Transcript electronics 1 - Computer Engineering 2009

ELECTRONICS ENGINEERING 1
INTRODUCTION
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ELECTRONICS
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the science dealing with the development and
application of devices and systems involving the
flow of electrons or other carriers of electric
charge, in a vacuum, in gaseous media, in
plasma, in semiconductors, in solid-state and/or in
similar devices, including, but not limited to,
applications involving optical, electromagnetic and
other energy forms when transduced or converted
into electronic signals.
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APPLICATIONS OF ELECTRONICS
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COMMUNICATIONS ELECTRONICS
ELECTRIC POWER
DIGITAL ELECTRONICS
AUTOMOTIVE ELECTRONICS
INDUSTRIAL ELECTRONICS
MEDICAL ELECTRONICS
CONSUMER ELECTRONICS
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2 TYPES OF ELECTRONIC SIGNAL
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ANALOG – ELECTRONIC SIGNALS THAT
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DIGITAL – ELECTRONIC SIGNALS THAT
THE AMPLITUDE CHANGES CONTINUOUSLY
WITH RESPECT TO TIME WITH NO BREAKS OR
DISCONTINUITIES.
ARE DESCRIBE AS DISCRETE; THEIR
AMPLITUDE MAINTAINS A CONSTANT LEVEL
FOR A PRESCRIBED PERIOD OF TIME THEN IT
CHANGES TO ANOTHER LEVEL.
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TWO TYPES OF ELECTRONIC
CIRCUIT
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DISCRETE CIRCUIT – Electronic
circuit that is composed of individual
circuit components.
INTEGRATED CIRCUIT (IC) –
Electronic circuit with thousands of
circuit components in a single package.
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CLASSIFICATIONS OF ELECTRONIC
COMPONENTS ACCORDING TO FUNCTION
ACTIVE
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SEMICONDUCTORS
ELECTRON TUBES
VDD (Visual Display Devices)
PASSIVE
RESISTOR, CAPACITOR & INDUCTOR
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ELECTRONIC COMPONENTS
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SEMICONDUCTORS
DIODE, TRANSISTOR, ICs, etc.
RESISTORS
CAPACITORS
INDUCTOR/ COIL
ELECTRON TUBES
VACUUM TUBES, PICTURE TUBES, CRT (Cathode Ray Tube)
VISUAL DISPLAY DEVICES
LCD (Liquid Crystal Display)
LED ( Light Emitting Diode)
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ELECTRONIC CIRCUIT REPRESENTATION
(ELECTRONIC CIRCUIT DIAGRAM)
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Block Diagram
Circuit Diagram (Schematic)
Pictorial Diagram
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Block Diagrams
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Block diagrams are used to understand (and design)
complete circuits by breaking them down into smaller
sections or blocks.
Each block performs a particular function and the
block diagram shows how they are connected
together.
No attempt is made to show the components used
within a block, only the inputs and outputs are shown.
This way of looking at circuits is called the systems
approach.
Power supply (or battery) connections are usually not
shown on block diagrams.
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Audio Amplifier System
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The power supply (not shown) is connected to the pre-amplifier and
power amplifier blocks.
Microphone - a transducer which converts sound to voltage.
Pre-Amplifier - amplifies the small audio signal (voltage) from the
microphone.
Tone and Volume Controls - adjust the nature of the audio signal.
The tone control adjusts the balance of high and low frequencies.
The volume control adjusts the strength of the signal.
Power Amplifier - increases the strength (power) of the audio signal.
Loudspeaker - a transducer which converts the audio signal to sound.
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Radio Receiver System
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The power supply (not shown) is connected to the audio amplifier
block.
Aerial - picks up radio signals from many stations.
Tuner - selects the signal from just one radio station.
Detector - extracts the audio signal carried by the radio signal.
Audio Amplifier - increases the strength (power) of the audio signal.
Loudspeaker - a transducer which converts the audio signal to
sound.
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Regulated Power Supply System
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Transformer - steps down 230V AC mains to low voltage AC.
Rectifier - converts AC to DC, but the DC output is varying.
Smoothing - smooths the DC from varying greatly to a small ripple.
Regulator - eliminates ripple by setting DC output to a fixed
voltage.
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Feedback Control System
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Feedback Control System
• The power supply (not shown) is connected to the control circuit
block.
• Sensor - a transducer which converts the state of the controlled
quantity to an electrical signal.
• Selector (control input) - selects the desired state of the output.
Usually it is a variable resistor.
• Control Circuit - compares the desired state (control input) with the
actual state (sensor) of the controlled quantity and sends an
appropriate signal to the output transducer.
• Output Transducer - converts the electrical signal to the controlled
quantity.
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Feedback Control System
• Controlled Quantity - usually not an electrical quantity, e.g.
motor speed.
• Feedback Path - usually not electrical, the Sensor detects
the state of the controlled quantity.
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Circuit Diagram
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Circuit diagrams show how electronic
components are connected together. Each
component is represented by a symbol.
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Wires and Connections
component
Wire
Wires joined
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circuit symbol
________
function
To pass current very easily from one part
of a circuit to another.
A 'blob' should be drawn where wires
are connected (joined), but it is
sometimes omitted. Wires connected
at 'crossroads' should be staggered
slightly to form two T-junctions.
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Wires and Connections
component
circuit symbol
function
Wires
not
joined
In complex diagrams it is often
necessary to draw wires crossing even
though they are not connected. The
'hump' symbol is preferable because
the simple crossing on the left may be
misread as a join where you have
forgotten to add.
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Wires and Connections
component
circuit symbol
function
Cell
Supplies electrical energy.
A single cell is often wrongly called a
battery, but strictly a battery is two or
more cells joined together.
Battery
Supplies electrical energy. A battery is
more than one cell.
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Wires and Connections
component
circuit symbol
function
DC supply
Supplies electrical energy.
DC = Direct Current, always flowing in
one direction.
AC supply
Supplies electrical energy.
AC = Alternating Current, continually
changing direction.
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Power Supplies
component
circuit symbol
function
fuse
A safety device which will 'blow' (melt)
if the current flowing through it
exceeds a specified value.
transformer
Two coils of wire linked by an iron core.
Transformers are used to step up
(increase) and step down (decrease)
AC voltages. Energy is transferred
between the coils by the magnetic field
in the core. There is no electrical
connection between the coils.
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Power Supplies
component
Earth
(ground)
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function
circuit symbol
A connection to earth. For many
electronic circuits this is the 0V (zero
volts) of the power supply, but for
mains electricity and some radio
circuits it really means the earth. It is
also known as ground.
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Output Devices: Lamps, Heater,
Motor, etc.
Component
Circuit Symbol
Function
Lamp
(lighting)
A transducer which converts
electrical energy to light. This
symbol is used for a lamp providing
illumination, for example a car
headlamp or torch bulb.
Lamp
(indicator)
A transducer which converts
electrical energy to light. This
symbol is used for a lamp which is
an indicator, for example a warning
light on a car dashboard.
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Output Devices: Lamps, Heater,
Motor, etc.
Component
Circuit Symbol
Function
Heater
A transducer which converts
electrical energy to heat.
Motor
A transducer which converts
electrical energy to kinetic energy
(motion).
Bell
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A transducer which converts
electrical energy to sound.
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Output Devices: Lamps, Heater,
Motor, etc.
Component
Buzzer
Inductor
(Coil,
Solenoid)
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Circuit Symbol
Function
A transducer which converts
electrical energy to sound.
A coil of wire which creates a
magnetic field when current passes
through it. It may have an iron core
inside the coil. It can be used as a
transducer converting electrical
energy to mechanical energy by
pulling on something.
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Switches
Component
Push
Switch
a. push-tomake
b. push-tobreak
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Circuit Symbol
Function
A push switch allows current to flow
only when the button is pressed.
This is the switch used to operate a
doorbell.
This type of push switch is normally
closed (on), it is open (off) only
when the button is pressed.
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Switches
Component
Circuit Symbol
Function
On-Off
Switch
(SPST)
SPST = Single Pole, Single Throw.
An on-off switch allows current to
flow only when it is in the closed
(on) position.
2-way
Switch
(SPDT)
SPDT = Single Pole, Double Throw.
A 2-way changeover switch directs
the flow of current to one of two
routes according to its position.
Some SPDT switches have a central
off position and are described as
'on-off-on'.
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Switches
Component
Circuit Symbol
Function
Dual On-Off
Switch
(DPST)
DPST = Double Pole, Single Throw.
A dual on-off switch which is often
used to switch mains electricity
because it can isolate both the live
and neutral connections.
Reversing
Switch
(DPDT)
DPDT = Double Pole, Double
Throw. This switch can be wired up
as a reversing switch for a motor.
Some DPDT switches have a central
off position.
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Switches
Component
Relay
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Circuit Symbol
Function
An electrically operated switch, for
example a 9V battery circuit
connected to the coil can switch a
230V AC mains circuit.
NO = Normally Open,
COM = Common,
NC = Normally Closed.
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Circuit Diagram and Component
Layouts
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Circuit diagrams show the connections as clearly as
possible with all wires drawn neatly as straight lines.
The actual layout of the components is usually quite
different from the circuit diagram.
A circuit diagram is useful when testing a circuit and
for understanding how it works.
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Drawing Circuit Diagrams
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not difficult but it takes a little practice to draw neat,
clear diagrams
a useful skill for science as well as for electronics
You will certainly need to draw circuit diagrams if you
design your own circuits
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Drawing Circuit Diagrams
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Follow these tips for best results:
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Make sure you use the correct symbol for each
component.
Draw connecting wires as straight lines (use a ruler).
Put a 'blob' ( • ) at each junction between wires.
Label components such as resistors and capacitors with
their values.
The positive (+) supply should be at the top and the
negative (-) supply at the bottom.
The negative supply is usually labeled 0V, zero volts.
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Drawing Complex Circuit Diagrams
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Try to arrange the diagram so that signals flow from
left to right: inputs and controls should be on the left,
outputs on the right.
You may omit the battery or power supply symbols,
but you must include (and label) the supply lines at
the top and bottom.
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End of Lesson 1
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