MOUSE
It’s a input device, technical name is PUCK & b’coz
of its shape the term mouse is used.
It is consist of the following components:
A roller ball which signals movement to the
system.
Two buttons ( except Macintosh mouse ) which
comes with only one button for selection.
Cable for connecting mouse to the system.
Connector for interfacing mouse to the system.
Principle of Operation
A small rubber ball protrudes through the base of the
device.
This ball is resting against 2 rollers, one for translating
the X-axis movement & other is for the Y-axis.
The rotation of the rubber ball is transmitted to these
2 rollers, which are positioned at right angles to one
another.
The amount & direction of rotation transmitted to
each roller varies, depending upon the direction of
movement of the mouse.
Each roller is driving a rotary encoder.
A rotary encoder is a small wheel which is
containing perforations.
The light from light emitting diode is passed
through this perforations & is interrupted as the
wheel rotates.
The interrupted light beam is converted into
electrical pulses by means of a photo detector.
These are interpreted by the mouse
controller to determine the amount of
movement in X & Y axis.
This information is transmitted to the PC,
for further processing.
The mouse button control a voltage the
status of this is available on the pins of
mouse connector & is detected by a
software.
Mouse has one, two or three buttons on the
top.
Types of Mouse
Mechanical Mouse :
It moves across a flat surface, a ball ( rubber
ball / rubber covering over a steel ball ) from the
underside of the mouse starts to rotate in the
direction of the movement.
As the ball rotates, it touches & turns 2 rollers
touching the ball inside the mouse.
These rollers are mounted at a 90 degree angle
to each other.
One roller is used for the back & forth
movements of the mouse, which corresponds to
vertical movements of the cursor on screen
while the other roller is used for horizontal
movement of the cursor on the screen.
Each roller is attached to an encoder which is
wheel like structure.
As the roller turns, these encoders rotate with
them.
Two pairs of contact bars touch the small metal
contact points provided on the rims of each of
these encoders.
• Each time a contact bar touches a point,
an electrical signal is generated.
• The signal generated by these rollers are
sent serially to the PC over the mouse’s
tail like cable.
• The mouse driver software converts these
signals into the distance, direction &
speed necessary to move the screen
cursor.
• Also pressing of any of the mouse buttons
sends a signal to the PC.
Optomechanical Mouse :
Basic construction is same as mechanical
mouse.
Only difference is in the sensing circuit i.e. a
combination of LED & photo detectors is used
to sense the distance traveled by the mouse.
2 rollers, each is connected to wheel.
Small openings on the rim of each wheel; as
the wheel rotates, a pair of LED & photo
detectors detect the number of openings
passed between them.
Each opening on the wheel allows the light from
the LED to fall on the photo detectors detect the
number of openings passed between them.
Each opening on the wheel allow the light from the
LED to fall on the photo detector & generate an
electrical signal.
Then these signals are passed to the PC, in turn, it
passes them to mouse driver s/w which then
converts them into distance, direction & speed
required for the movement of the screen cursor.
Optical mouse :
In this mouse, light source & photo
detector is used with a special mouse pad.
When the optical mouse is moved on this
special pad, light from the light source gets
reflected from the pad & special photo
detector inside the mouse detect the
horizontal & vertcal movements.
2 photo detectors – one is for detecting
horizontal movement of cursor & second is
for vertical.
The movement of the cursor on the screen depends
on the number of the signals that is passed to the PC (
using mouse driver) through the wire connected with
the mouse.
Uses of mouse:
As pointing device, objects can be easily dragged &
dropped to another location by means of a mouse.
Useful in making menu selections.
To use scroll bar to scroll windows for page up & down
also.
Due to it’s accuracy, speed, simple to
use & low cost – it is widely used as a
pointing device.
It is also called as “ X-Y position
indicator for a display system”.