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GCE MAY 2008 : (A2 3) Systems and Control in Product Design

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ADVANCED General Certificate of Education 2008 Technology and Design Assessment Unit A2 3 Unit 6 Systems and Control in Product Design A2V31 assessing [A2V31] TUESDAY 20 MAY, 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 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) and Questions 4(b), 5(c)(i) and (ii) should be made on the A3 pro forma answer pages provided. You are provided with an insert for use with Question 1. 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. A material data sheet is provided. A2V3S8 3748 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) To facilitate the game of Ten Pin bowling control systems are used to display information, to clear the lane of any fallen pins, to reset pins and return the bowl ready for play. Fig. 1(a) shows a control system which completes the following sequence after the player throws their first bowl. The pin station table lowers to collect any standing pins and then is raised so that the motorised sweeper will push any fallen pins into the pin pit. The pins move onto the elevator and at the top they go down a chute on to one of two conveyor belts. The conveyor belts carry the pins and place them into each of the pin stations. Once fully loaded, the floor rotates causing the bars to pivot and turn the bowling pins upright before lowering them onto the lane. After each throw the bowl falls into the pin pit where it is filtered into a return chute. It moves down the return chute and stops at the bottom of the elevator. The elevator lifts the bowl up and releases it onto the holding station ready for play. (i) Using the answer booklet briefly outline four distinctly different safety specification points relating to the motorised conveyor system used to return the bowls. [4] (ii) With reference to Fig. 1(a) briefly outline three main properties that make mild steel suitable for the housing. [3] (iii) Briefly outline how the housing would be manufactured from a sheet of mild steel. [2] (iv) Identify and briefly explain one suitable semi-permanent method that could be used to secure the housing to the wooden floor of the lane. [2] A2V3S8 3748 2 [Turn over (v) On the pro forma provided 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) At the beginning of each game a number is displayed which represents the number of frames played by an individual player. This number appears on large seven segment displays. A frame is when one player has thrown two bowls consecutively. Design a counting system that will display the number of frames played by an individual player. (Assume a player throws two consecutive bowls for each frame.) [12] 3748 The sweeper arm is operated by a high voltage motor/gearbox. Assuming a 5 volt, 10 millisecond pulse is produced when a bowl is detected, design a circuit that will switch on the sweeper arm motor but only when the pin station table is fully raised. [6] A2V3S8 Design a circuit that will detect the presence of a bowl entering the pin pit and provide a 5 volt pulse with a duration 10 milliseconds. [4] Design a system that will stop the bowl elevator belt when the holding station is full. The elevator belt should start again when a bowl has been removed from the holding station. [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) To facilitate the game of Ten Pin bowling control systems are used to display information, to clear the lane of any fallen pins, to reset pins and return the bowls ready for play. Fig. 1(b) shows a control system which completes the following sequence after the player throws their first bowl. The pin station table lowers to collect any standing pins and then is raised so that the motorised sweeper will push any fallen pins into the pin pit. The pins move onto the elevator and at the top they go down a chute on to one of two conveyor belts. The conveyor belts carry the pins and place them into each of the pin stations. Once fully loaded, the floor rotates causing the bars to pivot and turn the bowling pins upright before lowering them onto the lane. After each throw the bowl falls into the pin pit where it is filtered into a return chute. It moves down the return chute and passes through a set of rotating brushes and stops at the bottom of the elevator. The elevator lifts the bowl up and releases it onto the holding station ready for play. (i) Using the answer booklet briefly outline four distinctly different safety specification points relating to the motorised conveyor system used to return the bowls. [4] (ii) With reference to Fig. 1(a) briefly outline three main properties that make mild steel suitable for the housing. [3] (iii) Briefly outline how the housing would be manufactured from a sheet of mild steel. [2] (iv) Identify and briefly explain one suitable semi-permanent method that could be used to secure the housing to the wooden floor of the lane. [2] A2V3S8 3748 4 [Turn over (v) On the pro forma provided 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 pneumatic system that will control the correct sequence (see table (i)) in the insert for the pin setter, release mechanism and the sweeper during play. [12] 3748 design a suitable bearing and housing arrangement that will house the shaft that is driving the conveyor belt (see enlarged view). [6] A2V3S8 design a suitable mechanism that will provide a positive drive from the shaft driving the elevator belt to the shaft driving the brushes (see enlarged view). [4] design a suitable mechanism which is driven from the shaft on the motorised gearbox that will open the door through 90 degrees. [5] 5 [Turn over Section B Electronic and Microelectronic Control Systems Answer both questions in this section. 2 A circuit for indicating the temperature in a plant propagator is shown in Fig. 2(a) 5V Hot LED o/p1 Rth PIC i/pl o/p2 Safe LED Cold LED Rs 1k o/p3 0V Fig. 2(a) (a) (i) Briefly explain why the thermistor (Rth) and the resistor (Rs) are placed in the series arrangement shown in Fig. 2(a). [1] (ii) The thermistor shown in Fig. 2(a) has a resistance of 2500 at 10 C and a resistance of 1000 at 30 C. Calculate the corresponding voltage values at i/p1. [2] (iii) The PIC shown in Fig. 2(a) has an analogue input port (i/p1) with a voltage range from 0 V to 5 V and a digital equivalent range from 0 to 255. Calculate the digital values that correspond to temperatures of 10 C and 30 C. [4] (iv) Write a sub-routine that will check the analogue port every 60 seconds and illuminate the appropriate LED. Assume that the safe temperature range in the plant propagator is between 10 C and 30 C. [4] A2V3S8 3748 6 [Turn over (b) A power supply for the circuit shown in Fig. 2(a) has been proposed. It consists of a 6 V unregulated power supply unit and a Zener diode regulator. The proposed circuit is shown in Fig. 2(b) and must provide an output current of 20 mA. Rs 240 V 50 Hz 20 mA 5 mA 6 V unregulated power supply unit 5 V Zener diode Fig. 2(b) (i) State and briefly explain the function of the three main parts that make up an unregulated power supply unit. (ii) Calculate an appropriate value of the series resistor Rs. A2V3S8 [6] [2] 3748 7 [Turn over 3 A prototype design for a device to measure the flow rate of a river is shown in Fig. 3(a). The design uses a paddle wheel which drives a shaft with a disc fixed to it. A slotted opto switch is to be used in conjunction with a hole in the disc. During preparatory tests it was found that the disc rotated at 5 revolutions per second when the river flow speed was 10 kph. Disc Paddle wheel Flowing water Fig. 3(a) (a) (i) Briefly explain the operation of a slotted opto switch. [3] (ii) Suggest a suitable alternative method of detecting each revolution of the disc and justify your choice. [3] A2V3S8 3748 8 [Turn over In the diagram below Fig. 3(b) the pulses from the slotted opto switch are counted for a period of 20 seconds and the river flow speed is indicated on an LCD display. The LCD displays this speed until it is reset. Slotted opto switch Frequency divider ( N) 20 Seconds LCD Display Logic Gate t Fig. 3(b) (b) (i) State the purpose of the AND gate in Fig. 3(b). [2] (ii) Determine the number of pulses generated in the 20 second time period for a river flow rate of 10 kph and then determine the factor this number must be divided by to display the river flow rate in kph. [4] (iii) Design a frequency divider circuit based on the binary counter shown in Fig. 3(c). Assume that Qa is the Least Significant Bit (LSB). [5] Reset Clk Qa Qb Qc Qd Fig. 3(c) (c) The LCD display requires a reset from a falling edge trigger. Sketch a suitable arrangement of components to achieve this. A2V3S8 3748 9 [2] [Turn over Section C Pneumatic and Mechanical Control Systems Answer both questions in this section. 4 Modern motor vehicles contain many mechanical components and systems. (a) Using an annotated sketch explain what is meant by the following terms associated with gears. (i) Pitch circle diameter. [1] (ii) Pitch point. [1] (iii) Calculate the output speed on shaft X shown in Fig. 4(a) if the motor rotates at 240 rev/min. [4] A2V3S8 3748 10 [Turn over A 60 Teeth Motor 240 rev/min C 30 Teeth B 30 Teeth D 20 Teeth I 40 Teeth E 60 Teeth Shaft X H 40 mm Dia F 60 Teeth G 120 mm Dia Fig. 4(a) A2V3S8 3748 11 [Turn over Windscreen Wipers Motor Shaft Y Fig. 4(b) (b) Fig. 4(b) shows an incomplete prototype windscreen wiper system. On the proforma provided (Answer No 4(b)) name and sketch a suitable linkage arrangement which could convert the rotary motion of the motor from shaft Y into the necessary oscillating motion of the wipers. [4] (c) Fig. 4(c) shows an incomplete prototype drive system to transmit motion from shaft X through to the wheel. (i) Using an annotated sketch name and draw a mechanism which will accommodate the axial shaft movement between shaft X and P. [2] (ii) Using an annotated sketch name and draw a mechanism which will transmit rotary motion from shaft P to shaft M maintaining a steady speed. [2] (d) Briefly describe the main characteristics of a multigrade oil. A2V3S8 3748 12 [2] [Turn over Shaft X Shaft P Shaft M Wheel Fig. 4(c) (e) A gearbox and housing has a mass of 75 kg and is lifted vertically out of a vehicle. It gains 1500 kJ in potential energy before coming to rest. Calculate the vertical height through which the gearbox and housing is lifted. Assume g = 9.81 m/s2. [3] A2V3S8 3748 13 [Turn over 5 (a) When the air pressure inside a compressed air storage/receiver tank reaches a certain limit the pump and motor should stop. Using an annotated sketch briefly describe the function of a device to prevent the pressure from reaching dangerous levels if the pump fails to stop. [2] (b) A double acting cylinder has a stroke length of 140 mm and exerts a force during the outstroke of 500 N. Assuming an efficiency of 95%, calculate the work done on the outstroke. [3] Fig. 5 shows an incomplete pneumatic circuit. C 12 B 14 A 14 12 14 12 START 12V 0V Fig. 5 A2V3S8 3748 14 [Turn over (c) (i) On the proforma provided (Answer No 5(c)(i)+(ii)) complete the circuit to enable the following sequence to be achieved once the Start button has momentarily been pressed: A+ B+ C+ Slowly A B C . [6] (ii) On the proforma provided (Answer No 5(c)(i)+(ii)) modify the circuit to enable the double acting cylinders to be stopped as a safety feature at any time during the operation of the sequence. [3] (d) Briefly describe a pneumatic method which could be attached to double acting cylinders and be used to lift small flat objects. [1] (e) One method of holding objects firmly in place is to use the force exerted by a double acting cylinder. A toggle clamp is another method used to hold objects firmly in place. Using an annotated sketch draw a toggle clamp in both the locked and unlocked positions. [2] (f) Briefly describe one main advantage associated with hydraulic systems and one main advantage associated with pneumatic systems. [2] THIS IS THE END OF THE QUESTION PAPER A2V3S8 3748 15 [Turn over S 6/07 529-037-1 A2V3S8 3748.03INS1 Do not write your answers on this insert Return chute Pin elevator Sweeper arm motor Pin pit Chute Sweeper Arm Pin station table 7 2 Sweeper Conveyor belts 4 8 1 5 6 10 Mild steel housing Cleaning unit Bowl elevator belt Wooden floor lane Display board 3 9 Seven segment displays Motor Elevator system to return ball For candidates studying Electronics and Microelectronic control systems. Fig. 1(a) Holding station GCE Advanced Technology and Design Assessment Unit A2 3 Summer 2008 (for use with Question 1(a)) A2V31IN1 [Turn ove[Turn over Do not write your answers on this insert 2 Shaft Motorised gearbox Return chute Door Bars Pin pit Chute 10 9 8 6 5 Pin elevator 2 3748.03INS1 4 3 Pin station table Pin station table Motor Shaft Elevator belt Sequence Pin station table lowers slowly Cylinder activates to release the ten pins Pin station table rises slowly long delay for shot Pin station table lowers slowly Cylinder activates to grip remaining pins Pin station table rises slowly Pin station table lowers slowly Cylinder activates to release the remaining pins Pin station table rises slowly Table (i) Cleaning unit Wooden floor lane Shaft to Shaft drive brushes Brushes Sweeper Conveyor belts Mild steel housing Area for bearing Elevator system to return ball For candidates studying Pneumatic and Mechanical control systems. 1 A2V3S8 BM1F1 7 Fig. 1(b) Holding station GCE Advanced Technology and Design Assessment Unit A2 3 Summer 2008 (for use with Question 1(b)) [Turn over A2V3S8 3748.02 INS2 Question No. 1(a)(v) or 1(b)(v) Pro forma answer page (answer number 1(a)(v) or 1(b)(v)) ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 Summer 2008 A2V31IN2 Candidate Number 71 Centre Number A2V3S8 3748.02 INS3 Question No. 4(b) Pro forma answer page (answer number 4(b)) Shaft Y Windscreen Wipers ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 Summer 2008 A2V31IN3 Candidate Number Candidate Number 71 71 Centre Number Centre A2V3S8 3748.02 INS4 Question No. 5(c)(i) and (ii) 12 0V 12V C 14 START 14 Pro forma answer page (answer number 5(c)(i) and (ii)) 12 B 12 ADVANCED LEVEL TECHNOLOGY AND DESIGN Assessment Unit A2 3 Unit 6 Summer 2008 A 14 A2V31IN4 Candidate Number 71 Centre Number

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Additional Info : Gce Technology and Design May 2008 Assessment Unit A2 3, Unit 6: Systems and Control in Product Design
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