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Y Pant School
A Glowing Name Plate
Year 9 Project
1
Introduction
This is a major DESIGN and MAKE Project, but do not let that
worry you!
During years seven and eight you designed and made things using all
sorts of materials and processes. This project will draw on all of the
skills and knowledge learned during those projects to help you
produce a useable product.
The Project
We have all seen name plates and signs; they are an
everyday part of life. They take various forms and appear
in many different places. They all aim to attract us in some
way.
We are going to design and make a name plate that will be
seen by people during the day and during darkness.
Your task is to DESIGN a NAME PLATE FOR a
CHOSEN ROOM OF YOUR CHOICE. THE NAME
PLATE WILL INCORPORATE AN ELECTRONIC
CIRCUIT CONTAINING SOME NEW
COMPONENTS WHICH YOU WILL LEARN ABOUT
LATER IN THIS PROJECT.
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Organising your Project
We are going to use a combination of methods to make an attractive name plate.
To do this we will first ANALYSE the problem in class. An important factor for
your design is where it will be located.
Before we do anything else it is necessary to outline two of the ESSENTIALS in
this project:
1. The Name Plate must show up well during the day and when it is dark.
2. It must stand alone to display text clearly.
We are going to use a combination of materials to satisfy the requirements.
Everyone has use metal, wood, plastics, and electronics in projects. This project
is going to extend the skills that you have in a number of these areas.
The following pages describe electronic components and their uses. You will be
shown how to use them to produce a circuit that will help to illuminate your name
plate. There are many new processes to be learned, however, they are commonly
used in lots of things you take for granted. E.g. MP3 Players, Televisions, Hi-Fi’s
and Computers.
To help us produce the most attractive name plate everyone will have the
opportunity to use the STIKA-12, Camm-1 and Camm-2. These are
computer aided manufacturing tools that can produce accurate making
techniques. You will be shown these later in your project.
The use of Electronics, Plastics, Timber and CAD/CAM will help you to produce a
high quality advertisement.
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Consider Aesthetics, Typography and the Target
Market!!
Designing with Electronics
Using Electronics to solve design problems is not as difficult as you might
think. Most of you will remember the circuit you had to design for your
animated display, this circuit has a few more components but is not that
much more difficult to understand.
Designing Circuits
All circuits need three basic blocks: INPUT, CONTROL and OUTPUT.
You can use a block diagram to help you design a circuit suitable for our
needs.
PROBLEM:
Design a circuit, which will switch on a light emitting Diode when it begins
to get dark?
Solution in the form of a block diagram.
INPUT
Needs to
sense when
it goes dark.
INPUT
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CONTROL
Needs to switch
on the output
when the input
senses dark.
CONTROL
OUTPUT
Needs to light
up when the
control
switches it on.
OUTPUT
We’ll
look at all the
individual
components to
The Resistor
The Symbols of
components
are
shown above.
understand how each of them work, then put them
all together to make our final circuit.
Resistors
Resistors are very important in electronics because we often have to limit
the amount of current flowing in a circuit or parts of it. The most
common resistors consist of a thin film of carbon over a ceramic tube,
each end of which has a wire connecting leg. The resistance simply
depends on the type of carbon used.
Carbon Film is in the
middle of the Resistor.
Resistors are colour coded with four bands that can be read to give their
values in ohms. The higher the number in Ohms, the greater the
resistance.
To read a resistor’s value, look at its first colour band (opposite end to
the metallic band) and find this colour on the chart. Now look across the
chart to Column 1 and note the number. Do this for the other two colour
bands, going across the chart to Column 2 and then to Column 3.
If, for example, the resistor’s first colour band is yellow, we note ‘4’ in
Column 1 on the chart. If the second band is violet, we go across to
Column 2 and note ‘7’. If the third is red, we see two noughts in Column 3,
giving a figure of 4,700. This is the value in ohms of the resistor.
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The Resistor
Gold + or – 5%
Silver = or – 5%
Colour
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Grey
White
Band 1
0
1
2
3
4
5
6
7
8
9
Band 2
0
1
2
3
4
5
6
7
8
9
Band 3
Nothing
0
00
000
0000
00000
000000
Work out the resistance values of these resistors
Colour
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Band 1
Band 2
Band 3
Blue
Grey
Brown
Red
Red
Red
Brown
Black
Red
Total
The LED
Most of the circuits use a light emitting diode (LED) rather than a bulb.
LED’s give out less light, but they use less current and cost less. LED’s
also come in three colours: red, green and amber.
Unlike a bulb, an LED does not have a filament. It is too hard to explain
here how it works, but it is easy to use if you follow two simple rules:
Examples of different
LED’s.
Symbol for and LED
LED Rule 1
An LED must be used with a resistor in the circuit loop. This restricts
current flow and prevents the LED taking more current than is good for
it. If an LED takes too much current it will break.
LED’s are small in size,
they are 39mm.
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LED Rule 2
An LED must be connected in a circuit with its (-) leg facing towards the
(-) terminal of the battery. If you look at they bottom of an LED, there
is a small flat edge on the plastic, and the (-) leg is nearest to this.
An LED is a diode. This lets current pass only when it is connected in a
circuit the right way around. If it is connected backwards, nothing
happens and no light.
Diagram Shows LED
Symbol, Flat side of
LED, Shorter and
Longer legs.
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Semiconductor Devices
The Transistor
This is another device that can be
damaged by rough handling. Again it is
easy to break off the legs of the
Transistor by bending them.
The Transistor has three legs called:
 The Collector (C)
 The Base (B)
 The Emitter (E)
B
C
E
BC 108
(From underside)
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Transistor Symbol
BFY 51
What Transistors Do!
Step 1
If the collector and emitter legs of BC108 are connected as part of an
LED circuit, nothing happens. The transistor is acting like a switch
turned off.
Step 2
To turn the transistor on, a small current has to flow between base and
emitter. This can be supplied, for example, by a resistor. A very small
base current flowing causes a much larger current to flow between
collector and emitter, so that the LED lights up.
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To be really
sure how the
transistor
works, try following the two current paths around on the diagram with
the end of a pencil.
You might well ask at his point: why is a transistor needed to turn on an
LED? The answer is that it gives us a very sensitive switch because so
BC 108
little base current
is needed. So little, in fact, you can use your finger in
place of the resistor – making the circuit a ‘touch switch’.
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Finger here.
Thumb
here.
Variable Resistors
You can change the resistance of a variable resistor, unlike that of a
fixed resistor, by turning the spindle. You can set the resistance from
zero up to the value given on the base of the component. The maximum
resistance of our variable resistor is 100K, or 100,000 Ohms.
If using centre tag and
one side tag.
If using all three tags.
Slider
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Carbon Track
Spindle
A Variable Resistor
When the spindle rotates,
the slider turns with it. If
the spindle rotates
clockwise the resistance
between a and b increases
and the resistance between
b and c decreases.
Light Dependent Res
An LDR is really a variable resistor as it changes its resistance with the
amount of light that falls on it. In the dark it has a high resistance, and
in the light it has a low resistance.
An LDR
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Printed Circuit Boards
Modern electronic circuits use only a few wires to connect the main parts
together. The components are held together on a printed circuit board
called a PCB.
Printed circuit board is a thin fibreglass board about 1.5mm thick. On
one side of the board is a layer of copper, only about 0.25mm thick. To
use the board we must first draw our circuit onto the copper using a
special etch resist pen. Take great care at this stage because once the
board is placed into the etch tank mistakes cannot be altered.
PCB Layout
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A PCB Board
with
Components.
Etching
When you are happy with your circuit, you are ready to place it into the
acid (Ferric Chloride). This will eat or etch away all the copper not
protected by the special etch resist pen. Take care with this, as it is
poisonous and corrosive, don’t get it on your clothes or hands!!!
Once all the unwanted copper has been removed you can use the tongs to
remove your circuit from the acid and then was it under the cold-water
tap. The etch resist pen must now be removed to leave only the copper
tracks ready for us to start drilling. Use wire wool to remove the etch
pen.
An Etching Tank
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Note the protective gloves that must be worn when using this machine. You can see
the PCB in the acid, which is removing the copper, which is not needed.
After a circuit
board has been
placed into an
Etching Tank the
circuit tracks are
left in pen. Once
rubbed with wire
wool copper is
exposed.
Drilling
You will now need to drill holes in the circuit board for attaching the
components. The pins or legs of the components must pass through the
board, so they can be soldered to the copper side. To make these small
holes you will need a very small drill bit, which is easily broken if not
handled with care. Take your time and don’t forget to wear safety
glasses!!
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e-Printed PCB
Holes being drilled into a PCB
board.
The drill bit is very
small!!! So, be
careful.
Soldering
Take care when using soldering irons, avoid burning the leads and always
replace them in the soldering iron stand when you are not actually using
them. Do not leave them lying on a workbench.
The component pins and the board should be cleaned with a piece of fine
wire wool before soldering. The soldering iron bit is heated and then
‘tinned’ by putting a small amount of multicore solder on it. The solder is
hollow and has flux inside. Flux helps to keep the joint clean while it is
being heated. It is very important that the work is heated properly, in
order to get a good joint, which makes good electrical contact.
Hold the tip of the iron on the copper next to the component. Place the
solder onto the copper next to the iron. When the work is hot enough
the solder will melt and flow. Remove the solder and run the tip of the
iron around the pin of the component to make sure it is properly joined to
the copper.
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Example of Soldering Iron
Stand, Soldering Iron and Power
Source. The power source is
used to control current and
heat.
Always ensure
the solder joint is
neat and not
crossing the
tracks.
Always solder electronic
components correctly to a
PCB, if you do not the circuit
will not function and the
components could break.
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Remember to follow Health &
Safety Rules!!!
How does the circuit work?
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The Light dependent resistor (LDR) reacts to light changes. Its
resistance is high in the dark, and low in the light. In our circuit, when it
begins to get dark the resistance of the LDR will increase. As it
increases the input voltage to the transistor will go above 0.6 volts.
When this happens the transistor switches on, so switching on the LED.
The circuit also has a variable resistor; this allows you to adjust when the
control switches on the output. This variable resistor can be adjusted so
the LED comes on just as it begins to get dark, or when it is totally dark.
330 Ohms Resistor
Variable Resistor
Connection
LED Connections
Transistor
Connection
s
Battery
Connections
LDR Connections
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1K Resistor
Connecting
Tracks