Instructables
Picture of Soda Can Theremin w/ Analog Discvoery
block_diagram.png

Remember those old-school sci-fi movies with squeaky and eerie background music? Those unique sounds were made using a theremin, an electronic instrument that can be played without physical contact. When playing a theremin, the operator can control volume and pitch with his or her hand position relative to two antennas.

This project is going to demonstrate how to build a simple theremin on a breadboard using a soda can as the antenna! With simplicity in mind, the theremin in this project will only demonstrate pitch modulation. The design that is implemented is shown in the block diagram above. However, it doesn't take too much extra work to add volume control, so I encourage you to try it if you're looking for an extra challenge.

To keep it short and sweet, we won't get too deep into the theory of how a theremin works. Briefly though, the antenna (our soda can) acts as one plate of a capacitor. Your hand will act as the other plate of the capacitor. Thus, by moving your hand nearer and further from the can, you are changing the capacitance. This takes place within the variable-frequency oscillator portion of our circuit. As the capacitance in the oscillator changes, the oscillator's output frequency changes as well. This change in frequency can be heard at the speaker at the end of our circuit.

 
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Step 1: Gathering the Materials

Picture of Gathering the Materials

This project is completed using the Digilent Analog Discovery and Analog Parts Kit. The only other part needed is the soda can! Any metal object with a reasonable surface area would work as well.

The specific parts used in this design are shown in the picture above.

  • OP27 Operational Amplifier (x2)
  • OP37 Operational Amplifier
  • Small speaker
  • 100pF Ceramic Capacitor
  • 0.047uF Ceramic Capacitor
  • Small-signal Diode (1N3064)
  • 10kΩ resistor (x2)
  • 20kΩ resistor (x2)
  • 47kΩ resistor (x2)
  • 100kΩ resistor (x3)
  • a few breadboard pins and jumper wires
  • Breadboard (not pictured)
  • Soda can (not pictured)
  • Digilent WaveForms Software (Free Download)

All of these parts are right out of the Analog Parts Kit.

LancasterPA4 months ago

Wow, way out of my price range. I would have loved this toy but not at the expense of 5 tanks of gas. I'll keep looking for an engineer to come up with one of these that is affordable. Thanks!

I'm glad I'm not the only one who is quite honestly stunned at the price of this kit. Yes, it is a great little kit but I do dispute it being good value (at that price). Again, this is absolutely NOT a dig at the Instructable, that is very good indeed and I for one thank you for sharing it. I do recall finding a simple (?) circuit for a theremin type device many years ago. It would no doubt be far more simple nowadays with the abundance of IC's around. Maybe there is a 'cheap' way of making this toy after all???

Will_W_76 (author)  LancasterPA4 months ago

This project can be adapted to work with other equipment you may already have. I used the Analog Discovery because it has a lot of other benefits and offers a lot of convenience. Another user shared your concern. You can see my response to their comment below for more details. Feel free to contact me if you have any other questions!

Kevanf14 months ago

I'm really sorry but UK£185???? Or, US$310 for the Analog Discovery and parts kit? That's way too steep to make some weird sounds. I applaud your idea and construction but it's just too expensive. I couldn't afford that and I'm 51 years old. How could a child afford this? Maybe a step by step theremin build using separate components might be the way to go? I know, it's complex but at least it could be done bit by bit as finances allowed. I am really sorry for my negativity as I think the project is actually fantastic :)

The Analog Discovery and parts kit is really good value for anyone who wants to play around with electronics. You'll find though that commercial theremin kits are not cheap either.

Will_W_76 (author)  Kevanf14 months ago

This project can be adapted to work with other equipment as well. I used the Analog Discovery as a power source and waveform generator. You could use any other power source or waveform generator in it's place. (In place of the waveform generator you could build a second oscillator as well.)

I chose the Analog Discovery because it's small and USB-powered. Also, compared to the cost of other lab equipment that serves the same function, such as larger desktop oscilloscopes, the Analog Discovery is relatively inexpensive. The Analog Discovery is also an educational tool that is designed for a lot of other projects and purposes as well. It would be a good investment if you do this type of project frequently. But, as I said above, you can adapt the project to work with other equipment you may already have. Feel free to send me any questions if you need more details :)

Kinnishian4 months ago

I also applaud and like the instructable, but think the diligent analog discovery is absolute overkill and unfortunate. I think there is value in sharing the instructable and making it for the information education, but it is not an instructable that many people can replicate.

craftclarity4 months ago

Super cool!!!

carebare475 months ago

Hello,

I have not yet built this circuit. I found your drawings a little tricky to understand in places and I've re-drawn the schematic. Is it correct? Really interesting circuit, can't wait to make it. Thanks :)

Theremin Circuit Redrawn.jpg
Will_W_76 (author)  carebare475 months ago

Yes, that is correct! It looks like you were mostly confused by the drawing for the envelope detector. I can see now that the way I included the input and output voltages there may be confusing. I'll keep that in mind on future posts. I'll try to be more specific with the op-amp pins as well. Thanks for the comment!

If it's correct please feel free to use it in any way you wish.