2010 Technological Studies. Standard Grade Credit. Finalised Marking Instructions

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1 Technological Studies Standard Grade Credit Finalised Marking Instructions Scottish Qualifications Authority The information in this publication may be reproduced to support SQA qualifications only on a noncommercial basis. If it is to be used for any other purposes written permission must be obtained from the External Print Team, Centre Services, 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 External Print Team, Centre Services, 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.

2 Mark Allocation Marks. A manufacturer wants to use a cruise control system to keep a car s speed constant even when it goes up and down hills. The system should allow a driver to take their foot off the accelerator once the desired speed has been set. (a) Complete the control diagram below for the cruise control system. Speed sensor/ Tachogenerator Desired Speed or Set Level + - Control Unit Engine Wheels Constant Speed X (b) State the name of the control diagram symbol X. Error detector KU (c) This control system makes use of a feedback loop. State the type of control produced by this automatic system. Closed loop KU Page

3 . An interior designer wants three lamps to come on when a switch is activated. The lighting circuit is shown below. V Ω Ω 6 Ω (a) State two reasons why it is good practice to have the lamps wired in parallel rather than in series. (i) Other remains lit if one breaks KU (ii) Easy to spot the faulty lamp/be brighter KU (b) Calculate, showing all working and units, the total resistance of the lighting circuit shown above. R t = + + R R R = substitution = 67 R t = 7 7 Ω correct answer from given working The designer wants the brightness of the lights to be altered using the following component. (c) (d) State the name of the component shown above. Variable resistor KU State the name of the device that is used to measure current in a circuit. Ammeter KU Page

4 . A geothermal power plant uses the heat in the earth to help produce electricity. (a) Calculate the heat energy absorbed by litres of water which is pumped into the earth at C and comes out as steam at 4 C. ( litre of water has a mass of kg.) Eh = mc Δ T = 49 substitution temperature change E h = 967 J = 96.7 MJ correct answer from given working (b) For every 5 MJ of heat energy that comes from the ground, the power plant produces 5 4 MJ of electricity. (i) Calculate the efficiency of the power plant. η = Useful energy out % Total energy in = 5 4MJ 5MJ substitution = 5 6% correct answer from given working or 56 (ii) Explain why a system, such as the power plant, will not be % efficient. Energy is lost during production etc Page 4

5 . (continued) Marks (c) Geothermal is a source of renewable energy. State two other examples of a renewable energy source. Solar, tidal, biomass, wind hydro(electric) etc KU each (max ) (d) State two disadvantages of using fossil fuels, other than cost. Pollution Dwindling supply etc KU each (max ) (e) State two ways that energy can be conserved in the home. Insulation KU each (max ) Switching off unused appliances etc Page 5

6 4. A test rig in a furniture factory is operated by the pneumatic circuit shown below. Valve Valve 4 X (d) (ii) To on/off switch Valve Valve Y (a) Describe, using appropriate terminology, how the pneumatic circuit operates. When Valve is actuated...main air flows to valve then causes the DAC to outstroke. When fully outstroked it actuates valve 4 sending a pilot signal towards valve. After a delay valve actuates causing the DAC to instroke. This actuates valve which sends a pilot signal to valve causing it to change state and outstroke the piston. The sequence repeats until valve is no longer actuated. RNA for each valid point up to a maximum of Page 6

7 4. (continued) (b) State the full name of the following components. KU Valve Solenoid/Spring Return// valve for each part Component Y Reservoir KU Marks (c) State two ways to vary the length of a pneumatic time delay. Adjust the restrictor KU Change the volume of the reservoir KU To reduce damage it was decided to slow the piston movement as it outstrokes. The piston should still instroke quickly. (d) (i) State the full name of a pneumatic component that could be used to slow a piston in one direction. Uni-directional restrictor KU (ii) Mark (X) on the pneumatic circuit where this component should be inserted. (e) State the name of the following pneumatic actuators. Lever KU Diaphragm KU Page 7

8 5. A prototype circuit for a parking sensor in a car is shown below. Marks + 5 V V Z k Ω k Ω V out V (a) (i) State the name of component Z shown in the circuit above. Buzzer KU (ii) State the type of relay shown in the circuit above. Single Pole Single Throw (SPST) KU (b) Describe the operation of the circuit. As light level drops the resistance of the LDR increases and V out increases. When V out is at the appropriate level ( 7 V) the transistor switches on. This causes the relay to turn on and the buzzer to sound. for each valid point up to marks (c) Calculate, with reference to the Data Booklet, the value of V out when the light level on the LDR is 9 lux. From the Data Booklet, R ldr = k Ω correct value from Data Booklet R V out = V s R T = 5 substitution Allow FTE = 4 67 V correct answer from given working Page 8

9 5. (continued) (d) (e) State the voltage at which a transistor saturates. 7 V KU A diode is normally wired in parallel across devices such as relays. State the purpose of the diode. To protect the transistor KU Page 9

10 6. A music venue has a system to cut off the power supply if a band plays too loudly. The system is operated by a microcontroller. A flowchart for the control system is shown below. Start Initialise Is music too loud? No Yes Warning light on 5 second delay Warning light off 5 second delay Has this been done times? No Yes Is music too loud? No Yes Shut off power Stop Page

11 6. (continued) Input and output connections to the microcontroller are shown in the table below. Input Connection Pin Output Connection Sound sensor ( = loud, = quiet) 7 Power supply shut off ( = shut off, = power on) 6 Warning light Complete, with reference to the flowchart, Data Booklet, and the input/output connections, the PBASIC control program. init: let dirs = % set pins 7-4 as outputs, rest inputs let pins = all pins off symbol counter = b define counter address b 5 4 main: if pin = then main if sound level is quiet then jump to main set for next loop to for counter = to high 6 pause 5 low 6 for both pause 5 next counter if pin = then main high 7 end Page

12 7. Part of an electronic circuit used to control a central heating system is shown below. + V cc A-Temperature Sensor Z-Boiler B-Timer C-Test switch V (a) Complete, with reference to the Data Booklet and the wiring diagram, the logic diagram for the central heating system. A for each gate B C Z Page

13 7. (continued) (b) TTL Integrated Circuits (ICs) are used in the prototype but CMOS ICs are chosen for the final product. State two advantages of CMOS ICs over the TTL ICs. Low power consumption, high fan out, various power supplies etc KU each up to (c) An engineer designed and tested the circuit using a computer simulation. State two reasons why new circuits are often tested on a computer first. Easier to change, no faulty components, quicker to construct etc KU each up to (d) The engineer assembled the circuit on a breadboard and used an LED to show a high output. (i) (ii) State the full name of an LED. Light Emitting Diode KU Draw the symbol for an LED below. KU Page

14 8. A simplified diagram of a microcontroller system is shown below. RAM ROM EEPROM Program ALU I/O Port External devices CLOCK (a) (i) State the full name of the following microcontroller sub-systems. I/O PORT Input/Output port KU EEPROM Electronically Erasable Programmable Read Only Memory KU (ii) Describe the difference between RAM and ROM. RAM is a temporary form of storage, data lost when power switches off etc ROM is a permanent form of storage, cannot be changed etc KU for each correct description ( of each) (b) (i) State the name of the connections that are used to transfer data from one microcontroller sub-system to another. Bus (buses) KU (ii) Describe the function of the ALU. Does all internal calculations, processes data KU (c) (i) Convert the following binary number to decimal. % 9 (ii) Convert the following decimal number to binary. % () Page 4

15 9. A model train climbs a steep slope at an amusement park. A simplified diagram of the train drive system is shown here. rev/min teeth 8 teeth 5 teeth Part X 9 teeth Part Y (a) State the names of the labelled parts of the drive system in the diagram above. Part X Pinion KU KU Part Y Rack KU (b) A simplified diagram of the train drive system is shown. Calculate the speed of the 9 tooth gear. rev/min teeth 5 teeth 8 teeth 5 Output Speed = 8 9 substitution 9 teeth Part X = rev/min correct answer from given working OR substitution Speed 8T = /8 = 8 rev/min correct answer from given working 4 Speed 9T = 8 5/9 = rev/min correct answer from given working substitution Page 5

16 9. (continued) (c) Calculate the linear speed of the train along the track. The pitch of Part Y is 5 mm. Part Y Part X 9 teeth 5 mm Speed = pitch revs teeth = 5 9 substitution (allow FTE) = mm/min correct answer from given working 999 mm/min (d) State the names of the mechanisms below. (i) Worm and nut KU ignore order (ii) Worm and wheel KU (iii) State an advantage in the use of a worm in a lifting system. No overhaul, large speed change between input and output etc KU increase torque Page 6

17 . A microcontroller operates the motors in a robotic dog. To make the dog move in a life-like way the motors must be able to turn at a slower speed. (a) Describe, with the aid of a sketch, or sketches, how a microcontroller program can be used to make a motor turn at a slower speed. Normal Slower KU for mark and space correctly identified or defined KU for pulsed signal drawn or defined, or PWM stated KU for describing or drawing a changing ratio of mark and space for slowing To reduce damage to the robotic toy the program uses a soft start technique when operating the motors. The soft start is illustrated in the diagram below. The diagram below shows the output signal to the motor. (b) time Describe, with reference to the diagram, what will happen to a motor when the soft start is used. The motor will gradually speed up [END OF MARKING INSTRUCTIONS] Page 7

2013 Technological Studies. Standard Grade General. Finalised Marking Instructions

2013 Technological Studies. Standard Grade General. Finalised Marking Instructions Technological Studies Standard Grade General Finalised Marking Instructions Scottish Qualifications Authority The information in this publication may be reproduced to support SQA qualifications only on