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GCE JAN 2009 : (A2 3) Systems and Control in Product Design

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ADVANCED General Certificate of Education January 2009 Technology and Design assessing Unit 6 Systems and Control in Product Design A2V31 Assessment Unit A2 3 [A2V31] FRIDAY 16 JANUARY, MORNING TIME 2 hours 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number on the Answer Booklet provided and on the A3 pro forma answer pages provided. Answer three questions. Answer the one question in Section A and either the two questions in Section B or the two questions in Section C. Answers to Questions 1(a)(v) or 1(b)(v), Question 4(a)(v), 4(b) and Question 5(c)(ii), (iii) and (iv) should be made on the A3 pro forma answer pages provided. INFORMATION FOR CANDIDATES The total mark for this paper is 80, including a maximum of 4 marks for quality of written communication. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. At the conclusion of the examination, attach the A3 pro forma answer pages securely to the Answer Booklet with the treasury tag supplied. You are provided with an insert sheet for Question 1. Do not write your answers on this insert. A materials data sheet is provided. 4318 Section A This question is compulsory. You are advised to spend 1 hour and 15 minutes on this section. You are required to answer either 1(a) or 1(b). For candidates studying Electronic and Microelectronic control systems answer part (a) using the pro forma (answer 1(a)(v)) and an answer booklet. 1 (a) Fig. 1(a) shows a prototype test rig used to test the performance of tennis rackets. The following sequence occurs. The tennis racket is secured in position and Door 1 is closed. The hopper is filled with a set number of tennis balls and the operator selects at the control panel one of the three speeds for Motorised Gearbox A after closing Door 2. From the control panel the operator controls the Stepper Motor to set the distance between the tennis racket and the ball launcher. The operator selects at the control panel an angle between position 1 and position 2 at which the ball will hit the racket. This is controlled by Motorised Gearbox B. The test can only begin when the two doors are closed and the operator presses the start button on the control panel. When this happens, Motorised Gearbox A starts and a signal activates the electromechanical release at the bottom of the hopper to release a ball from the chute every 5 seconds. When the hopper and chute are empty Motorised Gearbox A stops allowing the operator to collect the tennis balls and change the settings if required. (i) With reference to Fig. 1(a) suggest a suitable composite for the central panel and briefly outline two main reasons why your choice would be suitable. [3] (ii) With reference to Fig. 1(a) suggest a suitable metal for the I profile test bed and briefly describe how it would be manufactured. [2] (iii) Using annotated sketches briefly outline two alternative methods that may be used to detect if the doors have been closed. [4] (iv) Briefly outline the type of logic function used for two distinctly different situations on the test rig. [2] 4318 2 [Turn over (v) On the pro forma provided (answer number 1(a)(v)) use Electronic and Microelectronic circuit diagrams with annotation to produce a viable solution that will fulfil each of the specified points stated below. (N.B. All brackets, housings, screws, nuts and bolts are not required) Design a circuit that will allow the operator, from the control panel, to move the Stepper Motor forwards and backwards to adjust the distance between the tennis racket and the ball launcher (Fig. 1(a)(i)). [6] Design a circuit that will indicate the angle at which the tennis racket holder is being held (Fig. 1(a)(ii)). This angle should then be shown on the seven segment displays on the control panel. [12] 4318 Design a circuit that will allow the operator to pre-select one of three speeds for Motorised Gearbox A. When the start button is pressed the motor should run at the selected speed (assume the start button is a push to make switch). [4] Design a circuit that will provide a 1 second pulse every 5 seconds that could be used to trigger the electromechanical release at the bottom of the hopper. [5] 3 [Turn over For candidates studying Pneumatic and Mechanical control systems answer part (b) using the pro forma (answer 1(b)(v)) and an answer booklet. 1 (b) Fig. 1(b) shows a test rig used to test the performance of tennis rackets. The following sequence occurs. The tennis racket is secured in position and Door 1 is closed. The hopper is filled with a set number of tennis balls and the operator selects one of the three speeds for Motorised Gearbox A after closing Door 2. From the control panel the operator controls Motorised Gearbox B to set the distance between the tennis racket and the ball launcher. The operator, from the control panel, then sets the angle of the tennis racket holder to either position 1 or position 2. The test can only begin when the two doors are closed and the operator presses the start button on the control panel. When this happens, Motorised Gearbox A starts and a signal activates the electromechanical release at the bottom of the hopper to release a ball from the chute every 5 seconds. When the hopper and chute are empty Motorised Gearbox A stops allowing the operator to collect the tennis balls and change the settings if required. (i) With reference to Fig. 1(b) suggest a suitable composite for the central panel and briefly outline two main reasons why your choice would be suitable. [3] (ii) With reference to Fig. 1(b) suggest a suitable metal for the I profile test bed and briefly describe how it would be manufactured. [2] (iii) Using annotated sketches briefly outline two alternative methods that may be used to detect if the doors have been closed. [4] (iv) Briefly outline the type of logic function used for two distinctly different situations on the test rig. [2] 4318 4 [Turn over (v) On the pro forma provided (answer number 1(b)(v)) use Pneumatic and Mechanical circuit diagrams with annotation to produce a viable solution that will fulfil each of the specified points stated below. (N.B. All brackets, housings, screws, nuts and bolts are not required) Design a suitable mechanism driven from the output shaft of Motorised Gearbox B that will move the carriage along the test bed (Fig. 1(b)(i)). [4] Design a gearbox using only gears with teeth between 20 and 100 that will provide an output speed of 1920 rpm from an input of 20 rpm. Then with the minimum number of additional gears with teeth between 20 and 100, show how you would achieve the second and third output speeds. (Show all calculations and state clearly the number of teeth for each of the gears (Fig. 1(b)(iii)). [12] 4318 Design a suitable system that will allow the operator to set the angle of the tennis racket holder to either position 1 or position 2 (Fig. 1(b)(ii)). [6] Design a suitable mechanism that will provide a positive drive from the output shaft of Motorised Gearbox A to shaft B in order to launch the tennis ball. Show how the design is attached to the shafts (Fig. 1(b)(iii)). [5] 5 [Turn over Section B Electronic and Microelectronic Control Systems Answer both questions in this section. 2 A voltage divider is connected to a power supply as shown in Fig. 2(a). +6 V LDR R1 1K Vo 0V Fig. 2(a) (a) (i) A light dependent resistor (LDR) can be used as the basis for a sensor to measure light. State the principal physical property of the LDR that is used in the measurement of light. [1] (ii) Under certain light conditions the resistance of the LDR shown in Fig. 2(a) will vary from 2000 to 2500 . Calculate the corresponding values for Vo. [2] (b) Part of a system for testing the clarity of recycled glass samples is shown in Fig. 2(b). The opaque box contains a light source which is to be placed on one side of the glass sample while the circuit from Fig. 2(a) is to be placed on the other side. A digital voltmeter (DVM) is to be used to display the results of the tests. Glass sample inserted Light source Voltage divider Circuit with LDR Opaque box Fig. 2(b) (i) It is required that the voltage to be displayed by the DVM, in millivolts, should represent the percentage clarity of the glass with the number displayed varying between 0 and 100. The voltage from the voltage divider is found to vary by a maximum of 50 mV. An amplifier is needed to meet this requirement. Determine the gain of the amplifier. [2] 4318 6 [Turn over (ii) Design a non inverting amplifier circuit based on an op-amp that will have the required gain from (b)(i). The gain of a non inverting amplifier is given by R 1+ f where R f is the feedback resistor. R [4] (iii) Digital Voltmeters are available with either seven segment LED displays or LCD displays. State one main advantage and one main disadvantage of each type of display. [2] (c) A simple pass/fail quality test for glass samples could be produced by using a PIC as shown in Fig. 2(c). The PIC has an analogue to digital converter (ADC). The voltage range of the ADC port (i/p1) is from 0 V to 6 V with corresponding digital values ranging from 0 to 255. +6 V o/p 1 PIC i/p 1 o/p 2 Fail LED Pass LED V1 0V Fig. 2(c) (i) Briefly outline what is meant by the term analogue to digital conversion. [2] (ii) When the input voltage V1 in Fig. 2(c) is greater than 0.8 V the glass sample is considered to have failed the quality test. Determine the digital value that corresponds to 0.8 V provided by the ADC. [2] (iii) For the PIC circuit shown in Fig. 2(c), write a suitable flowchart program that will continuously check the ADC port (i/p1) and turn on the appropriate LED. [4] 4318 7 [Turn over 3 A car wash system consists of an eight stage sequence where high pressure water is required at stages 1, 3, 6 and 8. The stages are incremented by the output from a 3-bit binary counter with outputs A, B and C, where A is the least significant bit. The high pressure water supply is switched on and off by a 110 volt solenoid valve which is controlled by a logic circuit. (a) (i) Draw a truth table for the logic circuit that controls the high pressure water solenoid, assuming that the output of the logic circuit is F. [5] (ii) Using a Karnaugh Map, deduce a minimised expression for the output F. [4] (iii) Draw a logic circuit that would produce the required output F. [2] (iv) The position of a vehicle in a car wash could be determined by using an ultrasonic system. Briefly explain how such a system could be used to achieve this. [1] Fig. 3(a) shows how a 110 V water solenoid valve is interfaced to the logic circuit from 3(a)(iii). 6V 110 V Relay Diode 6 V signal from logic circuit Rb Valve Transistor 0V 0V Fig. 3(a) (b) (i) State the function of each of the following components in the circuit shown in Fig. 3(a). transistor relay diode [3] (ii) Calculate a suitable value for resistor Rb in Fig. 3(a) if the gain of the transistor is 100 and the relay coil is 60 ohms. (Assuming that Vbe is 0.7 volts) [4] 4318 8 [Turn over BLANK PAGE (Questions continue overleaf) 4318 9 [Turn over Section C Pneumatic and Mechanical Systems Answer both questions in this section. 4 Fig. 4(a) shows a cam and follower mechanism used as part of a visual display. Roller Follower Camshaft running on plain bearings Gearbox Housing Cam Fig. 4(a) (a) (i) Briefly describe one advantage and one disadvantage associated with the use of a roller follower. [2] (ii) The top section of the gearbox housing can be removed to access the gearbox. State a suitable method to prevent oil leakage when the top section is in place. [1] (iii) The cam is mounted on a horizontal shaft which runs on plain bearings. During operation the cam has a torque of 1.1 Nm. Showing all calculations state how much work is done against friction after 500 revolutions. [3] 4318 10 [Turn over (iv) Showing all calculations state the power expended in overcoming friction when the cam rotates at 120 rev/min. [3] (v) On the pro forma provided (answer number 4(a)(v)), construct a performance/ displacement diagram which would accurately produce the following motion: 0 90 rise 40 mm with uniform velocity 90 120 dwell 120 180 rise 40 mm with uniform velocity 180 360 fall 80 mm with uniform acceleration and retardation. [4] A scale of 1 mm = 1 mm should be used. (b) On the pro forma provided (answer number 4(b)), using appropriate formal drawing techniques, construct a cam profile which would accurately follow the performance/ displacement diagram shown in Fig. 4(b). The diameter of the roller follower is 10mm and the minimum cam diameter is 30 mm. The roller follower is offset to the right of the cam centre line by 10 mm and the cam rotates in a clockwise rotation. [6] Displacement 70mm 0 90 180 270 360 Angular Rotation/Degrees Fig. 4(b) 4318 11 [Turn over Fig. 5 shows parts of a prototype pneumatic recycling station. Used cardboard boxes collected in the hopper are squashed by Cylinder D to reduce their storage size. 4318 Cylinder C Squashed Box Cylinder D Trap Door Conveyor Belt Fig. 5 1 2 Hopper Cylinder A Cylinder B 5 12 [Turn over (a) Briefly state what is meant by the term positive feedback technique when applied to pneumatic systems. [1] (b) (i) The rotary motion is transferred from the motor to the conveyor belt using a cone clutch. Using an annotated sketch outline the main features of a cone clutch. [2] (ii) Briefly describe two methods typically employed to activate clutches. [2] (c) The prototype pneumatic recycling station performs the following sequence once the Start valve is switched: Cylinder A outstrokes to secure box 2. Cylinder B outstrokes pushing box 1 onto the conveyor belt. Cylinder C outstrokes to close the trap door. Cylinder D outstrokes to squash box 1. Cylinder C instrokes. Cylinder D instrokes. Cylinder B instrokes. Cylinder A instrokes. (i) State the pneumatic sequence. [1] (ii) On the pro forma provided (answer number 5(c)(ii), (iii) and (iv)) draw a suitable interlocking/cascade sequential circuit to achieve the desired sequence. [9] (iii) During testing it was found that there was insufficient force to adequately squash the boxes. On the pro forma provided (answer number 5(c)(ii), (iii) and (iv)) add an additional double acting cylinder (Cylinder D1) to operate simultaneously with Cylinder D. [2] (iv) On the pro forma provided (answer number 5(c)(ii), (iii) and (iv)) add any necessary components to enable Cylinders D and D1 to outstroke slowly. [2] THIS IS THE END OF THE QUESTION PAPER 4318 13 [Turn over 935-054-1 M A D EN ED V Carriage slides along test bed A Fig. 1(a)(i) Emergency stop N O I RS E 2 1 4318.04 R 0 Front Sectional View On A-A Plan View Stepper Motor Tennis racket holder I profile Test bed Stepper Motor A Door 1 Position 2 45 End View Stepper Motor Position 1 Test bed Central panel Ball Launcher Chute Front View Tennis Racket Motorised Gearbox B Fig. 1(a)(ii) Door 2 Electromechanical release Hopper Fig. 1(a) For candidates studying Electronic and Microelectronic control systems. 3 Fig. 1(a)(iii) Reverse S tepper Motor F orward M in. Ball Launcher Mechanism Speed Motorised Gearbox A Output shaft Tennis Ball 1 2 Control Panel Emergency stop For candidates studying Electronic and Microelectronic control systems. Fig. 1(a) M ax. S tart Shaft B Angle GCE Advanced Technology and Design Assessment Unit A2 3 January 2009 (for use with Question 1(a)) Do not write your answers on this insert [Turn ove[Turn over 2 M A Carriage slides along test bed A Plan View Front Sectional View On A-A Emergency stop Fig. (b) (i) Fig 11(b)(i) D EN ED E V N O SI R 2 1 4318.04 BM1F1 R 0 I profile Test bed Motorised Gearbox B A Tennis racket holder End View Position 1 Door 1 45 Motorised Gearbox B Position 2 Fig 11(b)(ii) Fig. (b) (ii) Test bed Front View Tennis Racket Central panel Ball Launcher Door 2 Fig. 1(b) )Forocandidates sstudyinggPneumatic and Mechanical control systems. Fig 1 (b F r candidate studyin Pneumatic and Mechanical control systems Output shaft Motor speed 20 rpm 80 rpm Gearbox Motorised Gearbox A Hopper Control Panel Output speed 1 1,9200 r p m 1 , 9 2 rpm Output speed 2 2,400p m 9 6 0 r rpm Output speed 3 1,200p m 4 8 0 r rpm Input Shaft Shaft Shaft B C A Shaft D Shaft B Output Shaft E Start Button Emergency stop Ball Launcher Mechanism Electromechanical release Tennis Ball Fig. (b) (iii) Fig 1 1(b)(iii) Chute For candidates studying Pneumatic and Mechanical control systems. Fig. 1(b) GCE Advanced Technology and Design Assessment Unit A2 3 January 2009 (for use with Question 1(b)) Do not write your answers on this insert [Turn over [Turn over 4318.04 Question No. 1(a)(v) or 1(b)(v) A2V31IN2 Pro forma answer page (answer number 1(a)(v) or 1(b)(v)) ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 January 2009 Candidate Number Candidate Number 71 71 Centre Number Centre Number 4318.04 Question No. 4(a)(v) Displacement A2V31IN3 Pro forma answer page (answer number 4(a)(v)) Angular rotation/degrees ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 January 2009 Candidate Number 71 Centre Number 4318.04 Question No. 4(b) A2V31IN4 Pro forma answer page (answer number 4(b)) ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 January 2009 Candidate Number 71 Centre Number 4318.04 12 Question No. 5(c)(ii), (iii) and (iv) 5 3 START 1 14 A 5 1 3 14 A2V31IN5 Pro forma answer page (answer number 5(c)(ii), (iii) and (iv)) 12 B 12 ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 January 2009 12 5 5 1 1 3 3 14 D 14 C Candidate Number 71 Centre Number

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Additional Info : Gce Technology and Design January 2009 Assessment Unit A2 3, Unit 6: Systems and Control in Product Design
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