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Registered Member #2009
Joined: Tue Mar 03 2009, 07:07PM
Location:
Posts: 43
I want to build a polyphonic PRF type controller for a Tesla Coil
I've built Dan McCauley's Plasmasonic II, and found that the output is great for fidelity, but isn't very efficient as far as getting some serious volume output is concerned.
What I'd like to do is build something in between a Xenosonic type monophonic device, and the infinite possibility of combinations possible with the CW Plasmasonic type.
My end goal is to send 9 sine waves at the same time, in phase, and have them actuate the coil, perhaps on the enable pin of the fet drivers. (Probably the sine waves will have to be converted to square wave pulses).
Right now I'm thinking a zero crossing detector, but I'm having trouble finding a circuit using the newer ultra high speed comparators. Anyone know of one?
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
indiana wrote ...
My end goal is to send 9 sine waves at the same time, in phase...
So one sine wave then?
If you want lot's of sparks and bang, I think you'll need to modulate the coil like the DRSSTC boys do. Most importantly, unless you are able to linearly modulate the coil's output all you'll get is square-wave music anyway. Sending signals to the enable pins of the gate drivers only gives 1-bit control over the coil (ON or OFF). I'm working on a MIDI controller right now which is an interrupter plug in. It can play two notes at once, and I'm working on getting that number up to 4 or 8. I think what you're looking for is a MIDI controller, see Steve Ward's work for some videos and an explanation.
If this isn't the type of music output you want, then CW modulation is your only other option, and serious output and volume will not follow. You could use a zero-crossing detector and such to turn music into 1-bit data, but that sounds terrible IMO.
Registered Member #2009
Joined: Tue Mar 03 2009, 07:07PM
Location:
Posts: 43
9 different frequencies of sine wave, which would be harmonic to each other.
It occurs to me though, now that you say that, that it may not be possible to do what I was hoping to do with only one coil.
For those on here familiar with music theory, I want to send several octaves, which in 1 bit would look exactly the same as only the highest octave. In other words, for example I could send 400Hz, 800Hz and 1600Hz. But the 1600 frequency contains the lower frequencies inherently in 1 bit.
However, I want to replicate the way those waveforms would interact with each other acoustically. Which keeps bringing me back to amplitude modulation which seems to be a less than favored option based on conversations I've had here.
Imagine the plots of the 3 sine waves above. If you put them in phase and add them you get differing amplitudes, but the same zero crossing points.
Here's an image of something similar, but with a chord instead of octaves:
Maybe it would be appropriate to use an analog to digital converter... But then we're back to continuous wave aren't we?
Is there a way to do something in the middle somewhere? To augment the power output to reconstruct a sine wave in higher fidelity (or failing that a square wave), but maybe do it in bursts to keep duty cycle low enough to keep power output high.. ?
For example, as an idea, can anyone think of a way to send bursts at say 400Hz at a power level of 10... 800Hz at a power level of 6 and 1600Hz at a power level of 3 concurrently?
The only other method I could think of to increase amplitude would be to use more than one coil. One controller to operate several coils.
Then you could have, say the 400Hz on one coil, the 800 on another and the 1600 on another, and the resultant acoustics would be the three added in their actual physical pressure wave in the room...
It just seems like there should be a way to do it with one coil and still get a decent amount of power. If I had just 3 or 4 times the volume output of the Plasmasonic I'd be stoked. It doesn't have to be a monster like the DRSSTC's.
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Polyphonic Interrupt Type (Pulse Repetition Frequency) Tesla Coil Audio Modulation
