Light Theremin


Introduction: Light Theremin

The Light Theremin is a simple to build instrument that uses light and shadows to create sound. The theremin circuit used nomally for these insruments are quite complex, this one however is as simple as a 555 Timer IC and some basic components from your scrap box. so with out any more delay...Lets get started!

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Step 1: Materials

Your materials list is really quite short. You will need the following parts...
Please note that the quantity of each part is in the [ ].

-555 Timer IC [1]
-100uf Electrolytic Capacitor [1]
-1.0uf Disk Capacitor (Marked "104") [2]
-Photo Resistors [4]
-1K Resistor (colours: Brown, Black, Red, Gold) [1]
-a Switch [1]
-9v battery [1]
-A speaker [1]
-A IC proto board to keep it all nice and tidy [1]
-Some machine screws and nuts to hold down the board (optional)

Step 2: The Circuit

Following the schematic provided below. solder all components to the correct pins on the timer or in the correct holes on the proto board. The switch and four photo resistors will need to be mounted out side the box through hole's; so I suggest you solder leads going to and from it. The same rule applies for the battery pack, only you will or might want to secure this with some hot glue or super glue just to keep it in place. Do not solder the photo resistors yet they will be covered in a different step!

R1: 1K Resistor
R2,R3,R4,R5: Photo Resistors
C3: 100uf Capacitor
C1,C2: 1.0uf Capacitors
Spk1: Speaker
555 Timer: 555 Timer
Sw1: Switch

Step 3: The Case

You will of course need a box or container to hold the circuit. I went to Dollarama and picked up a small box from the craft asile. The boxes them selves are made of pine and thus can be painted or cut very easily. Be sure to find a box that will house you're circuit, but still offer lots of space. I gave my box a coat of "coffee"  colored stain to make it look old; the color alone is totality up to you. After the paint or stain has dried drill four holes for the photo resistors, one for the switch, and a 1/4" hole on the side with the speaker. For the switch and photo resistors the hole size will vary by the size of your components. Ta-Da! You're box is complete! now all thats left to do is to stuff it with the circuit.

Step 4: The Photo Resistor Array

The design is totally up to you. I just put all four in four separate corners. To do so you will have to use a drill bit that comes close to the size of your photo resistors. Then with the holes cut, place them in, and super glue them. Now solder the photo resistors as shown in the picture below. Now attach three wires, one to the left, one on the center two (the two photo resistor leads do get soldered together), and one to the right. Then lastly solder the other end of the wires to the correct pins as shown on the schematic.

Step 5: "Stuffing" the Box

Simply take your completed circuit and all other components attached and drop it in. Then armed with super glue, secure any loose items. Where you drilled the 1/4" hole on the side earlier, center the speker over it and super glue it in place. Then Mount the completed circuit board in a spot where it can sit comfortably and allow the box to open and close fully. Once you found that spot use some hot glue or screws to secure it, repeat this for the battery pack as well. Close the box and flip the switch...

Step 6: Using the L.T.

As you can see the sound the circuit makes will change when you wave your hand over the photo resistors or change the lighting in the room. Try different motions to produce different sounds, I observed that if you shake one hand really fast over one or two of the photo resistors the L.T. will give to a erie shaky sound. Or if you more your hand like a wave over one or all four photo resistors you'll get a wavy sound (no kidding!). Most of the sounds it produces sound like they are from a cheesy horror flick from the 60's or 70's! The total amount of sounds you can produce is only limited by your hands and lighting! Now sit down (well standing might be better) and enjoy!

You can see a HD video of the L.T. at this link:

Or watch the youtube video here...



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    62 Discussions

    I am really sorry but I have one more question. I hooked it all up and it didn't work, so I moved C1 between 1 and 2 and the first two resistors work, but the other two don't, what can I do to fix this problem?

    1 reply

    I heard some people have had this problem before. As far as I can say it can be a bad spot on the bread board or your using the wrong components. However one user had a issue like this awhile back, this is his message:

    I tested it on a breadboard, didn't work until i removed C2 and put it between pins 1 and 2. But then it worked like you described. Nice casing btw.

    I'd try that and see if it works. If not I suggest you try putting in 100k resistors where the light dependent resistors are and see if you get any results. I hope you get this project working, all the best. 



    6 months ago

    hello.. i just made this and 2 of the photoresistor works but others are not.. is it possible because of different type or anything? they had different pattern.. 2 thinner and 2 thicker.. please help. Thanks :)

    I made this and was able to get sound, but just barely. It was almost inaudible. Do you have any suggestions?

    Only change I'd make to the schematic diagram is jumper wire between pins 2 and 7 should be between pins 2 and 6.
    Great article. Thanks!

    hola tengo una duda el capacitor de 100 uf exactamente omo esta conectado para proto no entiendo bien ya lo hice tres y no me funciona no se que pueda estar mal ya lo revise todo ayuda que puede ser lo mas común que este fallando y como resolverlo

    Step 2 is just soldering the circuit. I skipped over that bit because there is really isn't too much to get into. Next time around, I'll be sure to add some more pictures and captions.


    thanks for posting this great idea but i have a question
    how can i add a jack female output and a volume potenciometer?
    please it is very important to me.

    1 reply

    The female output can be put in place of the speaker, or in parallel to the speaker. As for volume control I am sorry, I cant help you there.


    So where did you get your 1.0uf Disk Capacitor? I looked on the Radio Shack site and I couldn't find one, and I don't want to get a $30-something box with a bunch of capacitors I won't use.

    1 reply

    $30? Really? Wow, I just pulled mine out of a radio. I could have sworn they had them in an assorted pack for less than $7.

    Hello! I tried to make this light theremin but i didn't succeed to do that. I have just one question for you, what kind of photo resistor did you use? 5k-10k? Please help me if you can because i should finish it until thursday:(

    4 replies

    I am pretty sure they are 10K. However I have no way to truly test out their resistance. Like I said I just bought a pack of them from Radio Shack (The Source).

    No size doesn't matter. It just means your larger ones will be a bit more sensitive as they can gather more light than the smaller ones. If anything it means you'll just get more funky tunes from it.