Post on 02-Apr-2018
7/27/2019 T11 - Keyboard & Mouse
1/17
Keyboard
1
Mouse
7/27/2019 T11 - Keyboard & Mouse
2/17
Keyboard
One of the most basic system components is the
keyboard, which is the primary input device. It is used for
entering commands and data into the system.
The primary keyboard types are as follows: 101-key Enhanced keyboard
104-key Windows keyboard
83-key PC and XT keyboard (obsolete)
84-key AT keyboard (obsolete)
2
7/27/2019 T11 - Keyboard & Mouse
3/17
Keyswitch Design
Todays keyboards use any one of several switch types
to create the action for each key. Most keyboards use a
variation of the mechanical keyswitch. A mechanical
keyswitch relies on a mechanical momentary contact-
type switch to make the electrical contact that forms acircuit. Some high-end keyboards use a more
sophisticated design that relies on capacitive switches.
The most common type of keyswitch is the mechanical
type, available in the following variations: Pure mechanical
Foam element
Rubber dome
Membrane (most common)3
7/27/2019 T11 - Keyboard & Mouse
4/17
Membrane Keyswitch
4
7/27/2019 T11 - Keyboard & Mouse
5/17
Keyboard Interface
A keyboard consists of a set of switches mounted in a gridor an array called the key matrix. When a switch is
pressed, a processor in the keyboard identifies which key
is pressed. The keyboard processor can even handle
multiple keypresses at the same time. A 16-byte hardwarebuffer in the keyboard can handle rapid or multiple
keypresses, passing each one to the system in
succession.
The keyboard send signal to the PC via onr of the
following interface:
AT Serial (DIN 5) (No longer use)
PS/2
USB
5
7/27/2019 T11 - Keyboard & Mouse
6/17
Keyboard Connector
6
7/27/2019 T11 - Keyboard & Mouse
7/17
Keyboard Troubleshooting
Keyboard errors are usually caused by two simpleproblems. Other more difficult, intermittent problems can
arise, but they are much less common. The most frequent
problems are as follows:
Defective cables Stuck keys
Defective cables are easy to spot if the failure is not
intermittent. If the keyboard stops working altogether or
every keystroke results in an error or incorrect character,
the cable is likely the culprit. Troubleshooting is simple,
replace the keyboard with a known working keyboard to
verify whether the problem still exists. If it does, the
problem must be elsewhere.
7
7/27/2019 T11 - Keyboard & Mouse
8/17
Keyboard Maintenance
One of the best ways to keep a keyboard in top conditionis periodic cleaning. As preventive maintenance, you
should vacuum the keyboard monthly. You also can use
canned compressed air to blow the dust and dirt out
instead of using a vacuum. Before you dust a keyboardwith the compressed air, turn the keyboard upside down
so that the dirt and dust collected inside can fall out.
On all keyboards, each keycap is removable, which can
be handy if a key sticks. For example, a common problem
is a key that does not work every time you press it. This
problem usually results from dirt collecting under the key.
Remove the cap, spray some compressed air into the
space under the cap to dislodge the dirt. Then replace the
cap and check the action of the key. 8
7/27/2019 T11 - Keyboard & Mouse
9/17
Keyboard Maintenance
9
7/27/2019 T11 - Keyboard & Mouse
10/17
Mouse
A standard mouse consists of several components: A housing that you hold in your hand and move around on your
desktop
A method of transmitting movement to the system: either ball/roller
or optical sensors
Buttons (two or more, and often a wheel or toggle switch) for
making selections
An interface for connecting the mouse to the system; conventional
mice use a wire and connector, whereas wireless mice use a
radio-frequency or infrared transceiver in both the mouse and a
separate unit connected to the computer to interface the mouse to
the computer
10
7/27/2019 T11 - Keyboard & Mouse
11/17
Mouse
Two types of commonly used mouse : Mechanical mouse
the bottom of the housing contains a small, rubber ball that rolls as you move
the mouse across the tabletop. The movements of this rubber ball are
translated into electrical signals transmitted to the computer across the cable.
Need to clean regularly
Optical mouse (most common)
using an optoelectronic sensor to take successive images of the surface on
which the mouse operates. The mouse then detect relative motion on a wide
variety of surfaces, translating the movement of the mouse into the movement
of the cursor.
Laser mouse Laser mouse works like optical mouse. The only different is that it uses laser
light instead of LED. The use of laser enable this type of mouse to work in most
of the surfaces including glass.
11
7/27/2019 T11 - Keyboard & Mouse
12/17
Mechanical Mouse
12
Operating a mechanical
mouse.
1. Moving the mouse turns the
ball.
2. X and Y rollers grip the balland transfer movement.
3. Optical encoding disks include
light holes.
4. Infrared LEDs shine through
the disks.
5. Sensors gather light pulses to
convert to X and Y velocities.
7/27/2019 T11 - Keyboard & Mouse
13/17
Optical Mouse
13
7/27/2019 T11 - Keyboard & Mouse
14/17
Mouse Interface
The connector used to attach your mouse to the systemdepends on the type of interface you are using. Mice are
most commonly connected to your computer through the
following interfaces:
Serial interface (obsolete) Dedicated motherboard (PS/2) mouse port
USB port
Bluetooth or other wireless connection
14
7/27/2019 T11 - Keyboard & Mouse
15/17
Wireless Keyboard/Mouse
The three major technologies used by wireless inputdevices are as follows:
Infrared (IR)
Proprietary radio frequency (RF)
Bluetooth All three technologies use a transceiver connected to the
PS/2 or USB ports on the computer.
The transceiver receives signals from the transceiver built
in to the mouse or keyboard. These devices requirebatteries to function; therefore, a common cause of
wireless device failure is battery run-down.
15
7/27/2019 T11 - Keyboard & Mouse
16/17
Wireless Keyboard/Mouse
IR devices have a relatively short range (12 ft. maximum)and must have a clear line-of-sight between the input
device and transceiver.
Most wireless mouse/keyboard nowadays are using either
RF or Bluetooth. Both technologies do not require line-of-sight but RF has very short range (6 ft.).
16
7/27/2019 T11 - Keyboard & Mouse
17/17
Other Input Devices
Microphone (sound input) Webcam (video input)
Touch screen
Joystick / game pad
17