Let’s Build a Theremin

The Theremin, invented in 1920 by Russian inventor Leon Theremin, uses an electronic circuit called an oscillator to create different sounds. In our Theremin, we’re using the Arduino as an oscillator by programming it to select different tones based on changing light levels. The tone changes are made by waving your hand over a photocell, creating various sounds based on changing light levels. The circuit is built on a breadboard with electronic components, as shown in the Parts List. Although the Theremin can be built on an ordinary breadboard, the MakerShield makes the device small enough to carry in a shirt pocket or Maker bag. Figure 12-2 shows a Fritzing diagram of the Theremin. Also, the actual mini 8Ω speaker used in the Theremin project is shown in Figure 12-3.

Figure 12-2. The Theremin Fritzing diagram

The electronic sounds generated by the Arduino are wired to a simple transistor amplifier. Pay close attention to the 100 uF electrolytic capacitor’s orientation (shown on the Fritzing diagram) to prevent damage to the Arduino. Also, the NPN transistor’s pinout for either a 2N3904 or S9013 electronic component is shown on the Fritzing diagram’s breadboard. The mini 8Ω speaker color wire leads must be connected correctly (as shown in Figure 12-2) in order for the audio electronic sounds to be heard through it.

Figure 12-3. The mini 8Ω speaker

TECH NOTE

The 100 uF electrolytic capacitor is called a polarized capacitor because of its positive and negative electrical leads. Like an LED, electricity flows through it easily in only one direction.