AM
Location:
Posts: 64

Hello All.
Been reading for some time now and decided to "contribute" for what its worth...

The "singing arc/plasma speaker" seems to be gaining popularity of late and especially if YouTube is anything to go by.

However, unless anyone wants a roaring fire coming from the terminals, all of the designs, including the "simple" 555 driven ones are, IMHO, overly complicated.

I've now built loads using a ZVS driver, AC flyback (The DC ones tend to whistle) 2 watt amp, 1 transistor, a 12V 4A DC supply, simple Â£5 mp3 player and a few sundries to make it "arty and pretty". (I tend to sell them.)

I use a 2N3055 (coz I have a bucket of them) in the DC input and switch this with the OP from the amp.

I've not tried, but I'm sure this'd work with the ultra popular 2N3055 and the like, driver too.

I've yet to go above 12V and 4A for more arc and volume, so the arc is generally less than an inch, but the music clarity is surprisingly good.

If all you want is is a coffee table or work desk gimmick, it's a good, cheap and quick way to go.

Cheers.

MH.

flannelhead

Thu Apr 10 2008, 12:00PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Sounds interesting!
Could you happen to have any video?

Coronafix

Thu Apr 10 2008, 10:47PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Got any pics or a schematic?

Mark-H

Fri Apr 11 2008, 08:34AM

Registered Member #607 Joined: Tue Mar 27 2007, 10:39AM
Location:
Posts: 64

Thanks for the questions...
I'm inherently lazy and a bit slow on the video front.
However, I'll do one this weekend and bung it up on Youtube.

As for circuit diagrams, I don't have one as such as I just knocked them together using driver designs found all over the Web.

There's nothing complicated at all...

However, I'll smash a block diagram together this weekend and post that here along with a jpeg or two.

MH

Mark-H

Sat Apr 19 2008, 08:44PM

Registered Member #607 Joined: Tue Mar 27 2007, 10:39AM
Location:
Posts: 64

Sorry to have taken a week longer...
Here are some pictures and a block schematic of my setup.
Re reading my original post, maybe mine is as over complicated as building a "chip" version after all.
I'll post a video up on YouTube asap.
Cheers.

1208637856 607 FT43111 Singing Arc Block

Ken M.

Sat Apr 19 2008, 09:22PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

Pretty snazzy setup.

Mark-H

Sat Apr 19 2008, 09:34PM

Registered Member #607 Joined: Tue Mar 27 2007, 10:39AM
Location:
Posts: 64

Thanks...
I tend to sell most of what I build as "art", so I have to have it looking neat(ish.)
This is more of a lashup to demonstrate to those that want to buy.

Here's a short YouTube clip...

Cheers.

lpfthings

Sun Apr 20 2008, 01:10AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

Hmm, i have the same PSU that you are using there, except i mounted a fan on it and drilled a few holes so i cn run it at its max ratng....

flannelhead

Sun Apr 20 2008, 07:07AM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

Nice PCBs man!

Is the 1 watt amp LM386? That sound quality is kinda good from that simple setup.

...

Sun Apr 20 2008, 06:07PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

You should be able to get both a louder output and clearer sound with this kind of rig, although what you have seems resonable.

The first thing that you could do to improve it would be to properly bias that transistor, which would probably involve adding a resistor of about 200-400ohms (tweak this for best performance) from the +12v to the base of your transistor. You might also need to add a dc decoupling cap (1uf non polarised would work) in series with the amp if it doesn't have one yet. If my math is correct you would also need to change the 1k resistor to something closer to 10-50 ohms. Note that using this method will cause that 2n3055 to dissipate a decent amount of power, so you might need to put it on a larger heatsink.

Basically, what is happening right now is the transistor is only being turned 'on' 1/2 of the time. Imagine playing a pure sine wave into the amp, which will output the signal as a 2v peak-peak sine wave (assuming the amp is designed for 1w into a 4ohm load), which is centered around ground. However, the transistor only turns on for the positive cycles, (thats just how they work), so the audio is constantly being turned on/off at 10khz. By adding a bias resistor you are centering the wave at the current required to turn the transistor 1/2way on, so that when the signal goes positive it allows more current to flow (bigger output spark) and when the signal goes below negative it allows less to flow (smaller output ark).

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