Hello!

My intention was to build an easy and cheap theremin, using the arduino. I've already finished a classic variant (the model 144; www.theremin.us/144/144.htm; https://www.youtube.com/watch?v=DhvwaoKn7CY&t=4s) but now I wanted something cheaper.

The theremin was invented by Leon Theremin in 1919. Classically a theremin consists if two oscillating circuits, one fixed and one variable. The variation is achieved by moving the hand in front of an antenna. When those two slightly different oscillations are being mixed you get beats. The frequency of those beats is the difference between the frequencies of the two oscillations. This signal can be heard.

## Step 1: Parts You'll Need and Circuit

In my case I determine the distances of the hands with the ultra-sonic distance-sensor HC-SR04. You will also Need a digital potentiometer MCP41010, of course an arduino nano or similar, an audio-ic LM386 and some other small electronic parts (resistors, capacitors...). With the 470 kOhm-potentiometer you can adjust the maximum volume.

## Step 2: Sketch & Settings

The sketch is very simple. You just have to initialize the two distance-sensors, measure the two distances and convert them into the pitch and volume of the Signal. A small subroutine is responsible vor the Variation of the digital potentiometer.

There are two Options concerning the dependence of the pitch and volume from the distance of your hand to the sensor. You can either use a linear or an 1/distance-dependency. I've Chosen a linear-dependency for the volume and a 1/distance-dependency for the pitch.

## Step 3: Results

The whole circuit can be placed on a small wooden board. Intead of the HC-SR04 you can also try the sharp distance-sensor GP2Y0A41SK0F, which can measure distances between 4 - 30 cm.

I hope you liked this and maybe you want to take a look at my YouTube-channel: www.youtube.com/user/stopperl16/Videos

Thank's for visiting this instruction, bye for now stoppi

<p>This is fun! :)</p>