ENGG1015 Semester, 2011engg1015/fa11/handouts/02-elecsystems.pdf · 1st semester, 2011 ENGG1015 - Dr. K. Wong 5. System ComponentsSystem Components - Input Physical Input • Voltage

Electronic Systems

ENGG1015

1st Semester, 2011

Dr. Kenneth Kin-Yip Wong

Department of Electrical and Electronic Engineering

IntroductionIntroductionH ENGG1015:

H b id

1 semester

HybridToday

L time

Recall that ENGG1015 is about a hybrid top-

time

Recall that ENGG1015 is about a hybrid topdown introduction to EEE

Today:Today:A brief detour to the bottom

1st semester, 2011 ENGG1015 - Dr. K. Wong 2

Course TopicsCourse TopicsApplicationsHigh • Image & Video Processing

Systems

gLevel

• Computer & Embedded Systems• Computer Networky

Digital

Computer Network• Mobile Network

• Combinational LogicToday gLogic

Combinational Logic• Boolean Algebra

Today

Circuits • Basic Circuit Theory

ElectricalSignals

LowLevel

• Voltage, Current• Power & Energy



Electronic SystemsElectronic Systems

Process OutputInputPhysicalWorld

PhysicalWorld

All electronic/electrical systems must ultimately be y ydealing with the physical world:• Temperature of the air,• Time,,• Light,• Sound,• Human movementHuman movement…

Hierarchy (the use of sub-system), might hide that fact, but the all systems do interact with the physical world


System Components - InputSystem Components InputInputPhysical

• Voltage (V)• Current (I)

• Sound• Temperature• Light

C t h i l titi i t i t l titi th t

InputWorld( )

• Resistance (R)• Capacitance, Inductance…

• Light• Pressure• …

Convert physical quantities into internal quantities that are easy to manageIn EEE, it usually means converting a physical quantityIn EEE, it usually means converting a physical quantity into electrical signals, such as voltage (V), current (I), resistance (R), etc…ExamplesExamples• A microphone translates movement of air in the form of air

pressure into voltage• A light sensor translate light intensity (lumens) into• A light sensor translate light intensity (lumens) into

resistance• A thermistor translates temperature into resistance


System Components - OutputSystem Components OutputOutput Physical

• Voltage (V)• Current (I)

• Sound• Temperature• Light

C t i t l titi th t t

Output World( )

• Resistance (R)• Capacitance, Inductance…

• Light• Pressure• …

Convert internal quantities that are easy to manage into physical quantities that interact with the physical worldp yExamples• A speaker translates voltage values (V) into movement

f i i th f f i th t t dof air in the form of air pressure that generate sound• A light bulb that turns current values (I) into light • A motor that drives a wheel to spinoto t at d es a ee to sp• A solenoid that generates a pulling force on a shaft


System Components - ProcessingSystem Components ProcessingProcessocess

Performs the intended function of the system.Examples• Amplifies the electrical signal from a microphone• Control the power of the motor of a fan depending on

input voltagep gSlightly more complex example:• Mixes the voltage input from two different microphones,

lifi th i l d t l th lt th t illamplifies the signal, and control the voltage that will drive a signal indicator and output speaker


Complex Systems (1)Top-Level System Subsys B

Complex Systems (1)Subsystem A

SubsysB 1Subsystem A

SubsysCSubsys

B-2

B-1

Decompose a system into multiple sub-systems• Each sub-systems can be decomposed into more sub-Each sub systems can be decomposed into more sub

systems• A top-down approach

Compose larger systems by connecting smaller subCompose larger systems by connecting smaller sub-systems• Each composed system can be used to compose even

bigger systemsbigger systems• A bottom-up approach

The organization of sub-systems form a hierarchy


Complex Systems (2)Complex Systems (2)Top-Level System Subsys B

Subsystem ASubsys

B 1Subsystem ASubsys

CSubsysB-2

B-1

Engineers usually represent each sub-system g y p yas a block, forming block diagrams.The boundary of each sub-system is somewhat y yarbitrary• Up to the engineering team

But the key is to have a clean and well-defined interface


Quick Summary Quiz (1)Quick Summary Quiz (1)Which of these statements is false?• Smaller systems are easier to design and

develop.p• Smaller systems are more difficult to debug

if problem arisesif problem arises.• Each sub-team may be responsible for one

specific sub systems making managementspecific sub-systems, making management easier.S bdi idi l t h l t i l t• Subdividing a large system helps to isolate problems at sub-system boundaries.


Quick Summary Quiz (2)Quick Summary Quiz (2)Which item is a characteristic of a top-down approach?• Driven by system requirementDriven by system requirement• Driven by component integration

C t t t b i ll• Construct system by composing smaller parts

• Synthesis new ideas from existing components


Analog and DigitalAnalog and Digital

In electronic systems, the processing and transfer of a signal can broadly classified as analog or g y gdigital in nature.• Possible to mix-and-match

A l t i l ithAn analog system processes signals with continuous values• e.g. Temperature is now 23.132948123… °Ce.g. Temperature is now 23.132948123… C

A digital system processes signals with discrete values• e.g. The time now is 2:32pm, temperature is 24 °C


Analog SystemsAnalog SystemsAn analog electronic system processes signals with continuous values

Usually processes in continuous time asUsually processes in continuous time as well• Some sub-systems work with continuous

values in discrete time

The exact value of the signal matters

No approximation needed


Analog Systems - ProsAnalog Systems Prossound wave

Sound wave

OutputProcess

V V

Most physical quantities are continuous in nature:• e.g. temperature, time, humidity, pressure

The fundamental electronic quantities are also continuous in nature:• Voltage Current Resistance• Voltage, Current, Resistance

Analog processing is the most “natural” way of processing information from the physical worldp g p yFastest way to process any signal


Analog Systems - ConsAnalog Systems ConsSince exact value of a signal is needed, any degradation of signal will be reflected at the output.degradation of signal will be reflected at the output.

Examples:Interference sometimes called noise from outsideInterference, sometimes called noise, from outside the system:• Radio frequency interference (RFI)

Noise within the system:• Electric component’s behavior changes due to

temperature changetemperature change• Thermo noise in circuits

Non-ideal electronic componentsp• A resistor’s true value is never what it is designed• Degradation of components over time


Analog Systems – Cons (cont’d)Analog Systems Cons (cont d)Very difficult to store any exact value, in continuous timecontinuous timeDifficult to process signals based on previous valuesvalues• Echo cancellation• Reverb

Difficult to transport signals because signals degrades over any medium of transfer,

i ll i l di tespecially in long distances• Old TV systems suffer from “ghost images”• Radio station not received well• Radio station not received well…

Note: it is difficult, not impossible in above


Digital SystemsDigital SystemsA digital electronic system processes signals with discrete values in discrete timewith discrete values in discrete timeThe exact values of the input signal at discrete

i t i ti ti d i t di t lpoint in time are quantized into discrete values• e.g. all values are stored as integers only

• 24 5990010101 °C 25 °C• 24.5990010101 C 25 C• The process of obtaining data at discrete time or

space is called sampling.p p g• More on sampling & quantization later

The continuous values of the input signalsThe continuous values of the input signals represented by a series of finite number of discrete values.


Digital Processing SystemsDigital Processing SystemsAnalogSystemsSystems

Process OutputInputPhysicalWorld

PhysicalWorldWorld World

Digital

3, 5, 6, 7… 7.2, 6.1, 4.8, 3.14…

DigitalSystems ADC DAC


Digital Systems – ProsDigital Systems Pros Discrete values are easy to store, transport• No degradation over time & spaceNo degradation over time & space

Easy to process “back-in-time”• Knowing the past make predicting the future a lot g p p g

easierEnable very powerful and complicated processing of inputof input• e.g. complex logic, encryption, compression, etc

Immune to a lot more interferences from inside andImmune to a lot more interferences from inside and outside of the system than an analog system• E.g. RFI, circuit noise, non-idealistic circuits and

degradation o er timedegradation over time• Note: you can still interfere a digital system with

enough power


Quick Summary QuizQuick Summary QuizConsider an analog and a digital system, which of them is better in:• processing the exact value of a physicalprocessing the exact value of a physical

phenomenon?• processing the exact value of a physical• processing the exact value of a physical

phenomenon 1 day after the phenomenon has happened?has happened?

• producing the exact same result in two different occasions?different occasions?

Which one is better?c o e s be e


Input Stage: ADCInput Stage: ADCDigitalg taSystems

PhysicalWorld

PhysicalWorld

Input Process Output

Input Process OutputWorld World

3, 5, 6, 7… 7.2, 6.1, 4.8, 3.14…

ADC DAC


Input Stage: ADCInput Stage: ADCDigitalg taSystems

PhysicalWorld

PhysicalWorld

Process OutputInput

ADCWorld World

3, 5, 6, 7… 7.2, 6.1, 4.8, 3.14…

ADC DAC


Analog to Digital ConversionAnalog to Digital ConversionThe process of converting analog information into digital representation isinformation into digital representation is referred as analog to digital conversion• The circuit that performs the conversion isThe circuit that performs the conversion is

called an analog to digital convertor (ADC).The reverse process is called digital toThe reverse process is called digital to analog conversion, using a digital to analog convertor (DAC).Today: We’ll look at how to build a 1-bit ADC circuit• Review of basic circuit design• Extremely useful for project


1-bit ADC1 bit ADCADCvin out

Recall that an ADC converts (quantizes) an analog signal

ADCvin out

Recall that an ADC converts (quantizes) an analog signal into digital representationAn 1-bit ADC quantizes the analog input into a two possible outcomesoutcomes• hot VS cold• analog signal is presented VS not presented• input voltage is higher than certain value VS otherwise.• …

Use a single binary bit to represent 2 valuesUse a single binary bit to represent 2 values In other word, an 1-bit ADC makes a binary decision about the analog input.


1-bit ADC: logical design1 bit ADC: logical designEssentially, an 1-bit ADC is a comparator• Compares to a built in thresholdCompares to a built in threshold• Compares to a outside input value

An electronic ADC implements this concept using electronic circuitsp g


1-bit ADC (cont’d)1 bit ADC (cont d)vin

out = “1” if vin > vt out = “1” if vin > vref

vinvref

outvin out

Threshold Comparator

In the simplest case, an 1-bit ADC can be thought as a thresholding circuit

Threshold Comparator

as a thresholding circuit,• If the input voltage is higher than a built-in threshold vt,

then the output is “1”, otherwise the output is “0”.In a slightly more elaborated design, an 1-bit ADC can be implemented as a comparator circuit that compares the value of the ADC input v to anothercompares the value of the ADC input vin to another reference input (vref).


Peeling an ADC onionPeeling an ADC onionADCvin out 1 layer vin out

ADC “1” or “0”“1” or “0”

N h h h d f i d d

ADCvin outdown vref

out

Note that what we have done so far was indeed gradually unveiling the inner details of an ADCF th b t t t f l t di it lFrom the abstract concept of analog-to-digital conversion, we are moving downward to unveil more implementation details with the underlyingmore implementation details with the underlying circuits• A thresholding or comparator circuit

What are those “1”s and “0”s?Next:


I/O Characteristics of 1-bit ADCI/O Characteristics of 1 bit ADC10 0 1 0 1 0 1 0out

vin

vrefref

timet e


Implementing Logic LevelsImplementing Logic LevelsThe “0”s and “1”s in previous slides are merely symbols to represent two logical statessymbols to represent two logical states• e.g. the value 1/0, high/low, on/off, true/false,

hot/cold…hot/cold…

In actual circuit implementations, these “0”s and “1”s are represented by the voltageand 1 s are represented by the voltage (potential) presented at the output.• NOTE: There are other circuit implementations p

that uses current at the output node to represent “0”s and “1”s, but we will focus in voltage here.

What voltage should be used to represent “1” and what voltage to represent “0”?


Logic FamiliesLogic FamiliesThere are industrialindustrial standards on the voltage levels for grepresenting logic levels in di tdiscrete components.SSometimes referred as I/O standardsstandards.


Image source: http://www.interfacebus.com/voltage_LV_threshold.html

Own standard?Own standard?You can have your “own standard” when you build your own circuit e g :build your own circuit, e.g.:• digital VLSI designs

• e.g. 3.3V, 2.5V, 1.5V, 1.2V…• Your class project

• e.g. 12V

Usually uses the maximum allowable voltageUsually uses the maximum allowable voltage as “1”, and minimum allowable voltage as “0”Customary to label the max voltage as V orCustomary to label the max voltage as Vcc or Vdd

Minimum allowable voltage usually is 0 volt (notMinimum allowable voltage usually is 0 volt (not “0”).


Realistic Circuit I/O 1-bit ADCRealistic Circuit I/O 1 bit ADC10 0 1 0 1 0 1 0out

3 3

vin

3.3

vrefref

time

0

t e


Real CircuitsReal Circuits10 0 1 0 1 0 1 0out

3 3

vin

3.3

vrefref

time

0

t e



TutorialsTutorialsTutorials have started on Tuesday (Sep 6) and will repeat on Monday (Sep 12) with same content

You may attend either class A or class B’s tutorial session

First tutorial’s topic: review on circuitsFirst tutorial s topic: review on circuits• Extremely useful for your project


Pre-Project LabPre Project Lab2-4 pm Monday to Friday @ LG205 CYC b ildiCYC buildingStarts next weekStarts next weekCompulsoryGradedM F i 32 t d t ( ) iMon-Fri: 32 students (max) per sessionREAD the safety regulation before theREAD the safety regulation before the lab#1


Pre-Project Lab SignupPre Project Lab SignupNeed to sign up for the lab session that you intend to joinjSignup link active starting 2pm Friday, Sep 9 for 24 hours

Will b t d b it• Will be posted on course websiteOptional group signup• If you have already found your partners for project• If you have already found your partners for project,

signup to the SAME sessionProject group will be formed within the lab sessionj g pNeed login/password from EEE CSG for signup• Have already sent to your HKU email account on Sep 1• If NOT yet, send email to [email protected]• Or visit Rm 804, CYC building• First-come first-served• First-come, first-served



The Marshmallow ChallengeThe Marshmallow Challenge

18 minutesTeams of four (4)Teams of four (4)Tallest freestanding structure (on ground)Marshmallow on top (intact!!)www marshmallowchallenge comwww.marshmallowchallenge.com


In conclusion…In conclusion…All electronic/electrical systems can be di id d i t th i b t i tdivided into three main sub-systems: input, process, outputAnalog systems manipulate analog signals throughoutDigital systems handles digital data in process stageprocess stage1-bit ADC can be implemented using i l tsimple comparator

Logical values ≠ electrical valuesg


Documents

ENGG1015 Semester, 2011engg1015/fa11/handouts/02-elecsystems.pdf · 1st semester, 2011 ENGG1015 - Dr. K. Wong 5. System ComponentsSystem Components - Input Physical Input • Voltage