chapter 3 test Flashcards
What are touchscreens and what are the types?
- Allow the user to carry out the same functions as they would with a pointing device, such as a mouse.
- There are three common types of touch screen technologies: Capacitive, Infrared, Resistive (most common method at the moment)
capacitive touch screens?
- Composed of a layer of glass (protective layer), a transparent electrode (conductive) layer and a glass substrate
- Since human skin is a conductor of electricity, when bare fingers (or a special stylus) touch the screen, the electrostatic field of the conductive layer is changed
- The installed microcontroller is able to calculate where this change took place and hence determine the coordinates of the point of touching.
what are the two types of capacitive touchscreens?
surface and projective
capacitive touchscreens - surface
- Sensors are placed at the corners of a screen
- Small voltages are also applied at the corners of the screen creating an electric field
- A finger touching the screen surface will draw current from each corner reducing the capacitance.
- A microcontroller measures the decrease in capacitance and hence determines the point where the finger touched the screen.
- This system only works with a bare finger or stylus.
capacitive touchscreens - projective
- The transparent conductive layer is now in the form of an X-Y matrix pattern.
- This creates a three dimensional (3D) electrostatic field.
- When a finger touches the screen, it disturbs the 3D electrostatic field allowing a microcontroller to determine the coordinates of the point of contact.
- This system works with bare fingers, stylus and thin surgical or cotton gloves.
- It also allows multi-touch facility (for example, pinching or sliding).
capacitive touch screens advantages and disadvantages
Advantages
* Better image clarity than resistive screens, especially in strong sunlight
* Very durable screens that have high scratch resistance
* Projective capacitive screens allow multi-touch.
Disadvantages
* Surface capacitive screens only work with bare fingers or a special stylus
* They are sensitive to electromagnetic radiation (such as magnetic fields or microwaves).
infrared touch screens
- Infrared touch screens use a glass screen with an array of sensors and infrared transmitters.
- The sensors detect the infrared radiation.
- If any of the infrared beams are broken (for example, with a finger touching the screen), the infrared radiation reaching the sensors is reduced.
- The sensor readings are sent to a microcontroller that calculates where the screen was touched
infrared touch screens advantages and disadvantages
Advantages
* Allows multi-touch facilities
* Has good screen durability
* The operability isn’t affected by a scratched or cracked screen.
Disadvantages
* The screen can be sensitive to water or moisture
* It is possible for accidental activation to take place if the infrared beams are disturbed in some way
* Sometimes sensitive to light interference.
resistive touch screens?
- Resistive touch screens are made up of two layers of electrically resistive material with a voltage applied across them.
- The upper layer is made of flexible polyethylene (a type of polymer) with a resistive coating on one side
- The bottom layer is made of glass also with a resistive coating (usually indium tin oxide) on one side.
- These two layers are separated by air or an inert gas (such as argon).
*When the top polyethylene surface is touched, the two layers make contact.
Y - Since both layers are coated in a resistive material a circuit is now completed which results in a flow of electricity.
- The point of contact is detected where there was a change in voltage.
resistive touch screens advantages and disadvantages
Advantages
* Good resistance to dust and water
* Can be used with bare fingers, stylus and gloved hand.
Disadvantages
* Low touch sensitivity (sometimes have to press down harder)
* Doesn’t support multi-touch facility:
* Poor visibility in strong sunlight
how does a barcode scanner work?
- red laser shone on barcode
- light is reflected back
- sensors detect the light
- pattern is converted to digital
- micro-roster interprets the data
- each digit is made up of 2 dark and 2 white lines
most common use of barcodes and barcode scanners?
electronic point of sale
what are some input/output devices found at a checkout?
keypad
screen/monitor
speaker
printer
touchscreen
advantages of barcode scanner
advantages to company: easier+ faster to change prices on stock items, gives better/up-to-date sales info, allows automatic stock control, checks customer buying habits
advantages to customer: faster checkout queues, errors reduced, itemized bill, better track of ‘sell by date”s so there is fresher food
barcodes and stock management
- barcode identifies a (unique) product
- barcode can be used to look up a product in a database
-data about stock levels can be stored in a system - stock can automatically be deducted from the system
- automatic re-order is possible
- locate if an item is available in another location
