Wazid Ahsan Touch Screen Technology

8/13/2019 Wazid Ahsan Touch Screen Technology

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WAZID AHSAN

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A touch screen is an electronic visual display that

the user can control through simple or multi-touch

gestures by touching the screen with one or more

fingers.

The touchscreen enables the user to interactdirectly with what is displayed, rather than using

a mouse, touchpad, or any other intermediate

device .

Some touch screens can also detect objects suchas a stylus or ordinary or specially coated gloves.

http://en.wikipedia.org/wiki/Electronic_visual_display

http://en.wikipedia.org/wiki/Multi-touch_gestures


http://en.wikipedia.org/wiki/Mouse_(computing)

http://en.wikipedia.org/wiki/Touchpad

http://en.wikipedia.org/wiki/Stylus_(computing)

http://en.wikipedia.org/wiki/Stylus_(computing)

http://en.wikipedia.org/wiki/Touchpad

http://en.wikipedia.org/wiki/Mouse_(computing)





http://en.wikipedia.org/wiki/Electronic_visual_display







The first ever touch screen was developed by E.A Johnsonat the Royal Radar Establishment, Malvern, UK in the late1960s. Evidently, the first touch screen was a capacitivetype; the one widely used in smart phones nowadays.

In 1971, a milestone to touch screen technology wasdeveloped by Doctor Sam Hurst, an instructor at theUniversity of Kentucky Research Foundation. It was atouch sensor named ‘Elograph’. Later in 1974, Hurst inassociation with his company Elographics came up withthe first real touch screen featuring a transparent surface.In 1977, Elographics developed and patented a resistivetouch screen technology, one of the most popular touch

screen technologies in use today.

http://www.engineersgarage.com/articles/what-is-radar-technology





Let us now give an engineer’s eye to this

revolutionary technology. A touchscreen is a 2

dimensional sensing device made of 2 sheets of

material separated by spacers. There are four

main touchscreen technologies:

1) Resistive 2) Capacitive 3) Surface Acoustic Wave 4) Infrared



The resistive touchscreen consists of a flexible toplayer made of Polyethylene (PET) and a rigid bottomlayer made of glass. Both the layers are coated with aconducting compound called Indium Tin Oxide (ITO)and then spaced with spacers. While the monitor is

operational, an electric current flows between the twolayers. When a touch is made, the flexible screenpresses down and touches the bottom layer. A changein electrical current is hence detected and thecoordinates of the point of touch is calculated by thecontroller and parsed into readable signals forthe operating system to react accordingly.

http://www.engineersgarage.com/articles/operating-systems-tutorial








Some of the popular devices that use Resistive Touchscreen areNintendo DS, Nokia N97, HTC Touch Pro2, HTC Tattoo, SonyEricsson Satio, etc.

These systems transmit only 75% of light from the monitor. The

resistive touchscreen is further divided into 4-, 5-, 6-, 7- and 8-wired resistive touchscreen. While the constructive design of allthese modules is similar there is a major distinction in each of itsmethod to determine the coordinates of touch.

The Four wire Resistive Touchscreen uses both the layers tocalculate the axes information of the touch. Touch measurement in

the 4-wire is a 2 step process. The x-coordinate of the touch pointis calculated by creating a voltage gradient on the flexible layer, andthe y-coordinate is determined by creating a voltage gradient alongthe bottom layer.

Pros and Cons: Consequently, the 4-wire resistive touchscreen isless durable, feebly accurate and can drift with environmentalchanges. However these negatives are divulged only with large-sized touchscreen. These are relatively cheap, easily available andconsume low power.



the Eight wire Resistive Touchscreen is simply avariation of the 4-wire one with the addition of 4sense wires, two for each layer. The sensing pointsaid in reducing the environmental drift to increase

the stability of the system. The 8-wire systems areemployed in sizes of 10.4” or larger where the driftcan be significant.

The Five wire Resistive Touchscreen do not uses the

coversheet (flexible layer) in determining the touchcoordinate. All the position sensing is employed onthe stable glass layer. In this design, one wire goes tothe coversheet and four wires are deployed to thefour corners of the bottom sheet. The coversheet onlyacts as a voltage measuring probe. The functioning of

the touchscreen remains unscathed even withchanges in the uniformity of the conductive coatingover the coversheet.



Pros and Cons: Highly durable, accurate and reliable.This technology involves complex electronics and isexpensive. However, it can be used in sizes upto 22”.

The Six and Seven wire resistive touchscreen is also avariant to the 5 and 4 wire technology respectively. Inthe 6-wire resistive touchscreen an extra ground layeris added behind the glass plate which is said to

improve system’s performance. While, the seven –wirevariant has two sense lines on the bottom plate.However, these technologies are as prevalent as theircounterparts.

The Resistive Touchscreen works well with almost anystylus-like object.





The Capacitive Touchscreen Technology is the mostpopular and durable touchscreen technology used all

over the world at most. It consists of a glass panel

coated with a capacitive (conductive) material Indium

Tin Oxide (ITO). The capacitive systems transmitalmost 90% of light from the monitor. Some of the

devices using capacitive touchscreen are Motorola

Xoom, Samsung Galaxy Tab, Samsung Galaxy SII,

Apple’s iPad.There are two kinds of capacitive touch-surface and projected.



Surface-Capacitive screens, in this technique only oneside of the insulator is coated with a conducting layer.While the monitor is operational, a uniformelectrostatic field is formed over the conductive layer.Whenever, a human finger touches the screen,conduction of electric charges occurs over theuncoated layer which results in the formation of adynamic capacitor. The computer or the controller thendetects the position of touch by measuring the change

in capacitance at the four corners of the screen. Pros and Cons: The surface capacitive touchscreen

is moderately durable and needs calibration duringmanufacture. Since a conductive material is requiredto operate this screen, passive stylus cannot be usedfor surface capacitive touchscreen.





In the Projected-Capacitive Touchscreen

Technology, the conductive ITO layer is etched to

form a grid of multiple horizontal and vertical

electrodes. It involves sensing along both the Xand Y axis using clearly etched ITO pattern.



The projective screen contains a sensor at every

intersection of the row and column, thereby

increasing the accuracy of the system.





The Surface Acoustic Wave Touchscreen technologycontains two transducers (transmitting and receiving)placed along the X-axis and Y-axis of the monitor’s glassplate along with some reflectors. The waves propagateacross the glass and are reflected back to thesensors. When the screen is touched, the waves areabsorbed and a touch is detected at that point. Thesereflectors reflect all electrical signals sent from onetransducer to another. This technology provides excellentthroughput and image clarity.

Pros and Cons: 100% clarity is obtained as no metallic

layers are present on the screen, it can be operated usingpassive devices like stylus, glove or finger nail. Screen canget contaminated with much exposure to dirt, oil which mayhaunt its smooth functioning.





In the Infrared Touchscreen Technology, an arrayof X- and Y- axes are fitted with pairs of IR

Leds and photo detectors. The photo detectors

detect any change in the pattern of light emitted by

the Leds whenever the user touches the

monitor/screen.

http://www.engineersgarage.com/electronic-components/ir-infrared-led













PUBLIC INFORMATION DISPLAYS



Retail and restaurant systems.



Customer self service



Computer based training.



Used in industries.



Used in hospitals.





It saves a lot of time. Easy to handle.

No special commands to learn for operatingthe device.

No use of keyboards or other input devices.

Indeed a best device for interfacing.

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Wazid Ahsan Touch Screen Technology