Instructables
In this instructable, I will show you how to make a sound generator using 6 discrete electronic components. While making this sound generator, students will learn basic concepts about wave such as frequency, period, and duty cycle. Also, students can learn the function of some basic electronic components such as diode, IR transmitter/detector. I try to avoid using solder when I design this instructable. Unlike other sound generator, it does not require any transistor/IC chip. It will be easier for students to make this little toy.
If you like this instructable, please vote in Hack it contest and DIY audio contest.

Basic idea:

The block diagram is shown below (block diagram). The motor is rotating in constant speed. There are dark (non transparent) and transparent portions on the CD. When the dark portion of the CD is between the IR emitter/detector, the resistance of the detector will be high, and the voltage across the speaker will be low. When the transparent portion of the CD is between the IR emitter/detector, the detector receives the signal from emitter, and its resistance will be low, so the voltage across the speaker will be high. The voltage signal across the speaker is a square wave. By varying the speed of the motor and dark/transparent portions on CD, the frequency of square waves signal changes. You can hear the changes from the speaker.

 
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Step 1: BOM

BOM:

Two 1.5V AA battery and battery holder (Radioshack Model: 270-398)

One 3V DC motor and CD holder (Search “Spindle Motor for DVD CD Player” in Amazon)

A pair of Infrared LED Emitter and Detector (Radioshack Model: 276-142)

Two 1N4001 diodes (Radioshack Model: 1N4001) (optional)

One 22ohm and one 68ohm resistor (Radioshack Model: 271-312)

One 12-Position European-Style Mini Terminal Strip (Radioshack Model: 274-680)

Hookup wires (Radioshack)

Small speaker (Radioshack)

M3 screws, M3 nuts, ¾ inch thick plastic block, 1/16 inch thick X ¾ inch aluminum angle, ½ inch X ½ inch square plastic block, three 8mm M3 screw spacer, double-sided tapes (McMaster)

poofrabbit2 years ago
Congratulations on being a finalist in the DIY Audio Contest!! Good luck to you!
poofrabbit2 years ago
Hey congratulations on being a finalist in the hack it contest! Good luck to you!
bbsbb (author)  poofrabbit2 years ago
Thank you very much.
drjai072 years ago
nice

love the project!
Jaques Dudon did this years ago, and even designed very beautiful complex occulting wheels which resulted in multiple wave forms that sounded amazing. I duplicated his experiments and thoroughly enjoyed them! Have a look at his works here. You can translate the page into english from the menu on the left side... Thanks for this instructable!
bbsbb (author)  stringstretcher2 years ago
wow. thanks for the information. I did not know someone else did such beautiful job before.
DIVYA GARG2 years ago
very nice......
Tomdf2 years ago
What a creative concept! I didn't know you could just wash a CD off like that.
One could totally encode things on the disk, like morse code or songs.
Good suff!
sonicase2 years ago
hah, not bad