Industrial Electronics
N2
Module 1: Direct current principles
ATOMIC THEORY
An atom could be defined as the smallest part of an element that retains the
property of the element. The three main parts are made up of:
• Protons (positively charged);
• Neutrons (no electrical charge); and
• Tiny electrons (negatively charged).
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Module 1: Direct current principles (continued)
DIRECT CURRENT PRINCIPLES
Electrically, materials are classified as:
• Conductors: When valency electrons are easily removed from their
valency bands to be utilised for conduction purposes.
• Insulators: When valency electrons are not “easily” removed from their
valency bands.
• Semi-conductors: Subjected to certain conditions, these elements can be
considered to be either conductors or insulators.
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Module 1: Direct current principles (continued)
RESISTORS IN SERIES, PARALLEL, AND SERIES-PARALLEL
Resistors can be arranged in:
• Series:
• Parallel:
• And a combination of series-parallel.
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Module 2: Alternating current principles
GENERATING AN ALTERNATING VOLTAGE
When a conductor cuts through the lines of magnetic force between two
opposite poles of a magnet, a voltage is induced in the conductor. This is the
principle of operation of an elementary electric generator and it is used to
generate an AC voltage.
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Module 2: Alternating current principles (continued)
ALTERNATING CURRENT (AC)
When a voltage of alternating magnitude is connected across a
load, a current of alternating magnitude, is generated as a representation of
the current flowing in the circuit.
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Module 2: Alternating current principles (continued)
AC CIRCUITS CONTAINING R, L AND C COMPONENTS
In order to use effective values of voltage and current in any AC circuit, the
effect of resistance (R), inductance (L) and capacitance (C) must be
considered. The combined effect of the resistance (R), inductive reactance
(𝑋𝑋𝐿𝐿 ) and capacitive reactance (𝑋𝑋𝑐𝑐 ) together makes up the total opposition to
current flow in an AC circuit.
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Module 3: Measuring instruments: Analogue and
digital meters
THE MOVING-COIL METER
The basic moving-coil meter in can be used for measuring DC voltages and
DC currents as well as resistance.
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Module 3: Measuring instruments: Analogue and digital meters
(continued)
DAMPING MECHANISMS
Galvanometer damping is provided by two mechanisms:
• Mechanical which is caused mainly by the motion of the coil through the
air surrounding it; and
• Electromagnetic which is caused by induced effects in the moving coil as it
rotates in the magnetic field, provided that the coil forms part of a closed
electrical circuit.
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Module 3: Measuring instruments: Analogue and digital meters
(continued)
THE AVO METER
An AVO meter is an indicating device determining specific electrical
quantities, most commonly Amperes, Volts and Ohms.
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Module 3: Measuring instruments: Analogue and digital meters
(continued)
METER USES
The meter can be used as:
• An Ammeter, which must be connected in series with the load;
• A Voltmeter, which must be connected in parallel with the load; and
• An Ohmmeter, which must also be connected in parallel with the load.
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Module 3: Measuring instruments: Analogue and digital meters
(continued)
SAFETY PRECAUTIONS AND HANDLING
Read the operating instructions before using a multimeter. Although these
meters are relatively robust, well-constructed and manufactured, negligence
and carelessness can easily damage the instrument. Pay attention to the
correct settings, connections and polarity when using the instrument.
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Module 4: Synchro and servo systems
INTRODUCTION
A simple Synchro system can be thought of as the electrical equivalent of a
long metal shaft that transmits motion from one point to another. For
example, when one end of the shaft is being rotated mechanically, the other
end turns in exactly the same manner.
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Module 4: Synchro and servo systems (continued)
SYNCHRO MOTOR (TRANSMITTER)
A typical Synchro motor may have up to five conductors coming out of its
housing (two for the rotor and three for the starter).
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Module 4: Synchro and servo systems (continued)
APPLICATIONS
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Module 4: Synchro and servo systems (continued)
PRINCIPLE OF OPERATION
Lenz’s Law can be defined as a magnetic field that cuts through a coil to
induce a voltage in that coil, which causes a current to flow. This induced
current will in turn generate its own magnetic field, which will oppose the
original inducing magnetic field.
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Module 4: Synchro and servo systems (continued)
SYNCHRO TRANSMITTER-RECENER CONNECTIONS
The Synchro transmitter can be connected in the following ways:
• As a Synchro transmitter-indicator team;
• As a Synchro transmitter-indicator system with reverse rotation;
• As a Synchro system with 180° phase shift; and
• As a Synchro system with 240° phase shift.
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Module 4: Synchro and servo systems (continued)
ADVANTAGES OF SYNCHRO SYSTEMS TO MECHANICAL SYSTEMS
• No friction losses between sender and receiver;
• Utilises very little electrical energy;
• Small and light since data transfer is by means of electrical conductors;
• Transmission can take place around bends without modifications;
• Connection between transmitter and receiver can be by means of
conductors, infrared light, radar, radio frequency and micro moves; and
• In limited cases, flexible metal shafts are used.
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Module 4: Synchro and servo systems (continued)
SYNCHRO SYSTEMS VS SERVO SYSTEMS
When a Synchro system is redesigned with the appropriate servo motors,
servo amplifiers and feedback systems to accommodate larger currents,
torque and heavier loads (such as a gear train); then the Synchro system is
referred to as a servo system.
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Module 5: Transducer devices
INTRODUCTION
A transducer can be defined as a device that converts one form of energy
into another form of energy.
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Module 5: Transducer devices (continued)
THERMISTORS
Thermistors are non-linear resistors that are extremely sensitive to
temperature changes, exhibiting either PTC or NTC. Thermistors
applications include:
• Measurement and control of temperature (furnaces and kilns);
• Temperature compensation;
• Liquid level indicators; and
• Time delay devices.
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Module 5: Transducer devices (continued)
THERMOCOUPLES
Thermocouples are also temperature sensitive transducer devices. These
devices are extremely accurate and are employed in industries such as the
aircraft industry to monitor the exhaust gas temperature of a turbine engine.
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Module 5: Transducer devices (continued)
BIMETAL STRIPS
The bimetal strip is probably the most common and widely used device to
detect thermal change. Bimetal applications include features in:
• The motor vehicle industry;
• Domestic appliances, such as the refrigerator;
• Hot-water tank temperature control;
• Electrical power control; and
• Gas-operated appliances.
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Module 5: Transducer devices (continued)
LIGHT-DEPENDENT RESISTORS (LDR)
Light-dependent resistors have a variety of uses in the various industries but,
due to their relative slow response times (around 6–7 m seconds) their use is
generally limited to relatively slow-moving objects such as counting bottles,
cans or any other similar product in various industries.
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Module 6: The decibel
INTRODUCTION
The term (or unit) decibel, abbreviated as dB, is named after Alexander
Graham Bell who first applied the logarithmic principle to measurements he
performed during experiments of deafness. The decibel can be
mathematically defined as:
𝑃𝑃𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜
𝑑𝑑𝑑𝑑
𝑁𝑁𝑑𝑑𝑑𝑑 = 10log
𝑃𝑃𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖
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Module 6: The decibel (continued)
TRANSMISSION LINES
Any wire or conductor can be considered a transmission line. When
considering microwave frequencies, coaxial cable and parallel wires
generate rather great losses and we have to use another form of
transmission line such as waveguides and fibre optics.
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Module 6: The decibel (continued)
CHARACTERISTIC IMPEDANCE
The characteristic impedance is the ratio of the voltage to the current of a
wave travelling in either direction on a transmission line (implying that the
input and output impedances is common to the line).
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Module 6: The decibel (continued)
CURRENT RATIOS
By definition, we can see that the gain (or loss) of a network or transmission
line is not merely expressed in terms of power (watts), but it can also be
expressed in terms of current or voltage.
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Module 6: The decibel (continued)
CONCLUSION
The gain or loss of a network can be expressed as being a ratio between the
output and input of the system in terms its power (watts) voltage or current
expressed in decibel (dB). Although the decibel is not an absolute unit, it
indicates the relationship between two powers.
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Module 7: Semi-conductor diodes
INTRODUCTION
All materials exhibit certain resistive characteristics when analysed at room
temperature. Materials can be divided electrically into three main groups:
• Conductors;
• Insulators; and
• Semi-conductors.
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Module 7: Semi-conductor diodes (continued)
ENERGY LEVELS
The resistance of a semi-conductor material is greater than that of a
conductor, but considerably less than that of an insulator. The energy-band
diagram expresses the relationship between conductors, semi-conductors,
and insulators:
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Module 7: Semi-conductor diodes (continued)
DOPING
The method of adding impurities to pure Si or Ge to make it a better
conductor of electron flow is called doping.
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Module 7: Semi-conductor diodes (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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Module 7: Semi-conductor diodes (continued)
BIASING
There is forward biasing:
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And reverse biasing:
Module 7: Semi-conductor diodes (continued)
DIODE APPLICATIONS
Junction diodes are extensively used for rectification purposes in a wide
variety of industries. Other than their ability to supply half-wave or full-wave
rectification of an AC quantity, diodes are also used as protection devices in
inductive circuits and other types of loads.
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Module 7: Semi-conductor diodes (continued)
TYPES OF DIODES AVAILABLE
Types of diodes available includes:
• PN-junction diodes;
• Point-contact diodes;
• Zener diodes;
• Photo diodes;
• Light-emitting diodes; and
• Varactor diodes.
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Module 7: Semi-conductor diodes (continued)
LIGHT-EMITTING DIODE (LED)
A light-emitting diode will emit (give off) visible light when correctly biased
and energised. Their area of operation is in the forward bias region when the
recombination of holes and electrons within the junction region will release
energy in the form of heat and photons.
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Module 7: Semi-conductor diodes (continued)
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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Module 7: Semi-conductor diodes (continued)
PHOTO DIODE
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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Module 7: Semi-conductor diodes (continued)
VARACTER DIODE (VVC)
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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Module 8: Semi-conductor transistors
TRANSISTOR CONSTRUCTION
The transistor is a three-layer semiconductor device consisting of two PNjunctions arranged as:
• Two P-type and one N-type layer (called a PNP transistor); or
• Two N-type and one P-type layer (called a NPN transistor).
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Module 8: Semi-conductor transistors (continued)
TRANSISTOR BIASING
The biasing potentials, 𝑉𝑉𝑒𝑒𝑒𝑒 and 𝑉𝑉𝑐𝑐𝑏𝑏 for both PNP- and NPN-type transistors
can be seen:
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Module 8: Semi-conductor transistors (continued)
TRANSISTOR OPERATION
the emitter supplies the majority carriers, which is in turn are being collected
by the collector with the presence of a small base current.
Applying Kirchoff ’s current law we get:
𝐼𝐼𝑒𝑒 = 𝐼𝐼𝑐𝑐 + 𝐼𝐼𝑏𝑏
which relates to the emitter current = the sum of the collector and base
currents.
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Module 8: Semi-conductor transistors (continued)
TRANSISTOR CHARACTERISTIC CURVE
Transistors are employed as being either an “electronic” switch or an
amplifier. The characteristic curve seen below illustrates the various regions
of operation for a transistor.
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Module 8: Semi-conductor transistors (continued)
TRANSISTOR AMPLIFIER CIRCUITS
Since a transistor has three terminals, it can be connected in anyone of three
configurations:
• Common base;
• Common emitter; and
• Common collector configuration.
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Module 8: Semi-conductor transistors (continued)
TRANSISTOR COMPARISON TABLE
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