4. Hardware (IGCSE Computer Science)

monitoring system

* they send signals to the microprocessor/computer *signals are converted to digital (if necessary) using an analogue to digital converter (ADC) *the computer/microprocessor analyses the data received by checking it against stored values. * if new data is outside the acceptable range. A warning messages is sent to a screen or an alarm activated. * the microprocessor/computer has no effect on what is being monitored- it is simply 'watching' the process *

Actuator

(or transducers) takes signals from a computer & convert them into some form of motion e.g. operating motors, pumps, switches & valves)

capacitive benefits

* medium cost technology * screen visibility is good even in strong sun light * screen is very durable; takes a major impact to break the glass

infra-red/motion

* turn on the windscreen wipers on a car automatically *detect intruders in a burglar alarm system * count people entering/leaving the building

benefits of infrared

* Both systems allow multi-touch capabilities * The optical system allows the use of bare fingers, gloved fingers or a stylus for input. * both systems have good screen durability; it takes a major impact to break the glass

capacitive drawbacks

* allows only the use of bare fingers

pressure sensor

* detects intruders in a burglar alarm system * weighs things (e.g check the weight of a vehicle) * monitor/control a process where a gas pressure is important.

drawbacks of infrared

* it is a relatively expensive technology * heat-sensitive system only allow bare fingers to use the system.

infrared (heat and optical)

optical * uses glass as the screen material. *uses an array of sensors (in the form of a grid); the point of contact is based on which grid coordinates is touched.

Output Devices

A device that sends information from the computer

Optical mark recognition (OMR)

A process where scanned marks on a page are automatically converted to inputs.

Barometer

Measures atmospheric pressure

Biometric device

A device that recognises human physical characteristics, such as fingerprints.

Optical character recognition (OCR)

A process where text on a scanned document is recognised and converted to digital text.

Graph Plotter

Capable of producing highly accurate, very large drawings & posters

Accelerometer

Measures 'proper acceleration' (relative to free fall)

Odometer

Measures distance travelled

Wheel speed sensor

Measures speed of spin of a wheel

Photoelectric sensor

Measures the distance, absence or presence of an object

Gyroscope

Measures the rotation of something

Photodetector

Senses light or other electromagnetic energy

Mouse

The main input device for a computer that a person pushes across a surface to position the mouse pointer whose buttons are used to perform tasks such as making a selection, changing the view in a window, moving an item on the screen, or re-sizing an object.

Keyboard

The main text input device used and made up of wires that connect together in a grid pattern.

Hardware

The physical components of a computer.

Encoding

The process of converting data or information to a particular form.

pH sensor

• Monitor/control acidity/alkalinity levels in the soil in a greenhouse • Pollution/environmental monitoring rivers

light sensor

• Switch street lighting on at night and off during the day • Monitor/control light levels in a greenhouse • Automatically switch on a cars headlights when it gets dark

Digital

A signal, or data that consists of two states, 1 or 0.

Analogue

A signal, or data, that constantly varies.

Sensors

they are used in monitoring and controlling applications. * they send signals to the microprocessor/computer *signals are converted to digital (if necessary) using an analogue to digital converter (ADC) *the computer/microprocessor analyses the data received by checking it against stored values.

capacitive

*made up of many layers of glass that act like a capacitor, creating electric fields between the glass plates in layers. * when the top glass layer is touched, the electric current changes and the coordinates where the screen was touched is determined by an on-board microprocessor

what is resistive technology?

1. has an upper layer of polyester and a bottom layer of glass. 2. when the top layer is touched the top and bottom layer complete a circuit. 3. signals are then sent out which are interpreted by a microprocessor, the calculations determine the coordinates of where the screen was touched

what are the benefits of resistive technology?

1. it is relatively inexpensive technology 2. it is possible to wear gloves or a stylus as well as bare fingers to carry out an input operation.

what are the drawbacks of resistive technology

1. screen visibility is poor in strong sun light. 2. it doesn't permit multi-touch capability. 3. it is vulnerable to scratches and the screens wears out through time.

Input Device

A computer part that allows the user to enter information into the computer including a keyboarding, mouse, scanner, microphone, joystick, trackball, touch pad, touch screen, and light pen, etc.

Interactive whiteboard

A device that acts as a virtual whiteboard. It works in a similar manner to a touch screen, except that the board is an input device only.

Analogue-to-digital convertor (ADC)

A device that converts analogue data into digital data.

Digital camera

A device that encodes digital images and videos and stores them for viewing and later use.

Lights

Actuator is connected to the switch which turns the lights on/off Used in security lights; & in greenhouses to control lighting conditions

Speakers

Connected directly to a computer or built in - Digital data from the computer is converted into analogue form (using a digital to analogue convertor DAC) - sound signal is then amplified

Light Pen

Input device shaped like a pen that is dragged over a computer screen, tablet, or other surface in order to make menu selections, write handwritten notes, or draw

Scanner

Input device that can read text or pictures printed on paper and translate the information into a form the computer can use; serves as the eyes of the camera.

Trackball

Input device that contains a ball that when rotated changes the position of the pointer on the screen which the device remains stationary; sometimes used on laptops.

Joystick

Input device that is a lever that moves in all directions and controls the movement of a pointer or some other symbol; used mostly for games or CAD (computer assisted design).

Touch Screen

Input device that is a special monitor that is touched with the finger to make selections and often used at a kiosk or bank machine and with smartphones / tablets.

Touch pad

Input device used to position the mouse pointer that reacts to the touch of a finger as it is moved across the pad and is usually placed below the keyboard on a laptop computer.

Microphone

Input device used to record or transmit sound made by a person's voice when they talk or sing in order to communicate with another.

Laser Printer

Produce fast high quality volume printing Used where noise levels need to be kept low (office) Rely on large buffer memories - data for the whole document is stored before the pages are printed

Inkjet Printer

Produce good quality hard copies No large buffer memory so pages are printed a bit at a time - printing pauses Used where low output volumes are required - good at producing photo quality printouts

3D Inkjet Printer

Produce solid 3D models using modified inkjet technology (tomography) Thin layers of fine powder (plaster, resin & starch) are bonded together as a 3D model is slowly built up - known as prototypes Scale models are produced in colour before the real thing is manufactured

Motors

Turned on/off by the actuator Used in many domestic appliances, such as automatic washing machines (to make the drum rotate), cookers (to switch on fans), water pumps in central heating systems & automatic greenhouses to open windows

Multimedia Projector

Used for teaching, training, advertising & home entertainment systems

Mechanical Mouse

Uses a ball and rollers to determine how to move the mouse point.

Optical Mouse

Uses a tiny camera that takes over a thousand pictures per second to determine how to move the mouse pointer and has a small, red light-emitting diode (LED) that bounces light off the surface onto a sensor.

Dot matrix Printer

a printhead (made up of a matrix of pins) presses against an inked ribbon Used in noisy environments (e.g. garage workshops) & in applications where print quality is not very important Multi-part stationary e.g. bill with 3 parts - one for the customer, two for the garage, etc.

Barcode systems

•Libraries ~ borrowing cards whenever the book is borrowed it automatically gets told that person has taken a book out. •Stock control~ barcode of that number is looked up on a database and is treated as the key field, when it's found the stock item detail is shown on the screen. Each time the barcode is read the stock is reduced by 1. If the number in stock is less than or equal to this pre-set then more stock is automatically ordered and once it's been ordered a flag (a note) is added to prevent it happening again. When new stock arrives the stock levels get updated. People decide what is the appropriate stock level should be and the system then uses it

Barcode reader

•Series of dark and light parallel lines which vary in thickness •Each represented by a unique series of lines •When a barcode is scanned it is first read by a red laser or a red LED. •The dark parts don't reflect any light at all. •The reflected light is read by sensors called photoelectric cell •As the laser or led light is scanning across the barcode a pattern is generated and is the converted into digital data and that's what lets the computer actually understands the barcode