TOUCH SCREEN BASICS
Since their invention in the 1960s, touch screens have become a multimillion-dollar business. We use them weekly, sometimes daily, to withdraw cash and make deposits at the ATM. Once rarely seen outside of banks, touch screens are now used in numerous applications, for example: to preview compact discs at the store, make custom greeting cards, check-in at airports, vote, conduct financial trades and get directions in malls and other large buildings.
Touch screens have several advantages over other computer devices. Unlike moving a mouse, swiveling a joystick or pushing a key to perform a desired function indirectly, users can simply touch an object on a screen. Touch screens have virtually no moving parts and are therefore very durable and appropriate for frequent use in unlimited applications.
HOW TOUCH SCREENS WORK
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4-WIRE RESISTIVE SCREENS (PL AND FG)
The 4-wire Resistive Touch Screen consists of a conductive bottom layer of either glass or film and a conductive top film layer, separated by extremely small, transparent spacer dots. A voltage is applied across the conductive surface. Any type of probe, including fingers, gloved fingers, credit cards, pens, etc., that can be used to apply pressure against the top film will activate the screen. When ample touch pressure is applied to the top layer, the film flexes inward and makes contact with the bottom layer resulting in a voltage drop. This change in voltage is detected by the controller. By alternating the voltage signal between the top and bottom layer, the X and Y coordinates of the user’s touch are computed. In a Film on Glass (FG) construction, the bottom layer is an ITO coated glass. In a Polyester Laminated (PL) or film-film-glass construction the bottom conductive layer is polyester. An additional layer of Optically Clear Adhesive (OCA) bonds the bottom polyester layer to a backer typically made of glass or poly material.
COMPONENTS OF A TOUCH SCREEN
The touch screen is an input device that allows users to operate a device simply by touching the display screen. A basic touch screen has three main components: touch screen sensor, controller and software driver.
Touch Screen Sensor
Typically a glass panel with a touch-responsive surface.
A printed circuit board (PCB) that is the interface between the sensor and the display. The controller takes information from the touch screen and translates it into information a computer can understand, such as cursor control, right and left clicks, etc.
A computer program that allows the computer operating system and the controller to communicate and helps the controller recognize input.