Working of Keyboard
Team - 7
Abdul Kalam Ashad.A (13MX01)
Anish Kumar.B (13MX04)
Mohan Raj.T (13MX30)
What is a keyboard?
A Keyboard is an input device that uses an arrangement of
keys or buttons that have letters, numbers or symbols that
when pressed the letter on the keyboard then shows up on the
To display some symbols you need to press combination of
keys then the symbol you desire to display on the screen.
Components of keyboard
Most keyboards have 80 to 110 keys.
The inside of the keyboard is consists of a processor and the printed circuit board.
The numbers and letters on the keyboard are displayed keycaps--these are the
The keys are nested on rubber dome switches that contain carbon in the centre.
This causes each key to be pressed down and come right back up when you do not
press it anymore.
The keyboard connects to the computer via a six pin male plug or a PS/2 plug.
Keyboards and computers work together in a bi-directional format.
These bi-directional lines are the clock line coming from the keyboard and the
data line coming from the computer.
The computer will send a signal to the keyboard through the clock line letting
it know that the line is clear to send. If the line is not clear, the keyboard will
hold the information until the line opens.
Working of keyboard
When the key is pressed a small rubber dome is pressed down it connects
a pair of conducting lines together on the circuit.
It sends an electrical signal to the processor built into the keyboard.
When this signal reaches the processor, It is aware of the pressed key's
location on the keyboard grid.
The location on the grid is compared to a character map stored in the
A match between the location and a defined character is quickly
established, at which point the keyboard transmits the data to the
Multimedia or Gaming keyboard
A device that controls the movement of the cursor or pointer on a display
screen. A mouse is a small object you can roll along a hard, flat surface.
Its name is derived from its shape, which looks a bit like a mouse, its
connecting wire that one can imagine to be the mouse's tail, and the fact that
one must make it scurry along a surface.
Types Of Mouse
Components of Roller Mouse
Switch detects clicks of left mouse button.
Switch for middle button.
Switch for right button.
Old-style connection to PS/2 socket on computer.
Chip turns back-and-forth (analog) mouse
movements into numeric (digital) signals computer
6. X-axis wheel turns when you move mouse left and
7. Y-axis wheel turns when you move mouse up and
8. Heavy rubber wheel.
9. Spring presses rubber ball firmly against X- and Yaxis wheels so they register movements properly.
Working of Roller Mouse
A mouse contains a rotating ball with two rollers held at right angles to each
other which touch the ball. The rollers register the x and y axis movements of
Each roller is attached to an optical encoder, a disc which has gaps in its surface.
The rotation of the encoder interrupts two beams of light between the LEDs and
These pulses of light are fed to the computer and are used to determine the speed
and direction of the mouse's movement.
When the mouse move, or press or release mouse buttons, the mouse circuitry
sends data to the host (PC), indicating what state changes have occurred since
the previous state indication.
Components of Optical Mouse
1. An LED at the back generates red light
and shines it horizontally, from the back of
the mouse toward the front (from the left
to the right of this photo).
2. A plastic prism bends (refracts) the light
from the LED at an angle, down onto the
3. A light-detector chip measures light
reflected back up from the desk,
converting the analog movements of your
hand into digital signals that can be sent to
4. The scroll wheel at the front of the mouse is mounted on a switch mechanism
that detects both how much it's rotated and whether you've pressed it (it
functions like the central button of a conventional mouse). Rotations of the
scroll wheel can be detected in a variety of different ways. Some mice use
potentiometers (broadly, variable resistors), similar to the volume control on a
radio but able to turn around multiple times. Others use various kinds of rotary
switches or optical (rotary) encoders to convert analog wheel movements to
5. A microswitch detects when you press the right mouse button. There's an
identical switch on the other side to detect the left mouse button.
6. The USB or PS/2 cable connection carries digital information from the mouse to
Working of Optical Mouse
The LED produces a red light that is emitted horizontally.
A plastic prism refracts the light onto a surface.
Light reflected back up from the desk is detected by a light-detector
chip which converts analog movement into digital signal.
When you press the right mouse button or left mouse button the micro
chip detects and transmit the digital signal to computer.
A touchpad is a simple, easy and reasonable pointing device.
It allows the users to drag their fingers along in the direction they want the
mouse pointer to go.
Working of Touchpad
Its surface tracks the motions and pressure of a finger and correlates it to the
There are two common technologies that enable touchpads to work , capacitance
Capacitance is the most common method and enables the touchpad to hold an
It creates two arrays, one vertical and one horizontal, and when your finger
touches a spot on the touchpad, it locates the coordinates of that location.
The pad sensors then convert the location from the touchpad to the location on
Most newer touchpads also have a function for scrolling, just as a middle mouse
There is a location on the touchpad called a hot spot that enables this function.