2007 Technological Studies

Standard Grade – Credit

Finalised Marking Instructions Scottish Qualifications Authority 2007 The information in this publication may be reproduced to support SQA qualifications only on a non-commercial basis. If it is to be used for any other purposes written permission must be obtained from the Assessment Materials Team, Dalkeith. Where the publication includes materials from sources other than SQA (secondary copyright), this material should only be reproduced for the purposes of examination or assessment. If it needs to be reproduced for any other purpose it is the centre's responsibility to obtain the necessary copyright clearance. SQA's Assessment Materials Team at Dalkeith may be able to direct you to the secondary 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.

1. The temperature of a steam room in a leisure centre is controlled automatically.

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.

_____________________________________________________________________

(b) Complete the control diagram for this system.

(c) State the name of the control diagram symbol shown below.

_____________________________________________________________________

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RNA

Temperature

sensor

Control

unitValve

Desired

temperature

Set

temperature___________

closed loop KU1

error detector KU1

RNA — completefeedback

1

RNAaccept amplifieraccept TD

1

driver

2. A DVD is ejected from a games console using the gear system shown below.

(a) State the name of the parts of the gear system.

A ___________________________________________________________________

B ___________________________________________________________________

(b) State the type of input motion and output motion of the gear system shown

above.

Input Motion ________________________________________________________

Output Motion ______________________________________________________

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pinion KU1

rack KU1

minus KU if wrong way round1

oscillating KU OR rotary1

reciprocating KU OR linear1

pairings have to be correct

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.

Part of the circuit diagram for the system is shown below.

(a) State the purpose of the variable resistor in the voltage divider sub-system.

_____________________________________________________________________

(b) State the full name of Component

_____________________________________________________________________

(c) With reference to the circuit diagram, state the function of the following

components.

(i) Component X function

________________________________________________________________

(ii) Component Y function

________________________________________________________________

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Bank card

Lamp

Rollers

LDR

230 V M+5V

1.5kΩ

0 V

Vout

R

V1

Y .

Roller

motor

to adjust the sensitivity KU (not voltage)1

DPDT switch KU1

to act as a switch KU1

to change motor direction KU1

3. (continued)

The variable resistor is set to 1.5 kΩ and the light level is at 200 lux.

(d) (i) Determine, with reference to the Data Booklet, the resistance of the

LDR.

________________________________________________________________

(ii) Calculate the output of the voltage divider sub-system, Vout .

(iii) Determine the voltage V1 when component X is saturated.

(iv) State the purpose of resistor R in the circuit.

________________________________________________________________

Another part of the circuit uses the resistor network shown.

(e) Calculate the total resistance of this network.

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1.2 kΩ

300 Ω

220 Ω

590ΩΩ RNA (will accept up to 600ΩΩ)1

to protect the transistor KU 1

RNA substitution1

RNA answer from given working1

2out cc

1 2

RV V

R R

590 52090

1 41V

==++

== ××

== ⋅⋅

RNA substitution1

RNA answer from given working

1

RNA answer from given working

1

1 2parallel

1 2

total

R RR

R R

220 300 220 300

126 92

R 126 92 1200

1326 92

==++

××==++

== ⋅⋅ ΩΩ

== ⋅⋅ ++

== ⋅⋅ ΩΩ

RNA substitution1

RNA answer from given working1

V1 == Vout – Vbe

== 1.41 – 0.7

== 0.71V

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4. A washing machine is operated by a microcontroller.

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: _________________________ ‘set pins 7–4 as outputs, rest inputs

_________________________ ‘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.

speed: ______________________________ ‘set for . . . next loop to 200

______________________________ ‘switch on drum motor (pin 7)

______________________________ ‘5 ms delay

______________________________ ‘switch off drum motor (pin 7)

pause 10 ‘10 ms delay

______________________________ ‘loop until completed

return ‘return to main program

(ii) State the full name of the technique used to control the motor speed in

the program above.

________________________________________________________________

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let dirs = %11110000 RNA 1

symbol counter = 60 RNA 1

RNA each correct line 1

pulse width modulation KU (full name not pwm)1

for counter = 1 to 200

high 7

pause 5

low 7

next counter

4. (b) (continued)

(iii) Describe, with the aid of a sketch, how this technique is used to control

the speed of a motor.

________________________________________________________________

________________________________________________________________

________________________________________________________________

________________________________________________________________

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switching power on and off OR pulsing OR

mention of mark and space KU 1

altering ratio KU 1

KU Sketch 1

(or appropriate labelling of sketch)

1

0

5. A ten–pin bowling alley uses a mechanical system to return the bowling balls.

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.

________________________________________________________________

(ii) State the name of another suitable type of belt

________________________________________________________________

(iii) Suggest a reason why Pulley A is the driver in the belt system.

________________________________________________________________

(b) Calculate the potential energy when a 8 kg bowl is raised a height of 1.47 m.

(Show all working and units.)

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Bowling station

Pulley A

(drive pulley)

Toothed belt

less slippage KU 1

vee belt KU 1

to ensure tension as the ball is raised RNA1

RNA substitution1

RNA answer from given working1

RNA correct units1

Ep == mgh

== 8 × 9.81 × 1.47

== 115.36J

5. (continued)The motorised chain drive is used to drive the belt.

(c) Calculate, showing all working and units:

(i) the velocity ratio of the chain drive system;

alternative:

(ii) the rotational speed of the 125 tooth sprocket;

(iii) the output power of the motor, if the motor shaft produces a torque of

3.7Nm.

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RNA

125 Teeth

Chain drive

35 Teeth

Electric motor

400 rev/min

RNA substitution1

RNA answer from given working

1

speed == UR × motor speed

== 0.28 × 400

== 112 rev/min

RNA substitution1

RNA answer from given working

1

P == 2ππnt

== 2 × 3.14 × (400 ÷ 60) × 3.7

== 154.9 W

RNA1 RNA1

Driver (speed) Driven (teeth)VR

Driven(speed) Driver (teeth)

12535

== ==

== 25/7 or 3.57 (reduction)

RNA1 RNA1

35125

7/25 or 0.28 (increase)

6. A pneumatic circuit is used in a drilling operation.

(a) Describe, using appropriate terminology, how the pneumatic circuit operates.

When Valve 1 is actuated _____________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

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Cylinder B

Cylinder ADrill

Cylinder A Cylinder B

Valve 1

Valve 2

Valve 3 Valve 4

Valve 5 Valve 6 Valve 7 Valve 8

and Valve actuated, pilot air actuates2

Valve , outstroking Cylinder A. Valve is then actuated by 3

Cylinder A which, in turn, actuates Valve , outstroking4

Cylinder B. Valve is then actuated, actuating Valve which 8

instrokes Cylinder A. Valve actuates Valve which then instrokes 5

RNA for each relevant point1

Cylinder B. The system is then reset.

6

3

4

or

×

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6. (continued)

The circuit diagram shows two forms of air, pilot and main air.

(b) Describe the difference between the two types.

_____________________________________________________________________

_____________________________________________________________________

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.

________________________________________________________________

(ii) Draw the symbol for this component below.

(iii) Mark (X) on the circuit where this component should be inserted.

To further improve the circuit, it was decided to include a time delay beforeCylinder A instrokes.

(d) (i) State the name of the two components required to produce a pneumatic

time delay.

1 _______________________________________________________________

2 _______________________________________________________________

(ii) State how the length of the time delay could be varied.

________________________________________________________________

(e) State the name of the actuator on Valve 8 .

_____________________________________________________________________

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pilot air — actuates valves KU1

main air — operates cylinders KU1

unidirectional restrictor KU1

KU restrictor1

reservoir KU1

restrictor KU1

adjust restrictor/change size of reservoir KU1

roller trip KU1

KU bypass line1

(box not necessary)

see diagram

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7. An automatic door in an office complex is operated by a motor (M) which is

controlled by three inputs.

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.

(ii) State, with reference to the Data Booklet, the full name of the ICs

required to build the circuit.

IC Number 7408

Full Name: ______________________________________________________

IC Number 7432

Full Name: ______________________________________________________

(iii) State the name of the family which these ICs belong to.

________________________________________________________________

(iv) State the supply voltage (Vcc) from which this family of ICs operate.

________________________________________________________________

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A(1 when dark)

B(1 when pressed)

C(1 when pressed)

M

0 0 0 0

0 0 1 1

0 1 0 0

0 1 1 1

1 0 0 0

1 0 1 1

1 1 0 1

1 1 1 1

RNA1

RNA1

RNA1

Quad Or 4, Two Input, And Gate KU1

Quad Or 4, Two Input, Or Gate KU1

TTL KU1

5v KU1

7. (continued)

(b) (i) Complete the wiring diagram for the door control system.

(ii) State the purpose of the dot on the ICs.

________________________________________________________________

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.

________________________________________________________________

(ii) Draw the symbol for an LED below.

1 arrow is acceptable

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RNA

Vcc

0V

Input A

Input B

Input C

7408 7432

Output (M)

RNA1RNA1

RNA ALL power lines1

to indicate pin 1 KU1

light emitting diode KU1

KU1

8. A disco light box is controlled by a microcontroller.

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.

cw: if sensorA>150 then acw ‘test potentiometer positionlet pins = %10100000 ‘motor clockwise, red onpause 10 ‘10 ms delaylet pins = %10000000 ‘motor clockwisepause 10 ‘10 ms delaygoto cw ‘jump to label cw

acw: if sensorA<30 then cw ‘test potentiometer positionlet pins = %01010000 ‘motor anticlockwise, yellow onpause 10 ‘10 ms delaylet pins = %01000000 ‘motor anticlockwisepause 10 ‘10 ms delaygoto cw ‘jump to label cw

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RNA

Light box

Mirror

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) 0

8. (continued)

(a) Complete, with reference to the PBASIC program and the input/output

connections, the flowchart for the part of the program shown below.

(b) Name the microcontroller parts (A to E) shown in the diagram below.

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Is SensorA

>150?

Motor C/WRed On

10 ms delay

10 ms delay

PBASIC acccepted

Motor ACWYellow On

10 ms delay

10 ms delay

Is SensorA<30?

Yes Yes

No No

Red Off Yellow Off

Memory sub-system

A B

C D

E

The “real

world”

A ________________________

B ________________________

C ________________________

D ________________________

E ________________________

RNA both outputs1

1

11

ROM KU1

RAM KU1

ALU KU1

I/O Port KU1

Clock KU1

RNA ALL delays1

9. Electricity can be generated from both finite and renewable sources.

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.

Tidal _______________________________________________________________

Solar ________________________________________________________________

Wind _______________________________________________________________

(b) State two other examples of renewable energy sources.

1 ___________________________________________________________________

2 ___________________________________________________________________

(c) State two examples of finite energy sources.

1 ___________________________________________________________________

2 ___________________________________________________________________

[END OF MARKING INSTRUCTIONS]

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obstructions for shipping, etc KU1

inconsistent supply, cost of infastructure etc KU1

noise pollution, etc KU1

Wave, hydro, geothermal, etc (nuclear not accepted)

KU each (max marks)1

Coal, gas, oil, peat, nuclear, etc

2

KU each (max marks)1 2