2007 Technological Studies
Standard Grade – Credit
Finalised Marking Instructions
 Scottish Qualifications Authority 2007
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sources.
These Marking Instructions have been prepared by Examination Teams for use by SQA Appointed
Markers when marking External Course Assessments. This publication must not be reproduced for
commercial or trade purposes.
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1.
The temperature of a steam room in a leisure centre is controlled automatically.
KU RNA
A valve opens to release steam when the temperature is below the set level. When
the temperature of the room is hot enough, the valve is closed.
(a)
State the type of control produced by this automatic system.
closed loop 1 KU
_____________________________________________________________________
(b)
1
0
Complete the control diagram for this system.
1 RNA — complete
feedback
Temperature
sensor
Set
temperature
(c)
Control
unit
driver
___________
2
1
0
Desired
temperature
Valve
1 RNA
accept amplifier
accept TD
State the name of the control diagram symbol shown below.
error detector 1 KU
_____________________________________________________________________
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2.
A DVD is ejected from a games console using the gear system shown below.
KU RNA
B
A
(a)
State the name of the parts of the gear system.
pinion 1 KU
A ___________________________________________________________________
rack 1 KU
B ___________________________________________________________________
minus 1 KU if wrong way round
(b)
2
1
0
State the type of input motion and output motion of the gear system shown
above.
oscillating 1 KU
OR rotary
Input Motion ________________________________________________________
reciprocating 1 KU
OR linear
Output Motion ______________________________________________________
pairings have to be correct
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3.
An ATM cashpoint detects a bank card using a darkness
sensor. Rubber rollers then grip the card and feed it into
the machine for reading.
KU RNA
Lamp
Bank card
Rollers
LDR
Part of the circuit diagram for the system is shown below.
Roller
motor
+5V
230 V
M
V1
1.5kΩ
Y
R
X
Vout
0V
(a)
State the purpose of the variable resistor in the voltage divider sub-system.
to adjust the sensitivity 1 KU
(not voltage)
_____________________________________________________________________
(b)
State the full name of Component Y .
DPDT switch 1 KU
_____________________________________________________________________
(c)
1
0
1
0
With reference to the circuit diagram, state the function of the following
components.
(i) Component X function
to act as a switch 1 KU
________________________________________________________________
(ii) Component Y function
to change motor direction 1 KU
________________________________________________________________
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3.
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(continued)
The variable resistor is set to 1.5 kΩ and the light level is at 200 lux.
(d)
(i)
KU RNA
Determine, with reference to the Data Booklet, the resistance of the
LDR.
1
0
Ω 1 RNA
Ω)
590Ω
(will accept up to 600Ω
________________________________________________________________
(ii)
Calculate the output of the voltage divider sub-system, Vout .
Vout =
(iii)
R2
V
R1 + R2 cc
= 590 × 5
2090
1 RNA substitution
= 1 ⋅ 41V
1 RNA answer from given working
2
1
0
Determine the voltage V1 when component X is saturated.
V1 = Vout – Vbe
(iv)
= 1.41 – 0.7
1 RNA substitution
= 0.71V
1 RNA answer from given working
2
1
0
State the purpose of resistor R in the circuit.
to protect the transistor 1 KU
________________________________________________________________
1
0
Another part of the circuit uses the resistor network shown.
300 Ω
1.2 kΩ
220 Ω
(e)
Calculate the total resistance of this network.
R1R 2
R parallel =
R1 + R2
Rtotal
= 220 × 300
220 + 300
1 RNA substitution
= 126 ⋅ 92Ω
1 RNA answer from given
working
= 126 ⋅ 92 + 1200
1 RNA answer from given
working
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= 1326 ⋅ 92Ω
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4.
A washing machine is operated by a microcontroller.
KU RNA
The drum motor is connected in Pin 7 and a common
programming technique is used to control the drum
motor’s speed.
(a)
Complete the initialisation for the PBASIC program with reference to the
comments and the Data Booklet.
init:
let dirs = %11110000 1 RNA ‘set pins 7–4 as outputs, rest inputs
_________________________
2
1
0
symbol counter = 60 1 RNA ‘define counter address b0
_________________________
(b)
(i)
Complete the PBASIC sequence to control the drum motor’s speed with
reference to the comments and the Data Booklet.
for counter = 1 to 200
speed: ______________________________
‘set for . . . next loop to 200
high 7
______________________________
‘switch on drum motor (pin 7)
pause 5
______________________________
‘5 ms delay
1 RNA
each correct line
low 7
______________________________
‘switch off drum motor (pin 7)
pause 10
5
4
3
2
1
0
‘10 ms delay
next counter
______________________________
‘loop until completed
return
(ii)
‘return to main program
State the full name of the technique used to control the motor speed in
the program above.
pulse width modulation 1 KU (full name not pwm)
________________________________________________________________
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4.
(b)
(continued)
(iii)
KU RNA
Describe, with the aid of a sketch, how this technique is used to control
the speed of a motor.
switching power on and off OR pulsing OR
________________________________________________________________
mention of mark and space 1 KU
________________________________________________________________
(or appropriate labelling of sketch)
________________________________________________________________
altering ratio 1 KU
________________________________________________________________
1 KU Sketch
1
0
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5.
A ten–pin bowling alley uses a mechanical system to return the bowling balls.
KU RNA
Bowling station
Pulley A
(drive pulley)
Toothed belt
A toothed belt helps raise the bowling balls to the bowling station.
(a)
(i) State an advantage for using a toothed belt over a flat belt.
less slippage 1 KU
________________________________________________________________
1
0
(ii) State the name of another suitable type of belt
vee belt 1 KU
________________________________________________________________
1
0
(iii) Suggest a reason why Pulley A is the driver in the belt system.
to ensure tension as the ball is raised 1 RNA
________________________________________________________________
(b)
1
0
Calculate the potential energy when a 8 kg bowl is raised a height of 1.47 m.
(Show all working and units.)
Ep = mgh
= 8 × 9.81 × 1.47
1 RNA substitution
= 115.36J
1 RNA answer from given working
1 RNA correct units
3
2
1
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5.
(continued)
The motorised chain drive is used to drive the belt.
KU RNA
125 Teeth
Chain drive
35 Teeth
Electric motor
400 rev/min
(c)
Calculate, showing all working and units:
(i) the velocity ratio of the chain drive system;
VR =
Driver (speed)
=
Driven(speed)
= 125
35
Driven (teeth)
Driver (teeth)
25/7 or 3.57 (reduction)
1 RNA
alternative:
1 RNA
35
125
7/25 or 0.28 (increase)
1 RNA
(ii)
1 RNA
2
1
0
the rotational speed of the 125 tooth sprocket;
speed = UR × motor speed
(iii)
1 RNA substitution
= 112 rev/min
1 RNA answer from given
working
2
1
0
the output power of the motor, if the motor shaft produces a torque of
3.7Nm.
P
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= 0.28 × 400
= 2π
πnt
= 2 × 3.14 × (400 ÷ 60) × 3.7
1 RNA substitution
= 154.9 W
1 RNA answer from given
working
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6.
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A pneumatic circuit is used in a drilling operation.
KU RNA
Cylinder B
Drill
Cylinder A
Cylinder A
Cylinder B
Valve 5 Valve 6
Valve 7
Valve 8
or
Valve 2
×
Valve 3
Valve 4
Valve 1
(a)
Describe, using appropriate terminology, how the pneumatic circuit operates.
and Valve 2 actuated, pilot air actuates
When Valve 1 is actuated _____________________________________________
Valve 3 , outstroking Cylinder A. Valve 6 is then actuated by
_____________________________________________________________________
Cylinder A which, in turn, actuates Valve 4 , outstroking
_____________________________________________________________________
Cylinder B. Valve 8 is then actuated, actuating Valve 3 which
_____________________________________________________________________
instrokes Cylinder A. Valve 5 actuates Valve 4 which then instrokes
_____________________________________________________________________
Cylinder B. The system is then reset.
_____________________________________________________________________
_____________________________________________________________________
1 RNA for each relevant point
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6.
(continued)
KU RNA
The circuit diagram shows two forms of air, pilot and main air.
(b)
Describe the difference between the two types.
pilot air — actuates valves 1 KU
_____________________________________________________________________
main air — operates cylinders 1 KU
_____________________________________________________________________
2
1
0
For safety reasons, it was decided to slow the piston on Cylinder B as it outstrokes.
The piston should still instroke quickly.
(c)
(i) State the name of the pneumatic component which could be added to the
circuit to slow the outstroke of the piston on Cylinder B.
unidirectional restrictor 1 KU
________________________________________________________________
1
0
(ii) Draw the symbol for this component below.
1 KU restrictor
1 KU bypass line
(box not necessary)
2
1
0
1
0
see
(iii) Mark (X) on the circuit where this component should be inserted. diagram
To further improve the circuit, it was decided to include a time delay before
Cylinder A instrokes.
(i) State the name of the two components required to produce a pneumatic
time delay.
(d)
reservoir 1 KU
1 _______________________________________________________________
restrictor 1 KU
2 _______________________________________________________________
2
1
0
(ii) State how the length of the time delay could be varied.
adjust restrictor/change size of reservoir 1 KU
________________________________________________________________
(e)
1
0
State the name of the actuator on Valve 8 .
roller trip 1 KU
_____________________________________________________________________
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7.
An automatic door in an office complex is operated by a motor (M) which is
controlled by three inputs.
KU RNA
The Boolean expression for the system is M = (A•B) + C, where:
A is a darkness sensor;
B is a pressure pad;
C is an inside switch;
and M is the door motor.
(a)
(i) Complete the truth table for the system.
A
B
C
(1 when dark) (1 when pressed) (1 when pressed)
M
0
0
0
0
0
0
1
1
0
1
0
0
1 RNA
0
1
1
1
1 RNA
1
0
0
0
1
0
1
1
1
1
0
1
1
1
1
1
1 RNA
3
2
1
0
(ii) State, with reference to the Data Booklet, the full name of the ICs
required to build the circuit.
IC Number 7408
Quad Or 4, Two Input, And Gate 1 KU
Full Name: ______________________________________________________
IC Number 7432
Quad Or 4, Two Input, Or Gate 1 KU
Full Name: ______________________________________________________
2
1
0
(iii) State the name of the family which these ICs belong to.
TTL 1 KU
________________________________________________________________
1
0
(iv) State the supply voltage (Vcc) from which this family of ICs operate.
5v 1 KU
________________________________________________________________
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7.
(continued)
(b)
KU RNA
(i) Complete the wiring diagram for the door control system.
Vcc
7432
7408
Input A
Output (M)
Input B
Input C
1 RNA
1 RNA
3
2
1
0
0V
1 RNA ALL power lines
(ii) State the purpose of the dot on the ICs.
to indicate pin 1 1 KU
________________________________________________________________
1
0
When a pupil was modelling this circuit on a breadboard, an LED was used to show
a high output.
(c)
(i) State the full name of an LED.
light emitting diode 1 KU
________________________________________________________________
1
0
(ii) Draw the symbol for an LED below.
1 KU
1
0
1 arrow is acceptable
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8.
A disco light box is controlled by a microcontroller.
KU RNA
Different coloured lights are reflected by a rotating mirror. The mirror’s position is
sensed by a rotary potentiometer (POT).
Part of the PBASIC control program and details of the input and output
connections are shown below.
Mirror
Light box
Motor and
potentiometer
Input Connection
Pin
Output Connection
7
Motor Clockwise
6
Motor Anticlockwise
5
Red Light
4
Yellow Light
3
2
1
SensorA (POT)
cw:
0
if sensorA>150 then acw
let pins = %10100000
pause 10
let pins = %10000000
pause 10
goto cw
‘test potentiometer position
‘motor clockwise, red on
‘10 ms delay
‘motor clockwise
‘10 ms delay
‘jump to label cw
acw: if sensorA<30 then cw
let pins = %01010000
pause 10
let pins = %01000000
pause 10
goto cw
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‘test potentiometer position
‘motor anticlockwise, yellow on
‘10 ms delay
‘motor anticlockwise
‘10 ms delay
‘jump to label cw
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8.
(continued)
(a)
KU RNA
Complete, with reference to the PBASIC program and the input/output
connections, the flowchart for the part of the program shown below.
1
Yes
Yes
Is SensorA
<30?
Is SensorA
>150?
1
1
No
No
Motor C/W
Red On
Motor ACW
Yellow On
10 ms delay
10 ms delay
Red Off
Yellow Off
1 RNA
both outputs
1 RNA
ALL delays
5
4
3
2
1
0
10 ms delay
10 ms delay
PBASIC acccepted
(b)
Name the microcontroller parts (A to E) shown in the diagram below.
Memory sub-system
B
A
C
1 KU
RAM
B ________________________
D
1 KU
ALU
The “real C ________________________
world”
1 KU
I/O Port
D ________________________
1 KU
Clock
E ________________________
E
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1 KU
ROM
A ________________________
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9.
Electricity can be generated from both finite and renewable sources.
KU RNA
The Government is promoting the use of renewable sources such as tidal, solar and
wind.
(a)
Explain one disadvantage which must be considered when using each of these
sources. Each disadvantage may be used only once.
for shipping, etc 1 KU
Tidal obstructions
_______________________________________________________________
inconsistent supply, cost of infastructure etc 1 KU
Solar ________________________________________________________________
pollution, etc 1 KU
Wind noise
_______________________________________________________________
(b)
State two other examples of renewable energy sources.
Wave, hydro, geothermal, etc (nuclear not accepted)
1 ___________________________________________________________________
1 KU each (max 2 marks)
2 ___________________________________________________________________
(c)
3
2
1
0
2
1
0
State two examples of finite energy sources.
Coal, gas, oil, peat, nuclear, etc
1 ___________________________________________________________________
1 KU each (max 2 marks)
2 ___________________________________________________________________
[END OF MARKING INSTRUCTIONS]
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