[sdiy] Theremin controller

[Grant Richter]

That circuit is kind of cute. It uses two simple oscillators in to an  
EXOR gate with lowpass filtering. The the lower sideband square waves  
are turned into fixed length pulses by a monostable. The fixed length  
pulses are integrated to form a voltage proportional to frequency.  
Those voltages are then used to control a 8038 VCO and a VCA. This  
design is going to be a lot trickier to calibrate. You need an  
oscilloscope at least.

The main problem is there is no large inductor in series with the  
antenna. That means the range of control will only be about 6 inches  
and it will not behave like a true theremin.

On Mar 10, 2007, at 3:53 PM, James Dunn wrote:

> Yes, me too! Is it something similar to this circuit (at least the  
> first section using the NOT gate)?
> http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/E9/cir2.gif
> I've breadboarded this and it doesn't seem to be working. Does  
> anyone know how the 4098 should be wired? The schematic doesn't  
> show which pin is connected to the 15k resistor, and it's unclear  
> whether pins 3 and 4 are supposed to be connected to ground or  
> not.. I guess all other unlabelled pins are left open..?
>
> thanks
>
> James
>
>
> John Luciani wrote:
>> On 3/10/07, Grant Richter <grichter at asapnet.net> wrote:
>>> I have made a fairly useful proximity controller for the Synthi A.
>> ...
>>
>>> If people are interested I could write up the project for
>>> musicsynthesizer.com
>>
>> I would be interested in looking at a schematic.
>>
>> Thanks.
>>
>> (* jcl *)
>>
>>