Computer Mouse

Computer Mouse

The Computer Mouse

The computer mouse first came about in the early 1980's. The idea

being that the movement from the users hand could be turned into

signals that the computer could read moving the cursor around and also

allowing the buttons to function when pressed.

Today there are a few different types of computer mice on the market.

These being the mice that use the traditional tracking ball, the

optical mouse and the mouse that has no physical connection to the

computer.

The most common mouse found near a computer today is the traditional

mouse that uses the tracking ball. This is the same method as was used

when the mouse was first released in the 1980's. The track ball inside

the mouse touches the desk when it is moved. When the ball moves the

motion is detected by two perpendicular axis, one which detects x axis

directional motion and the other y-axis direction motion.

Tracking Ball Perpendicular axis motion detectors

Hole in which track ball would sit

The diagrams above show the tracking ball and the hole in which the

tracking ball sits. You can see the x and y axis motion detectors of

which the y-axis detector lies 90° from the x-axis detector. These

motion detectors are also known as rollers. When the mouse is in use

the tracking ball moves moving one or both of the rollers. Each roller

is connected to a shaft, which spins a disc. The disc has holes in it

and next to the disc is an infrared LED and an infrared sensor. As the

disc spins the hole in the disc breaks the beams of light generated by

the LED and the sensor picks up these pulses of light. The speed of

the pulses is related to how far the mouse has travelled. If the disc

spins faster the further the mouse would have travelled. A diagram

below shows one of these discs.

LED light LED sensor

Disc Shaft

So from the mouse which is mechanical the movement and distance can be

measured. This all starts at the track ball as explain above and ends

at the transducers, which send the information to the computer. Once

the distance, movement and direction data is gathered from the

physical and the pulses of light are picked up from the infrared

sensor the information is sent to the transducers. These transducers

translate the information into electrical signals. These signals are

translated into binary and sent to the computer. The computer will

understand the binary data thus moving the cursor on the screen as

appropriate. This shows that both physical and electrical operations