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T325: Technologies for Digital Media

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Title: T325: Technologies for Digital Media


1
T325 Technologies for Digital Media
  • Second semester 2010/2011 Tutorial 1

2
Outline
  • General introduction to the T325 course
  • Power for Digital Media
  • Introduction
  • Battery technology
  • Fuel cells.
  • Power from the environment.
  • Where does the energy come from?

3
General introduction
  • Learning outcomes
  • Course breakdown
  • Assessments
  • Study calendar
  • Plagiarism

4
Learning outcomes of the Course
  • To introduce you to the fundamental principles of
    selected technologies for digital media
  • To enable you to become a more independent
    learner, able to keep up to date in digital media
    technologies
  • To enable you to integrate knowledge from several
    sources in the presentation of an argument
  • To enable you to analyse, critique and synthesise
    examples of third-party material
  • To improve your understanding of the complexities
    of technological systems in terms of social,
    ethical and economic factors as well as the
    underlying technologies.

5
Course breakdown
  • Block 1 Enabling technologies
  • You will be presented with materials on hardware,
    such as disc drives, solid state (e.g. flash)
    memory, batteries, display screens and capture
    devices, and algorithms, such as error control
    coding and MPEG compression techniques.
  • Block 2 Intellectual property and security
    issues
  • You will be presented with materials on the
    technologies associated with digital rights
    management and watermarking.
  • Block 3 Mobile broadband
  • You will be presented with materials on
    developments designed to support broadband
    applications in a mobile world.

6
Course Assessment
  • Continuous assessment (50 of the course grade)
  • TMAs Two TMAs worth 10 of course grade each
  • MTA One MTA worth 30 of course grade
  • Final Exam
  • One Final Exam worth 50 of course grade
  • You must obtain
  • At least 40 average on the Continuous assessment
  • At least 40 average on the final exam
  • at least 50 overall in order to pass the course.

7
Study calendar
Week Start date Course block Course section(s) Assignments /due date
1 21/02/11 Block 1 Enabling technologies Power for digital media  
2 28/02/11   Information storage  
3 07/03/11   Error control coding  
4 14/03/11   Seeing and hearing multimedia  
5 21/03/11   Video and audio coding  
6 28/03/11   Video and audio coding  
7 04/04/11 Block 2 Intellectual property and security issues Intellectual property rights Security TMA01 04/04/2011
8 11/04/11   Digital rights management Digital watermarking  
9 18/04/11 Block 3 Mobile broadband Mobile evolution Network architecture MTA
10 25/04/11   Mobile evolution Network architecture  
11 02/05/11   Access and modulation  
12 09/05/11   Access and modulation TMA02 09/05/2011
13 16/05/11   Better and beyond  
14 23/05/11   Better and beyond  
15 30/05/11   Revision  
8
Plagiarism
  • Plagiarism is the act of taking some one else's
    work and passing it off as you own.
  • Using extracts, even those as short as phrases or
    single sentences, from another author (including
    authors of T325 course materials) without saying
    that you are doing so is plagiarism.
  • Plagiarism is not acceptable in any written
    material, because you are in effect stealing
    someone else's ideas.
  • When referring to or quoting from other people's
    work in your documents, the original source must
    always be properly cited.
  • Please refer to the T325 Course Guide for more
    information on how to avoid plagiarism

9
Power for Digital Media
10
Introduction
  • Power consumption is one of the main constraints
    on the design of electronic goods, and is a major
    consideration for mobile devices and even for
    mains-power equipment
  • most of the power consumed ends up as heat.
  • overheating of electronic circuits damages the
    components.
  • Need to reduce energy consumption in order to
    combat global warming.

11
Introduction
  • Power needs of digital equipment have generally
    been increasing
  • Powering consumer electronic and computer
    products alone in the UK every year - thats 23
    of the average household electricity bill.
  • There is a vast amount of research and
    development effort being put into improving the
    technologies.
  • The lithium ion battery first commercialized by
    Sony in 1991, it stores energy a factor of 5
    higher than that stored by the much older
    lead-acid batteries.
  • Receivers for digital audio broadcasting (DAB)
    available at the moment typically consume a lot
    more power than receivers for analogue radio
    broadcasts.
  • In the extreme, it is possible to construct a
    receiver for analogue AM broadcasts that requires
    no separate power source (crystal radio or
    crystal set).

12
Introduction
13
Battery technology
  • Batteries produce electricity from a chemical
    reaction, called an electrochemical reaction.
  • You get a battery when several cells are
    connected together

14
Battery technology
  • The chemical reaction depends upon the material
    used to make the anode, the material used to make
    the cathode and the material used for the
    electrolyte.
  • Different combinations of chemical are used for
    different batteries lead-acid batteries,
    alkaline batteries, nickel--cadmium (NiCd),
    nickel-metal hydride (NiMH), lithium and
    lithium-ion (Li-ion) batteries.
  • The chemistry, as well as the details of the
    physical construction, determines whether the
    batteries can be recharged or not.

15
Battery technology
  • Two categories of batteries
  • Primary batteries
  • Manufactured to be used once
  • Examples alkaline and lithium batteries
  • Secondary batteries
  • Rechargeable

16
Battery technology
  • Chemistry-related terminology
  • Elements The purest substances of the physical
    world are the elements (nickel, cadmium, zinc,
    potassium,).
  • Compounds Most elements can join to other
    elements to form compounds. (hydrogen joined (in
    an appropriate way) to oxygen forms water.)
  • Chemical reaction When elements combine to form
    a compound the process is called a chemical
    reaction. Chemical reactions can also take place
    between two or more compounds or between elements
    and compounds.
  • Atoms, molecules and ions The basic building
    block of an element is an atom. An atom consists
    of a nucleus, which has a positive electrical
    charge, and electrons, which have a negative
    electrical charge.

17
Battery technology
  • Voltage
  • The voltage of a battery cell is determined
    primarily by the materials used for the
    electrodes and the electrolyte.
  • To get higher voltages, cells are connected in
    series, with the result that the voltages add.
  • The voltage determined by the chemistry will only
    be found at its maximum when no current is being
    drawn from the battery.
  • If too much current is drawn, and also as the
    battery becomes discharged, the voltage at the
    battery terminals will reduce.

18
Battery technology
  • Maximum current output
  • The current drawn from the battery in any
    application is determined by the load and by the
    battery voltage.
  • A battery that can deliver high currents will
    have a low internal resistance.
  • One that cannot deliver high currents will have a
    high internal resistance.

19
Battery technology
20
Battery technology
  • Capacity (running time)
  • The words power and energy are used loosely
    in common speech
  • Power is the rate at which energy is being
    transferred. In SI units
  • Energy is measured in joules (J) and power in
    watts (W)
  • 1W corresponding to energy being transferred at a
    rate of one joule per second (1 J/s).

21
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.2
  • Identify the misuse of terms such as energy,
    power or watts in the following extract from a
    newspaper report. Rewrite it so that it is
    technically correct
  • The company says that one of its typical phones
    needs a charge of 160 milliamps on Britains
    240-volt electric grid. That means it is an
    appliance rated at 38 watts -- more than double
    the energy needed for a typical energy-saving
    light bulb. (Source Alok Jha, 2005)

21
Arab Open University-Lebanon TutorialI 2010
22
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.2
  • The rating of 38 W is a power rating, not energy.
    Also, the 160 mA is an electrical current, not a
    charge, so it would be better to write
  • The company says that one of its typical phones
    needs a charging current of 160 milliamps on
    Britains 240-volt electric grid. That means it
    is an appliance rated at 38 watts -- more than
    double the power needed for a typical
    energy-saving light bulb.

23
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.5
  • (a) If the battery voltage is V volts and the
    load has a resistance of R ohms, what current
    flows from the battery?
  • (b) On a single graph, plot the current against
    resistance for a 1.5V battery and a 3.6V battery,
    for a resistance range of 10 to 200 ohms.

23
Arab Open University-Lebanon TutorialI 2010
24
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.5
  • (a) From Ohms law, the current is given by the
    voltage divided by the resistance, V/R.
  • (b)

25
Battery technology
  • Capacity (running time)
  • The length of time a battery can supply a given
    power is determined by the amount of energy
    stored in the battery.
  • for example, a battery storing 10 kJ (10000 J)
    could ideally run for 10000 s delivering 1W.
  • Question express the battery capacity in terms
    of amp-hours (Ah), amps multiplied by hours.
  • For example, a battery with a capacity of 1 Ah
    could supply 1 A for 1 h, or else it could supply
    2 A for 0.5 h or 0.5A for 2 h. More generally, if
    a battery can run at a current i for t hours,
    then its capacity is capacity i t.

26
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.7
  • A 1.2V battery has a capacity of 800 mAh. How
    long could it run if the load uses 50 mA?

27
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.8
  • A 1.2V battery has a capacity of 800 mAh. How
    long could it run if the load has a resistance of
    30ohm?
  • The current drawn from the battery is 1.2/30
    0.04 A, which is 40 mA.
  • It could run for 800/40 20 h.

27
Arab Open University-Lebanon TutorialI 2010
28
Battery technology
  • Capacity (running time)
  • The time t the battery can be used is given by
    tcapacity/i.
  • Small digital devices, such as mobile phones,
    typically draw rather less than 1A, so it is more
    convenient to work in terms of milliamps (mA)
    rather than amps,
  • A 1.2V battery has a capacity of 800 mAh. How
    long could it run if the load uses 50 mA?.
  • power current x voltage.

29
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.9
  • A 1.2V battery is specified to have a capacity of
    800 mAh. What energy does the battery store? Give
    your answer in both watt-hours and joules.

29
30
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.9
  • 800mAh is 0.8 Ah. So the battery stores 1.2 x 0.8
    0.96 Wh, which is 0.96 x 3600 3456 J.
  • Since the 800 mAh specification for the battery
    capacity can only be approximate, and the usable
    energy is anyway dependent upon factors such as
    temperature and the current being drawn from the
    battery, it would not be meaningful to express
    the energy stored in the battery to four
    significant figures. Without knowing any further
    details of variation that could be expected from
    the capacity, I would round the answer here to
    two significant figures, giving it as 3500 J

30
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31
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.10
  • What is 1kWh expressed in joules?
  • 1000 x 3600 3 600 000 J, which is 3.6 MJ.
  • .

32
Weight and size figures of merit
  • Comparing batteries weight, size but also
    capacity
  • An AAA battery is smaller and lighter than an AA
    battery, but generally has a lower capacity.
  • different technologies (different chemistries and
    different physical constructions) can give
    different capacities for the same size or weight.
  • Figures of merit for battery technologies
    numbers expressing how much capacity you can get
    for a given size or how much for a given weight.

33
Weight and size figures of merit
  • Volumetric energy density is the amount of energy
    stored per unit volume. It can be expressed in
    units of joules per metre cubed (J/m3)
  • Gravimetric energy density (also known as
    specific capacity) is the amount of energy stored
    per unit mass. Again, there are various units
    that might be used, such as joules per kilogram
    (J/kg), watt-hours per gram (Wh/g) and
    kilowatt-hours per kilogram (kWh/kg).

34
Weight and size figures of merit
  • Volumetric power density is the power that can be
    delivered, per unit volume. There are various
    units that could be used, such as watts per
    centimetre cubed (W/cm3) or watts per litre
    (W/L).
  • Gravimetric power density (also known as specific
    power) is the amount of power that can be
    delivered per unit mass. Again, there are various
    units that might be used, such as watts per
    kilogram (W/kg) or watts per gram (W/g).

35
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.13
  • Suppose a battery has the following parameters
  • voltage, 1.2V
  • capacity, 800mAh
  • weight, 24 g
  • volume, 8.4cm3
  • Calculate the volumetric energy density and the
    gravimetric energy density of this battery.
  • For the volumetric energy density, give your
    answer in both J/cm3 and Wh/L, and for the
    gravimetric energy density give your answer in
    both J/kg and Wh/kg. Give all your answers to two
    significant figures.

36
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.13
  • Battery capacity 1.2 x 0.8 0.96 Wh.
  • In joules, this is 0.96 x 3600 3456 J.
  • To three significant figures, 3460 J (use three
    significant figures for intermediate results).
  • Volume 8.4cm3, which is 0.0084 L.
  • Volumetric energy density 3460/8.4 410 J/cm3.
  • Or, 0.96/0.0084 110 Wh/L.
  • Mass 24 g, which is 0.024 kg.
  • Gravimetric energy density 3460/0.024 140 000
    J/kg.
  • Or, 0.96/0.024 40 Wh/kg.

36
Arab Open University-Lebanon TutorialI 2010
37
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.13
  • Suppose the battery of Activity 1.13 can deliver
    a current of 1A. Calculate its volumetric power
    density in W/L and its gravimetric power density
    in W/kg, assuming the battery voltage is 1.2V.
  • Drawing such a high current, the battery voltage
    will fall quite quickly. Calculate the same
    figures as in part (a) for when the battery
    voltage has dropped to 0.8V.

38
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.14
  • (a) 1 A at 1.2V is a power of 1.2W.
  • Volume (from previous activity) is 0.0084 L. So
    the volumetric power density is 1.2/0.0084 140
    W/L.
  • The mass (from the previous activity) is 0.024
    kg, so the gravimetric power density is 1.2/0.024
    50 W/kg.
  • (b) 1 A at 0.8V is a power of 0.8W. So the
    volumetric power density is 0.8/0.0084 95 W/L.
  • The gravimetric power density is 0.8/0.024 33
    W/kg.

39
Battery technology
  • Number of recharge cycles
  • Some batteries cannot be recharged at all. These
    are known as primary batteries, contrasted with
    secondary batteries which can be recharged.
  • As the battery discharges there are chemical
    reactions taking place at the two electrodes,
    involving the material of the electrodes and the
    chemicals in the electrolyte.
  • To recharge the battery those reactions have to
    be reversed, which may not be possible, or may
    only be partially possible.

40
Battery technology
  • Number of recharge cycles
  • Even a secondary battery, which can be recharged,
    will be limited in the number of times it can be
    recharged before it deteriorates so that it no
    longer retains charge very effectively.
  • The way in which the battery is used and,
    especially, in which it is charged can have a
    significant influence on how effectively it can
    be recharged and, therefore, on how many cycles
    the battery can go through before it retains too
    little charge to be useful.

41
Battery technology
  • Battery charging and safety
  • A battery is charged by passing an electrical
    current through it in the opposite direction from
    the direction that current flows when it is in
    use.
  • General rules are that it is important not to
    attempt to charge a battery too fast and that
    the charging should stop once the battery is
    fully charged.
  • For some chemistries these rules are more strict
    than others. Li-ion batteries need careful
    charging, Care also needs to be taken over the
    discharging of Li-ion batteries.

42
Battery technology
  • Battery charging and safety
  • Discharging a battery too fast -- such as if
    there were to be a wire connecting the anode to
    the cathode directly (called a short circuit)
    -- can result in a battery overheating. and this
    can result in the battery exploding.
  • To ensure that none of these damaging or
    dangerous circumstances occur, Li-ion batteries
    are supplied packaged with control and protection
    electronics, which might even include
    intelligence a microprocessor that controls
    the battery is referred to as a smart battery.

43
Battery technology
  • Shelf life
  • The shelf life of a battery is the length of time
    a battery can be stored, even if it is not being
    used.
  • shelf life can be very important in some
    applications ( example of military
    applications)
  • When not in use, all batteries gradually lose
    charge, a process referred to as self-discharge.
  • Standard NiMH batteries can lose as much as
    20--30 of their charge in a month, and Li-ion
    batteries of the order of 5 per month.

44
Battery technology
  • Environmental issues
  • Of considerable importance, but not a topic that
    we shall be covering in any detail, is the impact
    that battery manufacture, use and disposal have
    on the environment.
  • Primary batteries are very inefficient in the use
    of energy.
  • The amount of energy used to manufacture a
    battery is much greater than the amount of energy
    that will be usefully delivered to the equipment.
  • Secondary batteries are generally more efficient
    in these terms than primary batteries, but it
    still takes substantially more energy to recharge
    a battery than you get out of it from the
    charging.
  • Disposing of used batteries can damage the
    environment.

45
Battery technology
  • Battery comparisons
  • At the time of writing (2008), the main types of
    battery in common use for digital equipment, such
    as personal radios, laptop computers, mobile
    telephones and MP3 players, etc., are alkaline
    primary batteries, NiMH secondary batteries and
    Li-ion secondary batteries.

46
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47
Fuel cells
  • The idea that fuel cells might be used to
    generate electricity for small portable devices
    like laptops is a relatively recent development.
  • Until now, fuel cells have tended to be used for
    more specialised applications -- providing
    electricity for use in space rockets
  • However, with the increasing demand for power by
    digital devices, and the inability of batteries
    to keep up, the attraction of being able to
    revive a laptop by pouring in a cupful of liquid
    fuel has led to a substantial research effort
    aimed at producing a small, cheap and safe fuel
    cell for electronic devices.

48
Fuel cells
  • A fuel cell is an electrochemical energy
    conversion device.
  • It produces electricity from various external
    quantities of fuel (on the anode side) and
    oxidant (on the cathode side). These react in the
    presence of an electrolyte.
  • Fuel cells are different from batteries in that
    they consume reactant, which must be replenished,
    whereas batteries store electrical energy
    chemically in a closed system.

49
Power from the environment
  • there is a lot of interest in finding ways of
    picking up power from the environment, removing
    the need for providing an energy supply up
    front, or at least reducing the amount of energy
    being drawn from a battery. This is referred to
    as energy scavenging or energy harvesting.
  • Though at first sight this idea might sound
    exotic, solar-powered calculators are in fact
    harvesting energy from the ambient light and have
    been around for decades.
  • One application for which energy scavenging or
    harvesting might become very important is in
    providing power for wireless sensor networks.

50
Performance comparisons
  • For batteries, the figures of merit were
    important in assessing the performance. Similar
    measures can be used for other sources of power.
  • Tables 1.6 and 1.7 are taken from a paper
    (Flipsen, 2006) comparing a range of power
    sources, including batteries, fuel cells and even
    the human body.

51
Performance comparisons
52
Where does the energy come from?
  • The energy always has to come from somewhere,
    however, and Figure 1.10 traces it back to its
    original source.

53
Where does the energy come from?
  • At present, most energy for digital devices, as
    for all electrically powered equipment,
    ultimately can be traced back to fossil fuels.
  • One solution is to find alternatives to fossil
    fuels, but the particular responsibility of the
    information and communication technology (ICT)
    industry is to attack the problem from the other
    direction and work to reduce energy consumption.
  • Indeed, concern about the growth of energy use
    has led to the issuing of a directive by the
    European Union, establishing a framework for the
    setting of ecodesign requirements for energy
    using products

54
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.20
  • Read the following announcement from Samsung, and
    use the information in it to answer the following
    questions.
  • (a) Estimate the assumed running power of the
    laptop, averaged over a month (assume there are
    four weeks in a month).
  • (b) How many litres of fuel must there be in the
    docking station?
  • (c) Approximately how many litres of fuel does
    the writer assume are contained in a coffee cup?

55
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.20

56
SELF-ASSESSMENT ACTIVITIES
  • Activity 1.20
  • (a) It uses 1200Wh to run for 8 h a day, 5 days a
    week, for a month (which we take to be 4 weeks).
    At 5 days per week that is 20 days, and 8 h a day
    gives 160 h. So the power drawn must be 1200/160
    7.5W.
  • (b) 1200Wh with a volumetric energy density of
    650 Wh/L means it must use 1200/650 1.85 L.
  • (c) It is supposed to be able to run for 15 h on
    a coffee cups worth of fuel. So 15 h would
    need 15 x 7.5 112.5 Wh. This would need
    112.5/650 0.173 L. (This is about 1/3 of a
    pint, which is reasonable.)
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