Building a theremin and learning some electronics along the way.

I had a week off, so i thought lets build a theremin how hard can it be

I figured i go buy a brass rod at the hardware store and i had a box laying around. Turns out it’s kind a hard to bend a 6mm solid brass rod. And it’s also hard to cut a thread on them. But now i can do both so lessons learned. Three days well spend….

Well i wanted to get it working fast so i thought put in an esp32 that has capacitive touch, so i can use my antennas.
It kinda worked, i got 7 different distance readouts for volume and 5 for pitch….
So thats a fail…

Than i figured 3v3 would probably not be good enough, i need a stronger electric field. So i did some research and found the d-lev. With some nice instructional videos how to make air coils. So i designed a coil holder in fusion 360 and hand wound two of them. Also liked the led pattern so i drilled some holes in my box and put in some adressable leds.

I’m not an electrical engineer, but i like tinkering. But the schematics on the d-lev and on this site for building are way to complex for me. But i found a tutorial for a colpitts oscilator. So that was doable. Turns out it wasn’t so great, but it was a start. It lead me to the clapp oscilator, and i build it in a simulator and started to see how it works. Changed a couple of things and build it on a breadboard.

And i didn’t realy expect this, but i got 424Vpp and without grounding 30 to 40 cm range on my pitch antenna (seeing the wave change on the oscilloscoop)

I thought i’d share and maybe ask some questions if i get stuck somewhere.

https://imgur.com/C9B7vwY

https://imgur.com/8cRuKjw

https://imgur.com/4fGhCkE

https://imgur.com/Hl2KInz

Welcome to the club. The Clapp oscillator is a very good choice, high Q due to the air coil too. Temperatur stability and pitch response behavior will be fine. 

Yes, welcome to the club MaltWhiskey!  

"Than i figured 3v3 would probably not be good enough, i need a stronger electric field."

If I were building an analog Theremin I'd probably go with Buggin's amazing oscillator:

  http://www.thereminworld.com/forums/T/33275?post=221506#221506

With the right coil you can easily get 2 to 4 hundred volts peak-to-peak at the antenna with a 3.3V supply.

Also: voltage regulation of the oscillator supply is more or less mandatory for stability.  For some oscillators it is critical, but all oscillators benefit from supply regulation to one degree or another.

To view stability and sensitivity on your scope, set the delayed sweep to the inverse of the mains frequency.  E.g. for 60Hz use 16.666ms, for 50Hz use 20ms.  This will put a zero at the mains electric field, and allow you to observe things without all of the jitter that it imparts.  It's kind of like heterodyning.