How to Build a Homemade Theramin Using Scrap Materials

Building your own theramin at home using scrap materials is a fun electronics project that can be done on a budget. Here is a step-by-step guide on how to make your own homemade theramin from scratch.

What is a Theramin?

A theramin is an electronic musical instrument that is controlled without any physical contact from the player. It was one of the first electronic instruments ever created.

The theramin produces sound by using two metal antennas. One antenna controls pitch while the other controls volume. When your hands get close to the antennas, the electromagnetic field from your body's capacitance is altered, which creates the eerie wavering sounds the theramin is known for.

By waving your hands near the antennas, you become part of the instrument's circuitry! No musical background is required to play the theramin.

Gathering Materials and Components

Many of the parts needed to build a homemade theramin can be salvaged from old electronics and appliances. Here are the main components you'll need:

Wooden board or box - The base for mounting all the components. I used an old wooden picture frame.
9v battery - Provides power for the circuit.
9v battery connector - Connects the battery to the wires.
Wires - For making connections between components. I stripped some wires from an old USB cable.
Soldering iron - To solder all the electrical connections.
Transistors - I used 2N3904 transistors, but many types will work. These amplify the antenna signals.
Resistors - 1M ohm and 100k ohm resistors are ideal values. Resistors control current flow.
Capacitors - I used a 47nF and 100nF capacitor. The capacitors filter the audio signal.
LM386 audio amplifier IC - This integrated circuit amplifies the audio signal to drive a speaker.
Potentiometers - To control pitch and volume. 10k-100k ohm potentiometers work well.
Antenna wire - I used stiff copper wire for the pitch and volume antenna.
Mini speaker - Salvage one from an old device or use a small 8 ohm speaker.
Jumper wires - For easy prototyping.

Constructing the Circuit

Here are the step-by-step instructions for assembling the theramin circuit on a prototyping breadboard:

1. Power Supply

Connect the 9v battery to the breadboard power rails using the battery connector cable.

2. Volume Control Circuit

Connect the 100k ohm resistor from power to ground.
Connect the volume antenna wire to power through the 100k volume potentiometer.
Connect the potentiometer wiper to the transistor base through a 1M resistor.
Connect the transistor emitter to ground and collector to +9v.

3. Pitch Control Circuit

Connect a 47nF capacitor between power and ground.
Connect the pitch antenna wire through a 10k pitch potentiometer to ground.
Connect the potentiometer wiper to the second transistor through a 100k resistor.
Connect this transistor's emitter to ground and collector to +9v through a 100nF capacitor.

4. Audio Amplifier

Connect the LM386 chip's pins as per the datasheet.
Connect pin 3 to the volume transistor collector.
Connect pin 2 to the pitch transistor collector through a 1M resistor.
Connect the speaker across pins 5 and 6.

Creating the Chassis

Now that the circuit is complete, you need to assemble everything into a chassis:

Mount the circuit board, potentiometers, and speaker into a wooden box or picture frame base using screws or hot glue.
Drill holes for the antenna wires to poke through the top side of the chassis.
Glue down the antenna wires so they stand upright.
Securely mount the battery connector and power switch (optional).

Make sure no metal parts touch the antenna wires, as this can create unwanted capacitance and interfere with the pitch control.

Some DIY theramin builders also add fun decorative touches like retro knobs for the dials and blinking lights!

Playing Your Homemade Theramin

Once assembled, your homemade theramin is ready to start making alien sounds!

Turn it on and let it warm up for a minute.
Experiment waving your hands near the antenna to control the pitch and volume.
Move farther away to lower the volume and pitch. Get close to raise them.
Try playing simple melodies by moving your hand to "play" different notes.
It takes practice, but you'll soon be warbling like a science fiction movie!

The eerie sound of the theramin is like no other instrument. Enjoy exploring the unique nature of playing music without touch! This homemade version shows that anyone can build their own electronic works of art.