introduction to touch screens

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Seminar

Touch screen Technology

By

Junaid Shah

Enr No. 110229MSc IT -Semester I

Teacher In charge

Mr. Aasif Ali Banka


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OVERVIEW

1. Introduction.

2. History.

3. Types.4. Capacitive Touch Screen in Detail.


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INTRODUCTION

A touch screen is an Electronic Visual Display

that can detect the presence and location of atouch within the display area and respond

accordingly.


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HISTORY

The first touch screen was acapacitive touch screendeveloped by E.A. Johnsonat the Royal Radar

Establishment, Malvern, UKin 1965.

In 1971, the first "TouchSensor" was developed byDoctor Sam Hurst (founder

of Elographics) while he wasan instructor at theUniversity of Kentucky.


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Components in General

A basic touch screen has three main

components :

Touch sensor

Controller

Software driver


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Touch Sensor

A touch screen sensor is aclear glass panel with a

touch responsive area.

The touch sensor isplaced over a display

screen so that the

responsive area of the

panel covers the viewable

area of the screen.


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Controller

The controller is the actual hardware circuitrythat connects between the touch sensor anddrivers.

Take information from the touch sensor and

translate it into information that PC/device canunderstand.


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Software Driver

The driver allows the touch screen and

computer to work together as an interface.

This makes touching the screen as same asclicking the your mouse at the same location

on the screen.


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Different Technologies of Touch

Screens

1. Resistive Touch Screen,

2. Surface Acoustic Wave Touch Screen,

3. Infra Red Touch Screen,

4. Capacitive Touch Screen.


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Resistive Touch Screen

A resistive touch

screen panel is

composed of two

thin, electrically

conductive layers

separated by a

narrow gap.


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Surface Acoustic Wave Touch Screen

Surface Acoustic Wave (SAW) technology

uses ultrasonic waves that pass over the touch

screen panel. When the panel is touched, a

portion of the wave is absorbed. This change

in the ultrasonic waves registers the position

of the touch event and sends this information

to the controller for processing


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Infra Red Touch Screen

An infrared touch screenuses an array of X-Yinfrared LED and photo-detector pairs around theedges of the screen todetect a disruption in thepattern of LED beams.

These LED beams crosseach other in vertical and

horizontal patterns. Thishelps the sensors pick upthe exact location of thetouch.


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Capacitive Touch Screen

A capacitive touch screen panel consists ofan insulator such as glass, coated with atransparent conductor such as Indium Tin

Oxide (ITO).As the human body is also an electricalconductor, touching the surface of the screenresults in a distortion of thescreen's electrostatic field, measurable as achange in capacitance.


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Overview of Capacitive touch Sensing


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CONSTRUCTION OF CAPACITIVE

TOUCH SENSOR


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Software ReceptionThe software then feeds this

frequency change due to change in

Time Constant and then feeds this

data to an algorithm which in turn

makes the requisite logical action.


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