How CDs Work Stefanie Xenakis 2005 History of the CD * Introduced in 1980s *Patented by Philip and SONY *Goal 1: Large storage space *Goal2: Perfect Copies CD Material *Mostly polycarbonate plastic *Impressed with microscopic bumps *Bumps arranged on CD as a spiral *Order of materials: 1) Polycarbonate plastic 2)Thin reflective aluminum layer 3) Acrylic layer for protection CD Material (cont) CD Spiral *Starts from inside and goes to outside *Data track 0.5microns wide *1 micron= 1 millionth mm *1.6microns separate one track from each other other *Stretched spiral is 3 miles CD Spiral (cont...) CD Bumps/Pits *Minimum.83microns long *125 nanometers high *Nanometer=1 billionth of a meter *Pits from our view on aluminum side *Bumps at lasers view CD Components *CD player reads data *Disc drive has 3 important components that each have a job 1)Drive motor- spins disc( rpm) 1st Important Component 2)Laser/lens system-focus in on and reads bumps 2nd Important Component 3)Tracking system-aligns laser to follow track 3rd Important Component Laser Focus *Passes plastic layer, reads bumps *Reflects off aluminum to receptor AKA optic-electronic device *Receptor detects changes in reflectivity *Reflectivity on bumps is read differently than the CD lands *Reads 0s and 1s AKA digital signal *Digital signal enters DAC *DAC=digital analouge converter Laser Focus (cont) *DAC turns digital signal into sound waves *Sound waves go through AMP to boost sound through speakers *AMP=amplifier Before the CD Floppies Records *Simpler version of CD *Instead of laser theres a needle *Needle called a stylus *Stylus held in place by arm *Spirals are visible to eye *Amplified through speakers like CD *speed must be exact * Too slow=pitch drops;Too fast=pitch rises Records (cont) Bibliography How CDs Work. May 3, Tsun-Hui, Yao Tang. Conpact Discs(CDs). May 3, 2005. Bibliography What is a CD. May 3, Turntable History. May 3, 2005. About Me My name is Stefanie Xenakis and I am thirteen years old. I am Greek and have been to Greece about 7 times. My birthday is October 28, 1991 and my favorite animal is a monkey. I have three dogs and one cat. All of my dogs are poodles. There names are Tina, Rocky, and Lucy. I play the flute and my favorite sports are volleyball and basketball.