Intoduction to Keyboards:-
Keyboards are important computer input devices that have been used since the first personal computers arrived. Keyboards are similar to a typerwriter in the sense that they have a similar layout to a typewriter with a few extra keys specific for use on a computer system. Keyboards are typically used to control the computer and interact with them. Keyboards are rectangular in shape and keys on the keyboard include alphabets, digits, special symbols and other keys.Keyboards have a varied number of keys in which standard is 103 or 104 and sometimes as many as 130 keys. Some may even have as less as 90 keys for use in laptops etc.
Types of keyboards and their working:-
The grounds on which keyboards are classified is the switch technology that is used in a particular keyobard. The switch technology is the deciding factor for the reliability of the keyboard and is responsible for keep all the keys working and away from as much wear and tear as posssible. The trends today are to use a combination of the various technologies (which results in a hybrid technology) to improve the performance of the keyboard and decrease its production cost.
(1) Dome-switch keyboard
They are also known as direct-switch keyboards. This is the most used technology in the present day world. These are basically a mix of membrane and mechanical keyboards that are explained later. In this type of a keyboard, there are two circuit board traces (lines) below each of the keys on the keyboard. The keys themselves have a ‘dome’ made of rubber right below them which are coated with a conductive material. When a key is pressed, the dome goes down and shorts the two circuit traces. This comlpetes the whole circuit and then the function of the key that was pressed is executed. It is notable that the traces are usually gold-plated.
The basic advantage of this type of keyboard is that they are very silent in operation owing to the rubber dome. However, the feedback from the keyboard is not much sensitive as the dome is of rubber. They find widespread use in offices and homes and other such places.
(2) Capacitive keyboard
A capacitive keyboard uses a pulse train to convey which key was pressed. In a capacitive keyboard, a key press is ‘felt’ on a pattern printed on the underlying circuit board. When this happens, the capacitance of the pattern changes and it results in a pulse train that is sensed to detect the key pressed and perform the respective operation. This pattern is covered by an insulating film. These keyboards are rugged and damage resistant as well as inexpensive.
(3) Mechanical-switch keyboard
Mechanical keyboards get their name from the way they function. A mechanical keyboard has real switches placed beneath each key on it. When pressed, it translates into an electrical signal that helps perform the required operation. Such keyboards are not uniform when it comes to response time and it differs from model to model. They are more apt for high-end uses.
(4) Hall-effect keyboard
These keyboards do not have any actual switch. Rather, they make use of magnets and ‘Hall effect’. This technology is different in the sense that unlike others, it does not detect keystrokes when a key is pressed. This type of keyboard detects a key press when the key is depressed. When this happens, a magnet moves which is detected by a Hall-effect sensor. Being extremely reliable, highly durable and having a long life, these keyboards are preferrable when there is a crucial application to be dealt with. Examples of use of these keyboards include those in aircraft cockpits and nuclear power plants. Obviously, they are very expensive.
(5) Membrane keyboard
Flat in shape and often used in photocopy machines, membrane keyboards have three layers. The uppermost level is touched or used by the user. The bottom-most layer has some conductive strips corresponding to that on the bottom of the top layer forming a grid when placed together. The middle layer prevents the two from being in contact constantly. Pressing of the top layer by the user leads to a complete circuit between the top and the bottom layers through the middle layer which results in the desire operation being performed. These keyboards do not provide a tactile feeling when pressed and hence a sort of visual or audio signal is used to indicate a keypress to the user.
Keyboards are important computer input devices that have been used since the first personal computers arrived. Keyboards are similar to a typerwriter in the sense that they have a similar layout to a typewriter with a few extra keys specific for use on a computer system. Keyboards are typically used to control the computer and interact with them. Keyboards are rectangular in shape and keys on the keyboard include alphabets, digits, special symbols and other keys.Keyboards have a varied number of keys in which standard is 103 or 104 and sometimes as many as 130 keys. Some may even have as less as 90 keys for use in laptops etc.
Types of keyboards and their working:-
The grounds on which keyboards are classified is the switch technology that is used in a particular keyobard. The switch technology is the deciding factor for the reliability of the keyboard and is responsible for keep all the keys working and away from as much wear and tear as posssible. The trends today are to use a combination of the various technologies (which results in a hybrid technology) to improve the performance of the keyboard and decrease its production cost.
(1) Dome-switch keyboard
They are also known as direct-switch keyboards. This is the most used technology in the present day world. These are basically a mix of membrane and mechanical keyboards that are explained later. In this type of a keyboard, there are two circuit board traces (lines) below each of the keys on the keyboard. The keys themselves have a ‘dome’ made of rubber right below them which are coated with a conductive material. When a key is pressed, the dome goes down and shorts the two circuit traces. This comlpetes the whole circuit and then the function of the key that was pressed is executed. It is notable that the traces are usually gold-plated.
The basic advantage of this type of keyboard is that they are very silent in operation owing to the rubber dome. However, the feedback from the keyboard is not much sensitive as the dome is of rubber. They find widespread use in offices and homes and other such places.
(2) Capacitive keyboard
A capacitive keyboard uses a pulse train to convey which key was pressed. In a capacitive keyboard, a key press is ‘felt’ on a pattern printed on the underlying circuit board. When this happens, the capacitance of the pattern changes and it results in a pulse train that is sensed to detect the key pressed and perform the respective operation. This pattern is covered by an insulating film. These keyboards are rugged and damage resistant as well as inexpensive.
(3) Mechanical-switch keyboard
Mechanical keyboards get their name from the way they function. A mechanical keyboard has real switches placed beneath each key on it. When pressed, it translates into an electrical signal that helps perform the required operation. Such keyboards are not uniform when it comes to response time and it differs from model to model. They are more apt for high-end uses.
(4) Hall-effect keyboard
These keyboards do not have any actual switch. Rather, they make use of magnets and ‘Hall effect’. This technology is different in the sense that unlike others, it does not detect keystrokes when a key is pressed. This type of keyboard detects a key press when the key is depressed. When this happens, a magnet moves which is detected by a Hall-effect sensor. Being extremely reliable, highly durable and having a long life, these keyboards are preferrable when there is a crucial application to be dealt with. Examples of use of these keyboards include those in aircraft cockpits and nuclear power plants. Obviously, they are very expensive.
(5) Membrane keyboard
Flat in shape and often used in photocopy machines, membrane keyboards have three layers. The uppermost level is touched or used by the user. The bottom-most layer has some conductive strips corresponding to that on the bottom of the top layer forming a grid when placed together. The middle layer prevents the two from being in contact constantly. Pressing of the top layer by the user leads to a complete circuit between the top and the bottom layers through the middle layer which results in the desire operation being performed. These keyboards do not provide a tactile feeling when pressed and hence a sort of visual or audio signal is used to indicate a keypress to the user.