Peripherals (1)


CD Drive

Rollerball Mouse

Mice first appeared around 1968. The most common mouse is the rollerball mouse, but how is the movement of your hand translated into cursor movement on the screen?

Mice work in a very simple manner. A ball inside the mouse touches the mousepad and rolls whenever the mouse is moved.

Inside the mouse are two spindles touching the ball. The spindles are angled at 90 degrees to each other.

As the ball moves, one or both spindles are also moved. One spindle is responsible for detecting movement in the X direction and the other in the Y direction.

Each of the spindles is connected to a disk at the end. A series of holes or notches run round it. On one side of this disk is an infrared LED, and on the other an infrared photodetector. As the disk rotates, the holes break the light and you get pulses of light.

An on-board processor converts these pulses of light into a form that can be understood by the computer. This optomechanical arrangement is used by most mice.

Nevertheless, the days of rollerball mice are on the decline.






Installing a Harddisk Drive