T325: Technologies for Digital Media Second semester – 2011/2012 Tutorial 1 Arab Open University - T325 – Spring 2012

Arab Open University - T325 – Spring 2012

T325: Technologies for Digital MediaSecond semester – 2011/2012

Tutorial 1


2Outline

• Presentation of the T325 course• Power for Digital Media• Introduction • Battery technology• Fuel cells.• Power from the environment.• Where does the energy come from?


3General introduction

• Learning outcomes • Course breakdown• Assessments • Study calendar • Plagiarism


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 analyze, critique and synthesize 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.

4


5Course 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.


6Course Assessment

• Continuous assessment (50% of the course grade)• TMA: One TMA worth 20% of course grade• 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

Week Start date Course block Course section(s) Assignments /due date

1 20-Feb-12Block 1: Enabling

technologiesPower for digital media

2 27-Feb-12 Information storage

3 5-Mar-12 Error control coding

4 12-Mar-12 Seeing and hearing:

multimedia

5 19-Mar-12 Video and audio coding

6 26-Mar-12

7 2-Apr-12Block 2: Intellectual property and security

issues

Intellectual property rights & Security

8 9-Apr-12 Digital rights management &

Digital watermarking

9 16-Apr-12Block 3 Mobile

broadband Mobile evolution & Network architecture

10 23-Apr-12

11 30-Apr-12 Access and modulation

TMA11/12/2011

12 7-May-12

13 14-May-12 Better and beyond

14 21-May-12

15 28-May-12 Revision

Stu

dy c

ale

nd

ar


8Plagiarism

• 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


10Introduction

• 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.


11Introduction

Miscellaneous contains smaller electronics such as chargers, home audio equipment, game consoles, etc. Also contain non-electronics such as portable fans, irons, etc.

• Power needs of digital equipment have generally been increasing

• Powering consumer electronic and computer products alone in the UK every year - that’s 23% of the average household electricity bill.


12Introduction


13Introduction

Crysta

l rad

io

Porta

ble a

nalo

gue F

M ra

dio

DAB radi

o

Mob

ile te

lepho

ne on

stan

dby

Mob

ile te

lepho

ne in

use

Lapto

p com

puter

Deskt

op co

mputer

in us

e

Deskt

op co

mputer

in ‘s

leep’

mod

e

TV with

liqu

id cr

ystal

disp

lay (i

n use

)

TV with

liqu

id cr

ystal

disp

lay (o

n stan

dby)

Low en

ergy l

ight

bulb

for a

small

room

Car, dr

iven

at 50

mph

and c

onsu

ming 5

0 mpg

0.00002 0.17 2.2 0.0056 0.54 18110

3

210

1.8 20

2300

Typical power (W)


Battery technology

• Batteries produce electricity from a chemical reaction, called an electrochemical reaction.

• You get a ‘battery’ when several cells are connected together

14


15Battery technology

• The chemical reaction depends upon:• the material used to make the anode • the material used to make the cathode • 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.


Battery technology

• Two categories of batteries • Primary batteries • Manufactured to be used once• Examples: alkaline and lithium batteries

• Secondary batteries• Rechargeable

16



• 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.



• 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.



• 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.• Internal resistance is a characteristic of the battery itself


Battery technology 20



• 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 the International System of Units (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).


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 Britain’s 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)”

22

22



Activity 1.2 : • “The company says that one of its typical phones needs a charge of

160 milliamps on Britain’s 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)”

• 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:

23



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.

24

24



Activity 1.5 : a) From Ohm’s 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



Activity 1.7

A 1.2V battery has a capacity of 800 mAh. How long could it run if the load uses 50 mA?

Answer:

Capacity = I * t => t = capacity / I = 800 / 50 = 16 h

27



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 30 ohm?

Answer• 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.

28


Battery technology

• Capacity (running time)• The time t the battery can be used is given by t= capacity / 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,

• power = current x voltage.

29



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.

30

30



Activity 1.9 - Answer• 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

31

31



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



• Volumetric energy density is the amount of energy stored per unit volume. In SI units, 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. • Gravimetric energy density SI unit is joules per kilogram

(J/kg), • Other units can be used such as watt-hours per gram (Wh/g)

and kilowatt-hours per kilogram (kWh/kg).

34



• Volumetric power density is the power that can be delivered, per unit volume. • The volumetric power density SI unit is W/m3

• 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. • The gravimetric power density SI unit is W/Kg• Other units might be used, such Watt per gram (W/g), Kilo-

Watt per Kg (KW/Kg), etc.

35


36SELF-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.



Activity 1.13 - Answer• 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.

37

37



Activity 1.14a) 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.

b) 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.



Activity 1.14 – Answer

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



• 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.



• 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.



• 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.



• 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.



• 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)

• Self-Discharge• 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.



• Environmental issues• Primary batteries• 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 • 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.


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 specialized applications; providing electricity for use in space rockets

• Interest for research in fuel cell batteries• Increasing demand for power by digital devices• Inability of batteries to keep up• The attraction of being able to revive a laptop by pouring in a

cupful of liquid fuel• Aims of research in fuel cells batteries• Producing a small, cheap and safe fuel cell for electronic

devices

46


47Fuel 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.


48Power from the environment

• Energy scavenging or energy harvesting• Finding ways of picking up power from the environment• Removes the need for providing an energy supply ‘up

front’, • Reduces the amount of energy being drawn from a battery. • Examples: solar-powered calculators are in fact harvesting

energy from the ambient light and have been around for decades.

• A very important area of application of energy harvesting: providing power for wireless sensor networks.


49Performance comparisons

• Figure of merits can be applied for other sources of power (than batteries)


Where does the energy come from? 50


51

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.

• Solutions• find alternatives to fossil fuels• reduce energy consumption (responsibility of the ICT

industry)

• European Union established a framework for the setting of eco-design requirements for energy-using products



Activity 1.20Read 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?



Activity 1.20

53



Activity 1.20 - Answersa) 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 cup’s 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.)

54


55

TEST YOUR KNOWLEDGE - QUESTIONS FROM PREVIOUS EXAMS


56

• In a fuel cell battery, the substance that makes it easier for a reaction to take place by lowering the activation energy is called• Compound• Barrier• Reactor• Catalyst • Fuel

(Fall 2011 – Final Exam)


57

• The batteries that have the property to be rechargeable are called:• Primary batteries• Primitive batteries• Secondary batteries• Alkaline batteries• Tertiary batteries

(Fall 2011 – MTA)


58

• The amount of energy stored per unit volume is defined as• Volumetric energy density• Gravimetric power density• Volumetric power density• Gravimetric energy density• Voltage

(Fall 2011 – MTA)


59

• What are the environmental issues related to the manufacture and use of batteries? Highlight those related to primary and secondary batteries

• Explain briefly how the battery works. Give examples of different batteries.

(Fall 2011 – MTA)


60

• A 1.2V battery has a capacity of 1700 mAh. How long could it run if the load has a resistance of 50ohm? What energy does the battery store? Give your answer in both watt-hours and joules.

(Fall 2011 – MTA)


61

• Suppose a battery has the following parameters:• Voltage: 1.2V• Capacity: 600 mAh• Weight: 24 g• Volume: 9 cm3

• Current delivered: 1A

• Calculate the volumetric energy density and the gravimetric power density in SI units.

(Fall 2011 – MTA)


62

• The chemical reaction inside a battery depends upon:• The material used to make the anode• The material used to make the cathode• The material used for the electrolyte• All of the above• None of the above

(Fall 2011 – MTA)


63

• Why power consumption constitutes an issue even for the mains-powered equipment?• Overheating of electronic circuits damages the

components.• Need to reduce energy consumption in order to combat

global warming• To minimize the cost of production of the equipment• a & b• a, b & c

(Fall 2011 – MTA)


64

• The following numbers appears on the back of a battery: 1.5 Volts, 12 grams, 10 cm3, 10 Ohms, 600 mAh.

• Calculate the volumetric and gravimetric energy density of this battery in SI units

• This battery is connected to a 30 Ohm resistance• What time this battery can last with this load?• Calculate the volumetric and gravimetric power density

in SI units.

(Fall 2011 – MTA)


65

• A 6V battery have the following characteristics:• Volumetric power density = 7.5 W/L• Energy supplied = 6J• Current delivered = 10 mA

• Calculate the volume of this battery in cm3 (3 marks)• Calculate the capacity of this battery in Ah (3 marks)• Supposing that the battery delivers the current mentioned

when connected to a 580 Ohms external resistance. What is the internal resistance of this battery? (2 marks)

(Fall 2011 – Final exam)

Documents

T325: Technologies for Digital Media Second semester – 2011/2012 Tutorial 1 Arab Open University - T325 – Spring 2012