Difference Between Touch Screens And Normal Keypads

Keypad generally comes in 4×4 , 4×3 , 3×4 matrices. Some multinational companies make their own keypads for their projects. Like we see in our daily life the keypad on ATM(Automated Teller Machine) and Photo copy machine is of many variations like 4×5 , 5×4 etc . The keypads on our cell phones also differ from each other like we have generally 4×4 keypad with some other buttons like call(Green colored )end call(Red colored ) but if we look at Black Berry sets their keypad is different from others.Some thing like keyboard. In the terms 4×4 , 4×3 first digit represents number of rows and second digit represents number of coulombs.Thus 4×4 keypad has 4*4=16 buttons on it and 4*3=12 has 12 buttons.Their are generally two types of keypads.
 

1. Manual keypad

The one on which their are buttons which we press by our finger.This type of keypads are the oldest one and are still in the ground one can easily see it on his her desktop or laptop.But their use is gradually declining by the Touch screens.In an NXN (N=number of rows and number of coulombs  keypad we first make all the rows and coulombs high (actually the 
pins of the intelligent unit to which the keypad is connected). Each button on keypad is identified by a row and coulomb  Like 2×3 represents second rows third button.Now when we press any key then the corresponding row and coulomb is grounded. we know read the status of the pins and identify which key is pressed.

    2.   Touch Screen keypad
Keypads that are popular today (Actually a sensor which identifies the place of disturbance on the screen and generates the output that is actually seen on the keypad .In the form of character or digit on cell phone screen).we can see them on many machines like ATM(Automated Teller Machine) Photo State machines
cell phones Automatic door locks and many others.Their are many technologies that identify your touch.Here are the names of few of them.

•  Resistive
•  Surface acoustic wave
•  Capacitive

Most of the technologies uses exactly the same method of layers in which their are layers on your screen some layers are grounded and some are charged. They both are opposite in direction. Now when we press on the surface of the screen the layers touches our fingers since our body is conductive it conducts the charge that is carried by the conductive layers and the grounded rows also goes in our finger flesh making a fully charged path with our finger. Which results as disturbance on the screen. The internal mechanism of the device thus recognizes the place of disturbance by necessary calculations.