touch screen sensor

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TECHNICAL SEMINAR Presented By: V Rakesh kumar 06R51A0558 MURTHY INSTITUTE OF TECHNOLOGY

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touch scereen sensor

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Page 1: Touch Screen Sensor

TECHNICAL SEMINAR

Presented By:V Rakesh kumar

06R51A0558MURTHY INSTITUTE OF

TECHNOLOGY

Page 2: Touch Screen Sensor

Touch Screen Sensor

Page 3: Touch Screen Sensor

What is a Touch screen?

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TOUCH SCREENS A touch screen is a computer display screen that is

sensitive to human touch, allowing a user to interact with the computer by touching pictures or words on the screen.

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How Does a Touch screen work? A basic touch screen has three main components: Touch sensor; Controller; Software driver.

The touch screen is an input device, so it needs to be combined with a display and a PC or other device to make a complete touch input system.

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Touch Sensor

A touch screen sensor is a clear glass panel with a touch responsive surface. The touch sensor or panel is placed over a display screen so that the responsive area of the panel covers the viewable area of the video screen.

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There are several different touch sensor technologies on the market today, each using a different method to detect touch input.

The sensor generally has an electrical current or signal going through it and touching the screen can cause a voltage or signal change. This change is used to determine the location of the touch to the screen.

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Controller

The controller connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand.

The controller determines what type of interface/connection you will need on the PC.

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Software Driver

The driver allows the touch screen and computer to work together. It tells the computer's operating system how to interpret the touch event information that is sent from the controller.

Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screen as same as clicking your mouse at the same location on the screen.

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Touch Screen Technology Resistive touch screen Capacitive touch screen Infrared touch screen Surface acoustic wave (SAW) touch screen Strain gauge touch screen Optical imaging touch screen Dispersive signal technology touch screen

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Resistive touch screen

Structure

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Resistive touch screens consist of a glass panel that is coated with electrically conductive and resistive layers made with indium tin oxide (ITO) .The thin layers are separated by invisible spacers.

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Types of resistive touch screens

4-wire resistive touch screens 5-wire resistive touch screens 8-wire resistive touch screens

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Characteristics

Cost effective solutions Activated by a stylus, a finger or gloved hand Not affected by dirt, dust, water, or light 75%~85% clarify resistive layers can be damaged by a very sharp

object

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Capacitive touch screen

Two types Projected-capacitive touch screen Surface -capacitive touch screen

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Projected-capacitive touch screen

Projected capacitive touch screens have front and back protective glassproviding optical and strength enhancement options.

Its middle layer consists of a laminated sensor grid of micro-fine wires, andoptical enhancement options.

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Structure

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Surface -capacitive touch screen

Structure

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Surface capacitive technology consists of a uniform conductive coating on a glass panel. Electrodes around the panel’s edge evenly distribute a low voltage across the conductive layer, creating a uniform electric field.

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Surface-capacitive touch screen

Working principle

A human body is an electric conductor, so when you touch the screen with a finger, a slight amount of current is drawn, creating a voltage drop. The current respectively drifts to the electrodes on the four corners. Theoretically, the amount of current that drifts through the four electrodes should be proportional to the distance from the touch point to the four corners.

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Characteristics:

Durable and resistant to scratches for demanding applications

Faster and more responsive Immune to surface contaminants Superior optical clarity, brighter display and less

surface reflection Must be touched by finger, will not work with

any non-conductive input

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Infrared touch screen

Infrared (IR) technology relies on the interruption of an IR light grid in front of the display screen. The touch frame contains a row of IR-light emitting diode (LED) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light.

The IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus, such as a finger, enters the grid, it obstructs the beams.

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Infrared touch screen

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Characteristics:

Clear as glass, improves reading ability Most durable surface

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SAW touch screen

Principle: Surface waves are readily absorbed when a soft

object such as a fingertip touches the substrate. SAW Touch Screen use pure glass with

transmitting and receiving piezoelectric transducers for both the X and Y axes.

The touch screen controller sends an electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass.

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SAW touch screen

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Characteristics:

Durable glass construction High optical clarity Activated by a finger, gloved hand or soft tip Not completely sealable, can be affected by

large amounts of dirt, dust, and / or water in the environment

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Technology Capacitive SAW Infrared Resistive

Transparence Very good >92%

Very good >92%

Very good >92%

75%~85%

Resolution Good Good Limited due tospacing of IRsensors

good

SurfaceContaminants/durability

Resistant tomoisture andother surfacecontaminants

Adversely affected bymoisture orSurfacecontaminants

Potential forFalse activationor dead zonesFrom SurfaceContaminants

Unaffected by Surfacecontaminants.Polyester topsheet is easilyscratched

Sensor substrate Glass with ITO coating

Glass with ITO coating

Any substrate Polyester top sheet, glasssubstrate withITO coating

Display size 8.4"-21" 10.4"-30" 10.4"-60" up to 19"

Touch method Human touch finger, gloved

hand or soft tip Can use any pointing device

Can use any pointing device

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Multi-touch technology

Multi-touch denotes a set of interaction techniques which allow computer users to control graphical applications with several fingers.

Products: Apple IPhone, iPod touch, MacBook Air, and

MacBook Pro Microsoft Surface ……

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