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!

Don't forget to visit my site:
http://www.wix.com/SimpleCircuits/Simple-Circuits

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:

http://www.flickr.com/photos/14462918@N03/3502046867/

Or watch the youtube video here...