Group 3 - Sony Walkman

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Main Function

The main function of the CD player is to read the data on a compact disk according to the desires of the user, then output the data through headphones in the form of sound. The main function includes subfunctions such as spinning the disk, moving the optical sensor to follow the disk, check battery power, and apply play settings.

View from Top

Human Machine Interface (HMI)

Close up of play buttons
  • CD function buttons
    • Play
    • Stop
    • Forward
    • Back
  • Hold button: Prevents buttons player from registering button presses when not desired
Close up of LCD screen
  • LCD Screen: Displays the following information:
    • Play mode (repeat, shuffle, etc)
    • Bass level
    • Track number and time elapsed
    • Volume buttons


  • Optical sensor
    • Reads the data from the disk
    • Senses the end of the disk
    • Measures how close the laser is to the data track it is following
  • Battery system
    • Checks to see the amount of battery power left


Spindle motor turned on it side

Parts of the device that are a source of motion, such as motors

  • Disk spinning motor (spindle motor)
    • Spins a shaft that is responsible for spinning the disk to be read
    • Must decrease speed of rotation as laser moves outward
  • Optical sensor motor
    • Moves optical sensor radially to follow tracks on disk
    • Must be able to follow tracks precisely
  • Speaker movements
    • Produce sound in headphones

Power Supply - Acuation

Batteries in CD player
    • 2 AA batteries
    • Has the capability to plug into DC converter and use external power supply
    • Power enters circuit board where appropriate amount of power is eventually distributed to both motors and other electronic components
    • Powers LCD screen
    • Motors spin the CD and move the optical sensor

Power Conversion

This includes the components that are responsible for a change of force or speed (mechanical advantage). In the CD player, there is electrical power conversion and mechanical power conversion.

Optical sensor power conversion components
  • The spindle motor (to rotate disk) does not have a mechanical power conversion, but does have an electrical one
  • The optical sensor is moved by a track that has extremely high precision in position that comes from a gear system
  • Electrical components are used to supply appropriate amounts of power to motors, LCD screen, and microprocessor

Motion Conversion

Only one major motion conversion component was found in the CD player.

  • Rotation gear motion is converted to linear motion of optical sensor by turning a threaded rod that translates the sensor along itself

Optical sensor


Mount point for microprocessor
  • The microprocessor on the circuit board
    • Must decide how to adjust the optical sensor’s position so that is continues to track the appropriate line on the CD
    • Takes input from user and applies appropriate programs – such as play, stop, forward, back, increase and decrease in volume
    • Applies type of play program – such as shuffle, repeat, play one track, etc
    • Shuts off motors when end of CD is reached
    • Monitors remaining amount of battery power