CAMBRIDGE TECHNICALS
IN ENGINEERING
LEVEL 3 UNIT 5 – ELECTRICAL AND
ELECTRONIC DESIGN
DELIVERY GUIDE
April 2015
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
CONTENTS
Introduction
3
Related Activities
4
Key Terms
6
Misconceptions/Areas of difficulty
9
Suggested Activities:
Learning Outcome (LO1)
10
Learning Outcome (LO2)
13
Learning Outcome (LO3)
15
Learning Outcome (LO4)
16
Learning Outcome (LO5)
18
ELECTRICAL AND ELECTRONIC DESIGN
2
OCR has collaborated with current practitioners to ensure that the ideas put forward in
this Delivery Guide are practical, realistic and dynamic. The Guide is structured by learning
outcome so you can see how each activity helps you cover the requirements of this unit.
We appreciate that practitioners are knowledgeable in relation to what works for them
and their learners. Therefore, the resources we have produced should not restrict or
impact on practitioners’ creativity to deliver excellent learning opportunities.
Whether you are an experienced practitioner or new to the sector, we hope you find
something in this guide which will help you to deliver excellent learning opportunities.
If you have any feedback on this Delivery Guide or suggestions for other resources you
would like OCR to develop, please email resourcesfeedback@ocr.org.uk.
Unit aim
All electrical and electronic devices rely on their components working effectively. This in
turn relies on effective manufacture, and ultimately on the successful design of electrical
components.
The aim of this unit is for learners to develop the ability to be able to apply knowledge of
AC and DC circuit theory to circuit design, and to apply a systems approach to electrical
design, developing knowledge of the component devices needed to be able to do this.
Learners will develop an understanding of the applications of electromagnetism
in electrical design, and the ability to be able to use both semi-conductors and
programmable process devices in their designs.
Unit 5 Electrical and electronic design
LO1
Be able to apply AC and DC circuit theory to circuit design
LO2
Understand the application of electromagnetism in electrical design
LO3
Be able to apply a systems approach to electrical design
LO4
Understand power supplies and power system protection
LO5
Be able to use semi-conductors in electrical and electronic design
Opportunities for English and maths
skills development
We believe that being able to make good progress in English and maths is essential to
learners in both of these contexts and on a range of learning programmes. To help you
enable your learners to progress in these subjects, we have signposted opportunities
for English and maths skills practice within this resource. These suggestions are for
guidance only. They are not designed to replace your own subject knowledge and
expertise in deciding what is most appropriate for your learners.
EnglishMaths
Please note
The timings for the suggested activities in this Delivery Guide DO NOT relate
to the Guided Learning Hours (GLHs) for each unit.
Assessment guidance can be found within the Unit document available from
www.ocr.org.uk
The latest version of this Delivery Guide can be downloaded from the OCR website.
3
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
This Delivery Guide has been developed to provide practitioners with a variety of
creative and practical ideas to support the delivery of this qualification. The Guide
is a collection of lesson ideas with associated activities, which you may find helpful
as you plan your lessons.
ELECTRICAL AND ELECTRONIC DESIGN
INTRODUCTION
3
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
RELATED ACTIVITIES
The Suggested Activities in this Delivery Guide listed below have also been related to other Cambridge Technicals in Engineering units/Learning Outcomes (LOs). This could help with
delivery planning and enable learners to cover multiple parts of units.
This unit (Unit 5)
Title of suggested activity
Other units/LOs
LO1
Circuit symbols
Unit 2 Science for engineering
LO1 Understand applications of SI units and measurement
LO1
Circuits and DC circuit layout
Unit 4 Principles of electrical and
electronic engineering
LO1 Understand fundamental electrical principles
LO1
Ohm’s Law and power calculations
Unit 1 Mathematics for engineering
LO1 Understand the application of algebra relevant to engineering problems
Unit 2 Science for engineering
LO3 Understand fundamental scientific principles of electrical and electronic engineering
Unit 4 Principles of electrical and
electronic engineering
LO1 Understand fundamental electrical principles
Unit 1 Mathematics for engineering
LO1 Understand the application of algebra relevant to engineering problems
Unit 4 Principles of electrical and
electronic engineering
LO1 Understand fundamental electrical principles
Unit 1 Mathematics for
engineering
LO1 Understand the application of algebra relevant to engineering problems
Unit 2 Science for engineering
LO3 Understand fundamental scientific principles of electrical and electronic
engineering
Unit 4 Principles of electrical and
electronic engineering
LO1 Understand fundamental electrical principles
Unit 1 Mathematics for
engineering
LO3 Understand exponentials and logarithms related to engineering problems
Unit 2 Science for engineering
LO3 Understand fundamental scientific principles of electrical and electronic
engineering
Unit 1 Mathematics for
engineering
LO4 Be able to use trigonometry in the context of engineering problems
Unit 2 Science for engineering
LO3 Understand fundamental scientific principles of electrical and electronic
engineering
Unit 4 Principles of electrical and
electronic engineering
LO2 Understand alternating voltage and current
LO1
LO1
LO1
LO1
Kirchhoff’s Laws
DC networks
RC circuits
AC circuits and power factor
ELECTRICAL AND ELECTRONIC DESIGN
LO1
Passive filters
Unit 1 Mathematics for
engineering
LO1 Understand the application of algebra relevant to engineering problems
LO1
Rectification voltage regulators and power
supplies
Unit 4 Principles of electrical and
electronic engineering
LO4 Understand power supplies and power system protection
LO1
Circuit protection
Unit 4 Principles of electrical and
electronic engineering
LO4 Understand power supplies and power system protection
LO2
Transformers
Unit 1 Mathematics for
engineering
LO1 Understand the application of algebra relevant to engineering problems
4
Title of suggested activity
Other units/LOs
LO2
Faraday’s and Lenz’s Laws
Unit 1 Mathematics for
engineering
LO1 Understand the application of algebra relevant to engineering problems
Unit 2 Science for engineering
LO3 Understand fundamental scientific principles of electrical and electronic
engineering
LO2
DC motors and generators
Unit 4 Principles of electrical and
electronic engineering
LO3 Understand electric motors and generators
LO3
Systems approach – block diagrams
Unit 4 Principles of electrical and
electronic engineering
LO4 Understand power supplies and power system protection
LO4
Op Amps – comparators
Unit 1 Mathematics for
engineering
LO1 Understand the application of algebra relevant to engineering problems
Unit 4 Principles of electrical and
electronic engineering
LO5 Understand analogue electronics
Unit 1 Mathematics for
engineering
LO1 Understand the application of algebra relevant to engineering problems
Unit 4 Principles of electrical and
electronic engineering
LO5 Understand analogue electronics
LO4
5
Summing op-amp
LO4
Logic gates
Unit 4 Principles of electrical and
electronic engineering
LO6 Understand digital electronics
LO4
Flip Flops – SR type
Unit 4 Principles of electrical and
electronic engineering
LO6 Understand digital electronics
LO4
Flip Flops – JK, D and T types
Unit 4 Principles of electrical and
electronic engineering
LO6 Understand digital electronics
LO4
BCD counters and display decoders
Unit 4 Principles of electrical and
electronic engineering
LO6 Understand digital electronics
ELECTRICAL AND ELECTRONIC DESIGN
This unit (Unit 5)
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
RELATED ACTIVITIES
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
KEY TERMS
UNIT 5 – ELECTRICAL AND ELECTRONIC DESIGN
Explanations of the key terms used within this unit, in the context of this unit
Key term
Explanation
Battery
A battery is a container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power.
In this unit, this is taken as alkaline and rechargeable (NiMh, Lithium-ion).
BCD counter
A digital circuit which has a clock input and a number of count outputs. The BCD (binary coded decimal) counter can count to ten on the application of a clock
signal.
Capacitive reactance
Capacitive reactance is the opposition to current flowing through a capacitor in an AC circuit. It is given by the formula Xc = 1 / (2πfC) with unit ohm.
Capacitors – charging
The time constant for a series capacitor/resistor combination is given by t=RC
and discharging and RC
When charging, capacitor voltage is described by the equation: Vc = Ve- t/RC, where the potential difference (p.d.) at time ‘t’ is Vc and at t = 0, the p.d. is Vo. Similar
time constant
defining equations exist for charging current and discharging voltage and current.
Circuit impedance (AC
circuit)
Circuit protection
In an AC circuit, impedance (symbol Z) is the measure of total opposition to current flow. It is made up from two components – resistance (R) and reactance (XL
and XC). Its calculation (and appropriate formula) depends on whether the circuit is capacitive, inductive or both.
Circuit protection is the intentional installation of a ‘weak link’ in an electrical circuit. This is a fuse or circuit breaker, referred to in these resources as a circuit
protection device.
Combinational logic
Combinational logic refers to a digital logic function made of primitive logic gates (AND, OR, NOT, etc.) in which all outputs of the function are directly related to
the current combination of values on its inputs. Any changes to the signals being applied to the inputs will immediately propagate through the gates until their
effects appear at the outputs.
Darlington pair
A Darlington pair is a pair of two transistors that act as a single transistor but with a much higher current gain.
DC network (electrical
network)
An electrical network is an interconnection of electrical components (e.g. batteries, resistors, inductors, capacitors, switches) or a model of such an
interconnection, consisting of electrical elements (e.g. voltage sources, current sources, resistances, inductances, capacitances).
ELECTRICAL AND ELECTRONIC DESIGN
In this unit, it is taken to mean a network consisting of a DC power source and at least five components (e.g. DC power source with two series resistors and three
parallel resistors connected in a series/parallel arrangement).
Diode
A diode is a semiconductor device with two terminals, typically allowing the flow of current in one direction only.
Electrical power and
the Power Law
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt (one joule per second).
EMC
EMC or electromagnetic compatibility in electrical and electronic equipment means an electronic or electrical product shall work as intended in its environment.
The electronic or electrical product must not generate electromagnetic disturbances, which may influence other products.
The Power Law relates power, current, voltage and resistance in a circuit with the formulae (for a dc circuit): P = I2R and P = VI
It is concerned with both radiated and conducted interference.
6
Explanations of the key terms used within this unit, in the context of this unit
Key term
Explanation
Faraday’s Law
A law stating that the electromotive force is induced in the circuit proportional to the rate of change of the flux linkage.
Flip Flop (bistable)
E = N (dF/dt) where E is the electromotive force, N is the number of turns and dФ/dt is the rate of change of flux.
Generator (electric)
An electric generator is a device for converting mechanical energy into electrical energy by electromagnetic induction.
High-pass filter
A high-pass filter is an electronic filter that passes signals with a frequency higher than a certain cut-off frequency and attenuates signals with frequencies lower
than the cut-off frequency.
Inductive reactance
Inductive reactance is the opposition to current flowing through a coil in an AC circuit. It is given by the formula XL = 2 πfL with unit ohm.
7
An input device is used to provide data and control signals to an information processing system. It includes switches photodiode, phototransistor, LDR, NTC
thermistor and the microphone.
Kirchhoff’s first Law
Kirchhoff’s first law (the current law) states that at any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of
currents flowing out of that node.
Kirchhoff’s second Law
Kirchhoff’s second law (the voltage law) states that the directed sum of the electrical potential differences (voltage) around any closed network is zero.
Lenz’s Law
A law stating that the direction of an induced current is always such as to oppose the change in the circuit or the magnetic field that produces it.
Logic gate
A logic gate is an elementary building block of a digital circuit. Most logic gates have two inputs and one output. At any given moment, every terminal is in one
of the two binary conditions - low (0) or high (1), represented by different voltage levels.
Low-pass filter
A low-pass filter is a filter that passes signals with a frequency lower than a certain cut-off frequency and attenuates signals with frequencies higher than the cutoff frequency.
Microcontroller
A microcontroller is a device that incorporates a microprocessor. A microcontroller will often also contain memory, input and output controllers and a range of
other special features. It is often a single integrated circuit.
Microprocessor
A microprocessor is a programmable device. It is an integrated circuit that contains all the functions of a central processing unit of a computer. Unlike a
microcontroller, the microprocessor often requires external memory and devices to provide inputs and outputs.
Motor (electric)
An electric motor is an electric machine that converts electrical energy into mechanical energy.
Op amp
An operational amplifier (Op-Amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.
Output device
An output device is a device to perform or indicate the result of an information processing system. It can include piezo-electric buzzers/sounders, lamps, light
emitting diodes (LED), LED 7 segment displays, dot matrix displays, liquid crystal displays (LCD), display modules, solenoids, relays and speakers.
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Input device
A flip-flop (often referred to as a bistable gate or latch) is a circuit that has two stable states and can be used to store information. It is often used in devices such
as counters, memory chips and microprocessors.
ELECTRICAL AND ELECTRONIC DESIGN
KEY TERMS
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
KEY TERMS
Explanations of the key terms used within this unit, in the context of this unit
Key term
Explanation
Parallel resistors
Parallel resistance refers to resistors connected in parallel. Total resistance is given by 1/R = 1/R1 + 1/R2 + 1/R3
Phasor diagram
Phasor diagrams are used to represent a rotating vector, simply called a phasor. This is a scaled line whose length represents an AC quantity that has both
magnitude (amplitude) and direction (phase) which is frozen at some point in time.
Power factor
The ratio of the actual electrical power dissipated by an AC circuit to the product of the root mean square (r.m.s.) values of current and voltage. The difference
between the two is caused by reactance in the circuit and represents power that does no useful work. Power factor is the cosine of the phase angle between
voltage and current.
Programmable device
A programmable device is an electronic component used to build reconfigurable digital circuits. It is often programmed using a programming language, and
has inputs and outputs along with other special features.
Programmable interface A PIC is a form of microcontroller. PIC stands for programmable interface controller. PIC microcontrollers appeal to hobbyists and experimenters, especially in
controller (PIC)
the fields of electronics and robotics due to their ease of use and application in control systems.
Programmable logic
controller (PLC)
A programmable logic controller (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes decisions
based upon a custom program to control the state of output devices. A PLC will often contain a microcontroller.
Rectification and
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one
direction. The process is known as rectification.
In the unit both full- and half-wave rectification are considered.
Resistance and Ohms
Law
Series resistors
Solar cell
Resistance is an electrical quantity that measures how a device or material reduces the electric current flow through it. The SI derived unit of resistance is the
ohm Ω Ohm’s law relates resistance to voltage and current flow in a circuit. V = IR
I = V/R and R = V/I
Series resistance refers to a resistor or combination of resistors connected in series. Total resistance is given by R = R1 + R2 + R3
A semiconductor device that converts the energy of sunlight into electric energy. Also called photovoltaic (PV) cell.
ELECTRICAL AND ELECTRONIC DESIGN
Systems approach
A systems approach is often used to design and evaluate engineering systems. It involves modelling a system using block diagrams to include inputs, outputs,
process elements and feedback.
Transformer (ratio
calculations)
The total voltage or current induced into the secondary winding of a transformer is determined mainly by the ratio of the number of turns in the primary to the
number of turns in the secondary.
Transistor
Np/Ns = Is/Ip and Np/Ns = Vs/Vp (where V is voltage, I is current, N is number of turns and p and s are primary and secondary respectively)
Voltage regulator
A transistor is a semiconductor device with three connections that regulates current or voltage flow and acts as a switch or gate for electronic signals.
Voltage regulator is a device or circuit which is connected between the power source and a load, which provides a constant voltage despite variations in input
voltage or output load.
8
Some common misconceptions and guidance on how they could be overcome
What is the misconception?
How can this be overcome?
Resources which could help
Use of radian measure in AC circuit
theory and waveforms (ω = 2πf)
Learners will need to appreciate that in electrical calculations involving sine waves that radians are used
as opposed to degrees (i.e. 2π radians = 3600).
http://www.electronics-tutorials.ws/
accircuits/phasors.html
Determining overall impedance
and phase angle using phasor
diagrams
Using values in degrees will result in incorrect solutions.
Teachers could explain that one cycle of a sine wave = 3600 = 2π radians. Web-based resources might
prove useful to illustrate this.
Impedance and phase angle can be determined using trigonometry; however, learners often find this
concept difficult to understand.
ELECTRICAL AND ELECTRONIC DESIGN
MISCONCEPTIONS/AREAS OF DIFFICULTY
http://www.electronics-tutorials.ws/
accircuits/phasors.html
An effective way of understanding phasor diagrams, and determining overall impedance (Z) and phase
angle (ø) might be by drawing scale diagrams. Impedance and phase angle can be determined using
Pythagoras’ Theorem and the cosine rule respectively.
Phasor diagrams might also represent voltage and current in an AC circuit.
9
Learners often confuse the terms power factor and phase angle, using them interchangeably and
incorrectly. The power factor is the cosine of the phase angle between the current and voltage in an AC
circuit. It is the ratio of the active (true) power and apparent power. Suitable relevant worked examples
may help.
http://www.engineeringtoolbox.
com/power-factor-electricalmotor-d_654.html
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Determining power factor (PF)
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
SUGGESTED ACTIVITIES
LO No:
1
LO Title:
Be able to apply AC and DC circuit theory to circuit design
Title of suggested activity
Suggested activities
Suggested timings
Also related to
Circuit symbols
Learners may already be familiar with a number of electrical and electronic devices and their
associated circuit symbols. Learners might extend their knowledge by researching a wider range of
circuit symbols. The Institution of Engineering and Technology (IET) provide authoritative resources
which may be a good starting point - http://www.theiet.org/students/resources/units-symbols.cfm
1 hour
Unit 2, LO1
1 hour
Unit 4, LO1
1 hour
Unit 1, LO1
Unit 2, LO3
Unit 4, LO1
2 hours
Unit 1, LO1
Unit 4, LO1
Teachers could develop a circuit symbol quiz to confirm understanding.
Circuits and DC circuit layout
Teachers might continue the topic of circuit design by introducing learners to circuits containing
electrical and electronic components. Learners could be tasked to identify components in the circuit,
such as DC power sources, to determine total resistance for series and parallel resistor combinations,
and to identify common features (such as the potential divider).
Resources explaining circuit layout and common circuit configurations might prove useful – such
as the following explaining resistor combinations (http://www.physicsclassroom.com/class/circuits/
Lesson-4/Combination-Circuits)
Learners could analyse circuit layout for a range of different circuits. It may also be possible for
learners to relate circuit diagrams to physical circuits.
Ohm’s Law and power
calculations
Learners might already be familiar with Ohm’s Law and the Power Law. Teachers might provide
learners with further opportunity to apply these to the design of circuits. Learners could determine
resistance, voltage and current in circuits using Ohm’s Law, and power using the Power Law. Webbased resources might prove useful such as the following: http://www.electronics-tutorials.ws/
dccircuits/dcp_2.html
Learners might also use simulation to analyse circuits, or build physical circuits to relate theory to
practice.
ELECTRICAL AND ELECTRONIC DESIGN
Kirchhoff’s Laws
Kirchhoff’s Laws are fundamental to the design and analysis of DC circuits. These are the voltage and
current laws (which are explained here: http://www.electronics-tutorials.ws/dccircuits/dcp_4.html)
Learners may already be familiar with these.
It may be possible to demonstrate Kirchhoff’s Laws using physical circuits by measuring voltages and
currents.
Teachers could develop further circuit examples where learners can apply Kirchhoff’s Laws to analyse
operation of a DC circuit.
10
Title of suggested activity
Suggested activities
Suggested timings
Also related to
DC networks
Once learners are familiar with Ohm’s Law, the Power Law, Kirchhoff’s Laws and common circuit
layouts then they might analyse more complex DC circuits (DC networks).
2 hours
Unit 1, LO1
Unit 2, LO3
Unit 4, LO1
1 hour
Unit 1, LO3
Unit 2, LO3
This could include the potential divider, and networks with one DC power source and at least five
components (e.g. DC power source with two series resistor and three parallel resistors connected in a
series/parallel arrangement).
ELECTRICAL AND ELECTRONIC DESIGN
SUGGESTED ACTIVITIES
Reference texts such as Electrical Circuit Theory and Technology (John Bird, 2013) may prove a useful
source of practice questions.
Again, learners might relate theory to practice by analysing, building and testing physical circuits.
Simulation could also be used.
See Lesson Element DC Networks.
RC circuits
RC circuits are commonly used in electronics as a means of providing timing circuits.
Learners could research and analyse the RC circuit, including the RC time constant.
Teachers could develop an experiment where learners investigate the charging and discharging of a
capacitor in series with a resistor.
AC circuits and power factor
Learners may already be familiar with AC circuits and the behaviour of electronic components in these 2 hours
circuits.
Teachers could develop problems for learners to solve problems using phasor and algebraic
representation of alternating quantities, e.g. graphical and phasor addition of two sinusoidal voltages,
reactance and impedance of pure R, L and C components.
Web-based resources might prove useful such as http://www.animations.physics.unsw.edu.au//jw/
AC.html and http://www.physics.ryerson.ca/sites/default/files/u11/guidelines/L5_RLC_Circuits.pdf
Learners might also solve problems relating to power factor (e.g. http://www.allaboutcircuits.com/
vol_2/chpt_11/3.html)
Again, learners might be able to explore AC circuits practically with access to suitable resources.
11
Unit 1, LO4
Unit 2, LO3
Unit 4, LO2
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Web-based resources may also prove useful such as http://www.electronics-tutorials.ws/rc/rc_1.html
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
SUGGESTED ACTIVITIES
Title of suggested activity
Suggested activities
Suggested timings
Also related to
Passive filters
Filters are circuits that are designed to reject unwanted frequencies in a signal. Two common passive
filters are the low-pass and the high-pass filter.
2 hours
Unit 1, LO1
Learners could research how filters work, and how circuit component values can be calculated to
provide suitable filtering. This will build upon knowledge of components in AC circuits. The following
may prove a useful starting point: http://www.electronics-tutorials.ws/filter/filter_2.html
Teachers could set learners practice problems to solve (i.e. to design a low-pass and high-pass filter to
a given specification).
If access to resources is available, then learners might be able to simulate or build and evaluate filter
circuits.
Power sources
Learners could begin by researching power sources such as batteries (i.e. alkaline, rechargeable (NiMh, 2 hours
Lithium-ion)) and the solar cell. Web resources may prove useful such as http://batteryuniversity.com/
learn/article/whats_the_best_battery (batteries) and http://pveducation.org/pvcdrom/solar-celloperation/solar-cell-structure (photovoltaic cells).
Learners might also be able to evaluate power sources, such as batteries and a solar cell practically.
Learners could present their findings as a poster.
Rectification, voltage
regulators and power
supplies
Learners could analyse the operation of a power supply circuit – including rectification (i.e. full
wave diode bridge, half wave diode bridge), capacitor smoothing and voltage regulators. Web
resources may prove useful such as http://www.allaboutcircuits.com/vol_3/chpt_3/4.html (rectifiers),
http://www.electrical4u.com/regulated-power-supply/ (voltage regulators) and http://www.
talkingelectronics.com/Download%20eBooks/Principles%20of%20electronics/CH-17.pdf (power
supplies).
2 hours
Unit 4, LO4
1 hour
Unit 4, LO4
Learners could investigate both linear and switch mode power supplies.
It may be possible for learners to analyse practically a linear power supply.
ELECTRICAL AND ELECTRONIC DESIGN
Circuit protection
Learners could research the purpose of circuit protection and how this might be achieved using a
fuse, diode, resettable thermal fuse, circuit breaker (e.g. over current and earth leakage types).
Again, web-resources could prove useful e.g. http://www.allaboutcircuits.com/vol_1/chpt_12/4.html
(fuses and circuit breakers) and http://jeelabs.org/2011/01/09/easy-electrons-%E2%80%93-diodes/
(diode protection).
Learners might also be able to explore circuit protection practically if access to resources is available.
12
LO No:
2
LO Title:
Understand the application of electromagnetism in electrical design
Title of suggested activity
Suggested activities
Suggested timings
Also related to
Transformers
Teachers could use practice examples to show learners how to determine primary and secondary
current and voltage ratio, and turns ratio for a transformer.
2 hours
Unit 1, LO1
2 hours
Unit 1, LO1
Unit 2, LO3
1 hour
Unit 4, LO3
ELECTRICAL AND ELECTRONIC DESIGN
SUGGESTED ACTIVITIES
Resources such as the following may prove useful: http://www.electronics-tutorials.ws/transformer/
transformer-basics.html
Learners could solve problems to design or select suitable transformers for given applications (e.g. for
a given input and output voltage and current requirement). This could be related to power supply
design.
Learners might also use data sheets to select suitable transformers.
See Lesson Element Transformers.
Faraday’s and Lenz’s Laws
Faraday’s and Lenz’s Laws relate to the behaviour of magnetic circuits (such as those found in motor
and transformers).
It may be possible to demonstrate magnetic circuit laws practically using a coil, magnet and meter.
Learners could research the laws and their application in more detail.
DC motors and generators
Learners might already be familiar with DC motors and generators. They might further investigate the
series and shunt motor/generator including their applications and operation.
It may be possible to learners to investigate practically the operation and characteristics of motors
and generators. This might include performance tests such as determining torque, current and speed
relationships.
The following explains the application of a range of DC motor types: http://electrical4u.com/types-ofdc-motor-separately-excited-shunt-series-compound-dc-motor/
13
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Teachers might use web-based resources to explain both laws such as http://electrical4u.com/
faraday-law-of-electromagnetic-induction/ (Faraday’s Law) and http://electrical4u.com/lenz-law-ofelectromagnetic-induction/ (Lenz’s Law).
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
SUGGESTED ACTIVITIES
Title of suggested activity
Suggested activities
Suggested timings
AC motors
Learners might complete their understanding of motors by investigating AC motors, including the
single phase motor and the 3-phase motor.
2 hours
Also related to
The following may prove a useful starting point: http://www.edisontechcenter.org/electricmotors.
html
It may be possible to explore AC motors practically with access to suitable resources.
Learners could investigate motor applications and performance characteristics. Findings could be
presented in poster form.
EMC and screening
Electromagnetic compatibility (EMC) is regulated by legislation and includes radiated and conducted
interference. Interference is usually overcome through good design practices, and by appropriate
magnetic screening.
2 hours
Learners could begin by researching EMC and its significance to electrical/electronic design. The
following may prove useful starting points: http://ofcom.org.uk/static/archive/ra/topics/research/
RAwebPages/Radiocomms/index.htm and http://www.ukqrm.org.uk/legislation.php
Learners could investigate the impact of radiated interference using a simple AM radio to detect
sources, and might also investigate the effect of applying magnetic screening (e.g. using tin foil).
Learners could present their findings as a short presentation.
ELECTRICAL AND ELECTRONIC DESIGN
14
LO No:
3
LO Title:
Be able to apply a systems approach to electrical design
Title of suggested activity
Suggested activities
Systems approach – block
diagrams
Block diagrams are often used to represent electrical and electronic systems. These typically represent 2 hours
input to the system, outputs from the system and an element of control or processing.
Suggested timings
Also related to
Unit 4, LO4
ELECTRICAL AND ELECTRONIC DESIGN
SUGGESTED ACTIVITIES
The following web-based resources illustrate a systems approach to design (using block diagrams)
and might prove useful http://www.bbc.co.uk/schools/gcsebitesize/design/electronics/industrial_
designrev2.shtml and http://www.hobbyprojects.com/block_diagrams/block_diagrams.html
Learners could be tasked to produce block diagrams for a range of electrical and electronic systems –
including domestic appliances and industrial processes.
Open and closed loop - input, Systems are typically open or closed loop. Open loop systems have inputs and outputs but no
output and feedback
feedback. Closed loop systems use some element of feedback (from the output of the system) in
order to provide consistent control.
2 hours
Learners could investigate open and closed loop systems, identifying applications of each type of
system. The following web-resource may prove useful:
http://www.electronics-tutorials.ws/systems/open-loop-system.html
Learners could produce a poster presentation illustrating the applications of both open and closed
loop systems.
Learners could continue their investigation of open and closed loop systems by considering in detail
the function and operation of a range of input devices. This might include: switches (i.e. latched and
momentary action), photodiode, phototransistor, LDR, NTC thermistor and the microphone.
2 hours
The following might prove useful, and shows a range of sensors and transducers:
http://www.electronics-tutorials.ws/io/io_1.html
Learners may be able to investigate practically the operation of input devices through
experimentation.
Output devices
There are many types of system output devices – including piezo-electric buzzers/sounders, lamps,
light emitting diodes (LED), LED 7 segment displays, dot matrix displays, liquid crystal displays (LCD),
display modules, solenoids, relays and speakers.
Learners might be tasked to research a range of output devices. The following illustrates the 7
segment display: http://www.electronics-tutorials.ws/blog/7-segment-display-tutorial.html
Again, if access to suitable resources is available learners could investigate practically the function and
operation of output devices.
15
2 hours
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Input devices
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
SUGGESTED ACTIVITIES
LO No:
4
LO Title:
Be able to use semi-conductors in electrical and electronic design
Title of suggested activity
Suggested activities
Suggested timings
Diodes and transistors
Diodes and transistors are fundamental components in electronic design.
3 hours
Also related to
Teachers might begin by introducing learners to the function and operation of diodes, and the
transistor as a switch and an amplifier. Online resources might prove useful, such as the following for
the diode: http://www.technologystudent.com/elec1/diode1.htm the transistor as a switch:
http://www.electronics-tutorials.ws/transistor/tran_4.html and the transistor amplifier:
http://www.allaboutcircuits.com/vol_3/chpt_4/5.html
Learners could investigate the operation of diodes and transistors practically if access to resources is
available, or through computer simulation.
See Lesson Element Diodes and transistors.
Darlington pairs and
Darlington arrays
The Darlington pair is a transistor arrangement commonly used to provide a switching function where 1 hour
more current is involved. Teachers could introduce the theory of the Darlington pair using suitable
resources e.g. http://www.technologystudent.com/elec1/transis2.htm
Learners might again be able to experiment with practical circuits or simulation tools.
Learners might extend their knowledge by researching the application and function of Darlington
pair arrays and transistor arrays.
Op Amps – comparators
Operational amplifiers (or op amps) are high gain amplifiers commonly used in electronic circuits.
Learners might already be familiar with op amps from previous studies. Web-based resources could
be used review fundamental op amp concepts such as:
http://www.allaboutcircuits.com/videos/73.html
2 hours
Unit 1, LO1
Unit 4, LO5
1 hour
Unit 1, LO1
Unit 4, LO5
Learners might investigate the op amp comparator configuration explained here:
http://www.electronics-tutorials.ws/opamp/op-amp-building-blocks.html
Again – practical experiments or simulations may be possible with the op amp as a comparator.
ELECTRICAL AND ELECTRONIC DESIGN
Summing op-amp
The op amp may also be used to provide a summing function (for voltage sources). The following
explains the summing op amp:
http://www.electronics-utorials.ws/opamp/opamp_4.html
Simulation may prove useful in understanding the op amp as a summing amplifier – with the
following free simulation tool showing this mode: https://www.circuitlab.com/circuit/mrp5kc/opamp-inverting-summing-amplifier/
Learners might also be able to design, build and evaluate a summing amplifier.
16
Title of suggested activity
Suggested activities
Suggested timings
Also related to
Logic gates
Learners might already be familiar with the fundamental concepts of logic and logic gates. The
following might provide a useful recap:
http://www.electronics-tutorials.ws/logic/logic_1.html
3 hours
Unit 4, LO6
2 hours
Unit 4, LO6
3 hours
Unit 4, LO6
2 hours
Unit 4, LO6
Learners might design and evaluate combinational logic circuits for a range of given problems, using
the following logic functions: AND, OR, NAND, NOR, NOT, XOR, NAND/NOR equivalent circuits
Simulation tools might prove a useful alternative to building practical circuits – the following is a free
online simulator: http://www.neuroproductions.be/logic-lab/
ELECTRICAL AND ELECTRONIC DESIGN
SUGGESTED ACTIVITIES
Learners may also develop truth tables representing logic functions.
Flip Flops – SR type
Flip flops are used in electronic circuits to store information – and are commonly found in registers
and counters. The SR type flip flop is perhaps the most fundamental.
Learners may already have some knowledge of the basic function and operation of flip flops. Webbased resources might prove useful as a recap:
http://www.circuitstoday.com/flip-flops
Flip Flops – JK, D and T types
Further flip flop types include the JK, D and T type.
Learners could investigate the function and operation of these types of flip flop. Useful resources include:
http://www.electronics-tutorials.ws/sequential/seq_4.html (D type)
http://www.brighthubengineering.com/diy-electronics-devices/46610-jk-and-t-flip-flops/#imgn_1
(JK and T types).
Learners could use simulation software to explore flip flop operation – or may be able to construct
circuits practically. The following is a free online simulation tool:
http://www.docircuits.com/public-circuit/457/d-flipflop
BCD counters and display
decoders
Flip flops may be used in a combination to provide counter and decoding functions.
Learners could research how flip flops can be used as a BCD counter and how they may be used to
drive an LED display.
The following might prove a useful starting point:
http://www.electronics-tutorials.ws/counter/bcd-counter-circuit.html (BCD counter) and
http://www.electronics-tutorials.ws/combination/comb_6.html (display decoder)
Learners might be able to build or simulate circuits, and could present their findings as a short
technical report.
17
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Learners could produce a presentation explaining the operation of the SR type flip flop.
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
SUGGESTED ACTIVITIES
LO No:
5
LO Title:
Understand the application of programmable process devices in electronic design
Title of suggested activity
Suggested activities
Suggested timings
Application of
programmable devices
Programmable devices are at the heart of a wide range of electrical and electronic equipment – both
domestic and industrial.
1 hour
Also related to
Learners could begin by researching the applications of programmable devices, including how
they are connected to (interfaced with) inputs and outputs. They might also identify the type of
programmable device being used. The following may prove a useful starting point:
http://www.engineersgarage.com/articles/embedded-systems
Learners could present their findings as a poster.
Microprocessors and
microcontrollers – system
layouts
Microprocessors and microcontrollers are two types of programmable devices. They are sometimes
called embedded devices that form the part of an embedded system.
2 hour
Learners might compare the application and features of these. The following YouTube video could be
used: http://www.youtube.com/watch?v=CmvUY4S0UbI
Learners could present their findings as a tabular comparison.
Programmable Interface
Controller (PIC)
Programmable Interface Controllers (PICs) are low-cost programmable devices found in many
electronic systems (such as washing machines, toys, and industrial controllers). They are a form of
microcontroller. The following explains the PIC:
http://www.circuitstoday.com/peripheral-interface-controller-pic
Learners might investigate the PIC in terms of its applications, and the features that make it a useful
device.
2 hours
Programmable Logic
Controller (PLC)
The Programmable Logic Controller (PLC) is commonly used in industrial control and automation
applications – and is another example of a programmable process device. PLCs are often robust
devices suitable for industrial environments.
2 hours
ELECTRICAL AND ELECTRONIC DESIGN
Learners could investigate PLCs and their applications – including how they are typically programmed
(e.g. using ladder logic).
The following explains the features of PLCs:
http://www.allaboutcircuits.com/vol_4/chpt_6/6.html
Learners might present a technical summary of a PLC.
18
Title of suggested activity
Suggested activities
Suggested timings
System layouts and analysis
for programmable control
systems
Learners could conclude their study of programmable devices by investigating in more detail their
application in programmable control systems.
2 hours
Also related to
This might include the type of programmable device being used, its relationship to input and output
devices and also an analysis of system operation.
ELECTRICAL AND ELECTRONIC DESIGN
SUGGESTED ACTIVITIES
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19
OCR LEVEL 3 CAMBRIDGE TECHNICALS IN ENGINEERING
Manufacturers’ websites might prove a useful source of information – with the following showing a
commercial solution for the microwave oven:
http://www.ti.com/solution/microwave_oven
Learners could investigate further systems (such as an industrial process controller, or an engine
management system) presenting their findings in poster form.
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