Skip to main content
shopping_basket Basket 0
Log in

The Evolution of a Light Theremin


From learning what a light theremin is to making a custom PCB.

I started out a little over two years ago on work experience, before going on to become a trainee engineer, having decided that I would like to pursue a career in electronic engineering. At work I get to do a wide variety of things, such as laser cutting, assembling kits and even some prototyping. Over the past two years I’ve spent quite a lot of time learning microcontroller basics, mainly working with Arduino and simple projects.

When I first started out I had very little electronics experience – pretty much just a basic understanding of Ohm's law. However, I feel like I’ve learned a lot over the past few years and I'm due to start a HND in electrical and electronic engineering this coming September.

There’s one particular project which follows my progress and it was the very first one I tried my hand at. Over the past two years I've returned to this project a number of times, developing it further and finished with a fully working PCB design. This is the evolution of the light theremin.


What is a light theremin and how does it work?

A light theremin is an instrument that makes a sound, the pitch of which changes based on varying light levels falling on a sensor.

My light theremin used a light-dependant resistor (LDR). This changes resistance according to how much light is falling on it, as light intensity increases resistance decreases and vice versa.

In this light theremin a resistor and an LDR form a voltage divider. An ATMEGA328-PU measures the voltage at this point via one of its analogue input pins. The microcontroller generates a tone, the frequency of is which determined by the voltage, and outputs this to a loudspeaker.

A Novice's Introduction to Arduino

My introduction to Arduino was via the Arduino Starter Kit and I ran through the example projects in the included book – I’d have been completely lost without this.


The sixth project in the book was the first time I had encountered a light theremin. This provided a fantastic tutorial on how to assemble a one on breadboard using an Arduino Uno, 10K resistor, piezo, photoresistor (LDR) and some jumper wires.

Out of all the projects in the Arduino Starter Kit this one jumped out at me and caught my attention the most, so much so that it had a big influence on my following project.

To read more about A Novice's Introduction to Arduino click here

Making a Light Theremin Instrument

Following my experiences with the Arduino Starter kit I decided that I wanted to have a go at making an improved version of the theremin. This time I used perfboard and a Minimal Shrimp circuit instead of an Arduino, adding some simple improvements also.


One of the big differences between this project and the last were that I drew the schematic myself instead of following a tutorial. Also this theremin would run from a battery supply and have a heavy duty enclosure, so that it could withstand wear and tear similar to what an effect peddle might.

To find out more about this project click here

Getting to know DesignSpark PCB

After enjoying the previous two light theremin projects I decided that I would have a go at making custom PCBs. My initial post about DesignSpark PCB details my first time ever using software for schematic capture and PCB layout.


There was a lot to learn, from how the software works, to how to layout a PCB! It did take me quite a while, but after some time I managed to get the Gerber files for a PCB uploaded to a board manufacturer.

To find out more about this learning process click here

First PCB Project – back to the drawing board

I received V0.1 of the light theremin PCB back from fabrication and assembled the boards. Unfortunately, the boards didn't work as I thought they would, so I had quite a bit of troubleshooting to do to in order to determine the problem.

To read about this stage in the development of the light theremin PCB click here

First PCB Project – Fourth Time Lucky

I fixed the problems identified in V0.1 and sent the new files to fabrication. However, it took another two attempts before I ended up with a board completely free of errors. I learnt a lot in the process and it's very easy to make silly mistakes.


Once I finally achieved a working design I made a custom acrylic case for this.

To learn how I addressed the remaining problems with the PCB click here

6 Posts later...

Over the course of these projects I think its safe to say I've come quite a long way. I’ve made some very silly mistakes, but learned a lot of invaluable lessons. Considering that I was completely thrown in at the deep end with schematic capture and PCB design, having never done this before and learning by experimentation and watching tutorial videos, I don’t think I did bad at all!

If you're interested in building your own light theremin you can find details attached.

Open Source Licence - Solderpad Hardware License v0.51 (SHL v0.51)

Trainee Electronics Engineer, currently studying towards my degree in Electronic Engineering at the University of Hudderfsield. Completed my HND in Electrical & Electronic Engineering from Bradford College 2017. Love to try new things and build interesting projects!


January 29, 2018 09:25

What is the PCB/schematic tool to open the schematic (.sch)? Not Eagle.

0 Votes

January 29, 2018 09:13

Please provide a PDF version of the schematics.

0 Votes

February 5, 2018 10:49

@mr_bandit we've added a PDF version of the schematic for you

September 17, 2015 22:45


I was looking for something about a RF Theremin but this was a really nice story and I felt really identified with it.

My first "advanced" circuit was a spectrum analyser (I didn't even know what it really was, I just liked to see the LEDs moving at the rhythm of the music) using some components that I had no idea how they worked, it was my first year on the university, of course it never fully worked. Some months later I tried something similar for my first PCB using a copper board, markers and ferric chloride and it worked!! (Even if it was a little bit ugly). Since then I have been living at this Electronics Design world that you have just entered for at least 6 years and until now I keep making mistakes and keep learning from them. Now I'm working on this and studying my Master in Electronics in Italy, mainly focused on this.

Last summer I gave a small a course about this subject at my University in Mexico and the topic that you mention was one of the main advices I gave in this course: "La práctica hace al maestro" (practice makes the master).

So, good luck with this and if you need any advice about circuit design or PCB design please don't hesitate on contacting me!!

September 14, 2015 09:47

I meant to say a midi synthesiser

0 Votes

September 14, 2015 09:35

Perhaps you could add a midi interface and power a sync from the Theremin?

DesignSpark Electrical Logolinkedin