Light Theremin

By Steve Hobley
Category: Music
Time Required: 1 hour
Difficulty: Easy

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.

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Steps

Step #1: Gather Your Parts

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.

11 Responses to Light Theremin

Steve Hobley on November 3rd, 2011 at 2:36 am said:

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

Steve

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Steven Dayton on November 16th, 2011 at 2:32 am said:

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

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Nick Normal on November 29th, 2011 at 5:45 pm said:

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

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Leif Burrow on November 30th, 2011 at 4:05 am said:

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).

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Jake Spurlock on January 15th, 2012 at 2:12 am said:

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…

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Nick Normal on February 26th, 2012 at 2:09 am said:

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.

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Nick Normal on March 1st, 2012 at 4:53 pm said:

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

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Nick Normal on July 19th, 2012 at 4:48 pm said:

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

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Nick Normal on July 19th, 2012 at 4:49 pm said:

Congratulations! If you have photos, please send them to weekendprojects@makezine.com – thanks!

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Nick Normal on July 19th, 2012 at 4:49 pm said:

Interesting hack – please send photos to weekendprojects@makezine.com – thanks!

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Ryan Hammond on April 6th, 2013 at 3:52 pm said:

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…

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