Introduction: Light Theremin

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of "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.

Picture of 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...


braintrain (author)2012-02-21

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?

TXTCLA55 (author)braintrain2012-02-22

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. 


jensenr30 (author)2011-03-01

Looks cool! I'm subbed!

luudvig (author)2010-04-07

Thanks, I built it and it works great!!

BimaW (author)2018-01-02

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 :)

KMSherni (author)2015-05-25

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

KMSherni (author)2015-05-25

pvoss1 (author)2013-04-17

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!

tedixxx (author)2012-06-18

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

Leeleelilac (author)2012-04-24

I wish the instructions on step one were more specific

Leeleelilac (author)Leeleelilac2012-04-24

I mean step 2. Maybe more of a step by step way of putting all the pieces together

TXTCLA55 (author)Leeleelilac2012-04-26

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.


adairo16 (author)2012-04-23

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.

TXTCLA55 (author)adairo162012-04-26

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.


darockerj (author)2012-04-26

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.

TXTCLA55 (author)darockerj2012-04-26

$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.

sevusz (author)2012-04-03

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:(

TXTCLA55 (author)sevusz2012-04-03

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).

TXTCLA55 (author)2012-02-16

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.


braintrain (author)TXTCLA552012-02-16

Thanks so much. BTW great instructable.

TXTCLA55 (author)braintrain2012-02-16

Glad to have helped, and thanks.


braintrain (author)2012-02-15

I bought a AVX 1.0uf 35v thru-hole tantalum capacitor radial 10%. Will this work instead of a 1.0uf disk capacitor? I also bought an audio jack instead of a speaker, so I can get it louder. Please respond because this is my science class instrument. I will get a grade for this. I am also asking if you can play any simple songs like twinkle twinkle little star or something along those lines.

TXTCLA55 (author)braintrain2012-02-16

I cant say for sure if it will or not. Really the best way is to just hook it up and see what happens. I do believe that radio shack (or the source) sells a packet of assorted capacitors, you might be able to find one in there. Hope this helps.


braintrain (author)TXTCLA552012-02-16

Thank you,
One other question, I just got the photo receptors today from radio shack, and I was wondering if it matters what size the photo receptors are. They came in a package of five, but all different sizes.

bibbibbib (author)2011-09-03

is the voltage rating for the 100uf capacitor 25v? or something else

TXTCLA55 (author)bibbibbib2011-09-03

The voltage my capacitor says is 16v at 100uf.

blinkyblinky (author)2011-07-09

104 capacitors are 0.1uF!

TXTCLA55 (author)blinkyblinky2011-07-09

Thanks, but apparently it works with both.

mgrc (author)2010-03-07

Mine won't work...I put in on a breadboard and re-checked everything twice. Does it matter if 2 of the photorisistors are slightly different sizes? Are they polarized (+, -). I also tried what datenkrieger said and removed C2 and put in between pins 1 and 2, but still nothing. I'm using an adjustable power supply set to 9v, so it's not that. my 555 timer said LM 555CN. I'm using a 100uf cap and two caps marked '104', just like you said. The speaker is marked at 8 ohms and it makes crackly sounds when I hook it straight up to a AA battery, so that works. I'll ask my dad, but do you have any ideas?

mgrc (author)mgrc2010-03-07

Nevermind, I got it. It turned out I had a bad spot on the breadboard, so I just moved everything over a bit, and still using Datenkrieger's idea, it works. I might need a better speaker because it really sucks with low pitch, it just makes ticking noise. Has anyone wired it up so a pair of photoresistors changes the pitch and the other pair changes the volume? It would be like a radio-wave theremin. Good instructable BTW. Thanks

TXTCLA55 (author)mgrc2010-03-08
Sorry to hear you have been having some problems, but I am also glad to hear that you managed to fix the issues as well. I think the problem some of you may be having with the capacitors is that some 555 timers may require different connections (probably due the manufactures design) in any case this should happen to any one in the future I would suggest trying this solution first before commenting. As for your issue with the sound (pitch and tone) the photo resistors should work like that already if not try using a fresh battery and the volume should improve. Hope this helps!
raisin_brain747 (author)2010-02-27

where can we get all the materials?

TXTCLA55 (author)raisin_brain7472010-02-27

You can get most of the materials from radio shack or the source as it has come to be known. Or you can get the components from online sellers like thats probably the cheaper option, however if you still cant find some of the components just rip open a old radio and your more than likely to find what you need sooner or later. Hope this helps you in your project(s) let me know if you are still having trouble location the components.

GreenD (author)2010-02-19

 I'm assuming light allows for current to pass through the photoresistors?

I wonder if there is a way to make the sound more pleasing...?

TXTCLA55 (author)GreenD2010-02-22

I don't know about that, I prefer the electronic whine of the device so I never really went much further to improve it; but if you can figure something out send me a message!

raisin_brain747 (author)2010-02-22

Would it be possible to add an oscillator and a pot. to control said osc.

TXTCLA55 (author)raisin_brain7472010-02-22

Yes. My first model worked like that, but I wanted to add something special, so instead I used photo resistors to do the job. 

MottGia1 (author)2009-11-24

Hey, you said we needed 2 "0.1uf Disk Cpacitor" but on both the next images you say we need 1.0uf capacitors, which ones do we really need then?

TXTCLA55 (author)MottGia12009-11-24

Opps my mistake. Its a 1.0uf capacitor. they should have a "104" marked on the side. Sorry for the confusion, its corrected now.

edspegeddd (author)TXTCLA552010-01-26

i'm confused about the capacitors as well.  I bought 0.1uf disc capacitors because they read "104Z" on the side, and look exactly like the ones in your picture.  the electronics store did not know of any 1.0uf capacitor with '104' marking... just the 0.1uf.  anyway, my circuit works it's just the volume output is very very low.  you can barely hear it.  any ideas?

TXTCLA55 (author)edspegeddd2010-02-03

Try using a new battery I had this problem to. The capacitors you are using could also be the ones to blame. If you cannot hear it with the new 9V battery I would suggest finding new capacitors; try opening a radio there will be lots in side.  Hope this helps!

MottGia1 (author)TXTCLA552010-01-27

Thank you

kappish028 (author)2010-02-01

oh i see.hehehe!!! thanks your the best! before i forgot can i see the back of this light theremin that you made if that is possible but if not its ok. last question can i bend this theremin?

TXTCLA55 (author)kappish0282010-02-03

There's not much to the back of it...just the wood the box is made of and the hinges for the lid. And you may do what ever you please with this circuit expect mass produce it and sell it on a consumer market! Hope that answers your questions.

kappish028 (author)2010-01-15

can i use any 555 timer? what kind of 555 timer did you use? sorry i dont know anything about electronics kindly help me thanks.i saw that there are LM555 and NC or NE 555 timers what is the differences in those timers?thanks!

TXTCLA55 (author)kappish0282010-01-16

Nope, there is no difference in the timers you have/saw. The letters simple stand for the company's model, not the type. All of those you listed above will work.

luudvig (author)2009-12-16

Does it matter how many volts the capacitor is on?

TXTCLA55 (author)luudvig2009-12-16

yes, in this circuit it does. Capacitors are essentially store houses, imagine it slowly filling up and then all at once emptying out. This is how capacitors work, they slowly build up electricity then all at once, lets it all go. They are normally used to stabilize the current in a circuit. In short you should probably use the ones I did or find something really close to it. Hope this helps!

blindrulz (author)2009-08-09

hey guyz comment this simply like wat is did

Laogeodritt (author)2009-07-24

Hello, This looks like an interesting project, thanks for posting. I have a few questions regarding the light theremin: Does it allow controlling the amplitude of the output with one control and frequency with another (as with the real theremin)? From what I understand of the IC and this circuit, it doesn't seem so... If not, do I understand the 555's specs correctly in that the amplitude of the signal is proportional to the input voltage, and so I could implement this feature by varying the voltage at the +V pin? What is the max voltage this puts out? Is there any risk of damaging drivers with an impedance in the 8-16 ohm range by hooking them up directly? (Or, in other words: what considerations should I make regarding the speakers - impedance, etc. - or the output to prevent damaging them?) Thanks, Laogeodritt

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