Multimedia, PLC/PLA, Microchip and Robots

Question 1

What is multimedia

Answer 1

On a computer means video plus sound.
Multimedia means using other ways of presenting information to users.

It means using sound, video and other media together in a single presentation. Often videos, animations and sound clips are included together with text and pictures.

Question 2

What are the charateristics of Video?

Answer 2

A three dimensional (3D) image displayed on a two dimensional (2D) VDU
The 3D to 2D conversion process is called rendering
3D graphics are frequently used in games, to give you the impression of moving through rooms and corridors.

Question 3

What are the two different ways of rendering?

Answer 3

Software: achieved by CPU (i.e. MMX CPU), cheap and slow
Hardware: achieved by 3D graphics accelerator (i.e. special 3D graphics card that supports rendering), more expensive but much faster. Some graphics accelerator cards can use up to three GPUs to perform the rendering process.

Question 4

What are the seven steps in the rendering process?

Answer 4

The objects are first constructed as a bare wire frame.
Z-sorting: the objects drawn are placed in order from front to back. An alternative is z-buffering, where only the pixels that will be visible are drawn.
Lines in the wire-frame that will not be visible are deleted.
The surfaces are shaded or covered in textures/colours.
Perspective correction: the image is adjusted to provide the illusion of perspective.
Shading is adjusted for various light conditions. This is called alpha-blending.
Fogging or depth-cueing is used to enhance the illusion of distance.

Question 5

Describe how objects are constructed using the bare wire frame?

Answer 5

3D word represents objects in 3D space, each having co-ordinates in X, Y, and Z axes
Objects are first constructed as a bare wire frame
Wire frame makes up polygons (i.e. flat surfaces joined together)

Question 6

Describe Z-sorting?

Answer 6

The next step is called z-sorting. In this step, the computer figures out what order the objects are.
The rendering engine then draws each object, from the back to the front.
An alternative is z-buffering, in which only the visible pixels are drawn.

Question 7

Describe wireframe coloring?

Answer 7

Next, the surfaces of the wireframe are filled in with colour or textures to make the surfaces look real. The process of colouring is called shading.

Question 8

Describe perspective correction.

Answer 8

Perspective correction: the image is adjusted to provide the illusion of perspective.

Question 9

Describe fogging or depth cueing?

Answer 9

Fogging or depth-cueing is used to enhance the illusion of distance.

Question 10

Describe alpha blending?

Answer 10

6-Alpha blending is used to create lighter areas on a surface. It can be used to create the appearance of fog, mist, steam or pools of light.

Question 11

What are the two different types of sound files?

Answer 11

Wave files

Midi

Question 12

What is the difference between Wave files and MIDI files?

Answer 12

Wave files store information about the actual sound waves, so that these waves can be reproduced later. The sound card plays a wave file by reproducing the sound wave described by the file. Examples include Windows *.wav files.
Musical instrument digital interface (MIDI) files store information about what each instrument is playing. These were originally created for computer-controlled musical instruments, but many sound cards are now able to reproduce the sounds as specified in the MIDI file.
MIDI files are recorded by connecting musical instruments, such as organs, to the computer.
Sound cards create music using one of two methods: FM synthesis and wave tables

Question 13

What is FM Synthesis?

Answer 13

Uses mathematical formulae to generate sound of different instruments
Poor quality (particularly Brass instruments)
Cheaper
Less ROM storage required

Question 14

What are wave tables?

Answer 14

Shorthand / compressed versions of actual recordings stored in ROM on sound card
Larger ROM wave tables = more accurate sound
Note: All modern sound cards use wave tables

Question 15

What does a soundcard contain?

Answer 15

A sound card contains a:
Digital Signal Processor (DSP)
Analogue to Digital Converter (ADC)
Digital to Analogue Converter (DAC)

Question 16

Describe the charateristics of the digital signal processer DSP?

Answer 16

Process digitised sound signals
Two methods of sound generation
FM Synthesis
Wave tables
Compression (storage) /decompression (playback) for storage

Question 17

describe ADC

Answer 17

Analog voice signal from microphone is digitised for storage, and later used
Input

Question 18

describe DAC

Answer 18

Digitised sound data is converted into analog voltages for playback on stereo speakers
Output

Question 19

What does PLC and PLA stand for

Answer 19

Programmable logic controller

Programmable Logic array

Question 20

What does a PLC / PLA do?

Answer 20

A computer device replacing an array of:
Timers
Counters
Switches
Relays
Before PLCs/PLAs, electricians had to connect hundreds of these components together using wire.
PLCs/PLAs simplified this situation by replacing these arrays and wires with a small computers that could be programmed to perform any function required.

Question 21

Describe a microchip

Answer 21

aka microcontroller
Single chip controlling a device
Contain all the components of a small computer
CPU
RAM
ROM
Serial and parallel ports
Counters / timers
Many microchips are only 8 or 16 bit CPU’s with a 10MHz clock although some functions, for example video controllers for video games, printer controllers and PC internal controllers may require a 32 or 64 bit CPU with a higher clock speed

Question 22

What are microchips used for?

Answer 22

Microcontrollers are:
cheaper - they often cost less than $5.
more reliable - they often only use as much technology as needed to accomplish the purpose. There is less technology in the system to break down.
Most microcontrollers are only 8 or 16 bit systems with clock speeds of only 10 MHz - this is all the power that most need to accomplish their tasks quickly. Some controllers (e.g. video controllers in a PC) need more power (i.e. 32 bit systems at 33MHz+ clock speeds).
smaller and more compact - a microcontroller fits on to a single chip.
available for a wide range of devices.

Question 23

Who uses microcontrollers?

Answer 23

Microcontrollers are used for
household appliances, such as: 
TV and VCR.
microwave.
stereo.
cars: 
engine management (fuel injection, gearbox, cruise control, etc.).
stereo.
alarm.
controllers in a PC. 
video controller.
sound controller.
network controller.
bus controller.
DMA controller.
interrupt controller.
calculators, digital watches, toys, video games.
traffic lights, lifts, etc.
test equipment.

Question 24

What are the advantages of a microchip compared to a PLC/PLA?

Answer 24

Cheaper – often less than $5
More reliable
Smaller, more compact
Used in an extremely wide range of computer controlled devices

Question 25

How are interrupts in a realtime device important?

Answer 25

Guaranteed interrupt response time
Increased reliability
Real time operating systems have timeouts, self monitoring behaviour
Real time applications have a wider range of input and output devices than PCs
Micro switches
Temperature and pressure switches
Load sensors
Drive motors
Delays and switches

Question 26

Describe the characteristics of a Robot?

Answer 26

A computer controlled device with moving mechanical arms
Moves in three axes (X, Y and Z) and can be orientated in three directions… have up to six degrees of freedom
Three methods of arm actuation
Motors and gears
Pneumatics (compressed air)
Hydraulics (compressed fluid)

Question 27

What are the advantages of Robots over people?

Answer 27

Robots
Cheaper to run - just need power and maintenance.
Work 24 hours a day, 7 days a week.
Work in hazardous environments. Faster than humans.
Precise and repeatable, with no variations in quality.
Don’t get bored.
No union.

People
Expensive to run - need tea breaks, annual leave, sick leave, etc.
Like sleep and weekends.
Need to have safety equipment and specialist training to work in a hazardous environment. Slower than robots
Can do repetitive tasks but quality may vary.

Question 28

Advantages of People over Robots?

Answer 28

People
Can learn new tasks, easily if the new task is similar to other tasks that they have done (e.g. painting a different car).
Can learn completely different tasks.
Able to identify and solve problems. Able to identify and solve previously unknown problems.
Cheaper to set up: only the cost of hiring a new person (cheaper than a robot) and then training (faster, easier and less expensive than a robot). People pay their own medical bills.
Unemployment - will look for other work.

Robots
Expensive to reprogram to do a new task, even if there are only minor changes needed (e.g. painting slightly larger panel).
Currently, only designed for somewhat specific tasks (e.g. lifting items or welding). Would need to be modified for a completely different task, but this may be prohibitively expensive.
Technology is only now appearing that allows robots to identify problems - but even then only able to identify specific known problems. Solving problems will require a lot more research.
More expensive to set-up and service - specialist engineers are needed.
Unemployment - need to find someone to buy the robot, then have it moved .