<=My Authentic Theremin

TW Optermen
A Theremin Cousin - 100% Radio Shack

Over the years my first simple electronic project has been published as a web standard. Visit Make Magazine


Here is an audio Sample1 .mp3 (176k ) this is exposure to natural daylight in my well lit room. This Optical is not very musical or playable like a true theremin, just fun.

Ask any theremin designer or seller for a sound sample, their response will reveal credibility or very vile gas.

Lights will add their own type of cool distortion, here is audio Sample2 .mp3 (113k). This is the fluorescent light around my magnifying glass getting near the sensor. Circuit benders would think this is music!

There is no Sound in Total Darkness!
The square wave pitch rises with the light level.

The power consumption of the circuit is extremely low. If you use this circuit to drive a mini amplified computer speaker input the optical circuits "AA" batteries would last years..  

Video of the RS Optical Theremin Performance by farnea on Jan 7, 2008 in tech

Using the DIY RS Optical Theremin pitch enhanced with the RS Sixth Voice, a GameBoy Advance SP as a drum box and some strobo leds.

Note: Q1 & Q2 could be replaced with a single CdS LDR light dependant resistor removed from a wall plug night light.

Board size 1.6" x 1.8" (40mm x 45mm)   


PDF (168k)  <= Etch your board using this file.

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Line out can connect to a medium size speaker directly. A C2  220 uf cap would be better for below 100 hz.

Go sub-sonic and shake the walls!

If bread boarding the phototransistors must be opposite to one another as in the schematic.

The phototransistors physically mount on the etched circuit board in the same direction. Look for the fat internal lead (collector). Either direction is fine as long as both transistors are the same.

You need a black plastic sleeve around the phototransistors to block the light coming from the sides. This will make the light exposure more directional toward the phototransistors front lenses. 

When constructing make certain the electrolytic capacitor negative side is faced away from the IC.

A triangular waveform which creates a better tone is generated at pins 2 & 6 which is the top connection of C1 of the TLC555. This can be made useable by tapping off here and driving the high impedance input of an additional Op-Amp like a TL082. This Op-Amp is needed for isolation of the triangular wave to avoid loading down the performance of the TLC555 circuit.  You might also try feeding the signal from here to your main amplifier, if it does not work it will distort the frequency of the sound.

RS Theremin Says "Hello World"
  Value Quantity Part# Price Packs Total Special Notes
Q1, Q2 Phototransistor 2 276-145 1.59 2 3.18  
U1  TLC555 1 276-1718 1.69 1 1.69  
C1  .047 uf 1 272-1068 1.29 1 1.29 Pack has two
C2  100 uf 1 272-1044 1.29 1 1.29  
R1  10 K 1 271-1335 
or  271-1126 
.99 1 .99 brown-black-orange-gold
R2  1 Meg 1 271-1356 
or  271-1134
.99 1 .99 brown-black-green-gold
Misc.
IC Sockets 8 Pin 1 276-1995 0.69 1 0.69 Use a Socket !
PC Board Generic 1 276-159 2.29 1 2.29 Etch your own PDF (168k) 
V1 Battery 4 AA Holder 1 270-409 1.89 1 1.89 Switch in Battery Holder
Line Out PC Board Term. 1 276-1388 2.29 1 xx Optional Pack of 4 
Enclosure 4x2x1 1 270-1802 2.69 1 xx Optional Box
 Prices as of Sept. 25, 2004    US Dollars  Total = 14.30 <=Batteries Not Included (-;