DET
Electronics Project
(Advanced Higher)
7528
August 2000
HIGHER STILL
DET
Electronics Project
Advanced Higher
Support Materials
CONTENTS
Introduction
Project example 1 – Temperature comparison system
Project example 2 – Frequency Shift Keying system
Project example 3 – Frequency meter
Project example 4 – Audio oscillator
Project example 5 – Electronic stopwatch
Project example 6 – Temperature probe
Project example 7 – Channel filter system
Project example 8 – Pulse delay generator
Project example 9 – Strain gauge
Project example 10 – Satellite status indicator
DET: Electronics Project (Advanced Higher)
1
DET: Electronics Project (Advanced Higher)
2
INTRODUCTION
The Electronics Project is intended to integrate the work covered by all the other
Advanced Higher Electronics units, but prior knowledge from Intermediate 2 and
Higher levels may also be required for particular project specifications. The project
has also to be conducted within time and resource restraints and finalised in a
documented report. With this in mind each of the ten project specifications presented
in the support notes is achievable within these restraints.
As stated in the Electronics Project NAB, each project should have a practical
application, involve analysis of an electronics problem and its solution, and be
presented to the student in a structured form. The project’s integrity should be based
on the following:
• the technical content is related to topics in the other Advanced Higher Electronics
units
• the technical level is as close as possible to the level in the other Advanced
Higher Electronics units
• the technical content is of interest to the student
• any associated information is easily accessed by the student
• materials and components are easily accessed by the student
• there is access to suitable computers and the Internet
• the necessary tools and machinery are easily accessed by the student
• the required test equipment is easily accessed by the student
• the time allocated is adequate for the work involved.
The project examples given in these support notes outline the specification and no
detail is presented regarding technical solutions. Hence Section 10 only in the Project
NAB is specifically dealt with. Proposed solutions, however, are suggested but
alternative methods may be adopted by individual centres. Project proposals should
be achievable within the technical range of the units and all concepts should be
familiar to the students without recourse to unfamiliar material.
Several solutions to some projects may be explained by small groups of 2/3 students
with each student developing one specific solution.
Outline details should be prepared for each project offered by a centre and these
should give an overview of the project with adequate information to allow a student to
select or reject it. A general description of the problem should be provided with its
main technical features. Additional information should also be provided regarding
resources and time scale.
DET: Electronics Project (Advanced Higher)
3
PROJECT EXAMPLE 1
Temperature comparison system
Introduction
You work as an electronic engineer for a company that specialises in the manufacture
of heat sensing equipment. The company has been asked to design a temperature
comparison system for a health and safety agency. The final design has to be compact
and capable of being carried from one site to another. Some form of comparison
circuit is required which will compare the temperatures in two sites or else compare
the temperature in one room with a reference temperature. In order to accomplish this
the design is divided into an analogue section that involves the sensing and signal
processing circuits, and a digital section which involves the analogue-to-digital
conversion and decoding circuits. As part of a two-man team you are responsible for
the analogue section which involves sensing the difference between two sensor inputs
and providing some form of filtering for the noise levels picked up by the sensor
cables. Finally an amplification of five has to be provided before the signals are
applied to the digital section.
Proposed solution
Sensor 1
Difference
Amplifier
Filter
Amplifier
Measured
Output
Sensor 2
Discussion between the two engineers produces the following conclusions and
the above block diagram which shows one solution to the problem. The two
temperature sensor outputs are compared by a difference amplifier and the output
applied to a filter. It is agreed that the filter should be at least a second order
Butterworth type which may provide some form of amplification. However an extra
stage of voltage amplification could be provided by the amplifier at the output to give
the required gain of five. Depending on the type of temperature sensors used, the
difference amplifier may have to provide a certain amount of gain. The temperature
comparison is best measured by means of a DVM. It was also agreed that the sensors
could be designed in a Wheatstone bridge configuration for greater sensitivity.
Requirements statements
The following requirements have to be met:
• the sensors should be capable of giving an output of at least 10mV/oC
• the filter should be capable of filtering out noise frequencies of between 1 kHz
and 10 kHz
• the overall gain at the output has to be five
• screened cable should be used where appropriate.
DET: Electronics Project (Advanced Higher)
4
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
5
PROJECT EXAMPLE 2
Frequency Shift Keying system
Introduction
You are a member of a telecommunications company which design communications
equipment for the data and computer communications industry. Your company has
been asked to design a Frequency Shift Keying (FSK) system for a modem which
forms part of a dedicated telephone line between two computer networks. The
modem will be used to convert digital signals to analogue signals and analogue
signals to digital signals. The method of FSK is used to transmit the digital data along
the analogue telephone lines by using two audio frequencies. The higher of the two
frequencies will be switched in for a high level (1) while the lower frequency will be
used for a low level input (0).
You have been asked to design an FSK transmitter and receiver which functions using
1070 Hz and 1270 Hz as the switching frequencies. The filtering and decoding
section will be tackled by another member of the team.
Proposed solutions
Transmitter
Data
In
Receiver
Filter
Decoder
Switching
Unit
After discussions it is decided to use a 555 timer as the transmitter together with a
switching transistor which will be used to switch between the two frequencies. A
phase-locked-loop is selected for the receiver because of its ability to lock at certain
frequencies within its operational range. The data is fed into the switching unit,
which is placed across RA of the timer. The switching unit is ideally a bipolar
junction transistor (BFY51). The 565 phase-locked-loop was selected as the receiver
because of its linearity and lock range specification.
Requirements statements
The following requirements are specified:
• the system has to switch at 1070 Hz and 1270 Hz
• the free running frequency of the PLL has to be the average of the two switching
frequencies i.e. 1170 Hz
• the timer has to be designed for 1070 Hz
• adjustable to give 1070 Hz precisely.
DET: Electronics Project (Advanced Higher)
6
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
7
PROJECT EXAMPLE 3
Frequency multiplier
Introduction
As a member of a team of six engineers who have been given a specification for a
new mobile phone design, you have been asked to design the receiver section of the
phone. The internal circuitry of the receiver section is complicated by the operational
frequency range of certain stages which have to function at a higher frequency than
the receiver’s incoming reference signal. Furthermore, because of variable signal
strengths the receiver section has to be capable of selecting the maximum signal and
locking onto it.
Proposed solutions
The team has come to certain conclusions, and agreed that some form of frequency
synthesis is required either by using a microprocessor or using simple frequency
multiplication. The secondary requirement for locking onto a particular transmitter
for maximum signal strength suggests the application of a phase-locked-loop such as
the 565 together with a counter circuit. A block diagram similar to the one shown
below is suggested.
Nfref
fref
Phase
Locked
Loop
Invertor
Counter
N
Requirements statements
The following requirements are specified:
• the reference frequency is 25 kHz
• the multiplied frequency has to be 250 kHz
• an invertor may have to be included if the counter clock is negative edge
triggered
• lock range of PLL (fL) specified as + 5 kHz
• capture range of PLL specified as + 3 kHz.
DET: Electronics Project (Advanced Higher)
8
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
9
PROJECT EXAMPLE 4
Audio oscillator
Introduction
You are an engineer working for a small company dealing in specialised audio
equipment, and you have been asked by a hearing deficiency clinic to design a
frequency generator capable of spanning the audio range. The output of the frequency
generator has to be capable of feeding into earphones or a loudspeaker and the
intensity of the sound has to be variable. The generator has to be capable of mains
and battery operation so that the patient has the option of testing hearing deficiencies
while moving in different environments.
Proposed solutions
Final discussions amongst the design team conclude that either some form of
oscillator such as the 555 timer can be used or else a fully integrated type such as the
8038 waveform generator. There is a full range of instrumentation for testing
frequency distortion, frequency linearity and sound intensity.
Requirements statements
The following requirements have to be met:
• the generator should give an undistorted and linear output in the frequency range
20 Hz to 20 kHz
• a 50% duty cycle is required
• buffering is required for both the loudspeaker and earphone connection
• single and double power supply operation may be required.
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
DET: Electronics Project (Advanced Higher)
10
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
11
PROJECT EXAMPLE 5
Electronic stopwatch
Introduction
You are employed by a company which manufactures electronic control and
monitoring equipment. The company has been given a specification to design a
complete control system for measuring and monitoring the performance of a gas
furnace. One of the parameters which has to be monitored is the temperature of the
furnace, and it has been found that in order to operate the furnace safely, it has to be
switched off and on every 100 seconds. As a member of a four man engineering team
you have been asked to design part of the switching and timing system which will
indicate if the furnace is switching off and on periodically. The timing circuit has to
be capable of resetting and also being switched on by the temperature sensors in the
furnace at the appropriate time. A typical circuit was suggested.
Switching input
from furnace sensors
555 timer
Counter
1
Counter
2
Counter
3
Reset and switch
on for furnace
Proposed solutions
After discussion the team concluded that some form of microprocessor control was
required in conjunction with the timing monitor. However financial constraints
caused the team to consider other possibilities such as a 555 timer in conjunction with
digital counters. The circuit can be tested using LEDs.
Requirements statements
The circuit has to meet the following requirements:
• the timer should be set at 10 Hz and this should be capable of being finely
adjusted
• the timer should operate for 100 seconds
• a low cost design is required.
DET: Electronics Project (Advanced Higher)
12
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
13
PROJECT EXAMPLE 6
Temperature probe
Introduction
You work for a company which designs and manufactures temperature control
systems. Your company has been asked by a telecommunications company to design
a temperature probe which could detect two temperature levels. The high frequency
transmitters they produce use crystals which are highly sensitive to changes in
temperature. In order to avoid instability they are housed in a microprocessor
controlled oven which must operate within 18oC and 25oC. Any variation outside
these threshold levels should produce an input to the microprocessor which should
then adjust the oven temperature. You are asked to design a suitable circuit in
consultation with the senior design engineer.
Proposed solutions
Consultation with the senior design engineer eventually produces several solutions. A
microprocessor solution is one option. A Wheatstone bridge circuit could be used in
conjunction with an amplifier circuit, two comparators could be used with two
thermistors or a window comparator could be used. A suggested system is shown
below which uses a window comparator.
Sensor
Amplifier
Window
Comparator
High/Low
Temperature
Indicator
Requirement statements
The system has to meet the following requirements:
• temperature range has to be 18oC-25oC
• a suitable thermistor should be used for the sensor
• an amplifier may have to be used to give the required voltage input to the window
comparator of 1 V
• LEDs have to be used for the indicator section – red for the upper threshold level
and green for the lower threshold level.
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
DET: Electronics Project (Advanced Higher)
14
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes , signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
15
PROJECT EXAMPLE 7
Channel filter system
Introduction
You are a member of a design and research team which has been asked to design a
filter system for an FM stereo receiver. Stereo frequency modulation signals are
transmitted on a carrier frequency of 88MHz to104 MHz and the standard transmitted
signal consists of three modulating signals. These are the sum of the left and right
hand channels (L+R), the difference of the left and right hand channels (L-R) and a
pilot tone of 19 kHz. The front end of the receiver is shown below.
Input
Channel Filters
(L+R) and (L-R)
signals
Left and right
hand channel
separation
circuits
Power
Amplifier
R
L
You have been asked to design the two filter configurations required to separate the
(L+R) and (L-R) signals which will eventually be applied to the left and right hand
channel separation circuits.
Proposed solutions
The conclusions reached after discussion is that either a fully integrated filter chip is
used or separate filters can be incorporated using Sallen-Key circuits. The advantage
of the individual filter circuits is that each can be tested individually.
Requirements statements
The following conditions have to be met:
• the (L+R) signal has to extend from 30 Hz to 15 kHz
• the (L-R) signal has to cover a bandwidth of 23 kHz to 53 kHz
• the gain of each filter used has to be 1.585
• second order filters have to be used.
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
DET: Electronics Project (Advanced Higher)
16
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
17
PROJECT EXAMPLE 8
Pulse delay generator
Introduction
You work as a line transmission engineer as part of a team responsible for designing
data transmission equipment and instrumentation for the propagation of high speed
data. As part of their systems tests, your company has asked you to design a pulse
delay generator which could be used as an accurate reference source to check the
propagation delay of several transmission lines. Some form of clock generator has to
be built together with a delay circuit which will be capable of outputting a range of
time delays which are compatible with the expected propagation delays of the
transmission lines under test. Finally the instrument has to be portable.
Proposed solutions
The design team eventually agree that some form of software programme will be used
for the test procedure, but other suggestions are the the use of an 8038 waveform
generator together with a shift register or the use of a 555 timer together with a shift
register. A suggested solution is shown in the block diagram below.
Clock
555
Timer
Shift
Register
Test pulse at the
input to the
transmission line
Oscilloscope
Test pulse at the
output of the
transmission line
Requirements statements
The system has to be capable of showing time delays between 2 µs and 16 µs,
and the shift register should be a serial in/serial out type.
1 µs test pulses have to be used.
The timer has to meet the following requirements:
• a clock frequency of 1 MHz
• a 50% duty cycle.
The instrument has to be portable and capable of being modified for operation outside
the range 2 µs to 16 µs.
DET: Electronics Project (Advanced Higher)
18
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
19
PROJECT EXAMPLE 9
Strain gauge
Introduction
You work for a test and measurement company that designs and manufactures
equipment for testing rotational and linear strains in shafts and beams. As one of four
engineers working on a strain gauge, which has to be capable of measuring and
comparing the stress of two beams, you have to design a robust strain gauge which
will be low cost and portable. A large batch is being ordered for similar beam
structures being tested globally hence cost effectiveness is important. As the
instrument wires will be subject to temperature variations the gauge may have to be
capable of being readjusted.
Proposed solutions
After lengthy discussions amongst the engineers, several solutions are agreed. A
microprocessor solution is one option. A digital type gauge is considered which uses
a Wheatstone bridge configuration but this is not considered robust enough. An
analogue strain gauge is thought to be more suitable for the application together with
a bridge and difference amplifier or instrumentation amplifier. However for cost
effectiveness a difference amplifier is preferred. A suggested block diagram is shown
below.
Wheatstone
Bridge
Difference
Amplifier
Analogue
Meter
Requirements statements
• The bridge will use two strain gauges and have some method of compensating for
temperature variation on the connecting wires.
• The difference amplifier should have a gain of 5-10.
• Small enough to be portable and easily plugged into fixed strain gauges on the
beams without damaging the strain gauges.
• Standard type strain gauges should be used.
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
DET: Electronics Project (Advanced Higher)
20
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
21
PROJECT EXAMPLE 10
Satellite status indicator
Introduction
As part of the telemetry department of a large satellite communications company you
and your two colleagues have been asked to design a simple status indicator which is
capable of indicating the correct operation of the eight on-board systems of a satellite.
The satellite signals are received by a ground station and transmitted to a control
centre where they are analysed. Data is represented in parallel form and indicates the
status of each sub-system on the satellite. For this purpose a visual display is required
at the output which will indicate the appropriate sequence for the correct operation of
each sub-system.
Proposed solutions
The three man telemetry team eventually agree on several solutions. The final option
will probably be a software programme solution, however, other solutions are to use
combinational logic with PALs, eight 555 timers in monostable mode for each
incoming pulse to produce an output on a VDU or to use a purely digital approach
with counters, multiplexers, demultiplexers and LEDs. One of these proposed
solutions is shown in the block diagram below. All integrated circuits are available
and test equipment is plentiful.
Clock
Counter
Data
Select
Parallel
Data In
Counter
Data
Select
Cable
Multiplexer
Transmitter (Ground Station)
Demultiplexer
LED
Display
Receiver
Requirements statements
• 8-bit counters should be used (74169 or similar)
• 8 to 1 and 1 to 8 multiplexers and demultiplexers should be used respectively
(74151 and the 74138 are suitable chips although similar chips can be used)
• the display should be eight LEDs
• A suitable clock at 60 Hz is provided.
DET: Electronics Project (Advanced Higher)
22
Procedure
You are expected by the company’s design quality standards to follow the appropriate
project steps from conception to the completion of the report, but note that you may
find that the natural flow of the project suggests alternatives due to the demands
placed on you. In these circumstances you should proceed with the natural flow
keeping in mind the stages detailed by the senior engineer. It is extremely important
that you keep your technical objectives very clear throughout the design and
development activity and that you also finish by the target completion date.
Information and resources available
You should use your personal data library and other material which you have
collected as your primary source of information.
You will have access to an electronics laboratory during the project. In the laboratory
is a range of manufacturer’s data books and supplier’s catalogues. There is also a list
of components available as standard stock from the store. You should work within
this range of components at all times. In the laboratory you will find electronics
books which may provide useful information.
Also in the laboratory there are test instruments, computer circuit simulation tools and
prototyping facilities. The test instruments consist of multimeters, power supplies,
oscilloscopes, signal generators, frequency counters and logic probes. Before making
use of these please check that you have acquired the requisite skills and if not find an
alternative test method. The circuit simulation tools may be used on a similar basis.
The prototyping facility consists of prototype boards which allow you to assemble
circuits without the use of solder. These should be used to develop your solutions as
they are easy to work with and allow circuit changes to be made quickly with minimal
damage to components.
DET: Electronics Project (Advanced Higher)
23