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GCE JUN 2008 : (AS 3) Systems and Control: Industrial and Commercial Practices

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ADVANCED SUBSIDIARY (AS) General Certificate of Education 2008 Technology and Design assessing Unit 3 Systems and Control: Industrial and Commercial Practices ASV31 Assessment Unit AS 3 [ASV31] FRIDAY 13 JUNE, MORNING TIME 1 hour 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 all three questions. Answers to Question 3(a)(iv) and Question 3(b)(i) should be made on the A3 pro forma answer pages provided. INFORMATION FOR CANDIDATES The total mark for this paper is 60, including a maximum of 3 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. ASV1S8 3747 1 An arrangement of switches is shown in Fig. 1(a). 6V B A Output 0V Fig. 1(a) (a) (i) Name the type of switches labelled A and B in Fig. 1(a). [1] (ii) State the logic function achieved by the arrangement of the two switches shown in Fig. 1(a) and draw a truth table for this. [2] (iii) The circuit in Fig. 1(a) is to be used as part of an emergency stop system that has been designed to disconnect the high voltage supply to a machine. The complete circuit for the emergency stop system is shown in Fig. 1(b). Explain the operation of the circuit when switch B is momentarily pressed. [4] 6V Single pole relay Switch A High voltage supply Switch B Machine circuit 0V 0V Fig. 1(b) (iv) Briefly explain how the circuit shown in Fig. 1(b) could be reset after either A or B have been momentarily pressed. (Include in your answer an indication of where any additional components would be connected.) [2] ASV1S8 3747 2 [Turn over (b) An astable circuit to control a flashing emergency light is shown in Fig. 1(c). The circuit uses a 555 timer and external components R1, R2 and C. The required output frequency of the circuit is 1 Hertz. 6V R1 10 K Vcc Discharge R2 2.2 K Reset Threshold Trigger Trigger Out Out Output Ground C 0V Fig. 1(c) (i) State what is meant by the term astable . [1] (ii) The circuit in Fig. 1(c) uses a polarised capacitor. Name a suitable type of polarised capacitor for this circuit and give a reason for your choice. [2] (iii) Calculate a suitable value for the capacitor shown in Fig. 1(c) given that T = C(R1 + 2R2)/1.44. [3] (iv) The mark/space ratio for the circuit in Fig. 1(c) is approximately 3:1. Sketch the output waveform for the circuit and indicate the mark, space and time period on the sketch. [4] ASV1S8 3747 3 [Turn over 2 (a) Fig. 2(a) shows a mechanical system which converts rotary motion from turning the handle into linear motion on the rack. (i) State the direction of rotation of the gear at E if the handle moves in a clockwise direction. [1] (ii) State one advantage and one disadvantage associated with using a chain and sprocket in comparison with a pulley system. [2] (iii) One rotation of the pinion gearwheel moves the rack 250 mm. Calculate the distance moved by the rack if the handle is rotated 10 times. [5] (iv) Using an annotated sketch describe how the handle could be attached to the handle shaft using a cotter pin. [3] (v) State one other method commonly used to fix gears to shafts. ASV1S8 3747 4 [1] [Turn over ASV1S8 3747 5 [Turn over Rack Pinion Gearwheel G 60 Teeth F 30 Teeth B Diameter 25 mm Handle Shaft D 25 Teeth C 60 Teeth Fig. 2(a) E 60 Teeth Handle A Diameter 100 mm (b) In your Answer Booklet name and draw a method of transmitting rotary motion from shaft A through to shaft B shown on Fig. 2(b). [3] Shaft A Shaft B Shaft B Shaft A Sh Fig. 2(b) ASV1S8 3747 6 [Turn over (c) Fig. 2(c) shows a cam and follower. (i) Describe the term stroke length when associated with a cam and follower. [2] (ii) Describe the term dwell when associated with a cam and follower. [2] Follower Cam Fig. 2(c) ASV1S8 3747 7 [Turn over 3 Fig. 3(a) shows an incomplete pneumatic system. A 14 12 B 5 1 3 Air Bleed C Y Fig. 3(a) (a) Name the activation methods for the following three-port valves: (i) Activation method at C. [1] (ii) Activation method at Y. [1] The air bleed shown in Fig. 3(a) is used to signal the five-port valve. (iii) Describe the operation of each of the components in the air bleed circuit. [4] (iv) On the proforma provided (Answer No. 3(a)(iv)) complete the circuit to enable the double acting cylinder to outstroke once A and B or C have been activated. [4] ASV1S8 3747 8 [Turn over D Fig. 3(b) (b) (i) On the proforma provided (Answer No. 3(b)(i)) complete the circuit shown in Fig. 3(b) to enable the single acting cylinder to outstroke and instroke slowly once three-port valve D has been activated. [4] (ii) Briefly describe one further method of controlling the stroke speed when using a double acting cylinder. [1] (c) A double acting cylinder is supplied with an air pressure of 0.5 N/mm2 and has a piston diameter of 30 mm. Calculate the force during the instroke if the piston rod has a radius of 3 mm. Please assume = 3.14. [4] ASV1S8 3747 9 [Turn over THIS IS THE END OF THE QUESTION PAPER ASV1S8 3747 10 [Turn over ASV1S8 0000 11 [Turn over S 6/07 531-013-1 ASV1S8 3747 12 [Turn over A 14 12 5 1 B 3 Air Bleed C Y Fig3(a) D Fig 3(b)

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Additional Info : Gce Technology and Design June 2008 AS 3, Unit 3 – Systems and Control: Industrial and Commercial Practices
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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