The Theremin was invented by Leon Theremin in 1919 and is one of the worlds first electronic musical instruments. Building your own Theremin is not the simplest electronic musical instrument project to tackle because most have somewhat complex schematics and hard to find parts. Although Theremins preceded synthesizers, it is easier to build a simple analog synth than a basic Theremin. However, there are some basic Theremin schematics available to get you on the path to more complex projects. An excellent starter design is a pocket photo-Theremin designed by Dave Porchnow of Popular Mechanics.
Materials
Most of the parts for building this simple and small Theremin can be obtained at your local electronic parts store and the total cost of the project should be less than $20. You will need two 555 timer ICs, two CdS photocells, two .01 mF capacitors, one 1K resistor, one 5K potentiometer, one 2-position PCB terminal, one 8-Ohm 1" speaker, a 9-volt battery snap, a split-level shielded box, one hookup wire, and a 9-volt battery.
Putting it Together
First, you need to build a Theremin circuit with photocells as close to the Popular Science writer Dave Porchnow's pocket Theremin circuit as possible. A link to the schematic is provided in the resources section of this article. This is one of the simplest Theremin schematics available and allows for a bit of experimentation with different photo cells. It is a great schematic to start with because it is simple and will pave the way for you attempting more complex designs.
Determine what pin on the 2-position PCB terminal will be positive and which will be ground. All of the circuit's positive sections should be routed to the positive pin of the PCB terminal, including the hot wire from the battery connector, and all of the ground circuits should be routed to the other pin, including the cold wire from the battery connector. Solder all of the wires to the pins at one time.
Take apart the split-level shield box and insulate the inside with tape or plastic. This will keep the electronics within from shorting out if a wire touches the metal of the box. Install the circuit in the box so that the two photocells stick out of the box on opposite sides. Wire the speaker so that it is outside of the box on the front end and the battery clip so that it sticks out of the back end. Plug the battery in and you will begin to hear sound. The sound volume can be controlled by adjusting the potentiometer and the sound itself can be controlled by adjusting the amount of light the photocells are exposed to.
Tags: 2-position terminal, 9-volt battery, basic Theremin, battery connector, controlled adjusting