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Registered Member #1004
Joined: Sat Sept 15 2007, 06:09PM
Location: West Midlands, UK
Posts: 2
right, to start with i may as well say that the aim of this project is to produce a 'table top' audio modulated SSTC, with the emphasis being that the sound produced is as clear as possible because in the end i want to try something pretty special with them.
By 'table top' i was thinking of having streamers no longer than a 2-3 inches as a maximum.
So, i think the best place to go from is to say what i've understood from all the different information i've found on t'internet to do with SSTC's. This Block diagram pretty much sums up what i'm thinking right now but to be honest it doesn't really seem sensible to switch a HV supply (like 240VAC) when i could much more easily switch something like 12VAC and just add more windings to the secondary coil to get a p.d. across the secondary enogh to to attain a break out voltage.
The first round of questions i've got are as follows and any help people can offer will be much appreciated and also if i say anything chronically stupid or get something wrong feel free to correct me.
Q1. What kind of voltage do i need to be producing accross the secondary windings to get the desired 2-3 inch streamers and/or a reasonable volume level
Q2. Are my assumptions about tone control and volume control right or wrong?
Q3. What governs the resonant frequency of the coil? (since i need to contruct one with a RF above 2KHz - human hearing range)
Q4. Do certain shapes of break out points work better for producing a sound (i.e a large one that will produce a corona as aopposed to a small break out point that you get streamers from)
Q5. would i be better building a much simpler SSTC first before going for something like this?
Q6. what differences and or advantages are there between a single resonance SSTC and a dual resonance SSTC and furthermore would either desin be more beneficial to doing what i want to do?
I think i'll leave it at that for now, as i said before any help would be much appreciated.
Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
with a 12v supply the output will be much like a flyback, no streamers, small starting spark length but can pull it out a few cm, you will still get sound from this if you start the arc manually. as for the frequency, nyquist states the sample rate must be 2*maximum frequency in the sound. so 20khz*2=40khz. Most TCs operate above 100khz anyway. this frequency is determined by the inductance of the secondary coil and its own capacitance (interwinding and environment) plus its topload capacitance
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425
Hi EP-90, welcome to the forum!
wrote ...
right, to start with i may as well say that the aim of this project is to produce a 'table top' audio modulated SSTC, with the emphasis being that the sound produced is as clear as possible because in the end i want to try something pretty special with them.
Just wondering about your context here -- is this a school project, something you're doing for kicks, what would you like to try that's "pretty special"? (Good to know before we launch into any design).
wrote ... By 'table top' i was thinking of having streamers no longer than a 2-3 inches as a maximum.
This is a nice power to start with -- reasonably low, you're probably looking at maybe 200W for a brush discharge approaching this size.
wrote ...
So, i think the best place to go from is to say what i've understood from all the different information i've found on t'internet to do with SSTC's. This Block diagram pretty much sums up what i'm thinking right now but to be honest it doesn't really seem sensible to switch a HV supply (like 240VAC) when i could much more easily switch something like 12VAC and just add more windings to the secondary coil to get a p.d. across the secondary enogh to to attain a break out voltage.
Often it's not quite as easy as adding more secondary windings -- solid-state tesla coils can be very picky, and it's surprisingly difficult to build a coil that will give a 3" CW brush discharge from only 12V. If you've got 48V to work with, things will be a lot easier -- for this kind of design, higher voltage and lower current is your friend.
The block diagram isn't so clear. We understand exactly what you want to establish, but you're tackling this from what looks like a student perspective. In this case, I think you may wish to discard the block diagram, and instead model some existing systems into block diagrams. For instance:
Steve Conner on this forum has a driver which revolves around the use of a CD4046 phase-locked-loop chip. In essence:
NkHz Fres signal > frequency modulation on the signal > gatedrivers > main power to MOSFETs > primary.
Others have designed audio-modulated tesla coils (mostly small ones at your scale) which use a single transistor as class-A modulation.
NkHz Fres signal > gatedrivers > Class-A modulated main power supply to MOSFETs > primary.
Another approach is to build a proper pulse-width modulator, a la Richie Burnett's site.
NkHz Fres signal > pulse-width modulation according to audio signal > gatedrivers > main power to MOSFETs > primary.
Already we have covered three topologies. I suggest you study the complexities and the respective audio qualities of each (if you can find videos), and then decide which you may think you are most able to build using your current skills.
wrote ... Q1. What kind of voltage do i need to be producing accross the secondary windings to get the desired 2-3 inch streamers and/or a reasonable volume level
If you want to talk in terms of pure voltage, 2-3 inches "might" "translate" to about "50-75kV". This is really speculative -- in such a scenario, you don't care what the voltage is -- you just want your plasma and your music.
wrote ... Q2. Are my assumptions about tone control and volume control right or wrong?
I think it's better to analogise this is "audio modulation" and "carrier power", somewhat like a radio. With a tesla coil, you'll have a constant output power, and you modulate that output power to ionize more/less air to make your sound.
wrote ... Q3. What governs the resonant frequency of the coil? (since i need to contruct one with a RF above 2KHz - human hearing range)
With some minor research, you should have found that the resonant frequency is determined mostly by the self-capacitance and the self-inductance of the secondary coil. Your resonant frequency for a tabletop coil will probably well exceed 500kHz.
wrote ... Q4. Do certain shapes of break out points work better for producing a sound (i.e a large one that will produce a corona as aopposed to a small break out point that you get streamers from)
Ideally, for good sound, you don't want streamers, you want a dense ball of plasma. At frequencies less than 10MHz, this is difficult to achieve. For your application, a thin wire (which promotes corona propagation over the whole surface) will probably give best sound quality.
You do need to watch out that you're not spreading out the corona so much that it extinguishes on negative peaks, otherwise you will notice distortion. This is the kind of thing you may experiment with yourself!
wrote ... Q5. would i be better building a much simpler SSTC first before going for something like this?
Absolutely. Try to coax sparks (in the right place) from an SSTC secondary and driver circuit before you attempt any audio modulation projects.
wrote ... Q6. what differences and or advantages are there between a single resonance SSTC and a dual resonance SSTC and furthermore would either desin be more beneficial to doing what i want to do?
If you want high quality polyphonic sound, a DRSSTC, which is a burst-mode system, is not going to do that for you. Even if you want monophonic sound, stick with interrupting a regular SSTC.
Registered Member #790
Joined: Sun May 20 2007, 12:03PM
Location:
Posts: 14
Matt Bingham wrote ...
Steve Conner on this forum has a driver which revolves around the use of a CD4046 phase-locked-loop chip. In essence:
NkHz Fres signal > frequency modulation on the signal > gatedrivers > main power to MOSFETs > primary.
Others have designed audio-modulated tesla coils (mostly small ones at your scale) which use a single transistor as class-A modulation.
NkHz Fres signal > gatedrivers > Class-A modulated main power supply to MOSFETs > primary.
Another approach is to build a proper pulse-width modulator, a la Richie Burnett's site.
NkHz Fres signal > pulse-width modulation according to audio signal > gatedrivers > main power to MOSFETs > primary.
Already we have covered three topologies. I suggest you study the complexities and the respective audio qualities of each (if you can find videos), and then decide which you may think you are most able to build using your current skills.
Hello everybody! First of all, sorry about my english, its not so good
I saw what you wrote, and i want to ask you something:
What type of the designe,from these three you wrote, would you recomend for building audiomodulated sstc?
Registered Member #1169
Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251
Bjørn Bæverfjord wrote ...
It seems like he has not been logged on to the forum since then. Hopefully someone else will find the answers useful.
Hello 4hv.org after much deliberation and passive observation, I finally decided to become a member of your fine community. Like EP-90, I too am new coiling. Hence why I hesitated joining such an elite group of high voltage junkies. Although I may not understand all the jargon being discussed in this thread I did find it helpful. I just recently ordered and thoroughly read though McCauley’s books on the DRSSTC and conducted my own research on the theory behind Tesla Coils. I too am interested in building an Audio Modulated Tesla Coil as part of a school project.
Before I continue asking any questions I thought it might be responsible on my part to sort of disclose any technical background I might have on the subject so that you “professionals†might have a better understanding of where I am coming from. Like I said I said before, I am completely new to coiling. However I have done quite a bit of preliminary research on the subject beforehand. I am currently a senior at Oregon State University. I am majoring in Industrial Engineering so my background on electronics is limited; however I have had some classes on the fundamentals of electrical engineering.
With that being said, I am interested in building the “miniBrute†featured in the book DRSSTC†miniBrute Reference Design†by McCauley at I am assuming most of you know who and what I am talking about when I mention this book considering Eastern Voltage Research Corporation is a moderator of this forum.
I was wondering if there was an easy way to replace the basic/advanced external “handheld†modulator that is mentioned in the book and replace it with a modulator that with take pure output from an audio output jack on a computer and turn it into a square wave or a signal that that can be interpreted by the Tesla. In other words I want modulate the Tesla to produce music from a computer playing a .midi or something equivalent. I am looking for complete schematics/how-to’s or text that I can pull-a-part and study on my own time.
I did E-mail customer support and easternvoltageresearch.com and they said it could easily be done however the exact procedure on how to do so is not readily available.
Again I feel the need to ask that “technical jargon/abbreviations†be kept to a minimum to avoid any confusion however if it is unavoidable you can rest assured that I will look up anything that I do not understand.
I truly appreciate you guys taking the time to help a newcomer. Also any tips and comments concerning this subject will be digested thoroughly, I promise. I also wont leave you hanging like RP-90 did Matt Bingham.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
<- Scroll down to "Audio Interrupter"
There are simpler ones, but this one adjusts the pulsewidth depending on the input amplitude, so it sounds a lot better than a simple zero-crossing or level detector connected to a one-shot.
Registered Member #1169
Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251
Anders M. wrote ...
<- Scroll down to "Audio Interrupter"
There are simpler ones, but this one adjusts the pulsewidth depending on the input amplitude, so it sounds a lot better than a simple zero-crossing or level detector connected to a one-shot.
Anders M.
so this can replace the basic modulator used in "Minibrute" design? ie just as simple as hooking it up to the coax cable.
And if so, should i use fiber optics to prevent any discharge from the Tesla coming in contact with whatever device is driving the signal?
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First time coil building - many questions
