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Stream Operator
Joined: Oct 13, 2007 Posts: 6221 Location: near Austin, Tx, USA
Audio files: 267
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Posted: Mon Sep 22, 2008 3:45 am Post subject:
USB Guitar Theremin Subject description: Help me design one for my strat |
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Hi,
I've got a guitar-mounted USB sensor that detects gravity and acceleration plus it has an expansion port suitable for measuring a Theremin's output. I would like to develop a suitable Theremin so I can wave my hand over the bridge of my guitar and make sounds.
The current project accomplishes audio effects by sensing the guitar's motion, and you can read all about that by cliking on my www button below. But what would be really cool would be to add a Theremin to this device.
The USB interface can provide a +5V output and has both analog and digital input capabilites. I guess I'm a little confused about Theremin theory and operation. I have a master's degree in electronics plus experience doing digital and analog design and software programming, so I'm sure i could handle the technical details if only given the right theoretical understanding of a Theremin's operation.
I once designed a Theremin with a capacitance multiplier circuit, perhaps that is where I should start, I dunno. Actually I forgot about that but it was an NCSU university lab for some years... At any rate I'm looking for a good simple solution that the average guitarist can build or at least buy and install him/her self.
The circuit was capacitance sensor => relaxation oscillator => speaker or something simple like that. What is your suggestion, i.e. how would you build this device? _________________ "Let's make noise for peace." - Kijjaz |
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Inventor
Stream Operator
Joined: Oct 13, 2007 Posts: 6221 Location: near Austin, Tx, USA
Audio files: 267
|
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Back to top
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Inventor
Stream Operator
Joined: Oct 13, 2007 Posts: 6221 Location: near Austin, Tx, USA
Audio files: 267
|
|
Back to top
|
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Inventor
Stream Operator
Joined: Oct 13, 2007 Posts: 6221 Location: near Austin, Tx, USA
Audio files: 267
|
Posted: Fri Sep 26, 2008 6:59 am Post subject:
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I have now prototyped and tested both versions and some variants as well. I was only able to get a capacitance multiplication of about five times out of the capacitance multiplier in practice. The circuit's slowest operation with the multiplier is about 5 kHz nominal and without it is about 25 kHz nominal. Either version works fine.
The 5 kHz version would suffice as a super-minimal Theremin because you could listen to the signal as-is. For use in my project, however, I need an output signal that is either a lot slower or is an analog level, one or the other. To slow it down I could use a CMOS counter chip, and to create an analog value I could create a frequency to voltage converter (but that would involve a lot of design and test). Right now I'm thinking the divider application would work best, though it does require a chip that I don't have on hand... _________________ "Let's make noise for peace." - Kijjaz |
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