TONBRIDGE SCHOOL
Design & Technology Scholarship 2014
Practical Test
Monday 3rd February 2014
Time allowed: 1 hour
Department of Design Technology
Version 3 January 2014
Instructions to candidates
● This test is hard work! Don’t worry – complete as much as you can.
● You will be given a computer mouse.
● The object of the exercise is to take it apart and analyze its construction and
design, answering the questions as you do so.
● You fill in your answers on the answer sheet, which is on the computer.
● Log on to the computer, using this name and password:
User Name:
Password:
● You will find the answer sheet in your My Documents folder.
● Save your answer sheet (and do this regularly!) with your name as the file name,
in your My Documents folder.
● You will need to use the internet to look up various pieces of information.
● If you can’t find the information you are looking for, don’t waste time - go on to
the next question and do the one you missed if there is time at the end.
● You have one hour in total.
● You will be given:
- A tool kit, containing pliers, cutters, flat
screwdriver, pozidriv screwdriver, craft knife and
‘helping hands’ PCB holder.
- A soldering iron, de-soldering gun and solder
- A ruler
- A caliper
- Three Electronic components
- A PP3 battery and a battery clip
- A prototyping board
- A computer
● Before you use the computer, you need to
disassemble the mouse.
Department of Design Technology
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Here’s how to do it:
fixing screw
Remove the fixing screw
using the pozidriv
screwdriver (then keep the
screw somewhere safe!)
Carefully prise apart the two
halves of the case. The top
edge of the case (where the
buttons are) has two clips
which have to be disengaged.
Voila!
Now answer the questions which follow!
Department of Design Technology
Version 3 January 2014
Practical Answer Sheet
Your Name:
School:
1.
The case is made from a material called ABS. What do the letters ABS stand
for?
2.
Find out all you can about this material, and then give three reasons why this
material is a good choice for the mouse case:
Write in this box the URL(s) of the website(s) where you found this
information:
3.
Remove the cable from the mouse by lifting it out of its slot, and prising the
cable out of the mouse case, like this ….
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4.
… and then carefully lift up and pull out the complete printed circuit board
(PCB):
5.
The PCB isn’t fixed to the bottom of the case with screws. Describe how
the manufacturer has designed it so that the PCB is held firmly in place.
6.
Look at the electronic component labelled R2, to the left of the PCB. What is
the name of this component?
R2
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7.
This mouse PCB has been assembled wrongly at the factory, and the R2
component needs to be replaced.
8.
Using the de-soldering gun and the soldering iron, remove the component:
N.B.
9.
If you get stuck with this bit, ask for
help and we will show you again how to do it!
Now, using the tools provided, solder in the replacement for the component
R2. It is in your pile of bits attached to a piece of tape, labelled D2. This
component is a diode and it must be soldered so that the line on the diode
faces towards the top of the PCB, like this:
Bend the diode wires to the right positions with the pliers, insert into PCB,
solder, and then trim off the excess component lead on the reverse with the
cutters.
Department of Design Technology
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10.
Inside the mouse body there are two pieces of metal screwed to the case:
Have a careful look at these, and then answer these questions:
a. What do you suppose the purpose of these pieces of metal is?
b. What metal do you think has been used?
c. Why has the manufacturer chosen to use this particular metal?
11.
You now need to take some measurements.
In the centre of the top half of the mouse case is the roller wheel:
Roller wheel
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Using any of the provided tools, work out how to accurately measure the
diameter of the wheel and its thickness. Write your results in the table below:
Part to be measured
Dimension (in mm)
Diameter of the roller wheel
Thickness of the roller wheel
12.
Do a simple sketch (or a series of small sketches) showing how you measured
the diameter of the wheel. You don’t need to draw the whole mouse – just
the wheel!
13.
The mouse is made by a company called Logitech. They are a very wellknown manufacturer of computer mice. Google them, and write their US
postal address (not their UK address!) for Consumer Sales in the box:
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14.
Like most computer mice these days, this one is optical, and doesn’t have any
moving parts (except the roller wheel and the buttons!). The heart of the
optical mouse is an LED – Light Emitting Diode.
One of the important characteristics of a mouse is how fast it can keep track
of the user’s hand movements. This is called the ‘tracking speed’.
Google Microsoft, and find your way on their site to their Products page,
and look up the Explorer Touch Mouse.
What is the maximum life of the mouse batteries?
15.
Find your way to the Technical Data Sheet, and by opening it (don’t save
it), find out what the values are of these technical specifications:
Weight:
Tracking speed (maximum):
16.
You have been given an LED (light emitting diode), one other electronic
component and a special board for trying out electronic circuits called a
Prototype Board.
The prototype board has lots of holes, in which component wires are
inserted. The holes are joined together underneath as shown below:
Each column of holes in the
top section are connected
together underneath with a
metal strip
The top row of holes are
all connected together
underneath with a metal
strip
The bottom row of holes are
all connected together
underneath with a metal strip
Each column of holes in
the bottom section are
together underneath with
a metal strip
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Here is a diagram of an arrangement (a circuit) that will operate an LED,
similar to the circuit inside the optical mouse which produces the light. It uses
an LED, another electronic component and a 9 volt battery connector clip.
Study the diagram carefully:
Electronic
component
Battery clip
LED
● Using the prototype board, see if you can plug the components into it so that this
circuit is created. The LED has a long lead and a short lead – the long lead is
the one that must be connected to the electronic component.
● When you have completed it, carefully connect the 9v battery to the battery
connector clip.
● You will know the circuit is correct if the LED lights up!
● Tell your supervisor when you have done it so that he can see your work.
Finished!
Don’t re-assemble your mouse as we will want to look at
your soldering.
Now, make sure your answer document has been saved, and tell
us that you have finished.
Department of Design Technology
Version 3 January 2014