MALAVIYA NATIONAL INSTITUTE OF TECHNOLOGY JAIPUR

Department of Electronics and Communication Engineering

SEMINAR PRESENTATIONON

TOUCH SCREENS

Submitted By: Guided By: Submitted To: Bhavyadeep Kaur M. Ravi Kumar Dr. Mohd. Samar Ansari2010UEC189 Assistant Professor Assistant Professor

CONTENTS: What are touch screens? Touchscreens and HMI How do touchscreens work? Types of touchscreen technology How the Touch screen Controller Interprets Screen Measurement Architecture of touchscreen Applications Advantages Conclusion References

TOUCH SCREENS What are touch screens?

A type of display screen that has a touch-sensitive transparent panel covering the screen.

Instead of using a pointing device such as a mouse or light pen, you can use your finger to point directly to objects on

the screen. It is an electronic visual display that the user can control

through simple or multi-touch gestures by touching the screen with a special stylus/pen and-or one or more fingers.

Most user friendly interface. Communicates with the PC, cell phones, tabs, etc. The user touches the screen to select options

presented on the screen. Associated hardware and software are used to determine the location of the press.

The easiest to learn and use of any available interface. Businesses both large and small are using touch

technology to create new products, reach new markets, increase productivity, and ease the flow of information.

Touchscreens or Human Machine Interface (HMI) Just move the hand or walk your fingers over a thing

and it works. Yes, it is the interactive gesture based technology. Ability of Direct manipulation inside the screen. A device which works on touchscreen technology is

coined as Touchscreen. A touchscreen is an electronic visual display capable

of ‘detecting’ and effectively ‘locating’ a touch over its display area. 

How Does a Touch screen Work?  A basic touch screen has three main

components: a touch sensor, a controller, and a software driver. The touch screen is an input device, so it needs to be combined with a display

and some electronic device to make a complete touch input system.

Touch Sensor

Is a panel with a touch responsive surface. Systems are built based on different types of

sensors.

However, in general sensors have an electrical current running through them and touching the screen causes a voltage change. The voltage change signals the location of the touching.

Controller AND SOFTWARE DRIVER

The controller, is the hardware that converts the voltage changes on the sensor into signals the computer or other device can receive.

Software tells the computer, smartphone, game device, etc, what's happening on the sensor and the information coming from the controller. Who's touching what where; and allows the computer or smart phone to react accordingly.

Types of Touchscreen Technology

A touchscreen is a 2 dimensional sensing device made of 2 sheets of material separated by spacers. There are

four main touchscreen technologies:

   Resistive  Capacitive  Surface Acoustic Wave   Infrared

Resistive Touchscreen Technology

1. Consists of a flexible top layer made of Polyethylene (PET) and a rigid bottom layer made of glass.

2. Both the layers are coated with a conducting compound called Indium Tin Oxide (ITO) and then spaced with spacers.

3. When a touch is made, the flexible screen presses down and touches the bottom layer.

4. A change in electrical current is detected.

5. The coordinates of the point are calculated by the controller and parsed into readable signals.

Capacitive Touchscreen Technology

The Capacitive Touchscreen Technology is the most popular 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 transmit almost 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 different types of capacitve touch screens such as:

1. Surface-capacitive touchscreen2. Projected-capacitive touchscreen

Surface-Capacitive screens:

In this technique only one side of the insulator is coated with a conducting

layer. While the monitor is operational, a uniform electrostatic field is formed over the conductive

layer.

Whenever, a human finger touches the screen, conduction of

electric charges occurs over the uncoated layer which results in the formation of a dynamic capacitor.

The computer or the controller then detects the position of touch by

measuring the change in capacitance at the four corners of the screen.

Projected-Capacitive Touchscreen:

In this, the conductive ITO layer is etched to form a grid of multiple horizontal and vertical electrodes. It involves sensing along both the X and 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. There are two types of projected capacitive touchscreen: Mutual Capacitance and Self Capacitance

Surface Acoustic Wave Touchscreen technology

• It contains two transducers (transmitting and receiving) placed along the X-axis and Y-axis of the monitor’s glass plate along with some reflectors.

• Waves propagate across the glass and are reflected back to the sensors.

• When the screen is touched, the waves are absorbed and a touch is detected at that point.

• Reflectors reflect all electrical signals.

Infrared Touchscreen Technology:

In the Infrared Touchscreen Technology, an array of 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.

How the Touch screen Controller Interprets Screen Measurement:

When the controller is waiting for a touch, the resistive layer of the touch screen is biased at +5V through four drivelines, and the coversheet is grounded through a high resistance.

When the touch screen is not being touched, the voltage on the coversheet is zero.

The voltage level of the coversheet is continuously converted by the analog-to-digital converter (ADC) and monitored by the microprocessor on the controller.

ARCHITECTURE OF TOUCHSCREEN TECHNOLOGY

4-WIRE RESISTIVE SCREENS :(MOSTLY USED)

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 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.

Application of Touch screen

Gaming/Entertainment/Multimedia Industrial and Medical Instrumentation ATMs and Banks Automobile Industry and Market Research

Now a days most of the old techniques of using electronic switches are replacing with computer enabled touch screen based controls. This gives great flexibility in working and operations.

ADVANTAGES : More reliable. Keyboards can have over 100 switches. The touch screen has

no moving parts. Less space. This is particularly important in places where space is limited,

such as the driver’s cab or the pilot’s cockpit. More portable With no need to print on or around any keys or switches, it is much easier to

make the system multi-lingual. With a keypad or keyboard, the switches are in a fixed position but the touch

screen can have any shape and size of ‘key’. Resistant to contamination. They are impervious to dust, chemicals, fluids

and the weather. Will not contaminate. Especially important in the food processing industry or

silicon foundries. Combined with RFID for security tag or credit card processing as required,

the system can be completely sealed. Can be used in hazardous areas like mining or petro-chemical industries

CONCLUSION Improved experience – Touchscreens provide end users an opportunity to interact with the

computer, improving the human-computer interface and improving the user’s experience. This may seem like a small thing to many, but this simple idea is one of the reasons that the iPad from Apple has been so successful with users. The device provides a pleasurable experience for the end user secondary to the intuitive touchscreen interface.

Easy access – Touchscreens provide an easy to understand, intuitive interface for the human brain. Touch is a natural way for us to interact with the world around us and pointing at something with our finger is as natural as breathing air.

Saves time – Fumbling with a mouse and keyboard isn’t always the easiest thing to do and touchscreen technology can help. I sometimes use my finger to navigate the touchscreen on my laptop instead of a mouse. I find that using my finger often works better than a mouse to reposition my cursor, access an open application or scroll through a web page. It’s not a big thing, but it improves my experience and makes things easier to access.

Sanitary – Often overlook, but never out of the mind of healthcare providers, is the unsanitary conditions created by a mouse and a keyboard.

They’re a great place to harbor germs collected on the hands of everyone that’s touches them. Washing one’s hands before and after using them is a successful strategy for fighting the spread of germs, but this simple solution isn’t always utilized to its logical end. On the other hand, touchscreens can be easily cleaned as part of a routine schedule.

Potential to save money – Full touchscreen technology requires no keyboard or mouse, which both cost money and have to be replaced. Of course this only makes sense if the touchscreen technology does not exceed the cost of a typical monitor. We’re not there yet, but we’re headed in the right direction.

REFERENCES:

o Webopedia.como Inventorsabout.como Engineersgarage.como Computerworld.com

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