Industrial Electronics
N4
Chapter 1 – Kirchhoff's Law
KIRCHHOFF’S LAWS
• Kirchhoff’s Current Law states that the algebraic sum of currents entering
a point will be equal to the algebraic sum of the currents leaving that point.
• Kirchhoff’s Voltage Law states that the algebraic sum of the individual
voltage drops in a closed network is equal to the algebraic sum of the
applied voltage.
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Chapter 1 – Kirchhoff's Law (continued)
APPLICATION OF KIRCHHOFF’S LAWS
In setting up two equations you must understand that theory will form the
basis. Furthermore, the concepts of Ohm’s Law are equally applicable since
Kirchhoff’s Laws has as origin Ohm’s Law.
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Chapter 2 – Superposition Theorem
INTRODUCTION
The Superposition Theorem states that all current magnitudes and directions
may be determined by considering each supply on its own.
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Chapter 2 – Superposition Theorem (continued)
CURRENT- AND VOLTAGE DIVISION
• The current will divide between the two resistors and will always take the
path of least resistance.
• The voltage will divide between the two resistors and the largest resistor
will also have the largest voltage drop.
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Chapter 3 – Thevenin’s Theorem
INTRODUCTION
Thevenin’s Theorem specifies that a complex network consisting of
impedances and voltage sources may be replaced by a constant voltage
source with a series impedance.
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Chapter 3 – Thevenin’s Theorem (continued)
APPLICATION OF THEVENIN’S THEOREM
It is however important that you must have a thorough background of Ohm’s
Law since Thevenin’s Theorem has that law as basis.
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Chapter 4 – Series RLC-networks
THE EFFECT OF AN ALTERNATING QUANTITY ON A RESISTOR
Below we see:
• A resistor connected across an alternating current supply (a);
• A graphical representation of the phase relationship between the current
and the supply voltage (b); and
• A phasor diagram (c).
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Chapter 4 – Series RLC-networks (continued)
THE EFFECT OF AN ALTERNATING QUANTITY ON AN INDUCTOR
Below we see:
• An inductor connected across an alternating current supply (a);
• A graphical representation of the phase relationship between the current
and the supply voltage (b); and
• A phasor diagram (c).
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Chapter 4 – Series RLC-networks (continued)
THE EFFECT OF AN ALTERNATING QUANTITY ON A CAPACITOR
Below we see:
• A capacitor connected across an alternating current supply (a);
• A graphical representation of the phase relationship between the current
and the supply voltage (b); and
• A phasor diagram (c).
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Chapter 4 – Series RLC-networks (continued)
THE SERIES R-L NETWORK
This is a network consisting of an inductor and resistor connected in series.
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Chapter 4 – Series RLC-networks (continued)
THE SERIES R-C NETWORK
This is a network consisting of a capacitor and resistor connected in series.
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Chapter 4 – Series RLC-networks (continued)
THE SERIES RLC-NETWORK
This is a network consisting of a resistor, capacitor and inductor connected in
series.
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Chapter 4 – Series RLC-networks (continued)
CONDITIONS FOR RESONANCE
The following conditions will exist for • 𝑍 = 𝑅 and is minimum
resonance in a series RLC-network. • 𝜃 = 0°
• 𝑋𝐿 = 𝑋𝑐
• 𝑉𝐿 = 𝑉𝑐 and is maximum
• 𝑉𝑆 = 𝑉𝑅
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• I is maximum
• 𝑓Γ =
1
2×𝜋× 𝐿×𝐶
1
2
Chapter 5 – Parallel RLC-networks
THE PARALLEL RL-NETWORK
This is a network consisting of an inductor and resistor connected in parallel.
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Chapter 5 – Parallel RLC-networks (continued)
THE PARALLEL RC-NETWORK
This is a network consisting of a capacitor and resistor connected in parallel.
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Chapter 5 – Parallel RLC-networks (continued)
THE PARALLEL RLC-NETWORK
This is a network consisting a resistor, capacitor and inductor connected in
parallel.
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Chapter 5 – Parallel RLC-networks (continued)
CONDITIONS FOR RESONANCE
The following conditions will exist for
resonance in a parallel RLC-network. • 𝑍 is minimum
• 𝑋𝐿 = 𝑋𝑐
• 𝜃 = 0°
• 𝐼𝐿 = 𝐼𝑐 and is maximum
• I is minimum
• 𝐼𝑇 = 𝐼𝑅
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• 𝑓Γ =
1
2×𝜋× 𝐿×𝐶
1
2
Chapter 5 – Parallel RLC-networks (continued)
THE TUNED NETWORK
A more practical parallel network is illustrated below and is termed a ‘tuned
network’ or a ‘tank circuit’.
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Chapter 6 – Q-factor, Bandwidth and Complex
Notation
THE Q-FACTOR
The Q-factor of a network is also termed the ‘magnification factor’ and is
applicable to either a series- or parallel resonant network. This factor is
mathematically expressed by:
𝑋𝐿
𝑄=
𝑅
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Chapter 6 – Q-factor, Bandwidth and Complex Notation (continued)
BANDWIDTH
The bandwidth may be defined as that range of frequencies between 𝐹1 and
𝐹2 where the power has fallen or dropped to half its value.
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Chapter 6 – Q-factor, Bandwidth and Complex Notation (continued)
COMPLEX NOTATION
Complex notation is a method used to calculate different quantities in
alternating current networks in modulus and angle form which gives us a
much easier method of calculation.
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Chapter 7 – Basic Atomic Theory
THE STRUCTURE OF MATTER
Matter may be defined as anything that has mass and that occupies space
and can be composed of elementary substances that are found in nature.
Matter can be divided into the following groups:
• Solids;
• Liquids;
• Gasses; and
• Plasma.
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Chapter 7 – Basic Atomic Theory (continued)
ATOMS
An atom may be defined as the smallest part of an element that can
participate in a normal chemical reaction. All atoms consist of minute
particles of electrical charges arranged in a set pattern and consist of:
• Electrons;
• Protons; and
• Neutrons.
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Chapter 7 – Basic Atomic Theory (continued)
ENERGY SHELLS
In the diagram, the centre circle represents the nucleus consisting of the
protons and neutrons and the outer circle or circles indicates the shells for
the orbiting electrons.
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Chapter 7 – Basic Atomic Theory (continued)
VALENCY
The number of electrons in the outer shell of an atom, called the valence
shell, will determine the valency of that element. Valency is an indication of
the ability of an atom to gain or lose electrons and will determine the
electrical properties of that element.
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Chapter 7 – Basic Atomic Theory (continued)
CONDUCTION
Movement of electrons or conduction can and will take place in any given
conducting material, in a desired direction, should a source of power be
applied across such material. The conduction process can be by either hole
flow (transfer) or electron motion or by both.
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Chapter 7 – Basic Atomic Theory (continued)
ENERGY BANDS
In any given material, conducting or insulating, there are two distinct energy
bands in which electrons may exist, namely the conduction band and the
valence band but they will be separated by the forbidden gap.
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Chapter 8 – PN-Junction Theory
INTRODUCTION
There are two main elements that are used in the manufacture of semiconductor devices or components namely Silicon and Germanium. As the
name Semi-conductor suggests, it is not a very good conductor and
something needs to be done in order to improve on its conducting
capabilities.
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Chapter 8 – PN-Junction Theory (continued)
CRYSTAL LATTICE STRUCTURES
In the diagram, the circles represent the
nucleus of the atom and the squares
indicate the valence electrons in the
valence shell. This type of crystal lattice
structure is found in all crystalline
elements.
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Chapter 8 – PN-Junction Theory (continued)
DONOR DOPING
Donor doping is a mixing process that will generate a free (extra) electron in
the conduction band of the atom as well as crystal lattice structure.
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Chapter 8 – PN-Junction Theory (continued)
ACCEPTOR DOPING
Acceptor doping is a mixing process that will generate a hole in the
conduction band of the atom as well as crystal lattice structure.
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Chapter 8 – PN-Junction Theory (continued)
FERMI-LEVELS
The Fermi-level may be defined as the amount of energy the free electrons
as well as the holes possess within the material.
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Chapter 8 – PN-Junction Theory (continued)
THE PN-JUNCTION
A PN-junction is formed when a P-type material and an N-type material is
joined together. This joining together is not an electrical junction but is a
junction which is achieved through a manufacturing process in which
electrons and holes are uniformly distributed in the two types of material
provided they have been doped to the same extent.
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Chapter 9 – Semi-conductor Diodes
INTRODUCTION
A diode may be defined a single PN-junction two terminal device which will
offer a low resistance when forward biased and a high resistance when
reverse biased.
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Chapter 9 – Semi-conductor Diodes (continued)
THE DIODE AND CHARACTERISTIC CURVE
The characteristic curve is depicted below:
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Chapter 9 – Semi-conductor Diodes (continued)
BASIC RATING FACTORS OF A DIODE
Rating factors will assist during the design phase of circuits so that reliable
as well as satisfactory operation can be assured. They can be seen as:
Low current - Up to 49 ampere;
Medium current - 50 ampere to 199 ampere; and
High current - 200 ampere and higher.
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Chapter 9 – Semi-conductor Diodes (continued)
ELECTRICAL CHARACTERISTICS OF A DIODE
The electrical characteristics of a diode are based on the absolute maximum
rating system and provide information pertaining to the maximum values that
may not be exceeded for a given diode. These specifications are always
contained in the manufacturers’ specification sheets.
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Chapter 9 – Semi-conductor Diodes (continued)
THE DIODE EQUATION
𝑖 = 𝐼𝑠 (𝑒 𝑞𝑉/𝐾𝑇 )-1
Where i = forward current
𝐼𝑠 = reverse saturation current
q = electron charge
V = potential difference across the diode
K = Boltzmann’s constant
T = temperature
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Chapter 9 – Semi-conductor Diodes (continued)
FORWARD RESISTANCE OF A DIODE
All diodes are manufactured from semi-conductor materials and will have a
resistance caused by its atomic structure. This resistance is given by:
𝐾×𝑇
𝑅=
𝑞×𝐼
Where K = Boltzmann’s constant
T = temperature in Kelvin
q = electron charge
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Chapter 9 – Semi-conductor Diodes (continued)
THE DIODE LOAD-LINE
The load-line for a diode is obtained by considering the maximum values of
forward current and the maximum value of the forward bias for a particular
rectifier diode.
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Chapter 10 – Diode Applications
APPLICATION OF DIODES
Diodes have applications such as:
• Clippers; and
• Rectifiers.
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Chapter 10 – Diode Applications (continued)
RECTIFIER CONCEPTS
There are a number of concepts that will determine the magnitude of the
output obtained from a rectifier. These are:
• The transformer ratio;
• Average dc-voltage;
• Ripple voltage;
• Ripple factor; and
• PIV-rating.
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Chapter 10 – Diode Applications (continued)
FILTER NETWORKS
A filter can be defined as a component that will remove the ripple (pulsating)
component from the output of a rectifier circuit.
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Chapter 10 – Diode Applications (continued)
NO-LOAD VOLTAGE
The no-load voltage of any power supply may be defined as that voltage
which is supplied by the secondary winding of the transformer when the load
to that power supply is not connected.
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Chapter 10 – Diode Applications (continued)
VOLTAGE REGULATION
Voltage regulation may be defined as that change in the output voltage (fullload) for varying load conditions.
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Chapter 10 – Diode Applications (continued)
VOLTAGE MANIPULATION
At times, greater voltages are required and for this purpose we make use of
voltage multiplication circuits which may, depending on the design, supply
two or more times the peak input value as an output.
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Chapter 11 – Special Diodes and Applications
THE ZENER DIODE
The zener diode is constructed so that it is mainly used in the reverse bias
mode. When operated in the forward bias mode, however, its forward
characteristics are similar to that of an ordinary junction diode.
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Chapter 11 – Special Diodes and Applications (continued)
THE VARACTOR DIODE
The varactor diodes are semi-conductor, voltage-dependent, variable
capacitors. Their mode of operation is determined by the capacitance that
exists at the PN-junction when the device is reversed biased.
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Chapter 11 – Special Diodes and Applications (continued)
THE TUNNEL DIODE
The tunnel diode is also termed an Esaki diode. It is also a two-terminal
device and is almost exclusively used as a high-frequency component in the
following applications:
• An amplifier;
• An oscillator; and
• A switch.
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Chapter 11 – Special Diodes and Applications (continued)
PHOTO-DIODES
A photo-diode is a semi-conductor PN-junction device whose area of
operation is restricted to the reverse bias region.
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Chapter 12 – Transistors
INTRODUCTION
The transistor is a three-terminal two junction component and is commonly
referred to as a ‘junction transistor’ but it must be noted that there are other
types of transistors also available.
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Chapter 12 – Transistors (continued)
THE TRANSISTOR
The junction transistor consists of two types of extrinsic or doped semiconductor material. It has three terminals and one type of doped material (Nor P-type) sandwiched between two types of the other type of doped material
(N-or P-type). This arrangement provides us with the opportunity of obtaining
two types of transistors namely an NPN- or PNP-transistor.
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Chapter 12 – Transistors (continued)
OPERATING REGIONS OF A TRANSISTOR
• The cut-off region is that region where the emitter-base as well as the
collector-base junctions is reverse biased.
• The active region is that region where the emitter-base junction is forward
biased and the collector-base junction is reverse biased.
• The saturation region is that region where the emitter-base as well as the
collector-base junctions is forward biased.
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Chapter 12 – Transistors (continued)
THE SWITCHING SPEED OF A TRANSISTOR
Response is not always immediate when an input current is applied to the
base of a transistor since the electrons have, what is termed a ‘transit time’,
to move across the junction as well as the junction capacitance to overcome.
This rise time may be defined as the time it takes for the collector current to
rise from 10% of its maximum value to 90% of its maximum value.
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Chapter 12 – Transistors (continued)
THE TRANSISTOR AS A SWITCH
A transistor can be utilised as an electronic switch as seen in the following
diagram:
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Chapter 12 – Transistors (continued)
THE TRANSISTOR AS AN AMPLIFIER
The three configurations or modes of amplifier operation are:
• Common emitter;
• Common base; and
• Common collector (emitter follower).
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Chapter 12 – Transistors (continued)
COMMON EMITTER AMPLIFIER DEVELOPMENT
It is important to consider bias in this operation:
The biasing potentials, 𝑉𝑒𝑏 and 𝑉𝑐𝑏 for both PNP- and NPN-type transistors
can be seen:
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Chapter 12 – Transistors (continued)
COMMON EMITTER GRAPHICAL ANALYSIS
The common emitter has three main characteristic curves which defines its
behaviour. It will be possible to determine the transistor operation for static
as well as dynamic conditions. These are the:
• Input characteristics;
• Transfer characteristics; and
• Output characteristics.
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Chapter 13 – Amplification Classes, Coupling
Methods and Feedback
INTRODUCTION
All amplifiers fall into a specific category of amplification which is dependant
upon the application of the amplifier as well as the coupling method used.
The class of amplification refers to the conduction period of the output signal
compared to the input signal.
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Chapter 13 – Amplification Classes, Coupling Methods and Feedback
(continued)
CLASSES OF AMPLIFICATION
There is:
• Class A amplification;
• Class B amplification;
• Class AB amplification; and
• Class C amplification.
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Chapter 13 – Amplification Classes, Coupling Methods and Feedback
(continued)
AMPLIFIER COUPLING METHODS
It is sometimes required to connect two or more transistors in cascade in
order to increase the gain since one transistor may not supply the required
gain on its own. This can happen through:
• RC-inter-stage coupling;
• Direct inter-stage coupling;
• Transformer inter-stage coupling; and
• Pull-pull amplifiers.
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Chapter 13 – Amplification Classes, Coupling Methods and Feedback
(continued)
CROSS-OVER DISTORTION
Distortion may be defined as a condition that will occur when the output
waveform is not an amplified version of the input waveform.
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Chapter 13 – Amplification Classes, Coupling Methods and Feedback
(continued)
FEEDBACK
Feedback can be defined as a process whereby a part of the output signal is
fed back to the input in anti-phase so as to stabilise the gain of the amplifier
or similar circuit.
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Chapter 14 – Hybrid-Parameters
INTRODUCTION
Any transistor has a relation to current, voltage and impedance and is very
often referred to the parameters of the transistor. ‘Hybrid-parameters’ literally
means ‘of mixed origin’.
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Chapter 14 – Hybrid-Parameters (continued)
THE TRANSISTOR AS A TWO-PORT DEVICE
The treatment of ac-analysis will be done in a manner that makes no
distinction between an NPN and PNP transistor. This is depicted below:
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Chapter 14 – Hybrid-Parameters (continued)
SMALL SIGNAL ANALYSIS (COMMON EMITTER)
All amplifiers are basically two-port devices in that it will consist of two input
terminals and two output terminals.
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Chapter 15 – Uni-Junction and Field Effect
Transistors
INTRODUCTION
The Uni-Junction Transistor is mainly used in digital circuits and for the firing
circuits in SCR-Control (Silicon Controlled Rectifier).
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Chapter 15 – Uni-Junction and Field Effect Transistors (continued)
THE UJT-TRANSISTOR
The construction of a UJT-transistor consists of a
piece of N-type silicon material on which a heavily doped P-type material is
attached and is termed the emitter. The UJT is a three-terminal device but
only contains one PN-junction.
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Chapter 15 – Uni-Junction and Field Effect Transistors (continued)
FIELD EFFECT TRANSISTOR
These have the following characteristics over bi-polar transistors:
• No off-set voltage when used as a switch;
• Small gain-bandwidth;
• Low noise level;
• Relatively immune to radiation;
• Extremely high input impedance; and
• Good thermal stability.
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Chapter 16 – Power Control
INTRODUCTION
Power control forms an integral part in the electronic as well as electric field
in modern industry today.
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Chapter 16 – Power Control (continued)
THE SILICON CONTROLLED RECTIFIER
An SCR may be defined as an ordinary diode with a control element namely
the gate.
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Chapter 16 – Power Control (continued)
DELAY ANGLE AND CONDUCTION ANGLE
The delay angle may be defined as that part of the waveform for which no
conduction will take place whereas the conduction angle may be defined as
that part of the waveform for which conduction will take place.
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Chapter 16 – Power Control (continued)
SCR APPLICATIONS
SCR may be used for speed control or for a light dimmer.
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Chapter 16 – Power Control (continued)
SCR CONTROL METHODS
These include:
• Phase control;
• Cycle control;
• Cyclotronic control; and
• Duty control.
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Chapter 16 – Power Control (continued)
THE DIAC
A Diac is a two terminal bi-directional semi-conductor component which is
normally used in conjunction with a Triac. A Diac can conduct in both
directions and may be seen as two diodes connected back-to-back.
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Chapter 16 – Power Control (continued)
THE TRIAC
A Triac is a three terminal bi-directional gate-controlled semi-conductor
component which is normally used in conjunction with a Diac. This
component has the advantage that it may be triggered by a positive pulse on
the gate for one half of the input waveform as well as a negative pulse on the
other half of the input waveform thereby giving us full-wave control in a single
component.
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Chapter 16 – Power Control (continued)
POWER CONTROL USING A DIAC AND TRIAC
Using a Diac and a Triac gives us the opportunity to make use of full-wave
control. The purpose of the diac is mainly to allow a negative pulse on the
gate during the negative half of the input waveform and to allow a positive
pulse on the gate during the positive half of the input waveform.
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Chapter 16 – Power Control (continued)
THE QUADRAC
A Quadrac is a three terminal bi-directional semi-conductor component and
consists of a Diac and a Triac in one package and has the characteristics of
each component on its own.
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Chapter 16 – Power Control (continued)
CONTROL SYSTEMS
There are two types of main control systems available in industry today:
• Open-loop control systems; and
• Closed-loop control systems.
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Chapter 17 – Operational Amplifiers
INTRODUCTION
All circuits have to be constructed using discreet components (transistors,
resistors, capacitors, inductors, diodes, etc.) and that it is quite a
cumbersome effort. The operational amplifier solves this problem to quite an
extent in that an amplifier is now available in a single integrated circuit (IC)
package.
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Chapter 17 – Operational Amplifiers (continued)
THE OPERATIONAL AMPLIFIER
Various modes of operation can be obtained from an operational amplifier
and the operation is based on the concept of a differential amplifier.
An operational amplifier has two input terminals namely an inverting input
marked - and a non-inverting input marked +. A single output can be
obtained depending on which of the above terminals have been utilised as
the input.
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Chapter 17 – Operational Amplifiers (continued)
MODES OF OPERATION
The good characteristics, size and cost of operational amplifiers makes them
very versatile in a number of applications, such as:
• The inverting amplifier;
• The non-inverting amplifier;
• The inverting summing amplifier; and
• The voltage follower.
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Chapter 17 – Operational Amplifiers (continued)
MATHEMATICAL FUNCTIONS USING OPERATIONAL AMPLIFIERS
Operational amplifiers can be used for mathematical decision making
applications such as:
• The differentiator; and
• The integrator.
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Chapter 18 – Function Generator and
Oscilloscope
INTRODUCTION
In the field of Electronics it is required that use is made of different test
instruments to perform our task. Some of these instruments are used to
provide specific quantities such as the function generator and other
instruments are used to be able to measure, but more so to observe such as
the oscilloscope.
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Chapter 18 – Function Generator and Oscilloscope (continued)
FUNCTION GENERATOR
A function generator is an instrument that is capable of delivering a choice of
waveforms and whose frequencies are adjustable over a fairly large range.
The output wave forms available include:
• Sine waves;
• Triangular waves;
• Square waves; and
• Saw-tooth waves from terminals A, B and C.
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Chapter 18 – Function Generator and Oscilloscope (continued)
OSCILLOSCOPE
An oscilloscope is a measuring instrument which is not only capable of giving
the magnitude of a measurement but also the shape of the variable. It may
be used in the following applications:
• Studying waveforms and indicating phase relationships of waveforms;
• Ac- and dc-voltage measurement;
• Amplification gain;
• Frequency determination and/or distortion indication.
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Chapter 18 – Function Generator and Oscilloscope (continued)
SYNCHRONISATION
The signal to be studied and the time base signal must be synchronised in
order to ensure a stable signal on the oscilloscope screen.
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Chapter 18 – Function Generator and Oscilloscope (continued)
SIGNAL ANALYSIS
We need to consider the layout of the CRT-screen:
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Chapter 18 – Function Generator and Oscilloscope (continued)
WAVEFORMS
During the process of utilising test instruments such as oscilloscopes and
function generators one will meet up with various forms of waves such as
sine-waves.
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Chapter 19 – Transducers
INTRODUCTION
A transducer can be defined as a device that converts one form of energy
into another form of energy.
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Chapter 19 – Transducers (continued)
SELECTION OF TRANSDUCERS
There are numerous types of transducers available for use. The following
criteria need to be taken into account when selecting a transducer:
• Determine the physical quantity that needs to be measured.
• Which transducer principle is best suited to measure a particular quantity?
• What is the level of accuracy that will be required for this measurement?
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Chapter 19 – Transducers (continued)
TRANSDUCER APPLICATIONS
There are the following applications possible:
• Mechanical transducers; and
• Electrical transducers.
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Chapter 19 – Transducers (continued)
CAPACITIVE TRANSDUCERS
The capacitor is most commonly used include the following:
• Air;
• Mica;
• Paper;
• Ceramic; and
• Electrolytic and each material will have its own given dielectric constant.
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Chapter 19 – Transducers (continued)
INDUCTIVE TRANSDUCERS
Inductive transducers make use of a change in magnetic field characteristics
since it is impossible to alter the inductance value of the inductor.
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Chapter 19 – Transducers (continued)
PHOTO-SENSITIVE TRANSDUCERS
Semi-conductors exhibits the phenomena to change its characteristics when
exposed to light whether it be natural light or artificial light hence the term
‘photosensitive’ which literally translates to being sensitive to light.
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Chapter 19 – Transducers (continued)
THERMO-COUPLES
It is possible to generate a voltage by means of a thermo-couple. A thermo
couple consists of two dissimilar metal wires joined at one end termed the
sensing or hot junction and terminated at the other end termed the reference
or cold junction.
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