FOR OFFICIAL USE Centre No. Subject No. Level Paper No. Group No. Marker's No. Total Marks [C036/SQP141] Intermediate 2 T i m e : 2 Technological Studies hours 30 minutes NATIONAL QUALIFICATIONS Specimen Question Paper Fill in these boxes and read what is printed below. Full name of centre Town First name and initials Surname Date of birth Day Month Year Candidate number Number of seat 1 Answer all the questions in Section A and any two questions in Section B. 2 Read every question carefully before you answer. 3 Write your answers in the spaces provided. 4 Do not write in the margins. 5 Do not sketch in ink. 6 All dimensions are given in millimetres. 7 Before leaving the examination room you must give this book to the invigilator. If you do not, you may lose all the marks for this paper. [C036/SQP141] 1 © Marks SECTION A Attempt ALL questions 1. The control circuit shown in Figure Q1 should switch on the motor of a cooling fan if the temperature inside a small greenhouse rises above a specified level. Supply 12 V –t M 560 Ω 0V Figure Q1 (a) The motor switches when the voltage (Vbe) between the base and the emitter of the transistor reaches 0.7 V. Calculate the resistance of the thermistor for this condition. 4 (b) How could this circuit be modified to allow different “switch-on” temperatures, without changing the type of thermistor used? 1 (5) [C036/SQP141] 2 Page two Marks 2. Figure Q2 shows a small hoist designed to raise loads of up to 1.5 kN. In operation, the effort required to lift this load was found to be 350 N. Figure Q2 Effort (input) = 350 N Load (output) = 1.5 kN (a) How far does the effort (input) move when the load (output) is raised 1 m? 2 (b) For the movement described in part (a), calculate: (i) the energy output (the work done on the load); 2 (ii) the energy input (the work done by the effort). 2 (c) Explain why the energy input is always greater than the energy output for any type of machine. 2 (8) [C036/SQP141] 3 Page three Marks 3. An architect’s model for a public exhibition uses a lighting system which has two switches and three 6 volt bulbs supplied by a 6 volt battery. The lights can be turned on by any one of the two switches. (a) Give two reasons why the 6 volt bulbs should be connected in parallel rather than in series in this lighting circuit. 1 2 2 (b) Draw a circuit diagram to show how the bulbs and switches should be connected to the battery so that the required specification is obtained. 5 (c) Each bulb has a resistance of 20 Ω. Calculate the power one bulb will use when it is on. 4 (11) [C036/SQP141] 4 Page four Marks 4. The incomplete pneumatic circuit diagram shown in Figure Q4 represents part of a system for testing the reliability of a new type of door hinge. The piston is shown fully instroked. The reciprocating piston rod operates the hinge (not shown) repeatedly until it fails. Valve A B Figure Q4 (a) State the full name of valve A. 2 (b) (c) Valve A is to be used as a master switch to control the system. On Figure Q4 above, complete the required circuit connections. 4 A uni-directional flow restrictor is shown at point B. Put a tick against the statement in the following list which best describes the effect of the flow restrictor on the motion of the piston rod. Tick one box. It has no effect on either the instroke or the outstroke. It slows both the instroke and the outstroke. It slows the outstroke, but does not affect the instroke. It slows the instroke, but does not affect the outstroke. 1 (7) [C036/SQP141] 5 Page five Marks 5. The control panel in a rally car includes a warning lamp to remind the driver and navigator to fasten their seatbelts. The warning lamp should operate if the ignition is switched on and a seatbelt is unfastened. The sensors are listed below: (a) Sensor A: Driver seatbelt UNFASTENED = logic ‘1’ Sensor B: Navigator seatbelt UNFASTENED = logic ‘1’ Sensor C: Ignition switch ON = logic ‘1’ A solution for the specified system requires one 2-input AND gate and one 2-input OR gate. Draw a suitable logic circuit for this solution. [C036/SQP141] 6 Page six 4 Marks 5. (continued) (b) A different solution for the control system, using three gates, is shown below. Complete the truth table for this control system. Sensor A (D) L Sensor C Output to LAMP (E) Sensor B (c) A B C 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 (D) (E) L 4 From the truth table in part (b), write down the Boolean expression for L. L= [C036/SQP141] 7 2 (10) Page seven Marks 6. A closed loop control system should contain most of the following elements. reference signal process (a) error detector AND gate feedback loop feedback sensor On the diagram below, write the names of the appropriate elements in the spaces provided. Show the direction of feedback. Output 6 (b) A common example of a closed loop control system is found in a domestic central heating system. For this example: (i) name the feedback sensor; (ii) what does the feedback sensor monitor? 2 (8) [C036/SQP141] 8 Page eight Marks 7. The van shown in Figure Q7 is being used to transport building materials. The vehicle has a total weight of 12.0 kN acting at point A, and the weight of the building materials is 9.0 kN acting at point B. 3.0 m 1.3 m 0.5 m B A R1 R2 Figure Q7 (a) (b) Draw a line diagram for this system, showing the four forces and their relative positions. 4 Calculate the following forces: (i) Reaction R1 acting at the front axle; 4 (ii) Reaction R2 acting at the rear axle. 3 (11) [C036/SQP141] 9 Page nine SECTION B Attempt any TWO questions 8. The diagram, Figure Q8(a), shows part of a system which separates two sizes of box on a production line. The size of a box is detected by two light sensors as it approaches the lift. When the box arrives at the lift, cylinder A moves the lift to the correct level if required, and cylinder B pushes the box onto one of the outgoing conveyors. Boxes in Light sensors Cylinder B Lift Cylinder A Small boxes out Large boxes out Figure Q8(a) Opposite each of the light sensors there is a light source, producing a beam which is cut by boxes as they pass. For clarity the light sources have not been included in the diagram. [C036/SQP141] 10 Page ten Marks 8. (continued) Figure Q8(b), below, shows a schematic diagram of the circuit. Cylinder B Valve 4 Solenoid 2 Valve 5 Valve 3 Valve 2 Cylinder A Valve 1 Note: Solenoid 1 is actuated by a large box. Solenoid 2 is actuated by a small box. (a) Solenoid 1 Figure Q8(b) Refer to the circuit diagram and explain how the system operates when a large box is sensed. When a large box is sensed approaching the lift, Solenoid 1 5 [C036/SQP141] 11 Page eleven Marks 8. (continued) (b) The piston in cylinder A is 50 mm diameter. Calculate the maximum force cylinder A can apply if the air supply pressure is 0.2 N/mm2. (Show all working and units.) 5 (c) The two light sensors are arranged as shown in Figure Q8(c), in order to detect the size of a box as it approaches the lift. Sensor 1 Sensor 2 Lift Figure Q8(c) [C036/SQP141] 12 Page twelve Marks 8. (c) (continued) A truth table showing the control of Solenoid 1 and Solenoid 2 is also shown. Each sensor produces a logic ‘0’ when a box passes it. Each solenoid is activated by logic ‘1’. Sensor 1 Sensor 2 Solenoid 1 Solenoid 2 0 0 1 0 0 1 0 0 1 0 0 1 1 1 0 0 Disallowed (i) The second line of the truth table has been disallowed. Why? 2 (ii) Complete the logic diagram shown below for Solenoid 2, to satisfy the truth table. Sensor 1 Solenoid 2 Sensor 2 [C036/SQP141] 13 2 Page thirteen Marks 8. (continued) (d) Pin-out diagrams for five different types of TTL integrated circuit are shown below. TTL Integrated Circuits +Vcc +Vcc +Vcc Gnd Gnd 7400 Quadruple 2-input OR gate 7402 Quadruple 2-input NOR gate +Vcc Gnd 7404 Hex INVERTER +Vcc Gnd 7408 Quadruple 2-input AND gate (i) Gnd 7400 Quadruple 2-input NAND gate Refer to your solution in Q8(c)(ii) and select two TTL integrated circuits from the above group that could be used to construct the circuit. Enter the identification number of each in the spaces provided in Figure Q8(d) below. 2 +5 V Inputs Sensor 1 Sensor 2 +Vcc +Vcc I.C. no............ Output Driver I.C. no............ Gnd Output to Solenoid 2 Gnd OV Figure Q8(d) (ii) [C036/SQP141] Complete all the connections needed for your solution in Q8(c)(ii). Do not show internal connection details of the integrated circuits. 14 Page fourteen 4 (20) Marks 9. The load/eject table of the CD-ROM drive for a computer is driven open by a motor which runs at 600 rev/min. Details of the operating mechanism are shown in Figure Q9 below. part of load/eject table F E D OPEN CLOSE F E D motor A C B belt load/eject table Figure Q9 Component F is attached to the load/eject table and is driven by gear E to open and close the table. (a) Name the mechanism made up of components E and F. 1 (b) Pulley A Pulley B 10 mm diameter 25 mm diameter Gear C Gear D Gear E 20 teeth 60 teeth 40 teeth Calculate the speed of gear E, giving your answer in revolutions per second. 4 [C036/SQP141] 15 Page fifteen Marks 9. (continued) (c) If the pitch of the teeth on component F is 1.5 mm, calculate the linear speed of the table as it opens. State your answer in mm/second. 2 (d) If the table moves 120 mm as it opens, how many seconds will it take to open fully from the closed position? 2 (e) State one advantage of using a belt drive in this mechanism. 1 [C036/SQP141] 16 Page sixteen Marks 9. (continued) (f) When the load/eject table closes fully, it closes a microswitch, and lights a LED. The part circuit is shown in Figure Q9(f). 5V R 0V Figure Q9(f) When the voltage across the LED is 2.1 V, the current flowing through it is 10 mA. Calculate the value of resistor R which will give 2.1 V across the LED. 4 [C036/SQP141] 17 Page seventeen Marks 9. (continued) (g) Two possible systems for opening the load/eject table are shown in the block diagrams in Figure Q9(g). The motor starts when an eject button is pressed and should continue to run until the load/eject table is opened fully. Eject button Latch Motor driver Motor driver Motor Drive system Load/ eject table Linear motion Motor Drive system Load/ eject table Linear motion reset System 1 Delay Eject button System 2 Latch reset Note: Microswitch is closed when the load/eject table is fully open Micro switch Figure Q9(g) (i) Name the type of control used in System 1. 1 (ii) Which of the components in System 2 is a feedback sensor? 1 (iii) In System 2, are the sensors (eject button and microswitch) analogue or digital devices? [C036/SQP141] Eject button 1 Microswitch 1 18 Page eighteen Marks 9. (g) (continued) (iv) Which of the two systems will ensure that the load/eject table opens fully every time? 1 Give one reason why the other system may not open the load/eject table fully. 1 (20) [C036/SQP141] 19 Page nineteen Marks 10. A hot drinks machine must heat 0.2 kg of water ready to pour into a cup. A system designed to do this is shown in Figure Q10. inlet valve Figure Q10 Heating element outlet valve (a) Calculate the energy needed to heat 0.2 kg of water from 18 °C to 90 °C. The specific heat capacity, C, of the water is 4190 J/(kg K). 2 (b) The heating element shown in Figure Q10 is rated at 3 kW and is connected to a 240 V supply. (i) Calculate the current drawn by the heating element. 2 (ii) From a selection of 3A, 5A or 13A, which fuse should be used to protect the heating element? 1 Give one reason for your answer 1 [C036/SQP141] 20 Page twenty Marks 10. (continued) (c) (i) Calculate the time taken for the heating element to raise the temperature of the water from 18 °C to 90 °C. State your answer in seconds. 2 (ii) The water temperature will fall after the heater has been turned off. Suggest one way of reducing the rate at which this happens. 1 [C036/SQP141] 21 Page twenty-one Marks 10. (continued) (d) The water heater is controlled to the following specifications: the heating element must only switch on if the water heater is full; the heating element should switch on if the water temperature is below 80 °C; the heating element should switch off when the water temperature reaches 90 °C; hot water should be dispensed when the “dispense” button is pressed; the water heater should automatically refill with water after dispensing. The flowchart below will satisfy the specification when complete. Write down the missing expressions (i) and (ii). Start fill No Is heater covered with water? Yes (i) Is temperature > 90 °C? Yes No (ii) Yes No Is “dispense” No switch pressed? Yes empty [C036/SQP141] 22 Page twenty-two switch heater on 4 10. (continued) (e) The water heater is controlled by a microcontroller which is connected to the input and output devices shown in Figure Q10(e) via the pins indicated in the interface table below. INPUT “dispense” switch (1=pressed) “high level” sensor (1=covered) “low level” sensor (1=covered) Pin 7 6 5 4 3 2 1 0 OUTPUT inlet valve inlet valve (1=open) outlet valve (1=open) high level sensor heater low level sensor outlet valve Figure Q10(e) The main control program calls two sub-procedures: “empty” pours hot water into a cup when the “dispense” switch is pressed. “fill” refills the heating system with cold water after it has emptied. Flow charts for each sub-procedure are shown below. “empty” sub-procedure “fill” sub-procedure empty fill open outlet valve open inlet valve No Is heater system empty? Yes Is heater system full? Yes close outlet valve close inlet valve wait 2 seconds return return [C036/SQP141] 23 Page twenty-three No Marks 10. (e) (continued) A PBASIC listing of the empty sub-procedure is shown below. empty: pouring: high 5 if pin0=1 then pouring low 5 pause 2000 return ‘sub-procedure empty ‘ ‘ ‘wait 2 seconds ‘return to main program (i) Three lines of the sub-procedure have no comment to explain their function. Write down a comment for if pin0=1 then pouring ‘ low 5 ‘ 1 1 (ii) From the flowchart given, use PBASIC to write the sub-procedure fill. 5 (20) [END OF QUESTION PAPER] [C036/SQP141] 24 Page twenty-four [C036/SQP141] Intermediate 2 Technological Studies NATIONAL QUALIFICATIONS Specimen Marking Instructions [C036/SQP141] 25 © Marks Deduct W mark when incorrect unit stated at final answer. 1. (a) R1/R2 = V1/V2 1 R/560 = 11.3/0.7 1 11 ⋅ 3 × 560 0⋅7 R = 1 = 9.04 kΩ 2. 1 (5) (b) Change value of lower resistor, or use variable resistor. (a) Distance ratio = 5 1 5 × 1m = 5m 1 (b) Output work done = force × distance 1.5 kN = 1500 N = 1500 × 1 = 1500 J = 1.50 kJ (i) Input work done = 350 × 5 = 1750 J = 1.75 kJ correct unit at answer (Nm or J) (ii) (c) 3. 1 (a) Friction (or energy loss) occurs between moving parts of system, generating heat, causing some of input energy to be lost from system. Any 2 valid points or other appropriate statement one mark each up to (2) 1 2 1 W 2 (8) 1 In series they would not have correct operating voltage and would light dimly; in parallel would be connected to rated voltage. 1 Three bulbs in parallel Two switches in parallel Switches in series with bulb network and supply Two out of three symbols correct Connections correct Power = VI = V2/R = [C036/SQP141] 1 If one bulb fails, other two will still function; in series, if one fails, all stop working. (b) (c) 1 W 26 6×6 = 1⋅8 W 20 Correct equation Substitution Answer Correct unit at answer (W) Page two 1 1 1 1 1 1 1 1 1 (11) Marks 4. (a) actuator valve type lever/lever 3/2 valve 1 1 (b) correct air connections, 1 mark each correct symbol for pilot air lines Valve A (c) 5. (a) 1 (7) It slows the outstroke, but has no effect on the instroke. A B C Lamp (b) correct symbol, 1 mark each gate correct connections W mark each A B C (D) (E) L 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1 1 0 1 1 1 0 0 0 0 0 1 0 1 1 0 1 1 1 0 0 0 0 1 1 1 1 1 1 W mark per correct row (c) L = A.B.C + A.B.C + ABC or L = C.(A + B) W mark each correct term up to 1W marks W mark correct operator (ie +) [C036/SQP141] 27 Page three 3 1 2 2 4 2 (10) Marks 6. (a) feedback loop feedback sensor Reference signal Output Process Error detector 1 mark for each correct answer up to six. (b) (i) Temp. sensor, thermistor. 1 (ii) Measures room temperature. 7. (a) 1 (8) 12.0 kN 1.2 m 9.0 kN 1.3 m 0.5 m R2 R1 W mark for force, W mark for position, for each of four forces (b) 6 (i) ΣMR2 = 0 (clockwise +ve) or equivalent statement. 4 1 +(R1 × 3) – (12 × 1.8) – (9 × 0.5) = 0 1 R1 = 21.6 + 4.5 1 = 8.7 kN 1 (ii) ΣFV = 0 (upwards +ve) or equivalent statement. + 8.7 – 12 – 9 + R2 = 0 1 1 R2 = 12 + 9 – 8.7 R2 = 12.3 kN [C036/SQP141] 28 1 (11) Page four Marks 8. (a) When large box is sensed approaching the lift, solenoid 1 actuates a 5/2 valve (or valve 1). This causes an outstroke of cylinder A, (or raises the lift). The outstroke speed is controlled by a uni-directional flow restrictor. A 3/2 roller-trip valve (or valve 5) is actuated at the end of the oustroke. This sends a pilot signal via a shuttle valve to actuate a 5/2 valve (or valve 3). This causes an outstroke of cylinder B, (or pushes the box onto the conveyor). The outstroke speed is controlled by a uni-directional restrictor. A 3/2 roller operated valve (or valve 4) is actuated at the end of the oustroke. This sends a pilot signal to both 5/2 valves. Cylinder A instrokes (or lowers the lift), and cylinder B instrokes. (b) Area 2 = πd 4 Recognise valve being actuated first. W Note effect on correct cylinder, either as a correctly termed cylinder movement, or as an effect on the system’s movement. Note that speed of movement is controlled. W Note positional sensor. W Note that control signal passes through a shuttle valve. Note effect on correct cylinder, either as a correctly termed cylinder movement, or as an effect on the system’s movement. Note that speed of movement is controlled. W W W W Note positional sensor. W Note that control signal passes to both 5/2 control valves. Note that both cylinders instroke. W Calculation of effective csa 3 Formula and substitution Answer with units 1 1 W = π 50 4 = 1960 mm2 2 Force = pressure × area = 0.2 N/mm2 × 1960 mm2 = 392 N [C036/SQP141] 29 Page five Marks 8. (continued) (c) (i) It would suggest a box floating in mid-air, which is not possible under normal operating conditions. Recognition of practical absurdity. 2 Correct logic symbol. Correct connections 1 1 (ii) Sensor 1 Solenoid 2 Sensor 2 Correct IC selected from pin-out diagrams provided. Numbers written onto ICs on diagram: 2 at 1 mark each. (d) (i) ICs required; 7404 and 7408 (ii) Inputs 2 +5 V Sensor 1 Sensor 2 +Vcc +Vcc 7404 Solenoid Driver Circuit 7408 Gnd Output to Solenoid 2 Gnd 0V Connection from sensor 2 to an inverter input W Connection from inverter output to AND gate input W Connection from sensor 1 to second input of AND gate (must be gate already used for output from inverter). W Connection from AND gate output to solenoid driver circuit input W Connection from 5V to pin 14 on each chip 1 Connection from 0V to pin 7 on each chip Alternative solutions using different connections will need to be followed through line by line. [C036/SQP141] 30 Page six 1 (20) Marks 9. (a) rack & pinion Correct mechanism 1 (b) 600 rev/min ÷ 60 sec/min = 10 rev/sec 10 rev/sec × 10 mm/25 mm = 4.0 rev/sec 4.0 rev/sec × 20T/60T = 1.33 rev/sec Speed conversion factor Speed ratio of pulley drive* Speed ratio of gears C&D* Final answer with units 1 1 1 1 *(W marks for inverted speed ratios) (c) speed = tooth pitch × no of teeth/sec =1.5 mm/tooth × 1.33 rev/sec × 40 teeth/rev = 80 mm/second (d) Time = distance ÷ speed = 120 mm ÷ 80 mm/second = 1.5 seconds Number of teeth per second calculated. Product of number of teeth/second and pitch W Correct answers and units 1 Correct relationship between distance, speed and time, stated either explicitly or implicitly through the correct substitution of known values. 1 Correct answers and units 1 (e) If system jams internally or is jammed externally, the belt will slip, preventing damage to the electric motor due to overloading OR Effective at transmitting moderate torque over a larger shaft separation than spur gears. Any appropriate answer (f) 10 mA = 0.01 A R = V/I = (5 V–2.1 V)/0.01 A = 2.9 V/0.01 A = 290 Ω Maintaining unit consistency in calculation Explicit or implicit statement of Ohms Law Value substitution: V(1), I(W) Answer with units (g) (i) Open-loop control (ii) Microswitch (iii) digital digital (iv) System 2 Dust/grit may impede the free running of the drive mechanism OR An external object may impede the movement of the CD-ROM drive OR Delay value may not be long enough to allow the load/eject table to be opened fully. [C036/SQP141] 31 Page seven Correct Correct Correct Correct Correct statement statement statement statement statement Suitable expression W 1 W 1 1W 1 1 1 1 1 1 1 (20) Marks 10. (a) Eh = mC∆T = 0.2 × 4190 × (90–18) = 60.3 kJ (b) (i) Current, I = P/V = 3000/240 = 12.5 A (ii) 13A fuse. Smallest fuse larger than rated current or working current. Would blow 3A and 5A fuses instantly because it is much larger than either rating. (c) (i) time = energy required/power of supply = 60 300 ÷ 3000 = 20.1 seconds (ii) Use thermal insulation to cover the walls of the container. (d) (i) Switch heater OFF or LOW or LOGIC 0 (ii) Is Temperature <=80 °C? OR Is Temperature <80 °C? (e) (i) Appropriate response repeat until water is at low level or repeat if lower water sensor is still wet Close the outlet valve (ii) fill: not_full: high 6 if pin1 = 0 then not_full low 6 return Correct temperature difference Correct answer and units 1 1 Conversion factor for power Correct answer and units 1 1 Choice of correct fuse Clear explanation for selection 1 1 Either energy conversion factor or power conversion factor. Top and bottom line of fraction must have consistent units. Correct answer and units 1 1 Identify “thermal insulation” 1 Reference to heater and correct state 2 Reference to temperature and 80 °C 2 make clear that lower fluid level sensor line is being interrogated (W) make clear that program loops until condition is false (W) 1 Identify correct valve (W) Identify that valve is closing (W) 1 open correct valve (1) make reference to correct input (1) indicate an appropriate loop (1) switch same output device off (1) return statement (1) [END OF MARKING INSTRUCTIONS] [C036/SQP141] 32 Page eight 5 (20)