Unit 6
Applied design,
planning &
prototyping
A level coursework assessment
Pupil name:
Tutor name:
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Contents
Client brief
Pages 3
Design brief
Pages 3 to 6
Research
Pages 6 to 21
Technical specification
Pages 22 to 26
Design evaluation
Page 27
Formative evaluation
Pages 28 to 29
Planning
Pages 30 to 50
production
Pages 51 to 62
evaluation
Pages 63 to 64
Bibliography
Page 65
Appendices
Page 66 onwards
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Client Brief
In the normal everyday household, there are a lot of appliances which run off electricity and these
appliances can cause obstructions by means of cables. I need something to play my music from my
phone, iPod or iPad, without adding to the mountain of untidy cabling in my house.
I must be able to hear the music clearly when I am in the same room as the speakers and the
speaker system must be at least 25w in output power.
The speaker can be placed anywhere in the same room as the audio device dock. The speaker casing
could be made to look like a piece of furniture or an item that would not be thought of as a speaker
case.
The speaker system must not be mains operated and must be portable. The audio dock must be able
to hold all kinds of audio devices without potentially causing any damage to the device.
For when there is little space, the audio dock could attach to the speaker housing. This could also
help for portability. Also for ease of portability, the whole system must be light but strong so it can
withstand small impacts when being carried around.
This will be a product that will eventually batch produced to retailers so it must be easily assembled
and cheap to make so profit is still high.
The cost of making the whole system must be less than £70; bearing in mind this is harder to do
when making only one as making a few means wholesale prices on parts.
Any materials can be using in the speaker housing but it must be strong and this is the same for the
audio dock but bear in mind the dock must be able to attach to the speaker housing.
Design Brief
Key requirements
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The music must be clearly heard in the room that it is in.
The speaker systems output power must be more the 25w
The speaker should be able to be placed anywhere in the same room as the audio dock.
It would be a unique feature if the speaker housing was made to not look like a speaker
housing at all, but more of a small piece of furniture.
Must not be mains operated.
The audio dock must be able to hold many different kinds of audio devices.
The audio devices must be safely housed on the audio dock.
The audio dock must be made to easily attach to the speaker housing.
The whole system must be portable.
The audio dock and the speaker housing must be not too heavy but strong to be able to
withstand small impacts.
Must be able to be batch produced.
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The cost of producing one must be less than £70.
The aesthetics
The product comes in two parts: one part is the speaker housing and the other part is the audio
dock. The speaker housing will be made to not look like a speaker but a piece of furniture so it could
have another use like storing something or be a base for photos or computer desktop screens.
The speaker system can be made out of any material but it must be reasonably light but heavy
enough to show good quality. The speaker housing would be better if it was made out of would
because sound from the speakers resonates better through wood (like on a guitar). To further
amplify the speakers and to give a richer sound, the speakers in the speaker housing could be placed
deeper in the housing so the sound waves can diffract off of the walls of the inner speaker housing
(like in an acoustic guitar).
For the audio dock, aesthetics can be simple but it must be able to house different audio devices
safely and attach to the speaker housing easily. It must also be able to house the electronics. When
attached, the audio dock and the speaker housing must match aesthetically and not look out of
place.
Materials
Any materials can be used for the speaker housing and the audio dock. For the speaker housing,
wood would be a better choice of material because sound resonates much better through wood
than metal or plastic. The audio dock can be made from any material but if it is made out of metal,
the electronics must be grounded for safety.
Number required
Only one prototype in required at the moment, but the end product after testing must be able to be
batch produced with costs bellow £70 per system. Also, when products are mass produced, parts
would be much cheaper because of wholesale prices.
Scale of production
The production is separated into stages: - The Brief: this is what this document is; it outlines the
client’s needs and gives a basic view of the project.
The Research: This will involve techniques such as brainstorming, to quickly think of ideas for the
form and inner workings of the product. Freehand sketching will be used to get the ideas onto paper
to decide whether to adapt to it in latter stages or to bin it.
Research is the last technique and will involve primary, secondary and tertiary research to determine
what already exists in the market and whether there are any demands or niches available in the
market.
Technical Specification: This to show every little intricate detail of the product and what it is capable
of and will be laid out using the ACCESS FM template. Most important in that is the function, form
and size, and materials.
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Design ideas: from the research stage, two of the brainstormed ideas and sketches get picked for
further development. These two designs have to be different in the way they operate or their
aesthetics.
Production constraints will also be highlighted in this stage including:- the technology used,
materials, availability of resources and environment.
Final Solution: The final solution should take all of the different subsystems into account from
previous designs and apply them to the final design. This includes modelling and testing on
Computer Aided Design software.
Formative evaluation: This is the stage that decides which one of the ideas will be used for the final
design by means of a panel of colleagues and what development needs doing to that product.
The product chosen will be evaluated against the specification which will help for seeing what
development needs doing.
The final design: This is a detailed design of the chosen initial design showing how the design
operates and how it is to be manufactured.
Numerical values will be included as well as scientific reasons for the choice of materials. Different
types of drawings may need to be done which include: - freehand sketches, general arrangement
drawings, detailed drawings, circuit diagrams, flow diagrams and schematic diagrams.
Project planning: the project will be planned, identifying tasks, producing an outline plan, using
planning tools like Gantt charts and doing progress checking to keep on top of the project.
Manufacturing Regulations: This is included in the planning stage and should outline the regulations
that you may encounter in the production of the prototype.
Manufacturing of prototype: This is when the prototype is produced using my own skills and
technologies that I have studied considering health and safety in the form of a risk assessment.
Evaluation: This is where the product is tested and evaluated for its performance against its
specification as it must match the specification to be fit for purpose. Once the tests are done,
modifications can be suggested.
Quality
The speaker system must be lightweight but heavy enough to be felt as good quality. The quality can
also come in the form of output which is audio. If there is good clear audio then it is a good quality
product. The product must also be strong to withstand minor impacts when being carried around.
Function
The function of this product is to provide music wirelessly from an audio dock to a speaker in the
same room. It must also be portable, which means it must be light and strong but without adding to
the cost.
The speaker housing is to be disguised as a piece of small furniture and the audio dock must be able
to attach to the speaker housing.
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Technology
Different technologies could be used to make this product including saws, hydraulic sanders wood
steamers (to bend the wood) and lathes or welding for metal work. Different technologies will be
used for the two different parts of the system as they may both be made out of different materials.
Costs
The total cost allowed to spend on this product is £70 but when it is being batch produced this may
be decreased as more savings can be made on wholesale prices for parts and manufacturing
processes. The costs can be separated into electrical costs and material costs as both parts of the
system houses electrical components and both have different housings.
Completion date
The completion date for this product is the 07th February 2013.
Health and safety issues
Possible health and safety issues will mostly come in to action with the manufacturing stage as
powerful tools are going to be used like lathes and welders.
Legislations will be taken into account in the planning and production stages for health and safety.
Research
To be able to produce the best possible product for the required specification, I must do relevant
research on mainly the aesthetics and the inner electronic workings.
I firstly researched the electronic circuits for existing products like wireless headphones.
(http://www.ee.iitm.ac.in/~ee07b090/documents/TI_contest_report.pdf)
This is the system outline for a wireless audio transmitter receiver module. It is a good start to the
research but it is too complicated to be made in the given time set and will most probably cost over
the £70 barrier.
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This is a very basic system outline which shows the basics of what is needed for wireless audio
system.
Whilst I was researching what current products use as electronic systems I looked up modules that
may be able to do the job. This one from Maplin seemed to be a possible contender but little
information is given on possible schematics and applications
(http://www.maplin.co.uk/search?criteria=RF+transmitter).
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With further research, I found another more in depth and realistic subsystem outline for my
electronic circuitry. Although it is basic, it shows that transmitting by radio frequency is a better and
easier way to go (http://www.engr.sjsu.edu/rkwok/projects/speakerB.pdf).
This schematic is very basic and uses transistors to drive the
signal, the first transistor acts as a frequency modulator for
the radio frequency waveband.
(http://www.hqew.net/circuit-diagram/A-Low-PowerWireless-Audio-Power-Amplifier_12476.html)
With this schematic (above) is the receiver
circuit which is more complicated as it also
includes the audio amplifier (IC2).
These two circuits made me decide to split the electronics into systems of transmitter, receiver and
then amplifier. It also showed me that there are specific integrated circuits out there that can do the
majority of the work in a transmitter, receiver or amplifier system.
FM transmitter system
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FM transmitter circuit 1)
This first transmitter circuit choice is basic and doesn’t rely on potentially expensive integrated
circuits. (http://www.circuitstoday.com/medium-power-fm-transmitter-circuit)
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Up to 100 metres when tuned
Can change frequency with C6
Transistor Q1 amplifies microphone (audio)
Transistor Q2 acts as an oscillator in FM Band
The output of Q1 is given as the base of Q2
Q2 also performs modulation
C7 couples the FM signal to the antenna
9V DC power
FM transmitter circuit 2)
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The second transmitter circuit has more room for adjustments with the different controls but still
doesn’t require an integrated circuit and instead uses transistors.
(http://electroschematics.com/1041/quality-fm-transmitter/)
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Works off 9V battery
Potential range of 500m (250m)
Power output 200mW
Gives VHF fm frequency
To make it stereo, a stereo encoder must be attached :
http://electroschematics.com/315/stereo-encoder/
or buy one http://www.maplin.co.uk/rf-encoder-decoder-chipset-35636 (not stereo)
FM transmitter circuit 3)
The final transmitter circuit uses the BA1404 integrated circuit, which is well known in the FM
transmit ion sector. The unique selling point of this circuit is that it transmits stereo audio signals in
the FM waveband and it is powered by two AA batteries, meaning it could be very portable.
(http://www.circuitstoday.com/stereo-fm-transmitter-using-ba1404)
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FM receiver system
FM receiver 1)
This covers the portability point of the system but it may not be powerful enough for what I want it
for. (http://electroschematics.com/4663/small-fm-receiver/)
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Small Receiver
87 to 108MHz
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FM receiver 2)
This is an integrated circuit also well known in its industry. The TDA7000 can tune in to wavebands
from 70Hz to 120MHz and it can be powered by a 9v battery, meaning great portability. The only
problem with this integrated circuit is that it doesn’t give out a stereo output, for stereo output to
be given (to go on the amplifier), a stereo decoder must be used and the LM1310 is perfect for the
job which can be powered by the same 9v battery.
(http://electronics-diy.com/TDA7000_FM_Receiver.php)
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Amplifier after receiver
The amplifier is a major part of the whole system as it must give very good quality audio and a
reasonable audio volume but potential from a low power source for ease of portability.
Amplifier 1)
This first circuit is very simple and uses the LM386 integrated circuit to amplify the micro amps of
audio coming from the intro. This can be powered by a 9v battery but its output is below the
required 25w. (http://www.buildcircuit.com/audio-amplifier-using-lm386/)
Amplifier 2)
The second amplifier circuit uses the UA741 and has a high power source which is a set back as it
only lets out half a watt of power. (http://www.circuitstoday.com/signal-tracer-circuit)
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Amplifier 3)
This circuit is very in depth and uses two integrated circuits: the LM358AN and the LM386N-3. The
first IC produces a stereo signal and the second IC amplifies the audio.
(http://www.ece.ucsb.edu/yuegroup/Teaching/ECE2C/Lab/Lab1a.pdf)
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I moved on to researching Amplifier integrated circuits on the RS components website. This came up
with about 180 different amplifier chips that I picked from for potential amplifiers in my system.
(http://uk.rs-online.com/web/c/semiconductors/amplifiers-comparators/audio-amplifier-ics/?sortby=default&sort-order=default&applieddimensions=4294511066&lastAttributeSelectedBlock=4294959930)
I found out that there are different classes of IC amplifiers from class D (which require low power but
have lower quality) to Class A (which require a lot of power but give very good quality output). The
trick is to find one in between the Class A and Class D amplifiers.
Choice 1)
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24watt stereo 2ch
9v – 12v supply
Requires a system logic microcontroller
http://uk.rs-online.com/web/p/audio-amplifier-ics/7089744/
Choice 2)
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11 watt stereo amplifier
Class A/B
Wide supply range of 9v to 40v
http://uk.rs-online.com/web/p/audio-amplifier-ics/5343295/
Choice 3)
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30w output with 8ohm speaker
Supply range of 20v to 66v
http://uk.rs-online.com/web/p/audio-amplifier-ics/5343302/
Choice 4)
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68w output power
Class A/B
Supply of 20v – 94v
http://uk.rs-online.com/web/p/audio-amplifier-ics/5342955/
Choice 5)
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56w output power
Class B
20v to 94v supply
http://uk.rs-online.com/web/p/audio-amplifier-ics/5342933/
Choice 6)
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6 to 18v supply
2 x 24w speaker output
Stereo output
Or 4 x 12w speakers
Class B
http://uk.rs-online.com/web/p/audio-amplifier-ics/4840852/
All of these amplifiers give different properties but only some of them could cover the required
specification. The advantages and disadvantages of each different amplifier must be taken into
account before one is chosen, and that must also be done for the transmitter and receiver system.
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Aesthetics
The speaker housing design must give the allusion that it isn’t a speaker housing and that it is a
normal piece of furniture or item in the house.
There are not many speakers like this but I have found a few that could be thought of as other
objects and not speakers.
This speaker looks a lot like the Sydney
opera house and could be seen as a
model or an ornament in the house.
Up close the three speakers are still
visible which would give it away as a
speaker (besides the sound coming out
of it).
If I was to make this I would extrude
(inwards) the speakers into the
housing so they cannot be seen.
Apart from the bad sides of the design,
it is a very sleek and eye catching
design.
This design (on the right) caught my eye as it has two
primary uses, which are providing sound (music), and
holding books and CD’s. This design is called the sound
shelf and it is unknown whether they are wireless but
that would be a very good feature and would add to the
value.
There are two different styles shown here, but they are
both not portable and are more of a household item.
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These speakers are wireless desk speaker and
give the allusion of a very well designed lamp.
They wouldn’t be very portable but the concept
could be taken into account with my design.
Seeing all
speaker
of the above designs sprung on the idea of my
being multifunctional and I thought that it could
incorporate this idea of remote control/phone
holder.
This
and has a
design (on the right) holds remotes on either side
centre pocket for a book or maybe an iPad.
This picture on the left gave me the idea
of cutting groves on the speaker case to
allow for remotes or phones to be
placed on the case.
The picture on the right is a very good
idea but it depends on where in the
house it is placed.
For the audio dock something like
this on the left would be ideal, as it
would be a place to use the audio
device and hold it safely. The main
aspect of this one is the extrude in
the audio dock for the ipad.
Or something as simple as the one on
the right would be ideal.
All of these ideas can potentially be put into my final design or concepts of some of these designs
can be put in my final design to increase its value and functionality. A multifunctional item is much
more desirable in today’s market and especially in places with little space.
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Existing products
There are existing products to my system that transfer music wirelessly to a headphone or speakers,
but these tend to be very expensive. Here are a few examples in the market now:
This speaker system on the left is only for
apple devices, whereas my system will be
for all devices as it will run from a jack to
jack audio cable and not an apple cable.
This can be controlled from the computer
seen in the background and also charges
the iphone or ipad on the dock.
This speaker system on the right is a multi-room wireless
speaker system. This is too complicated for me to be able
to achieve in the give time set but it still follows the same
concept of wireless audio. The centre dock that the iPhone
is on is a 40w subwoofer and the other two speakers are
20w midrange speakers, so together they would make a
very good range of audio.
This speaker on the left transfers music though Airplay for apple
devices only. This is software based and not radio frequency based
which is much more complicated.
But it is very compact and potentially portable which covers my
specification.
This last design on the right is a very
of what my idea is based around as it
audio through the Radio Frequency and
and small dock to transfer the audio
only issue is that the speaker housing
imaginative and doesn’t cover the
but it is potentially portable.
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good example
too transfers
has a neat
from. The
isn’t very
specification,
Technical specification
Function
The purpose of the system is to provide audio from a source wirelessly through a speaker in the
same room as the source. The speaker is to be designed as such that it is not noticeably a speaker
and that it may be a design for multifunction such as being a remote holder, or phone holder.
On the top of the speaker housing, the audio dock must be able to attach securely and be easy to
take off. The audio dock its self, doesn’t have a specification but it must be able to hold a few types
of audio devices safely and it must be easily transported and attached to the speaker housing.
The whole system will be portable so it must not be mains operated, instead it will be battery
operated, and either rechargeable or alkaline batteries are okay for the job.
The design will be light but strong allowing for very minor impacts.
The circuitry will be based around 4 different subsystems:- the transmitter, receiver, stereo decoder
and the amplifier. The audio from the audio device, connects to the audio dock and in the audio
dock is the transmitter circuit. This circuit modulates the audio signal into FM radio frequency (so it
effectively makes your music a radio station). Then this is picked up at the same frequency that it is
emitted from the transmitter at the receiver circuit, which then demodulates the signal, converting
it back into audio. But the audio is only in mono, which means if there are two speakers everything
comes out at the same volume so stereo tracks might sound strange. This is why there is a stereo
decoder after the receiver as it decodes the mono audio signal to a stereo signal which then goes to
the amplifier system which gives out no less than 25w. The receiver, stereo decoder and amplifier
circuits are all situated in the speaker housing.
Form and size
The whole system will come in the form of an audio dock and a speaker housing (which may have
other uses). They are both required to be of such a weight that they feel well made and strong, but
not too heavy to be not very portable. The speaker housing will be made mostly out of wood as
sound resonates much better through wood (depending on the type of wood used e.g. mahogany or
maple are both used in top end guitars). The speaker housing may also include other materials to
allow for a more elegant design rather than a simple design.
The audio dock can be made out of any material, but it must be able to attach to the top of the
speaker housing easy and hold different types of audio devices securely. The part of the audio dock
that holds the audio devices could be lines with a soft material like suede rather than a hard material
like wood. This part of the system may have to deal with apple products, so it would be a good idea
to incorporate the apple dock, to also charge the apple product when plugged in.
There is no exact size that the speaker housing or the audio dock must be, but it is required to be
portable so the smaller the better but not too small to compromise the quality of the sound or the
designs.
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User Requirements
The user requires that the speaker can be operated from the audio dock anywhere in the same room
and that it is portable with the audio dock having the ability to attach to the speaker housing.
The user will also need to register the product for warranty purposes. The warranty covers all parts
except the battery for a period of a year. If the product should fail to operate as a result of fair wear
and tear or manufacturing fault then the warranty applies.
Performance requirements
The speaker system must produce at least 25w of output audio which should be efficient enough to
be heard at the other side of the room that it is in, and the system must be powered by batteries to
allow for the whole system to be portable. These batteries could be made rechargeable so the whole
station can be plugged in when not in use and charged.
Materials requirements
The main speaker housing will be made mostly out of wood. The wood used can be any sort of wood
but Mahogany or Maple would be a good choice as they are already used in musical appliances.
There may also be some metal or plastics for design décor to allow for a simple but modern design.
The audio dock can be made out of anything as it doesn’t emit any sound. It will probably be made
out of a combination of wood and metal for style and strength. For the part of the audio dock that
holds the audio devices, suede or another soft synthetic material could be used to allow the audio
devices to be safe and secure.
Component requirements
The electrical part of the system must be safely housed in its appropriate housing. For the
transmitter, this should be housed in the audio dock and the receiver, stereo decoder and amplifier
will be housed in the speaker housing. The electronic circuits will be built on a breadboard for the
prototype. Components that may be included in the circuits will be resistors, capacitors, batteries,
loudspeakers and possibly integrated circuits.
Quality and safety
The speaker housing must be of such a quality that it is noticeable through the weight and the
aesthetics. It must also be able to withstand minor impacts so metal being used on the outer shell of
the housings would be a good idea.
As the system is portable, the components must be safely secured inside the housings. For electrical
the safety the circuits must be grounded even though the voltages may be low.
The wood must be neatly sanded and coated to ensure that no injuries like splinters or cuts can
come from handling the housings of the speaker and the audio dock.
The same goes for the metal used on the housings, this must be grinded down to give blunt edges so
as not to cause injury but this must also not affect the aesthetics.
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Standards
Standards involved may include the CE marking for electrical goods, the British kitemark for British
standards on audio electrical goods and maybe ISO (international standards organisation) if the
product is popular and expands enough to go worldwide.
A standard that comes up in production and in the product is health and safety, as the product must
not be likely to inflict injury on the user and precautions must be taken when using dangerous
machinery in the production of the product.
Scale of production
Initially the product will be prototyped and tested to be then modified to give the final design. Once
the final design is produced, production will increase to batches, so the product must be able to be
made in stages so it can then be easily assembled. The easier it is to produce each individual
component and system and the easier it is to assemble, the cheaper production will cost, therefore
more profit margins are available. If the product gets more desirable, then mass production will be
undertaken.
Different systems will need different machinery, as the circuitry will be printed and the housings will
be machine cut.
Cost
The total cost for producing a whole speaker system mustn’t be over £70 as most market leaders at
the moment that are like this product are ranging from £120. The cost of production should be split
up into parts, one for production and one for parts and components. The parts and components
section will include the materials and electrical components needed. The production costs will
include how much it cost to print circuit boards, machine the housings and assemble the product.
Then after that, packaging must be accounted for, which will come in the form of a cardboard box
and polystyrene. All of these costs make the total costs of less than £70, bearing in mind that the
more products made at one, the less it will cost for each product as wholesale prices are given in
certain ranges.
The majority of the costs may come from the electrical components if integrated circuits are used.
Environment
As the system uses batteries, this could make the product more environmentally friendly, but the
use of rechargeable batteries would cut down on waste which makes the product even more
environmentally friendly.
The use of reclaimed wood would be a good way to help the environment and recycling the product
at the end of life could also help the environment and cut down on waste.
The environment that the system will be used in may be indoors or outdoors but the systems will
not be waterproof.
End of life
The system may last for quite a while as it will be made of high quality materials and if integrated
circuits are used then there is no reason for the system to fail electrically. But when the system is
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eventually unusable then it must be recycled accordingly as the wood may be reused as well as some
of the electrical components like the loudspeakers. To maximise the life span of the product,
minimal parts will be used but those parts will be made readily available to customers and a repair
service could be set up.
Aesthetics
Most portable wireless speakers on the market today concentrate mostly on the aesthetics so the
design of my system must be good enough to compete with these but it must also be simple to make
it easy to assemble and produce. Also if the design is simple, then it is more likely to suit more styles
of rooms, therefore increasing the customer base.
The speaker housing is to be made out of mostly wood for a better sound and must not look like a
speaker housing. Other materials can be added to enhance the design like metal or plastic. The
speaker housing should be multifunctional, maybe adding LEDs for mood lighting when the room is
dark.
The audio dock could also have LEDs to show its whereabouts but this will be much smaller than the
speaker housing and must be able to attach to the speaker housing. It must also have soft materials
to hold the audio devices for safety.
The whole look of the speaker system will depend on the overall theme as it must look like
something other than a speaker system. For example if the speaker housing was made to look like a
small simple n shaped bench then, it would be given a smooth wood effect. To make it more modern
stainless steel could be added to give an industrial effect.
Manufacturing
The Whole system will be manufactured in two stages:- the electronics stage and the housing stage.
The electronics stage will comprise of four different circuits, one for the audio dock and the other
three for the speaker housing. In the final modified design after the prototype, the three circuits that
go in the speaker housing could be made into one PCB to allow for more room in the speaker
housing.
All circuits will be turned into small PCBs allowing them to be quickly and easily manufactured at a
lower cost.
The housing production stage will be done in parts for both the audio dock and the speaker housing
as they both won’t just be one solid piece. They will be machine cut and sanded and grinded if
necessary for the required look. Then they will be stained or painted if necessary. After the paint, it
is time for assembly. All of the electronic components will have attachments inside the housings for
quick assembley.
Assembly
After the manufacturing of the individual parts, all of these parts must be securely put together. This
will probably be done by hand in batch production, but production techniques will be made to allow
for them to be machine assembled.
The assembly is also done in stages, which are: The audio dock and the speaker housing. The audio
dock comprises of the electronic components and PCB to be attached securely to the acquired
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attachments of the audio dock, then the casing of the audio dock is put together adding the soft
material for the audio device storage last.
It is much the same for the speaker housing but on a bigger scale as there are more electrical
components and the PCB will be bigger. Once the electronic components are attached to the innards
of the speaker housing, then the speaker housing can be put together with any technique, be it
screws or clips.
Then the whole system will be packaged ready for sale.
Design arrangement
This will depend on the final design of the system.
Parameters
Size (dimensions)
Power supply
Output wattage
Primary material
Primary function
Distance of wireless transmission
Weight
Loudness (decibels)
Cost
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Not specified. Must be portable
Battery
Greater than 25w (25w>)
Wood (any type)
Wireless loudspeaker
Greater than 2m (2m>)
Not specified (Must be portable)
= 10 log(base10) 25w = >14db
Less than £70 (<£70)
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Formative evaluation
My wireless speaker system is designed to be separated into two systems, the receiver/speaker
system and the transmitter/audio dock.
I made seven designs for the speaker system and four for the audio dock, all having completely
different aesthetics but they have the same function.
I decided to do a design evaluation matrix which allowed me to evaluate my designs against the
main points of the specification. This allowed me to narrow down my decision for a design to two
each for the speaker and the audio dock systems.
For the audio dock system I decided to take out the tripod bridge dock because it was too large for
an audio dock and this made it un-portable. It would also be too hard to manufacture as it has
complex curves and this could make the design more fragile which does not meet the required
design specification.
I also decided to take out the throne dock because it was the least aesthetically pleasing and themed
to the point that it may be harder to sell. It may also be too hard to manufacture with the different
angles of cuts in the base allowing for a low quality outcome.
The two designs left for the audio dock are the Arch dock and the simple audio dock. This was a
relatively easy decision as the simple audio dock complies with all of the specification needs and has
extra functions. Whereas the Arch dock is much more difficult to manufacture and although it has an
extra feature of a back rest for the audio device, it is not sufficient enough to hold a wider variety of
audio devices which is a required point on the specification.
I also asked the group and it was a unanimous vote for the simple audio dock for being simple and
full of features.
Then I had to choose a speaker housing from the seven ideas. By using the evaluation matrix, this
made my decision much quicker. I took out five designs that wouldn’t be good enough and that
didn’t cover all of the specification requirements for the client brief.
The lamp speaker was definitely out of the question as it did not cover the full specification. It would
also be too difficult to manufacture as there are too many manufacturing processes for the different
parts of the design. Another fault with the lamp speaker is that it is too large to be portable, but it
does have an advantage of being multifunctional as a lamp and speaker, but being a lamp, this
means material costs will be more expensive.
The canvas speaker was another design that didn’t comply fully to the specification as it is also not
portable. The canvas speaker is simple and therefore easy to manufacture but there are two
different materials, wood and paper. This means that it is also very fragile, which is the opposite of
what is asked for in the specification.
Another design that had problems was the Bendy bridge speaker. This was a simple design but a
suitable material couldn’t be found for the bendy legs which made the design undoable.
Even if a material would be found, it may not be strong enough to match the specification.
Most of the speakers bar two had the same issues of being hard to manufacture or not being cost
effective. When I got the list of designs down to two I decided to do more of an in depth evaluation
of the two, by doing a final design for both of them so I could compare the aesthetics more suitably.
27 | P a g e
I also had to take into account the advantages and disadvantages of both of the designs.
First of all the advantages: with the plane speaker, it disguises its speaker like aspects very well by
incorporating them into the hardware of the plane (the jet nacelles), which means it covers the
specification.
Another advantage with the plane speaker is that it has a theme that anyone could potentially like,
instead of a kids theme or an adults theme etc. It also is easy to disassemble for portability, as the
winglets come off and the jet nacelles come off.
The advantages of the bridge speaker are that it is a simple design that is easy to manufacture and
that could potentially be appealing to anyone.
This speaker is also more stable and less fragile as it is all in one piece instead of being in different
parts like the plane speaker.
Because of its simple design, the bridge speaker could also be cheaper to manufacture (as it is all in
one piece) and could potentially be 3D printed if it wasn’t to be made out of wood.
Another advantage with the bridge speaker is that every point is matched on the specification which
is vital as the client needs to be happy with the product.
The disadvantages of the plane speaker are that it is becoming very difficult to manufacture because
of little intricate details that are added. Also the fact that there are parts to the speaker design
means it takes longer to manufacture and that means it costs more to manufacture.
The plane speaker is also aesthetically not very pleasing as the jet nacelles have to be as big as the
speakers because the speakers go in the nacelles. This means that the jet nacelles are out of
proportion with the wing of the plane speaker, and the solution would be to increase the size of the
plane wing but this would make the plane speaker too large to be portable.
Also, a metal hook has to be manufactured for each of the nacelles to allow them to be attached to
the wing easily and to also provide stability.
The disadvantages with the bridge speaker are that it may be a bit large for a portable speaker (but
not too large to allow it to be un-portable). It may also be a bit of a challenge to get the curves on
the system exactly right.
Also the bridge speaker could be harder to service as the speakers may be hard to get to.
After doing some more in depth designing a testing, I have decided to choose the bridge speaker for
the main reasons that it is a much simpler design and that it still covers the full specification.
Also the advantages and the disadvantages of the bridge speaker outweigh those of the plane
speaker as the plane speaker has potentially many faults.
With the bridge speaker being a simpler design, this means that manufacturing will be cheaper and
quicker which allows the product to be batch produced in future for more sales.
I also took into account the classes vote which was for the bridge speaker.
Planning
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Parts List
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Transmitter circuit
Resistors
 47KΩ (x2)
 27KΩ (x2)
 5.6KΩ
 150KΩ
 270Ω
Capacitors




Other









1nF (x6) (not polarised)
10uF (x4) (Polarised)
220pF (not polarised)
10pF (x5) (not polarised)
Alkaline AA battery (1.5v) (x2)
Breadboard
Wires
Stereo audio socket
5mm dia ferrite core
0.5mm dia enamelled copper wire
Integrated circuit: BA1404
38KHz crystal
80cm copper wire
Amplifier circuit
Capacitors
 220nF (x2) (not polarised)
 100nF (not polarised)
 2200uF (Polarised)
 47uF (Polarised)
Resistors
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 10KΩ (x2)
 100KΩ
 100Ω
Others







NPN transistor
Switch (for Mode)
9v battery (x2)
Integrated circuit: TDA8561Q
24w<+ 8Ω or 4Ω (x2)
Breadboard
Wiring
FM receiver circuit
Parts (for TDA7000 circuit)
Resistors
 100kΩ
 22kΩ
 10kΩ
Capacitors


100nF (x3)
3.3nF (x2)
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







Others







330pF (x2)
220pF (x2)
180pF (x2)
22nF
10nF
2.2nF
1nF
150pF
100KΩ potentiometer
Integrated circuit: TDA7000
3.5 turns of variable coil (L1)
MV2105 Diode
Breadboard
Wires
9v battery
Parts (for LM1310 circuit)
Resistors
 1KΩ
 4.7KΩ
 15KΩ
Capacitors






Others
2.2uF (polarised)
470pF
470nF
47nF
220nF (x2)
15nF (x2)
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





Integrated circuit: LM1310
Variable resistor 4.7KΩ
LED
Switch
9v battery (12v supply)
Wires
Total Parts
Resistors
 47KΩ (x2)
 27KΩ (x2)
 5.6KΩ
 150KΩ
 270Ω
 10KΩ (x3)
 100KΩ (x2)
 100Ω
 22KΩ
 1KΩ (x2)
 4.7KΩ (x2)
 15KΩ
Capacitors
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



















1nF (x7) (not polarised)
10uF (x4) (polarised)
220pF (x3)
10pF (x5)
220nF (x4)
100nF (x4)
2200uF (polarised)
47uF (polarised)
3.3nF (x2)
330pF (x2)
180pF (x2)
22nF
10nF
2.2nF
150pF
2.2uF (polarised)
470pF
470nF
47nF
15nF (x2)
Others



















1.5v AA battery (x2)
Breadboard (x3)
Wires
Stereo audio socket
5mm dia ferrite core
0.5mm dia enamelled copper wire
Integrated circuit: BA1404 ****************************************
38KHz crystal *******************************************************
80cm copper wire (x2)
NPN transistor
Switch (x2)
9v Battery (x4)
Integrated circuit: TDA8561Q
*****************************************
24w<++ 8Ω/4Ω speaker (x2)
100KΩ Potentiometer
Integrated circuit: TDA7000 ***********************************************
3.5 turns variable coil
Dia ferrite core??
MV2105 diode
********************************************************
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 Variable resistor 4.7KΩ
 LED
Integrated circuit: LM1310 ************************************************
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Production processes
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Quality checks
FM transmitter circuit
o
o
o
o
o
o
Wires are showing no metal
Wires are not too long and flat on the breadboard
Parts are as close to the board as possible
Battery is firmly connected to the circuit
ON/OFF button has enough wire to fit to the audio dock
LED has enough wire to fit to LED glass and audio dock
FM Receiver Circuit
o
o
o
o
o
o
Wires are showing no metal
Wires are not too long and flat on the breadboard
Parts are as close to the board as possible
Battery is firmly connected to the circuit
ON/OFF button has enough wire to fit to the audio dock
Both LED’s have enough wire to fit to the LED glass and Speaker housing
Stereo Decoder Circuit
o
o
o
o
Wires are showing no metal
Wires are not too long and flat on the breadboard
Parts are as close to the board as possible
Battery is firmly connected to the circuit
Amplifier Circuit
o
o
o
o
o
Wires are showing no metal
Wires are not too long and flat on the breadboard
Parts are as close to the board as possible
Battery is firmly connected to the circuit
Speakers have enough wire to go through speaker housing to breadboard
Audio dock Main housing
o
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
Dimensions are correct to the CAD drawing within 2mm
43 | P a g e
Audio dock bottom cover and middle swivel
o
o
o
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
Dimensions are correct to the CAD drawing within 2mm
Holes have 3mm diameters exactly for screws
Middle swivel is smooth and fits a dock connector securely
Audio Dock Top back, back rest flap and LED glass
o
o
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
Dimensions are correct to the CAD drawing within 2mm
Led glass is made cloudy be sandy slightly
Audio Dock assembly
o
o
o
o
o
LED and LED glass is glued securely into place
ON/OFF button is secured into place
Screws for bottom cover are screwed in straight and not cross threaded
Top back rest easily lifts and is secured with back rest flap
Back rest folds neatly and securely into audio dock
Bridge speaker bottom part
o
o
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
Dimensions are correct to the CAD drawing within 2mm
Speaker holders are strong and are able to support speakers via bolts and nuts
Bridge speaker top part
o
o
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
Dimensions are correct to the CAD drawing within 2mm
Speaker holders are strong and are able to support speakers via bolts and nuts
Bridge speaker parts fabrication
o
o
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
Dimensions are correct to the CAD drawing within 2mm
ON/OFF button whole is not too big but may be slightly small for secure fit
Bridge speaker bottom cover, joining holes, pop screen and audio
dock cut out
o
o
Surface wood is very finely sanded and smooth
Edges are not sharp
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o
o
o
o
Dimensions are correct to the CAD drawing within 2mm
Pop screen just bigger than exact size to fit snugly but tightly
Audio dock cut out has not sharp edges
Top part joining holes have nuts secured by strong glue
Bridge speaker assembly
o
o
o
o
LED’s and LED glass is glued securely into place
ON/OFF button is secured into place
Screws for bottom cover are screwed in straight and not cross threaded
Joining screws tightly secure the top to the bottom
Whole system testing
o
o
o
o
o
o
o
o
o
o
Audio dock turns on and off
Audio dock flap holds audio device
Wood is smooth and edges curved
Bridge speaker turns on and off
Audio dock fits easily into cut out on bridge speaker
Circuitry and batteries in both compartments are secured
Audio dock transmits audio from device on set FM waveband
Bridge speaker receives audio, demodulates, decodes audio to stereo format and amplifies
audio out of the speakers.
Range of audio transmission is measured to be above or equal to a rooms width
Loudness at a measured distance is equal or over specification requirement.
Regulations, standards and
documentation
Legislation
The main legislation that needs to be abided by when in production is the Health and safety
legislations. This legislation covers human carelessness, personal habits, supervision and training,
the environment, guards, elimination of hazards, maintenance, personal attitudes and working
practices and personal protection.
The manufacturing health and safety regulations sector is split up into different sections whereby
two sections apply to my production procedures. These are woodworking health and safety and
engineering health and safety.
Woodworking is a major part of my production and therefore health and safety when in production
has to be considered.
According to the health and safety government site, woodworking has one of the highest accident
rates in manufacturing, caused mostly by moving machinery. In the woodworking health and safety
legislation, certain aspects have to be covered in the workshop and this includes keeping the
45 | P a g e
workplace tidy, training workers that use machinery, taking COSHH and risk assessments, and
lowering wood and dust inhalation with extractor fans.
Safety topics within woodworking include: working with machinery, vehicles and slips trips and falls.
Health topics include: manual handling, wood dust, and noise. All of these health and safety issues
have to be extinguished or prevented as much as possible.
As I am in the engineering sector, health and safety in this sector has to be looked into.
The same things apply to this sector as the woodworking sector.
Another big aspect of health and safety is working with electricity. The electrical components that I
am dealing with are not very hazardous but there are still things that can go wrong like exploding
LED’s and smoking potentiometer due to too much resistance or not enough resistance. This is why
precautions have to be taken.
Precautions taken to reduce any risks or hazards include a risk assessment and an assessment of
what legislations and regulations I come under in production (which is what this is). A COSHH
assessment is advised by the health and safety act but as there are no hazardous substances in the
woodworking workplace then this is un-necessary.
Other legislations include contracts, which are not required at the moment due to the fact that this
is a product still being designed and improved. It is when the product is fully developed that
contracts can be taken and these contracts can be between customers and employees.
If the product gets to the point where it is being produced in a company workshop then contracts
will be undertaken as well as company disciplinary procedures for employees. These disciplinary
procedures keep the workplace running smoothly and safely. The procedures are split up into stages
one to 5 where one is an oral warning and 5 is gross misconduct.
Regulations and standards
European standards are the home from which the main standards come from like the British
standards and the CE marking. It is necessary for me to cover because Britain is situated within
Europe and therefor some of the European standards apply to me, even if I am not selling abroad.
Products comply to their own set directive of standards which define
technical requirements. These directives must be complied by to be able to fit
the product with a CE marking. Therefore the CE marking indicates that the
product has conformed to directives that apply to it.
For all electrical products, as well as the CE marking, they have to conform to the EMC directives
(electromagnetic compatability). Because my product is made up of Resistors, capacitors and
integrated circuits etc. my system is tested for the directive as a whole system rather than
components because components are regarded as having no intrinsic function when on their own
but when put together as a system this changes.
As subsystems my product will be tested to comply with the EMC directive
because as a whole system this is regarded as a telecommunication device,
and therefor needs to be covered by the Radio terminal and
telecommunications equipment directive.
The whole point of the EMC directive is to stop electrical products emitting
46 | P a g e
unwanted electromagnetic pollution which could otherwise cause interference with other electrical
items. It also states that the products must be immune to a certain amount of interference.
Tests within the EMC directive include tests for radiation emissions, conducted emissions, and
radiated susceptibility.
Another major standards organisation that applies to my product is the British standards (kitemark).
BSI is the UK’s national standards body, and represents the UK in European standards bodies.
Standards are not compulsary unless stated by the legislation or regulations applicable to a certain
product. The standard states technical specifications and criteria to be used as a guidline.
This applies to my product as my Product is to be made in the UK and will be distributed in the UK so
it would be a big advantage if the product has conformed to British standards as it would be a good
selling point.
Documentation
Documentation is a big part of a products production. One type of documentation that I have
already used especially in research is data sheets and books. I used these for picking my electrical
components and integrated circuits. They give detailed information and parameters on that specific
product, and in some cases it gives you testing results for performance.
I also used catalogues which are a a book of products or components. I used this when I was buying
components like capacitors and resistors from Maplin and other electrical component shops.
I have had to wright specifications for my product, including a general specification which describes
its appearance and construction etc. I have also written a standard specification in the form of a
production processes document which outlines the materials and processes used in manufacture,
and I have also written a performance specification.
An important document that is used at the end of production is a quality document. This is used to
check the quality of a freshly made product and to analyse the product through production. If there
are any errors, the product doesn’t carry on through production but it is recycled to be used again
from the start of production to be fixed.
The last piece of documentation is traceability which is used for future purposes and for records.
When the item is sold it is referenced as sold for future records and censuses. If the customer has
problems with the product, they could reference the product number, situated inside the product
and then further action can be taken. If the product is modified in the future and released as a new
product then the new product will differ in traceability numbers to the old model, so by just quoting
the model number, the generation can be found.
A batch number can also be created to show what batch the product was made in so if there is a
problem with a certain batch and it happens to slip through quality testing then it can be reclaimed
by naming the batch number.
All of the traceability data will be situated on the inside of the under panel for the electrical
compartments on the audio dock and bridge speaker separately.
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Final design
See appendix
Production
FM transmitter circuit assembly
The first process was to assemble the FM transmitter circuit with the on/off button and led. This was
done on a Breadboard to allow for easy changes rather than having to solder and de-solder which
could be costly and time consuming. I followed the parts list and schematic diagram for the BA1404
stereo FM transmitter integrated circuit as well as using the schematic that I drew of the BA1404
circuit. I was able to space out the parts on the breadboard because the BA1404 circuit is the only
circuit to go on this breadboard. I firstly attached the BA1404 chip to the centre of the breadboard
so that either side of it had enough room for components. Trying to
use as little wire as possible, some components are crossed over
from one connection to another where necessary.
Step by step I assembled the circuit starting at the two inputs to
pins 1 and 18 from the audio jack socket/apple socket placed
temporarily at the edge of the breadboard. The two inputs at pins 1
and 18 then go through individual amps into the radio frequency
modulator which modulates the audio signal into a FM waveform.
I then set up the amplifier bypass with a 10uF electrolytic capacitor
connected to pin 2 which gets rid of excess noise or AC from DC.
And this goes to ground with pins 3 and pins 4 which are the low frequency ground and frequency
oscillator bypass respectively.
Pins 5 and 6 occupy the 38 KHz quartz crystal and the load capacitor which supply the chip the startup frequency for the frequency modulator.
The output at pin 7 goes to an LC resonator in the form of an inductor coil in parallel with a capacitor
connected to an antenna causing resonance. Pin 8 grounds the lower frequencies and through a
decoupling capacitor, grounds pin 9 as well. Pins 9 and 10 are the radio frequency oscillation output
and go straight to VCC through a parallel variable inductor and capacitor.
Pin 11 is the voltage supple and is not
connected as it is just a reference. Pins 12, 13,
and 14 make the RC mixer circuit. Pin 15 is the
VCC pin and supplies voltage to the chip. Lastly
pins 16 and 17 connect to the tuning circuit
which contains specific resistors or may even
be controlled by a trimpot. I also attached a
switch at the power input line to act as an
ON/OFF switch and the LED was connected in
series with a resistor.
50 | P a g e
FM transmitter testing
I tested the BA1404 chip by connecting the batteries held in an old remote control to make them
secure and I used a jack to jack lead to play music from my iPad into the BA1404’s designated input
pins. To hear the audio I used a household radio to pick up the signal. After a lot of fiddling with the
variable coil I found the waveband through the radio and heard the music sent from my iPad and
BA1404.
I added a ferrite core coil of 3.5 turns to the antenna output to boost the signal.
FM receiver circuit assembly
The FM receiver circuit was probably the most difficult out of all of the circuits because of the tuning
system. I also had problems getting the correct output voltage at 70mV and output current of 60uA.
The circuit runs off of a 9v battery connected to a positive rail and a negative rail (ground rail).
Straight after the positive input is the mono switch which cuts the power to the circuit, acting as an
on/off switch whereby the state is shown through an LED connected in parallel from the positive rail
to the negative rail in series with a resistor.
In order to construct the circuit I had to have knowledge of how it works internally and externally.
Starting with pins 10 and 11, I constructed the circuit taking into account what effect it will have.
Pins 10 and 11 are connected to the positive power line via a 3.3nF capacitor whilst pin 10 connects
to pin 11 in parallel by means of a 330pF capacitor. Inside the circuit pins 10 and 11 both go to the
intermediate frequency filter in the form of an op amp. This is a looping filter which regulates when
you change the frequency for output so both channels on the demodulator and mixer are changed
as well. Pin 12 is for decoupling the output of the intermediate frequency filter via a 150pF
capacitor. Pins 13 and 14 are used for the input stage of the circuit and go in to the oscillator mixer
inside the chip which is also connected to the tuning circuit. Pins 14 and 13 are compared internally
so in my circuit pin 14 is just connected to ground via a 220pF capacitor through pin 16 as pin 16 is a
ground for the whole circuit. Pin 13 on the other hand is connected to the antenna in series with an
180pF capacitor.
Pin 15 is used for comparison between the positive rail and the intermediate frequency filter output
in the circuit. Pins 17 and 18 are connected to the positive supply via two separate capacitors and
inside the chip the pins go to the demodulator circuit which basically turns the radio frequency
signal wave into a readable audio signal, able to be put through to an amplifier.
On to the other side of the chip, pins 9 and 7 are connected to one and other via a 3.3nF capacitor.
They both go into the mixer and intermediate frequency filter stage of the chip, along with pin 8
which connects directly to the power line through an 180pF capacitor.
Probably the most complicated part of the circuit is the tuning part of the circuit at pins 5 and 6. In
the datasheet for the chip, made in 1992, the tuning circuit comprises of parallel capacitors (variable
and non-variable) and an inductor. But variable capacitors are hard to come by so I have decided to
use a variactor diode. It has been acknowledged that when certain diodes are put into reversed bias,
they act as a variable capacitor dependant on the voltage supplied to it.
In my circuit, I make pin 5 go straight to the positive rail as pins 5 and 6 are compared inside the
circuit via a voltage divider (VCO) which goes to the mixer and then to the mute switch. At pin 6 a
variable inductor (used to tune to a certain frequency) is connected from the power line. The
variactor is connected to pin 6 in front of the inductor and goes off parallel to pin 6 and goes into a
voltage divider circuit which provides the variable voltage to the diode to create a variable
51 | P a g e
inductance. This voltage divider circuit comprises of a potentiometer at one end (varying the voltage
from 9v to 0v) and a 1nF capacitor to the positive line at the other end.
Pins 4 and 3 go straight to the positive line via two separate capacitors, where pin 4 provides a
decoupling for the loop filter and pin 3 goes to the noise source and mute circuit in the chip.
Onto the last two pins, pin 2 is the output pin where the audio has been processed and demodulated
to be able to be amplified to a speaker. The current of this output is dependent on the resistor used
in parallel with the pin 2 line, which is 22k(omega). This should give an output current of about
60uA, which wasn’t the case at first but after a bit of testing this problem was resolved.
Lastly, pin 1 is set up as the mute switch but as I don’t need a mute switch, I can set it as
permanently on by allowing a current of about 20uA to go into the chip at pin 1. I did this by
connecting a capacitor in series with pin 1 to the positive rail, and a 10K(omega) resistor in parallel
to the positive rail.
After I fully assembled the receiver circuit I had to test to see whether all of the measurable values
were correct and whether the output was amplifiable to produce an audible sound.
FM receiver testing
Testing the FM receiver was probably the hardest because there were a few things to consider when
troubleshooting. The first thing was the input stage (antenna), if this wasn’t sufficient a signal
wouldn’t be received. I tested readable values with a multi-meter, using the ammeter setting and
voltmeter setting.
I started with the mute switch which should have a current of around 20uA going into the pin. This
was measured at about 33uA which was sufficient. I then tested to see if the potentiometer was
actually working by putting the voltmeter between the negative rail and the output of the
potentiometer and turning the variable resistor knob. This resulted in a change of voltage from 9v to
0v which was as expected. I then tested the output stage at pin 2 which should have a current of
about 60uA and a voltage of 70mV.
52 | P a g e
After some more testing and troubleshooting, a readable output was found.
Stereo decoder circuit assembly
The stereo decoder assembly is probably the simplest circuit out of all of the circuits because it has
the least external components. The circuit is based on the LM1310N chip which is rare and hard to
find information on, which added a hint of difficulty to the circuit.
This turns out to be a relatively simple chip with pins 1 and 7 being the supply voltage and ground
respectively.
Pin 2 on the receiver chip goes straight to pin 2 on the LM1310 which is the input pin. The chip works
on a matrix system so some of the pins are very basic and just need to be connected to other pins,
like pin 3 and 11. Pins 4 and 5 are the output pins for left and right audio outputs and each comprise
of a resistor and capacitor in parallel to the positive line.
Pin 6 is connected to the positive rail through a resistor and LED which lights up when there is a
supply voltage and when the chip has a ground. Pins 8 and 9 are connected to each other via a
220nF capacitor and go straight to ground via a switch. These two pins are connected to pin 6
internally so if the switch is open the LED and resistor in series don’t have a ground, do so the chip
doesn’t turn on and the LED doesn’t light. Pin 10 is just a ripple rejection and is not needed.
Lastly pin 14 is connected to ground via a tuning circuit for the volume by means of two series
resistors (one of which is variable), both in parallel with a capacitor of 470pF.
Stereo decoder testing
The testing for the LM1310N chip didn’t need any values of voltage or current to be read as it
worked first time when a mono audio signal was placed in the input and the left and right outputs
were connected to the left and right channel inputs in the amplifier circuit. When the amplifier was
turned on, I checked both speakers connected to the outputs of the amplifier for a recognisable
audible sound and this is exactly what I got.
Stereo amplifier circuit assembly
The stereo amplifier circuit is probably the easiest assembly as it requires minimal external parts to
operate. I firstly placed the TDA8561Q chip on the left of the breadboard, which was tricky as I had
to bend the long pin legs carefully without breaking them to fit them precisely into the holes on the
breadboard.
I firstly connected up the input stages for the Left and Right audio channels. The left channel
comprises of pins 1 and 3 connected to each other whilst the input goes through a decoupling
capacitor of 220nF. The same goes for the Right channel but for pins 17 and 15.
Then pin 2 was put straight to ground as this pin grounds the circuit which also gives it the negative
supply voltage as the negative supply voltage is connected to ground.
Pin 4 is not connected to anything as this is a reference to supply ripple rejection.
Pins 7 and 11 are both power ground pins for the left and right channels and both go straight to
ground.
Pins 6 and 8 are the speaker outputs for the left channel and pins 12 and 10 are the speaker outputs
for the right channel and are both connected to a 30watt bass/mid woofer of 6ohms impedance.
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Pin 9 is not connected to anything, whilst pins 13 and 5 are both supply voltage pins for each channel
of audio amplification and are both connected from a power supply decoupled by 2 parallel
capacitors. Pin 16 on the other hand is a diagnostics pin which I haven’t decided to use this pin but it
can be used to say whether there is a problem via a Dynamic distortion detector and a short circuit
protector with the chip via an LED.
Pin 14 is the last pin to be connected and is for the mute button. This involves a potential divider
circuit and goes to an op-amp in the circuit so when the voltage is below a certain amount going to
the pin, it mutes the output to the speakers. Also attached to the potential divider circuit is a NPN
transistor. Attached from the power to the voltage divider circuit is a switch which acts as a mute
switch.
Stereo amplifier testing
To test the stereo amplifier on its own I connected up two 34w (max) 6 ohm impedance speakers
that I will be using in the full assembly. I then connected the audio jack from the transmitter circuit
to the amplifier circuit inputs and connected my iPad via a jack to jack lead to the circuit. Once
turned on the circuit is ready to amplify audio straight away. I then played a song on my ipad and
controlled the volume on my iPad, starting from a low volume to a reasonably loud volume which
was recorded from a metre away with a decibel meter. I also found the volume that the audio
becomes distorted.
The final thing to test on this system is the mute button. I pressed the mute button whilst having the
music playing at a moderate volume, and after a second or 2 the music muted, and I pressed the
button again to unmute the music.
Electronics testing
The overall electronics testing started with me assembling the receiver, stereo decoder and amplifier
together by putting the output of the receiver straight to the input of the decoder, and then
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connecting the left and right outputs of the stereo decoder to the left and right inputs of the
amplifier.
Firstly, I turned on the transmitter circuit, checking for the LED to light which it did. Once it was
turned on, I connected my iPad to the input jack of the transmitter via a jack to jack (male) lead.
Then I moved on to the receiver, decoder and amplifier circuits. I powered up all of the circuits
looking for the LED from the receiver to light and the LED from the decoder to light.
As soon as all of the circuits were powered up, I played a song on my iPad and adjusted the volume
from low to high. As soon as I played the song, I adjusted the inductor on the receiver circuit with a
precision flat head screwdriver, turning the ferrite core to a position in the coil where a signal was
vaguely received and then I adjusted the capacitance in the tuning circuit via the varaictor with the
potentiometer until I got a clearer signal of the audio that I was sending from the transmitter.
When I had tested that it was functioning properly, I had to test the system to the technical
specification.
I started with loudness which was tested from a metre away from the source and was measured
with a decibel meter on an iPod app. This measured at approximately 50 decibels at full volume
which is more than triple the value given in the specification.
I then measured whether the system is able to operate at a certain range. To do this I moved the
transmitter circuit to the opposite side of the room to the receiver circuit and played the music. This
resulted in a more distorted sound coming out of the amplifier but because this is a prototype, this is
passable as there is still room for slight developments of quality of electronic components like using
PCB’s instead of breadboards.
The other specification requirements do not require any electrical testing so this is the end of testing
for the electrical system.
Audio dock main housing
The first object I started with building was the audio dock main housing and because this is a
prototype, I couldn’t produce the audio dock as I designed it to be produced. Instead I had to work
from cut-outs instead of one solid block of wood but this still
resulted in a fully functioning product and doesn’t affect the
main design in any way as a prototype is to test and prove an
idea and it is better to test on a prototype rather than going
straight in with building the main design.
I started by gathering a board of wood of thickness 10mm
and drew the shapes that wood need to be cut to be then
put together to create the audio dock main housing.
I used a pencil and a straight edge to faintly draw the shapes
onto the wood to be cut out with a table saw. When using
the table saw, I took into account the dangers of using the
table saw and wore goggles, gloves and steel toed boots.
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Once all off the main sides and top was cut out, I used a jigsaw and a clamp to cut out the top back
rest and the LED holes. I started off the jigsaw by drilling a hole as big as the jig saw cutter so the
cutter could go into the hole and start cutting easier.
To cut out the button hole, I used a drill with a 17mm hole cutter attachment, marking the centre
with a hole-punch and a hammer so that the hole was straight.
I also had to cut out the extrusion for the audio device holder which was initially done manually with
a wood cutter but then it was sanded off by a round Dremmel sander tool.
The audio dock main walls are now ready to be assembled and I did this with glue. But before I could
glue the walls together, I had to cut out 45 degree angles
on the inside edges of each sides of each wall so all of the
walls would make a perfect shape. I initially did this by
using a small saw to make cut-out for the big saw to get
started. Once cut of, I sanded all of the edges down to as
perfect as possible to a 45 degree angle.
With all walls ready, I used strong wood glue to bring the
walls together as well as the top part of the audio dock. I
had now completed the audio dock main housing and left
the audio dock glue to dry until I needed to use the audio
dock again.
Audio dock bottom cover and middle swivel
I started with the bottom cover and crafted it out of a sheet of wood and a block of would. By
cutting out the bottom surface area from the sheet of wood with a jigsaw I created the bottom cover
and added the block of wood to the centre that was also cut out but with a normal wood saw. The
two parts of the bottom cover were glued together with strong wood glue. Once dried, I drilled holes
in each corner for the screws.
The middle swivel is still yet to be prototyped in the development of the product and as this is only
the first every prototype there is room to expand the product gradually adding extra features like
the middle swivel.
Top back rest and LED glass
The top back rest was produced when I cut out the top part of the main housing with a jigsaw and a
drill bit. All that is left to do is neaten it up by sanding down the edges with a thick grit to start with
and then eventually a softer sand paper for smoothness.
The LED glass was created by cutting out a strip of acrylic to certain measurements specified by the
engineering drawings. This was sanded slightly to give a cloudy effect to enhance the lighting from
the LED.
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Audio dock assembly
The assembly consisted of firstly checking that all the edges of the parts were smooth for safety
reasons, by sanding down with a Dremmel. I then attached the back rest to the top of the main
housing by means of two nails hammered in from the outside as making two small extrudes for the
hinges would be too difficult with the tools I had to hand.
I then pivoted the back rest to free it up a little bit from the nails but it still remained slightly stiff so
that it didn’t need much support.
The next part of the assembly was adding the
electronic components. I firstly glued the LED to
the LED glass and soldered two wires on to the LED
ends to add to the circuit board. After that I fitted
the LED glass and the button which both pushed
into place. Then I wired up the LED and the button
to the Transmitter circuit and glued the
breadboard to the inside of the bottom cover.
The last thing to do was to screw the bottom cover
to the bottom of the main housing with four 3mm
screws, one at each corner.
Bridge speaker bottom part
The bottom part of the speaker housing was probably the most difficult to make in prototype
manufacture and because this is a prototype, I couldn’t produce the bottom part of the speaker
housing as I designed it to be produced. Instead I had to work from cut-outs instead of one solid
block of wood but this still resulted in a fully functioning product and doesn’t affect the main design
in any way as a prototype is to test and prove an idea and it is better to test on a design rather than
going straight in with building the main design.
In the end I tried producing the bottom part with tools and materials that I had to hand but it would
take me too long in the timeframe that I had and that is why I decided to leave out the bottom part
in the production of the prototype and this could be used in the evaluation of production for further
development as if the part is too difficult to make, then it will cost too much too produce and It may
deem the product unsellable with such I high price compared to other market leaders.
Bridge speaker top part
The last major part of the production for the prototype was the top part of the speaker housing
which will now become the main part for the speaker housing in
my prototype production and because this is a prototype, I
couldn’t produce the top part (main part) of the speaker
housing as I designed it to be produced. Instead I had to work
from cut-outs instead of one solid block of wood but this still
resulted in a fully functioning product and doesn’t affect the
main design in any way as a prototype is to test and prove an
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idea and it is better to test on a design rather than going straight in with building the main design.
This part will be produced using the engineering drawing when it is put into full production for the
technicians use. This includes a bill of materials and specific measurements of parameters, angles,
areas, and volumes.
I created every section of the top part with a sheet of 10mm thick wood of which a drew on with a
pencil all of the shapes to be cut out with a
table saw and further shaped with other
tools like sanders, jigsaws, drills and saws.
I firstly cut out the 5 walls for the 5 sides of
the top part, taking into account the
dangers of using a table saw I wore goggles,
gloves and steel toed boots and I had the
teacher watching at all times.
When all of the sides were created, I had to
cut angles into the edges so they slotted
together perfectly. I did this by measuring
the angle on the top of the sides and
drawing what needed to be cut with a
pencil. Then I clamped the sides and started
cutting with a special, small saw to make
the cutting with the main saw easier. Once
all of the edges were cut I checked them
with the subsequent side to see whether
they were matched as perfectly as possible.
If not I sanded down if it was only a slight
change needed and I filed them down if it
was a large change needed.
After finishing the sides, I glued them all together by
firstly nailing them together to hold them and then
applying the glue for security. This meant I could
manufacture the top of the top part whilst the glue
was drying.
I made the top part in the same way but by using 3
separate planks that were measured in accordance
with the walls and then cut out with the table saw.
Once cut out, I nailed the planks to the 5 side walls and sanded down any differences in angles and
edges.
Once the outline of the top part was put together I had to neaten it up with a sander (Dremmel), by
sanding down the edges to smooth curved surfaces and using wood filler for any unnecessary
extrusions.
I also had to cut out the LED glass extrusion and a hole for the on/off button. I cut out the LED glass
extrusion firstly with a drill and drill bit the size of the jigsaw end so that the jigsaw can have a
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starting point. I then used the jigsaw to cut out the rectangular hole and used a file to cut any hard
to get areas. I then used a 17mm hole cutting tool extension for a drill to drill the hole for the on/off
button which was measured on a faint grid of lines to place at the correct point on the front of the
top part.
LED glass and components cut-out
The LED glass was created by cutting out a strip of acrylic to certain measurements specified by the
engineering drawings. This was sanded slightly to give a cloudy effect to enhance the lighting from
the LED.
The cut outs for the components were done in the above step but consisted of making holes for the
on/off button and the LED glass.
Bottom cover, audio dock cut-out and pop screen
The bottom cover was fabricated from a sheet of thin ply
wood, which was measured and drawn by hand with a
straight edge and a pencil. Because the sheet of wood
was thin, I decided to use a jigsaw to cut out the bottom
cover. Whilst I used the jigsaw I used the appropriate
safety equipment and clothing. I then drilled holes in
each corner for it to be attached to the underside of the
top part of the speaker housing.
The audio-dock cut out was unable to be cut out due to
the constraints of prototype construction. For the popscreen I used old tights material, and I cut out circles the
same size as the speaker hole. The pop-screen is used to
allow for the music quality to be less ‘tingy’ and richer
with less distortion and it also stops the user for seeing
in the whole which furthermore disguises the product
from being a speaker.
Bridge speaker assembly
The speaker assembly consisted of firstly gathering all of the electrical components that needed to
be fitted to the bridge speaker. This firstly started with the two LED’s, one from the receiver circuit
and the other from the decoder circuit, being attached to the LED glass fabricated from acrylic. I
then attached the LED glass with LED’s to the front of the top part of the bridge speaker housing.
That leaves the on/off button to be fitted to the front of the top part speaker housing which clicked
in. Inside the speaker housing, the speakers needed to be fitted and because I hadn’t fabricated a
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bottom part of which the speakers originally sat in
(due to production constraints), I had to put them
in the top part of the speaker design, which was
okay because there was plenty of room.
After the electronic components were placed I
had to wire them up, starting with the speakers
which had two wires each going to the amplifier
circuit. The speaker ends of the wires were
soldered along with the ends closest to the button
and the LED’s which were attached to the receiver
circuit and stereo decoder circuit.
Then I had to fit the electronic breadboards and
batteries to the top of the bottom cover with
glue, and then I screwed the bottom cover to the
underneath of the bridge speaker.
Whole system testing
The whole system testing was much the same as the electronics testing but with the electronics in
the housings.
Firstly, I turned on the transmitter circuit, checking for the LED to light which it did. Once it was
turned on, I connected my iPad to the input jack of the transmitter via a jack to jack (male) lead.
Then I moved on to the receiver, decoder and amplifier circuits. I powered up all of the circuits
looking for the LED from the receiver to light and the LED from the decoder to light.
As soon as all of the circuits were powered up, I played a song on my iPad and adjusted the volume
from low to high. As soon as I played the song, I adjusted the inductor on the receiver circuit with a
precision flat head screwdriver, turning the ferrite core to a position in the coil where a signal was
vaguely received and then I adjusted the
capacitance in the tuning circuit via the varaictor
with the potentiometer until I got a clearer signal
of the audio that I was sending from the
transmitter.
When I had tested that it was functioning
properly, I had to test the system to the technical
specification.
I started with loudness which was tested from a
metre away from the source and was measured
with a decibel meter on an iPod app. This measured at approximately 50 decibels at full volume
which is more than triple the value given in the specification.
I then measured whether the system is able to operate at a certain range. To do this I moved the
transmitter circuit to the opposite side of the room to the receiver circuit and played the music. This
resulted in a more distorted sound coming out of the amplifier but because this is a prototype, this is
passable as there is still room for slight developments of quality of electronic components like using
PCB’s instead of breadboards.
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The other specification requirements do not require any electrical testing so this is the end of testing
for the electrical system.
Evaluation
In order to evaluate my project, I had to test the end result against the required specification points
given by the client. It must first be known that the prototype that I produced did not fully match the
design I made on CAD because of the constraints of time, materials and tools, but this is a good point
to put forward for development as some parts like the bottom part were too difficult to make and
therefore this part can be deleted to reduce costs and time as it is only cosmetic. Although the
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aesthetics of the product were changed during prototype manufacture, this doesn’t mean that the
product is not fir for purpose and it is still possible for the product to meet the full specification
requirements as there were no specific requirements for aesthetics other than one stating that it
mustn’t look like a speaker system.
I used the parameters which are as shown below to test the product to the specification:
Size (dimensions)
Power supply
Output wattage
Primary material
Primary function
Distance of wireless transmission
Weight
Loudness (decibels)
Cost
Not specified. Must be portable
Battery
Greater than 25w (25w>)
Wood (any type)
Wireless loudspeaker
Greater than 2m (2m>)
Not specified (Must be portable)
= 10 log(base10) 25w = >14db
Less than £70 (<£70)
I touched on the testing for the different parts of the speaker system and the whole speaker system
in the production document.
Starting from the top, the dimensions are as expected because I designed the product to be portable
although the main speaker housing is on the larger side, both of the systems in the speaker system
will be significantly smaller when the electronics are produced on PCB’s, as this will make the
electronics so much smaller. With smaller electronics, the size of the housings can be so much
smaller meaning the portability will be so much better. At the moment, it could be said that the
prototype that I have produced is a slightly blown up version of what it will eventually be when it
hits production for the consumer market.
The power supply is achieved by batteries as stated in the specification which adds to the portability
of the product. In further development there could be a way to reduce the amount of batteries used
by linking the circuits, especially in the speaker housing electronics with the receiver, stereo decoder
and amplifier. Also with further development, the batteries used could be NiCad rechargeable
batteries, so that periodic maintenance of changing batteries is not needed and there could be a
rechargeable socket in the housing of the dock and the speaker housing for a quick recharge. But
this is not needed in this specification so it is an idea for the future of the product.
The materials used were not a major issue, but in the specification it was prescribed to use wood.
Using wood will lower the cost of production as wood is of a lower cost than metal and is easier to
work with.
The primary function of the product is to be a wireless speaker system, allowing you to place a
speaker unit anywhere in the room, whilst the music being played is coming from a device on a dock
at the other side of the room. The whole purpose of this is to lower the cables in a room for tidiness,
as a lot of electronics need wires to operate.
The first measurable parameter is the distance or range of transmission. This was required to be
above 2m but a rooms length is also stated in the specification, so either or would be okay. I decided
to test this parameter by putting the audio dock and audio device on a cabinet at one side of the
room and placing the speaker housing at the other side of the room. This room happened to be
approximately 3m wide. I played the music on my audio device and tuned the receiver circuit before
the test in another test. The signal was slightly vague but it was received and with a little
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development this would be a totally clean sound and therefore be a better product. Also, the
electronics will be much more substantial in the final product so this will furthermore increase
quality.
The weight of the product isn’t an issue, but obviously it must not be so heavy that it requires a lot
of effort to carry it. In this case the prototype was not too heavy as a whole system and actually felt
solid in its weight.
Loudness is a measure measured in decibels and to get an idea of how many decibels I would have
to achieve, I had to acquire a calculation. I knew what wattage the minimum wattage of the
amplifier should be which = 25w, and the equation I can use involves logarithms. The equation is =
10 log(base10) x wattage. This equates to 10 log(base10)24w = 14dB, therefore 14dB is the
minimum at which the speaker system can be. I tested the system and the wattage I had coming out
of my amplifier was two 25w(rms) speakers which technically equates to about 30dB. I used decibel
metre on my iPod as an app and played the music at close to maximum volume (before there was
any distortion) and the reading came out at approximately 50dB which nearly double the minimum
loudness.
The last parameter on the specification is the cost which is permitted to be £70 or bellow. Splitting it
up into sections of materials and electronics, the costs can be calculated. The materials came to a
price of zero because the materials used were reclaimed (recycled) which is a good idea to carry on
as it is a unique selling point that the product uses recycled materials and this also potentially
increases profit with less production costs.
The electronics were the biggest chunk of the costs which equated to approximately £60 which is
below the limit of £70 but it is an irrelevant figure as this will be dramatically reduced by buying
parts in bulk at wholesale prices and using printed PCB’s at next to nothing prices each when
produced in bulk. I could estimate that the cost of electronics could at least half when the product is
put into full production.
It is fair to say that I am evaluating the prototype which has some changes to the main design due to
production constraints which should be taken into account. From here, I can use the information I
gathered from production about certain parts on the design that could be changed or scrapped due
to difficulty in production. Although some may say that producing a prototype different to the main
design given is a failure, it could also be seen as a good thing as it gives points to modify the product
on as if I had not done a prototype, I would never have known that certain parts of the product were
too difficult to make and I may have just gone straight into production losing a lot of money on
products that are too overpriced due to production costs.
Modifications to the product are plentiful as this is the first draft. Most of the modifications will be
cosmetic to add to the desirability of the product. The one electrical modification that must be made
straight away is changing the breadboards to Printed Circuit Boards to make the product more
durable and add to the quality of the electrical system, which may also increase the quality of the
sound being amplified.
Another major modification is to add battery opening in the underside of the main housing and the
audio dock, so they don’t have to be taken apart to get to the batteries.
Less important modifications increase desirability, like adding the apple dock, radio channel changer
and extras like veneer finish and rechargeable docking station.
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I can conclude that the main points given by the client in the specification were covered and passed
but this doesn’t mean that the product is finished and ready for production. It is merely a stepping
stone to that and I believe that for it to achieve greater sales and popularity, it must be further
developed into a simpler, more developed and desirable product.
Bibliography
Google – www.google.co.uk
Autodesk inventor student edition - http://students.autodesk.com/
Wireless speaker system research – www.amazon.co.uk
Wireless speaker system circuits - http://electroschematics.com/
Materials research - http://www.hindleys.com/materials/plastics-and-foam/rods-and-tubes-andblock/
- http://www.diy.com/nav/build
Standards - http://www.bsigroup.com/
Legislation - http://www.cemarking.net/
Appendices
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