Light Theremin

By Steve Hobley
Time Required: 1 hour

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Anyone who’s shivered in the dark at a scary movie or laughed at the unintentional cheese-ball of a bad sci-fi (paging Ed Wood) knows the eerie sounds of the theremin. In the classic theremin design, two antennas control pitch and volume, and you play the instrument by moving your hands near the antennas without touching them.

This simpler design uses interrupted photons (light) instead of radio waves, and can be built with a handful of common components, including the versatile 555 timer chip. When we’re done, we’ll have a decent sounding mini-theremin. You can experiment with its sound by changing the type of light sensor used and the capacitance of the circuit.

Check out more Weekend Projects.

Steps

Step #1: Gather Your Parts

NextPrev

Gather together the breadboard, capacitors, speaker, resistors and photoresistor (or photodiodes).
TIP: I nearly always buy the large multi-packs of resistors; it saves time and money in the long run.
The schematic I based this project on called for a 0.47μF capacitor. I didn't have any, so I used two 0.22μF capacitors in parallel. The values add, giving 0.44μF -- and that's close enough!
We are going to be building a 555 timer-based "astable oscillator circuit." It sounds complicated, but really, it's not that hard.

Conclusion

The venerable 555 timer integrated circuit used in this project is the most popular IC of all time. You can learn more about it here and read about a chance encounter with the designer of the chip, Hans Carmenzind, on MAKE.

Steve Hobley

This week, I have been mostly working on...

I've been tinkering around with bits of technology since I was five years old. I used to take the telephone apart at home, just to see how it worked.

After a couple of years I could even put it back together again - and sometimes it would continue to work.

Steve Hobley

Can you tell me anything about what the circuit is doing? It might help to diagnose what could be wrong.

Steve
Steven Dayton

I now have it working. I posted my results on a blog. I made a modification by adding a 10k pot into the mix and am using two different .22uf capacitors so those variations give a lot of variation and flexibility to the pitch. I ended up going to Radio Shack to get the .22uf capacitors from the parts list. The rest of the parts I mail ordered. This is the first non Arduino based project I have gotten to work. Lots of fun to play with and irritate some of my older children. Thanks for a great project. If you would like to see what I did here is the link. http://sdmadeit.blogspot.com/2011/11/no-30-light-theremin.html
Nick Normal

We posted Ed’s Snap Circuit photos on the makezine blog:
http://blog.makezine.com/archive/2011/11/snap-circuit-light-theremin.html
Leif Burrow

Sorry, I should have mentioned… I built mine on a RadioShack Learning Lab and used the speaker that comes in it. I suspect that might have something to do with why I didn’t get good volume until I used the audio transformer (which is also built into the Learning Lab).
Jake Spurlock

Great idea. I have used LEDs with mine, but hadn’t thought to try IR LEDs. If you don’t have your camcorder, try using your TV remote…
Nick Normal

hi Priit, Check out Steve’s mod here on the blog: http://blog.makezine.com/2011/11/17/weekend-projects-light-theremin-mod/ – click through to his blog & send him a message if you need more info, but it looks like his 10k pot sits between ground and the electrolytic capacitor.
Nick Normal

hi Ian,
A capacitor stores charge, at a certain rating (.22uF and 100uF for this project). They’re composed of two plates (pos & neg) with a non-conductive material (dielectric) between them; the plate material and dielectric, along with other factors, determine the rating of the capacitors. Look at the cross-section of a Leyden Jar to understand the design. There’s a good picture in this How Stuff Works article from 2007 also: http://electronics.howstuffworks.com/capacitor.htm
Nick Normal

Hola Brenda. Prueba a conectar cátodo del capacitor al carril de tierra.
Nick Normal

Congratulations! If you have photos, please send them to [email protected] – thanks!
Nick Normal

Interesting hack – please send photos to [email protected] – thanks!
Ryan Hammond

Does anybody know if there’s a way to make this circuit work without the photoreceptor — more like a traditional theramin where you’re body’s EMF interferes with the EMF of an antenna? I’ve seen it done with a 555 timer very simply before so I know it’s possible…
Powerflash

This is not technically a theremin since it uses photo-resistance for voltage control of a single oscillator and does not use capacitance controlled heterodyne interference. Not a big deal, but noting it might be interesting for those with an interest in the history and development of the theremin and theremin-like devices. :-)
(hopefully this comment is not seen as hating/trolling)
- Steve Hobley
  
  Not by me :-)
  
  You are quite right, it’s not a Theremin internally, but externally it gives you an idea of how it feels to play the real thing.
  
  I built a vacuum tube Theremin a few years ago, and still find this to be the most playable/expressive of all the designs.
  - Powerflash
    
    Definitely very fun to play with! And there are many mod possibilities. Thanks so much for sharing this project.
victor

what is the value of the resistors?
Jorge Gutiérrez

Hi ! where does the bottom black cable come from , my theremin is not working yet :(
Patricia Tsoiasue

I had some trouble getting it all together, and had to get help from the surplus store crowd. Here’s my video… http://youtu.be/zk85jgmLU58
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Greg Smith

Funny, I’ve just been reading Us Conductors, a fictionalized account of part of Lev Termen’s (inventor of the theremin) life. Maybe when I’m finished the book I’ll try making this!

Serendipity is weird.

If anyone checking out this project is interested in going the opposite route, here’s the book’s site: http://usconductors.byseanmichaels.com/
Anthony Joshua Pinkerton-Esq

Yes! Built it! It’s presently driving the neighbor’s dogs crazy. Thanks for the guide. It was fun:)
Wanda

I cannot see the list of supplies. Can anyone suggest what type of speaker I should use?
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khanfr

Wanda , i also was confused but i just used a pizo
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mr_bandit

He was also a soviet spy: https://en.wikipedia.org/wiki/L%C3%A9on_Theremin

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Tools

Steps

Step #1: Gather Your Parts

Step #2: Install the 555 Chip and Power Lines

Step #3: Install the Resistors

Step #4: Add the Capacitors

Step #5: Install the Remainder of the Parts

Step #6: Experiment: Photodiodes vs. Photoresistors

Conclusion

Steve Hobley

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Light Theremin

Tools

Steps

Step #1: Gather Your Parts

Step #2: Install the 555 Chip and Power Lines

Step #3: Install the Resistors

Step #4: Add the Capacitors

Step #5: Install the Remainder of the Parts

Step #6: Experiment: Photodiodes vs. Photoresistors

Conclusion

Steve Hobley

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