Technology: How does a keyboard work?

We use the keyboard almost every day in our life but does anybody know how it actually works?

A standard keyboard consists of a small processor and a simple circuit which carries the information to your system. A large part of the keyboard is occupied by the key matrix, which is nothing but a conducting grid whch is placed beneath the keys of your keyboard. The basic principle of operation of the keyboard is the same as that of the switch.

When the switch is closed a small amount of current flows through the circuit. The processor now detects this current. Now the processor tracks the location of the origin of the signal in the grid. This location is compared on the key matrix to the character map in its ROM. The character map is nothing but a table which tells the processor the character which is to be taken as an input when a particular key on the keyboard is pressed. It also tells the processor about the exact position of each key.

For example, if the ‘shift’ key as well as ‘q’ key are pressed together, the character map tells the processor to accept capital letter ‘Q’ as the input. Whereas, if only ‘q’ key is pressed, the character map tells the processor to take small letter ‘q’ as the input.

Capacitive switch technology: Various switch technologies are used in different types of keyboards. The most common technology which is used on a wider scale is the capacitive switch technology. It is considered to be non-mechanical since the switches do not complete the circuit here as in the previous resistive technology case. In a capacitive switch, current flows constantly hrough all parts of the key matrix.

Each key has a spring and a tiny plate attached to the bottom. When a key is pressed, the two plates come close to each other. Due to the variation in the distance between the two plates, a small change in capacitance takes place, which in turn changes the current flowing through the key matrix. The processor in the keyboard now detects this change and acknowledges it as a key press for that particular location to the computer. Though capacitive switch keyboards are quite expensive, they have a record to have survived the race longer than the keyboards made from other technologies.

Keep tuned till I come back with more such information for you. Till then good bye and have a nice day!!!!!!!