How Do CD Players Work?

CD players are electronic devices that play compact discs (CDs). A CD player can be found at home, in the car, in a computer, and there are even portable devics. If a CD player could be taken back to the Dark Ages. it would surely be marked as witchcraft.

Difficulty: Moderately Easy

Instructions

The Compact Disc

1. To understand how the compact disc player works, you must first understand what a CD is. A CD is an optical disc that is only 1.2 mm thick. CDs have been on the market ever since 1982. They were first an expansion of laserdisc technology that started a few years earlier.

2. The bottom of a CD contains a layer of polycarbonate plastic with bumps in it. Then, on top of the plastic, is a thin layer of aluminum to cover the tiny bumps. Aluminum is used to make the CD reflective for the laser to read. A thin layer of acrylic is then placed on the CD to protect the aluminum. A label is then placed on the acryllic. Those materials, combined in that fashion, make a CD.

3. The tiny bumps in the polycarbonate plastic are arranged in a spiral of data. The spiral is extremely long. If it were stretched out it would be 3.5 miles long, but only half of a millionth of a meter wide. These bumps contain the data that the music or information that's in the CD.

The CD Player

4. The CD player reads the CD and plays back the information. They have been around as long as CDs have. The components in a CD player have to be extremely precise to read the miniscule bumps on a CD. There are three main components: a laser, drive motor, and a tracker.

5. The CD player casing doe not have to be as complicated. All it has to do is house the components and the CD. The casing can come in many different forms. The most commonly used is a single-disc CD player. However, a CD player can have hundreds of CDs stored inside it with a mechanism to go to which one the listener desires.

6. The drive motor of the CD player spins the disc. It spins the disc at a constant speed so the laser can read the bumps and the music can be heard without speeding up or slowing down.

7. The laser assembly shoots a laser at the CD, which is then reflected by the aluminum into a lens. The lens then sends a digital signal to the digital-to-analog converter (DAC). The DAC sends the sound to amplifier so it can be heard on the speakers connected to the CD player.

8. The tracker's main job is to move the laser along the bumps to find the desirec CD track. The beginning of each CD track is encoded so the tracker can find it.