Theremin antenna to control VCO

Posted: 6/10/2005 11:16:56 PM

From: melbourne, oz

Joined: 6/10/2005

Hi all -

I've put together a basic square wave oscillator circuit using a 555 timer chip, and can easily make a circuit where you adjust the frequency of the square wave using a potentiometer (I think that classifies this circuit as a VCO synth - correct me if i'm wrong...). My next step, however, is to replace the pot control with a theremin-style antenna. Unfortunately I'm still very much a beginner when it comes to electronics, so I have nooooo idea how this could work.

Does anyone have any advice they can offer me?

My ultimate aim is simply to build a theremin antenna circuit that functions exactly like a potentiometer (ie, variable resistor - NOT variable capacitor), in order to control many different types of modular synth circuits (sine wave VCO oscillators, etc) and perhaps other non-audio circuits too.

I don't understand how to build a simple oscillator which uses a single theremin antenna to adjust it's oscillation frequency, but if anyone is able to explain how to do this in simple terms I thought perhaps i could run the output of that through some kind of pitch-to-voltage or pitch-to-resistance converter (??) and subsequently into the CV input of the 555-based oscillator.

Anyone?? :)

Thanks! ~Jon
Posted: 6/11/2005 12:14:31 PM

From: ohio

Joined: 6/2/2005

Yes I would be interested in some info on this also. I was just wondering today if their was a way that I could turn on this electrical instrument I have by just moving my hand close to it so it would use the hand capasitance to turn it on and off. Is this Possible?
Posted: 6/21/2005 5:18:28 AM

From: melbourne, oz

Joined: 6/10/2005

hey, in case anyone can't quite grasp what i'm waffling on about, i've found some info about a gadget made by doepfer that does exactly what i'm after:

while you're there, check out the rest of their site and DROOL, kids. :)

anyhoo, this is a theremin minus the oscillators (or at least minus their outputs). instead, it produces control voltages. it also produces a gate output when the CV goes above a set threshold, so it would be useful for what blackdiscoball is describing, too.

according to the manual, it has a module inside that takes the pitch of the antenna-controlled theremin oscillator and converts this somehow into a voltage. i guess this voltage then gets compared with a reference voltage, producing a differential which is then amplified and shifted + or - to give the output CV.

anyone able to explain how to go about converting the oscillator frequency into a voltage, then comparing, shifting, amplifying etc??
Posted: 11/23/2006 5:50:46 AM

From: copenhagen, denmark

Joined: 11/23/2006

did you find a solution for this?
i would be very interested in hearing about this!
planning to build a machine (not sound) interface from theremin antennas as well...

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