Kitronik 2143K User manual

HIGH POWER AMPLIFIER KIT
PLAY IT LOUD AND PLAY IT PROUD WITH THIS
TEACHING RESOURCES
SCHEMES OF WORK
DEVELOPING A SPECIFICATION
COMPONENT FACTSHEETS
HOW TO SOLDER GUIDE
Version 2.
0

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Index of Sheets
TEACHING RESOURCES
Index of Sheets
Introduction
Schemes of Work
Answers
The Design Process
The Design Brief
Investigation / Research
Developing a Specification
Design
Design Review (group task)
Soldering in Ten Steps
Resistor Values
LEDs & Current Limit Resistors
LEDs Continued
Capacitor Basics
Ceramic Disc Capacitors
Instruction Manual
Evaluation
Packaging Design
ESSENTIAL INFORMATION
Build Instructions
Checking Your Amplifier PCB
Adding an On / Off Switch
Adding an On / Off Switch
Fault Finding
Designing the Enclosure
How the Amplifier Works
Online Information

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Introduction
About the project kit
Both the project kit and the supporting material have been carefully designed for use in KS3 Design and Technology
lessons. The project kit has been designed so that even teachers with a limited knowledge of electronics should have
no trouble using it as a basis from which they can form a scheme of work.
The project kits can be used in two ways:
1. As part of a larger project involving all aspects of a product design, such as designing an enclosure for the
electronics to fit into.
2. On their own as a way of introducing electronics and electronic construction to students over a number of
lessons.
This booklet contains a wealth of material to aid the teacher in either case.
Using the booklet
The first few pages of this booklet contains information to aid the teacher in planning their lessons and also covers
worksheet answers. The rest of the booklet is designed to be printed out as classroom handouts. In most cases all of
the sheets will not be needed, hence there being no page numbers, teachers can pick and choose as they see fit.
Please feel free to print any pages of this booklet to use as student handouts in conjunction with Kitronik project
kits.
Support and resources
You can also find additional resources at www.kitronik.co.uk.There are component fact sheets, information on
calculating resistor and capacitor values, puzzles and much more.
Kitronik provide a next day response technical assistance service via e-mail. If you have any questions regarding this
kit or even suggestions for improvements, please e-mail us at:
Alternatively, phone us on 0845 8380781.

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Schemes of Work
Two schemes of work are included in this pack; the first is a complete project including the design & manufacture of
an enclosure for the kit (below). The second is a much shorter focused practical task covering just the assembly of
the kit (next page). Equally, feel free to use the material as you see fit to develop your own schemes.
Before starting we would advise that you to build a kit yourself. This will allow you to become familiar with the
project and will provide a unit to demonstrate.
Complete product design project including electronics and enclosure
Hour 1
Introduce the task using The Design Brief sheet. Demonstrate a
built unit. Take students through the
design process using The Design Process sheet.
Homework: Collect examples of amplifiers and accessories. List the common features of these products
on the Investigation / Research sheet.
Hour 2
Develop a
specification for the project using the Developing a Specification sheet.
Resource: Sample of amplifiers products.
Homework: Using the internet or other search method, find out what is meant by design for
manufacture. List five reasons why design for manufacture should be considered on any design project.
Hour 3
Read Designing the Enclosure sheet. Develop a product design using the Design sheet.
Homework: Complete design.
Hour 4
Using cardboard
,
get the students to model their enclosure design. Al
low them to make alterations to
their design if the model shows any areas that need changing.
Hour 5
Split the students into groups and get them to perform a group design review using the Design Review
sheet.
Hour 6
Using the Soldering in T
en
S
teps
sheet
,
demonstrate and get students to practice
soldering. Start the
Resistor Value and Capacitor Basics worksheets.
Homework: Complete any of the remaining resistor / capacitor tasks.
Hour 7
Build the electronic kit using the Build Instructions.
H
our 8
Complete the build of the electronic kit. Check the completed PCB and fault find i
f required using the
Checking Your Amplifier PCB section and the fault finding flow chart.
Homework: Read How the Amplifier Works sheet.
Hour 9
Build the enclosure
.
Homework: Collect some examples of instruction manuals.
Hour 10
Build the enclosure
.
Homework: Read Instruction Manual sheet and start developing instructions for the amplifier.
Hour 11
Build the enclosure.
Hour 12
Using the Evaluation and
Improvement sheet, get the students to evaluate their final product and
state where improvements can be made.
AdditionalWork
Package design for those who complete ahead of others.

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Electronics only
Hour 1
Introduction to the kit demonstrating a
buil
t unit. Using
the
Soldering in T
en
S
teps sheet
,
practice
soldering.
Hour 2
Build the kit using the Build Instructions.
Hour 3
Check the completed PCB and fault fi
nd if required using Checking Y
our
A
mplifier PCB and fault finding
flow chart.
Answers
Resistor questions
1st Band 2nd Band Multiplier x Value
Brown Black Yellow 100,000 
Green Blue Brown 560 
Brown Grey Yellow 180,000
Orange White Black 39
Value 1st Band 2nd Band Multiplier x
180  Brown Grey Brown
3,900  Orange White Red
47,000 (47K)  Yellow Violet Orange
1,000,000 (1M)  Brown Black Green
Capacitor Ceramic Disc values
Printing on capacitor Two digit start Number of zero’s Value in pF
222 22 00 2200pF (2.2nF)
103 10 000 10000pF (10nF)
333 33 000 33000pF (33nF)
473 47 000 47000pF (47nF)

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
The Design Process
The design process can be short or long, but will always consist of a number of
steps that are the same on every project. By splitting a project into these
clearly defined steps, it becomes more structured and manageable. The steps
allow clear focus on a specific task before moving to the next phase of the
project. A typical design process is shown on the right.
Design brief
What is the purpose or aim of the project? Why is it required and who is it
for?
Investigation
Research the background of the project. What might the requirements be?
Are there competitors and what are they doing? The more information found
out about the problem at this stage, the better, as it may make a big
difference later in the project.
Specification
This is a complete list of all the requirements that the project must fulfil - no
matter how small. This will allow you to focus on specifics at the design stage
and to evaluate your design. Missing a key point from a specification can
result in a product that does not fulfil its required task.
Design
Develop your ideas and produce a design that meets the requirements listed
in the specification. At this stage it is often normal to prototype some of your
ideas to see which work and which do not.
Build
Build your design based upon the design that you have developed.
Evaluate
Does the product meet all points listed in the specification? If not, return to the design stage and make the required
changes. Does it then meet all of the requirements of the design brief? If not, return to the specification stage and
make improvements to the specification that will allow the product to meet these requirements and repeat from
this point. It is normal to have such iterations in design projects, though you normally aim to keep these to a
minimum.
Improve
Do you feel the product could be improved in any way? These improvements can be added to the design.
Design Brief
Investigation
Specification
Design
Build
Evaluate
Improve

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
The Design Brief
A manufacturer has developed a simple stereo amplifier
circuit. The circuit has been developed to the point where
they have a working Printed Circuit Board (PCB). Although
they are used to the design of High Power Stereo Amplifiers,
they have not designed an amplifier case before.
The manufacturer would like ideas for an enclosure for the
PCB and speakers to be mounted in. The manufacturer has
asked you to do this for them. It is important that you make
sure the final design meets all of the requirements that you
identify for such a product.
Complete Circuit
A fully built circuit is shown below.

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Investigation / Research
Using a number of different search methods, find examples of similar products that are already on the market. Use
additional pages if required.
Name Class

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Developing a Specification
Using your research into the target market for the product, identify the key requirements for the product and
explain why each of these is important.
Name Class
Requirement
Reason
Example: The enclosure should have
some holes.
Example: So that the sound can be heard.

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Design
Develop your ideas to produce a design that meets the requirements listed in the specification.
Name Class

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Design Review (group task)
Split into groups of three or four. Take it in turns to review each persons design against the requirements of their
specification. Also look to see if you can spot any additional aspects of each design that may cause problems with the
final product. This will allow you to ensure that you have a good design and catch any faults early in the design
process. Note each point that is made and the reason behind it. Decide if you are going to accept or reject the
comment made. Use these points to make improvements to your initial design.
Comment
Reason for comment
Accept or Reject

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Soldering in Ten Steps
1. Start with the smallest components working up to
the taller components, soldering any interconnecting
wires last.
2. Place the component into the board, making sure
that it goes in the right way around and the part sits
flush against the board.
3. Bend the leads slightly to secure the part.
4. Make sure that the soldering iron has warmed up
and if necessary, use the damp sponge to clean the
tip.
5. Place the soldering iron on the pad.
6. Using your free hand, feed the end of the solder onto
the pad (top picture).
7. Remove the solder, then the soldering iron.
8. Leave the joint to cool for a few seconds.
9. Using a pair of cutters, trim the excess component
lead (middle picture).
10. If you make a mistake heat up the joint with the
soldering iron, whilst the solder is molten, place the
tip of your solder extractor by the solder and push
the button (bottom picture).
Solder joints
Good solder joint Too little solder Too much solder

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Resistor Values
A resistor is a device that opposes the flow of electrical current. The bigger the value of a resistor, the more it
opposes the current flow. The value of a resistor is given in  (ohms) and is often referred to as its ‘resistance’.
Identifying resistor values
Band Colour 1st Band 2nd Band Multiplier x Tolerance
Silver 100 10%
Gold 10 5%
Black 0 0 1
Brown 1 1 10 1%
Red 2 2 100 2%
Orange 3 3 1000
Yellow 4 4 10,000
Green 5 5 100,000
Blue 6 6 1,000,000
Violet 7 7
Grey 8 8
White 9 9
Example: Band 1 = Red, Band 2 = Violet, Band 3 = Orange, Band 4 = Gold
The value of this resistor would be:
2(Red) 7(Violet) x 1,000 (Orange) = 27 x 1,000
= 27,000 with a 5% tolerance (gold)
= 27K
Resistor identification task
Calculate the resistor values given by the bands shown below. The tolerance band has been ignored.
1st Band 2nd Band Multiplier x Value
Brown Black Yellow
Green Blue Brown
Brown Grey Yellow
Orange White Black
Too many zeros?
Kilo ohms and mega
ohms can be used:
1,000 = 1K
1,000K = 1M

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Calculating resistor markings
Calculate what the colour bands would be for the following resistor values.
Value 1st Band 2nd Band Multiplier x
180 
3,900 
47,000 (47K) 
1,000,000 (1M) 
What does tolerance mean?
Resistors always have a tolerance but what does this mean? It refers to the accuracy to which it has been
manufactured. For example if you were to measure the resistance of a gold tolerance resistor you can guarantee
that the value measured will be within 5% of its stated value. Tolerances are important if the accuracy of a resistors
value is critical to a design’s performance.
Preferred values
There are a number of different ranges of values for resistors. Two of the most popular are the E12 and E24. They
take into account the manufacturing tolerance and are chosen such that there is a minimum overlap between the
upper possible value of the first value in the series and the lowest possible value of the next. Hence there are fewer
values in the 10% tolerance range.
E-12 resistance tolerance (± 10%)
10
12
15
18
22
27
33
39
47
56
68
82
E-24 resistance tolerance (± 5 %)
10
11
12
13
15
16
18
20
22
24
27
30
33
36
39
43
47
51
56
62
68
75
82
91

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
LEDs & Current Limit Resistors
Before we look at LEDs, we first need to start with diodes. Diodes are used to control the direction of flow of
electricity. In one direction they allow the current to flow through the diode, in the other direction the current is
blocked.
An LED is a special diode. LED stands for Light Emitting Diode. LEDs are like normal diodes,
in that they only allow current to flow in one direction, however when the current is
flowing the LED lights.
The symbol for an LED is the same as the diode but with the addition of two arrows to
show that there is light coming from the diode. As the LED only allows current to flow in
one direction, it's important that we can work out which way the electricity will flow. This
is indicated by a flat edge on the LED.
For an LED to light properly, the amount of current that flows through it needs to be controlled. To do this we use a
current limit resistor. If we didn’t use a current limit resistor the LED would be very bright for a short amount of
time, before being permanently destroyed.
To work out the best resistor value we need to use Ohms Law. This connects the voltage across a device and the
current flowing through it to its resistance.
Ohms Law tells us that the flow of current (I) in a circuit is given by the voltage (V) across the circuit divided by the
resistance (R) of the circuit.
R
V
I
Like diodes, LEDs drop some voltage across them: typically 1.8 volts for a standard LED. However the high brightness
LED used in the ‘white light’ version of the lamp drops 3.5 volts.
The USB lamp runs off the 5V supply provided by the USB connection so there must be a
total of 5 volts dropped across the LED (VLED) and the resistor (VR). As the LED
manufacturer’s datasheet tells us that there is 3.5 volts dropped across the LED, there must
be 1.5 volts dropped across the resistor. (VLED + VR= 3.5 + 1.5 = 5V).
LEDs normally need about 10mA to operate at a good brightness. Since we know that the
voltage across the current limit resistor is 1.5 volts and we know that the current flowing
through it is 0.01 Amps, the resistor can be calculated.
Using Ohms Law in a slightly rearranged format:
 150
01.0
5.1
I
V
R
Hence we need a 150 current limit resistor.

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
LEDs Continued
The Colour Changing LEDs used in the ‘colour’ version of the lamp has the current limit resistor built into the LED
itself. Therefore no current limit resistor is required. Because of this, a ‘zero ’ resistor is used to connect the voltage
supply of 5V directly to the Colour Changing LED.
Packages
LEDs are available in many shapes and sizes. The 5mm round LED is the most common. The colour of the plastic lens
is often the same as the actual colour of light emitted – but not always with high brightness LEDs.
Advantages of using LEDs over bulbs
Some of the advantages of using an LED over a traditional bulb are:
Power efficien
cy
LEDs use less power to produce the same amount of light,
which
means that they are
more efficient. This makes them ideal for battery power applications.
Long life
LEDs have a very long life when compared to normal light bulbs. They also fail by
gradually dimming over time instead of a sharp burn out.
Low temperature
Due to the higher efficiency of LEDs
,
they can run much cooler than a bulb.
Hard to break
LEDs are
much more resistant to mechanical shock
,
making them more difficult to break
than a bulb.
Small
LEDs can be made very small. This allows them to be used in many applications
,
which
would not be possible with a bulb.
Fast turn on
LEDs can light up
faster
than normal light bulbs, making them i
deal for use in car break
lights.
Disadvantages of using LEDs
Some of the disadvantages of using an LED over a traditional bulb are:
Cost
LEDs currently cost more for the same light output than traditional bulbs.
However, t
his
needs to be balanced against the lower running cost of LEDs due to their greater efficiency.
Drive circuit
To work in the desired manner
,
an LED must be supplied with the correct current. This could
take the form of a series resistor or a regulated power supply.
Directional
LEDs normally produce a light that is focused in one direction
,
which is not ideal for some
applications.
Typical LED applications
Some applications that use LEDs are:
Bicycle lights
Car lights (break and headlights)
Traffic lights
Indicator lights on consumer electronics
Torches
Backlights on flat screen TVs and displays

Road signs
Information displays
Household lights
Clocks

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Capacitor Basics
What is a capacitor?
A capacitor is a component that can store electrical charge (electricity). In many ways, it
is like a rechargeable battery.
A good way to imagine a capacitor is as a bucket, where the size of the base of the
bucket is equivalent to the capacitance (C) of the capacitor and the height of the bucket
is equal to its voltage rating (V).
The amount that the bucket can hold is equal to the size of its base multiplied by its
height, as shown by the shaded area.
Filling a capacitor with charge
When a capacitor is connected to an item such as a battery, charge will flow from the battery into it. Therefore the
capacitor will begin to fill up. The flow of water in the picture above left is the equivalent of how the electrical
charge will flow in the circuit shown on the right.
The speed at which any given capacitor will fill depends on the resistance (R) through which the charge will have to
flow to get to the capacitor. You can imagine this resistance as the size of the pipe through which the charge has to
flow. The larger the resistance, the smaller the pipe and the longer it will take for the capacitor to fill.
Emptying (discharging) a capacitor
Once a capacitor has been filled with an amount of charge, it will retain this charge until it is
connected to something into which this charge can flow.
The speed at which any given capacitor will lose its charge will, like when charging, depend on
the resistance (R) of the item to which it is connected. The larger the resistance, the smaller the
pipe and the longer it will take for the capacitor to empty.
Maximum working voltage
Capacitors also have a maximum working voltage that should not be exceeded. This will be
printed on the capacitor or can be found in the catalogue the part came from. You can see
that the capacitor on the right is printed with a 10V maximum working voltage.
C
V
R
BATTERY
V
R
BATTERY CAPACITOR
R
C

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Ceramic Disc Capacitors
Values
The value of a capacitor is measured in Farads, though a 1 Farad capacitor
would be very big. Therefore we tend to use milli Farads (mF), micro Farads
(F), nano Farads (nF) and pico Farads (pF). A F is a millionth of a Farad, 1F
= 1000 nF and 1nF = 1000 pF.
The larger electrolytic capacitors tend to have the value printed on the side of
them along with a black band showing the negative lead of the capacitor.
Other capacitors, such as the ceramic disc capacitor shown on the right, use a
code. They are often smaller and may not have enough space to print the
value in full, hence the use of the 3-digit code. The first 2 digits are the first
part of the number and the third digit gives the number of zeros to give its
value in pF.
Example: 104 = 10 + 0000 (4 zero’s) = 100,000 pF (which is also 0.1 F)
Work out what value the four capacitors are in the table below.
Printing on capacitor Two digit start Number of zero’s Value in pF
222
103
333
473
1F
= 1,000mF
1F
= 1,000,000

F
1F
= 1,000,000,000nF
1F
= 1,000,000,000,000pF

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Instruction Manual
Your amplifier is going to be supplied with some instructions. Identify four points that must be included in the
instructions and give a reason why.
Point to include
:
Reason:
Point to include
:
Reason:
Point to include
:
Reason:
Point to include
:
Reason:

High Power Amp Teaching Resources
www.kitronik.co.uk/2143
Evaluation
It is always important to evaluate your design once it is complete. This will ensure that it has met all of the
requirements defined in the specification. In turn, this should ensure that the design fulfils the design brief.
Check that your design meets all of the points listed in your specification.
Show your product to another person (in real life this person should be the kind of person at which the product is
aimed). Get them to identify aspects of the design, which parts they like and aspects that they feel could be
improved.
Good aspects of the design
Areas that could be improved
Improvements
Every product on the market is constantly subject to redesign and improvement. What aspects of your design do you
feel you could improve? List the aspects that could be improved and where possible, draw a sketch showing the
changes that you would make.