Pseudo theremin using optics

[Geoff C]

My cousin wants to make a theremin-like device after seeing
one in use, for his bands studio. The original analog
theremins are still available apparently but pricey. I
remember seeing a design idea in an electronics magazine a
long time ago which used a CdS cell and a car headlight and
used the illumination of the players hand as it came near the
light source to alter the note.

The circuit details don't bother me but I would like to know
if anyone has experience in playing with such a device. The
transfer function of hand distance change to note change is
important I guess but I don't have a good feel for this. Also,
I'm not too sure if a theremin always outputs a note or if is
nominally silent.

 

[Andy Wood]

Geoff C <nosppamhere@work.com> wrote:

My cousin wants to make a theremin-like device after seeing
one in use, for his bands studio. The original analog
theremins are still available apparently but pricey. I
remember seeing a design idea in an electronics magazine a
long time ago which used a CdS cell and a car headlight and
used the illumination of the players hand as it came near the
light source to alter the note.

I have a few pages torn from "Radio-TV Experimentor" magazine showing
the "Photo-Theremin". It was my first electronics construction
project. I can't really comment on how well it worked since I knew
less about music than I did about electronis at the time.

Besides, it was (gulp)) 40 years ago and I don't really remember much
now...

The circuit details don't bother me but I would like to know
if anyone has experience in playing with such a device. The
transfer function of hand distance change to note change is
important I guess but I don't have a good feel for this. Also,
I'm not too sure if a theremin always outputs a note or if is
nominally silent.

The Photo-Theremin has two CDS cells, one to control pitch, and one
for volume. I believe the original non-optical Theremins also had two
such controls.

Andy Wood
woodag@trap.ozemail.com.au

 

[Unbeliever]

Geoff,
You might also have a look at the motorola MC33794 efield sensor. It
apparently generates a low level electric field and detects loading on that
field by objects that approach. I'm sure you can get it interfaced.

Cheers,
Alf
alfkatz@remove.the.obvious.ieee.org


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