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 
-100uf Electrolytic Capacitor 
-1.0uf Disk Capacitor (Marked "104") 
-Photo Resistors 
-1K Resistor (colours: Brown, Black, Red, Gold) 
-a Switch 
-9v battery 
-A speaker 
-A IC proto board to keep it all nice and tidy 
-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
555 Timer: 555 Timer