FUNCTIONS OF VARIOUS INPUT DEVICES

Group 4:Prepared by:• Humaid Mustajab

TOUCH SCREENS

A touch panel is a piece of equipment that lets users interact with a computer by touching the screen directly.

INTRODUCTION TO TOUCHSCREEN A touch panel is a piece of equipment that lets users

interact with a computer by touching the screen directly. Incorporating features into the monitor like sensors that detect touch actions makes it possible to issue instructions to a computer by having it sense the position of a finger or stylus. Essentially, it becomes a device fusing the two functions of display and input.

There are four main touchscreen technologies: Infrared Touchscreens Surface Acoustic Wave Touchscreen Capacitive Touch Screens Resistive Touch Screens

RESISTIVE TOUCH SCREENS

With this method, the position on screen contacted by a finger, stylus, or other object is detected using changes in pressure.

The screen features a simple internal structure: a glass screen and a film screen separated by a narrow gap, each with a transparent electrode film (electrode layer) attached.

Pressing the surface of the screen presses the electrodes in the film and the glass to come into contact, resulting in the flow of electrical current. Detecting this change in voltage identifies the point of contact.

CAPACITIVE TOUCH SCREENS

With this method, the point at which the touch occurs is identified using sensors to sense minor changes in electrical current generated by contact with a finger or changes in electrostatic capacity (load).

Since the sensors react to the static electrical capacity of the human body when a finger approaches the screen, they also can be operated in a manner similar to moving a pointer within an area touched on screen.

SURFACE ACOUSTIC WAVES TOUCHSCREENS

These panels detect the screen position where contact occurs with a finger or other object using the attenuation in ultrasound elastic waves on the surface.

The internal structure of these panels is designed so that multiple piezoelectric transducers arranged in the corners of a glass substrate transmit ultrasound surface elastic waves as vibrations in the panel surface, which are received by transducers installed opposite the transmitting ones.

When the screen is touched, ultrasound waves are absorbed and attenuated by the finger or other object. Detecting these changes identifies the location.

INFRARED TOUCH SCREENS

A touch panel in this category features one infrared LED each at the left and right ends of the top of the panel, along with an image sensor (camera).

Retro reflective tape that reflects incident light along the axis of incidence is affixed along the remaining left, right, and bottom sides. When a finger or other object touches the screen, the image sensor captures the shadows formed when the infrared light is blocked.

The coordinates of the location of contact are derived by triangulation.

Differences in characteristics of touch-panel sensing methods

Sensing Methods

Resistive film CapacitiveInfrared optical

imaging

Electromagnetic induction

Light Transmittance

Not so good Good Excellent Excellent

Fingered Touch

Excellent Excellent Excellent No

Gloved Touch Excellent No Excellent No

Stylus Touch ExcellentNot so good

(special-purpose stylus)

Good (depends on material)

Excellent (special-

purpose stylus)

Durability Not so good Excellent Excellent Excellent

Resistance to Water

DropletsExcellent Excellent Good Excellent

LIGHT PENS

Information is provided to a computer in a number of ways. One way of providing information is by direct input from a

user.

INTRODUCTION TO LIGHT PENS

The most common interface for providing information to a computer system is the keyboard. The keyboard requires the user to type information in the same manner as a typist with a typewriter.

Another method of providing information to the system relies upon the relative position of a cursor to a location on a video display such as CRT. This can be accomplished by a mouse, light pens or other devices.

A light pen is very similar in appearance to a pen or pencil-type writing instrument and turn a traditional CRT monitor into a digital touch screen.

HOW DOES A LIGHT PEN WORK? The light pen differs from the traditional mouse in that the tip of the

light pen when placed in close proximity with the surface of a CRT monitor, receives light signals via a photo detector emanating form the surface of the CRT monitor.

Light pens interact directly with the monitor’s screen like a touchscreen, in providing the absolute positioning and pen-type input of a digitizing tablet but do not suffer from ambiguity that is a result of traditional mouse usage.

Light pens are preferred over mouse for a number of reasons. One reason is that usage of a light pen does not require a separate mouse pad and those utilizes less space. Light pens are more easier to work with(in tasks such as drawing and painting) as they are similar in structural built to a pen, pencil or paint brush.

SMART CARD READERS

A smart card reader is an electronic device that reads smart cards and can be found in the multiple environments around

the world.

WHAT ARE SMART CARD READERS? Smart card readers are devices that are used in multiple

professional as well as consumer level applications. They are activated using a smart card which maybe be contact-based or proximity-based.

Smart card readers are an efficient way to mark attendance and punctuality in offices and schooling environments, control transactions through credit and debit cards of a banking consumer and various other applications that require automatic data entry.

CONTACT AND CONTACTLESS SMART CARD READERS

There are two types of smart cards: contact and contactless. Both have micro processors and memory for efficient transactions and fast access.

A contact smart card reader have to be in contact with the card physically through eight channels on the card through which it can communicate with the processor, memory and ROM of the smart card. Since the card has to be in contact with the smart card the speed and convenience of the smart card is less efficient as compared with proximity-based cards.

A contactless smart card reader uses a radio band of 13.56Mhz frequency to communicate efficiently with the card. Use of a higher frequency enables the reader to relay information quickly to a maximum number of 8 proximity-based cards at once. Most readers only read the serial number of the card and do not utilize the onboard memory of the card.

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