Finally a meaningful application of the Theremin

Posted: 3/21/2013 10:01:16 PM

From: Colmar, France

Joined: 12/31/2007

Posted: 3/22/2013 5:25:56 PM

From: Toronto, Ontario

Joined: 3/6/2013

Well, wasn't the theremin a spinoff of proximity sensor research in the first place? 

Posted: 3/23/2013 5:22:13 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

The whole area of capacitive sensing has taken off big time in this last decade - Back when I obtained my PSoC consultancy accreditation from Cypress Semiconductors, their CapSense (incorporating configurable analogue and digital  modules in a programmable System-On-Chip, together with a MicroController, and these including configurable CapSense modules) was a major focus for these parts.

However, I have never seen any modern short-range capacitive sensor which is in any way similar to Lev's theremin - For one thing, no heterodyning is used. In most cases the sensors operate by charge transfer - a known charge transferred to a plate, and the voltage observed to determine the capacitance. Other methods include a constant current dumped onto the plate, and the voltage rise determined, usually by counting the time it takes for a discharged plate to cross a defined threshold voltage (this is effectively a timed charge-transfer).

The PSoC is extremely well designed for this sort of application, having configurable hardware counters and PWM's etc, as well as having (on the new parts) independent ALU's and DMA which allows multiple sensors to be created within the chip and these to operate as independent 'hardware' units that require no MCU overhead.. The powerful MCUs (in the new parts) allow processing of the data and, quite litteraly, a whole multi sensor system complete with the hardware and software required to implement "output" and other control functions (for example, motor commutation or audio generation or whatever) to be done in one chip - This becomes a "custom" chip which any engineer acn develop and program.

Capacitance sensing is now with us - on our laptops, on our cameras and phones.. Soon it will be so common we wont even mention it.

Lev may have been one of the first to explore it, and the first to bring a capacitive controlled appliance to market.. But most sensors of today have little relationship to his method of implementing capacitive sensing


ps - anyone thinking that I am advocating the PSoC, I AM NOT!  I think these parts are great, and there are applications where they are better suited, by miles, than anything else available.. My first theremins were based on the PSoC 1 and CapSense - From bitter expierience, I must say that CapSense IS NOT suitable for long-range theremin type applications.. I was not the only developer to go this direction - Just before I had completed my PSoC theremin, one came to market... It vanished, probably because its sensing range was too limited.. Effectively the range is limited to what any RC circuit can do, and by the low voltage available to the antenna when one is driving with an inductorless system at 5V.

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