USB theremin

just wondering if anyone has tried using a computer to measure capacitance of an antenna, via some kind of USB or parallel port connection, then turn the result into variable control voltages or computer generated tone...?

i'm not a computer or electronics expert by a long shot, so i'm in no position to start experimenting hard wiring my computer's USB ports etc! if you've had any experience with something of the sort, id love to hear about it...

love,

jon.

a bit more explanation:

the idea is to build a theremin-based controller for computer music software. i'm wondering if it's necessary to use some kind of external capacitance-to-digital converter (something like a QPROX chip... any suggestions?) then feed the digital output into the computer...

...OR is it possible to use some kind of computer software to measure capacitance rather than an external processor? this would be cheaper and less fiddly, i assume.

preferrably the whole system needs to work on at least 16-bit resolution - 8-bit isn't going to produce smooth enough gradients for a pitch antenna.

hope someone can enlighten me :)

jon

The Theremax has control voltage output.

The Etherwave can be modded to have control voltage output.

Jaycar sells a MIDI Theremin kit.

thanks tom... do you know of any theremins that produce pure digital output, as distinct to midi? midi would be easy for integrating with computer music software, but i find the format really restrictive - especially the 8-bit resolution.

i'm hoping to get a 16-bit (or more?) system happening, then use some kind of simple software routing to send the theremin signal to my music applications. the routing software could also be expanded to allow some kind of transformation of the theremin input before it gets sent to the third party software (ie, inverting the signal, amplifying it, applying high/low thresholds etc).

does this make any kind of sense?? :)

jon

I've been thinking along exactly the same lines for a long time: I imagine a cheap device functionally similar to a mouse which just inputs a stream of data which can then be interpreted by a computer as anything it likes; any weird effects/ nonlinearity etc could be dealt with at a software level.

I tried to use triangulating infrared receiver/transmitters; (Google ACRONAME Sharp GP2D12 and others in that range) with quite good results from a musical point of view, but with nothing like the precision and responsiveness of a theremin, although one of them might be suitable for whatever you have in mind.

In the end I bought an etherwave pro and a CV-MIDI converter from an Australian manufacturer. I built the theremax before doing this and found the sluggish/nonlinear/small range CV outputs no more useful than the infrared things, but admittedly gave up before really giving the theremax a chance; I just decided life was too short to waste any more time on it.

I'm in Sydney. Please let me know if you go any further with this concept.

ahoy! i've managed to get this project off the ground a little bit, with some initial success. you can read about my feeble attmpts at the ardunio forum:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1169728880

arduino is a programmable development board which i am using to interface to a QProx capacitance-to-digital sensor.

i still need to sort out a lot of problems, which i've listed on the forum i linked to above. if you're interested in the project, i'd love to hear comments or suggestions!

i'm also going to post a tutorial on the arduino site soonish, so that anyone who doesn't understand what's going on can replicate the project at home and see if they can get it working better than mine. probably won't be all that difficult...

cheers,

jon.