GCSE Design and Technology Electronic Products

Transcription

1 GCSE Design and Technology Electronic Products 45401/ Unit 1 Written Paper Mark scheme 4540 June 2017 Version: 1.0 Final

2 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Assessment Writer. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students reactions to a particular paper. Assumptions about future mark schemes on the basis of one year s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this mark scheme are available from aqa.org.uk 2 of 19 Copyright 2017 AQA and its licensors. All rights reserved. AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre.

3 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Level of response marking instructions Level of response mark schemes are broken down into levels, each of which has a descriptor. The descriptor for the level shows the average performance for the level. There are marks in each level. Before you apply the mark scheme to a student s answer read through the answer and annotate it (as instructed) to show the qualities that are being looked for. You can then apply the mark scheme. Step 1 Determine a level Start at the lowest level of the mark scheme and use it as a ladder to see whether the answer meets the descriptor for that level. The descriptor for the level indicates the different qualities that might be seen in the student s answer for that level. If it meets the lowest level then go to the next one and decide if it meets this level, and so on, until you have a match between the level descriptor and the answer. With practice and familiarity you will find that for better answers you will be able to quickly skip through the lower levels of the mark scheme. When assigning a level you should look at the overall quality of the answer and not look to pick holes in small and specific parts of the answer where the student has not performed quite as well as the rest. If the answer covers different aspects of different levels of the mark scheme you should use a best fit approach for defining the level and then use the variability of the response to help decide the mark within the level, ie if the response is predominantly level 3 with a small amount of level 4 material it would be placed in level 3 but be awarded a mark near the top of the level because of the level 4 content. Step 2 Determine a mark Once you have assigned a level you need to decide on the mark. The descriptors on how to allocate marks can help with this. The exemplar materials used during standardisation will help. There will be an answer in the standardising materials which will correspond with each level of the mark scheme. This answer will have been awarded a mark by the Lead Examiner. You can compare the student s answer with the example to determine if it is the same standard, better or worse than the example. You can then use this to allocate a mark for the answer based on the Lead Examiner s mark on the example. You may well need to read back through the answer as you apply the mark scheme to clarify points and assure yourself that the level and the mark are appropriate. Indicative content in the mark scheme is provided as a guide for examiners. It is not intended to be exhaustive and you must credit other valid points. Students do not have to cover all of the points mentioned in the Indicative content to reach the highest level of the mark scheme. An answer which contains nothing of relevance to the question must be awarded no marks. 3 of 19

4 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Question Marking Guidance Marks Design requirements up to 6 marks (3 x 2 marks) Award 1 mark for a simple, suitable requirement. Award a further mark if the requirement has a relevant explanation. Note: Do not credit requirements duplicated from the brief. I.e. references to attaching to the user, and weatherproofing. Examples of a 1 mark response: 1(a) It should be battery powered. It should be lightweight. The circuit should be securely fixed. It should have a colourful logo. It should be made from acrylic/polycarbonate/aluminium/other suitable specific materials. The product should be comfortable to wear. 6 Marks Examples of a 2 mark response: It should be battery powered so it is light and portable. It should be lightweight so it can be easily carried and not get in the way. The circuit should be fixed down so it doesn t rattle around and get damaged. It will be made from acrylic/polycarbonate/aluminium/other suitable specific materials as it is water resistant. It should be comfortable to wear so it doesn t rub or cause an injury. 1(b)(i) Completion of a system diagram up to 3 marks Award 1 mark each for a suitable component that meets the brief. Input components: PTM, SPST, SPDT, LDR, vibration sensor, tilt switch or similar suitable component. N.B. Do not accept just switch. Process components: 555, monostable, astable, transistor, microcontroller, PIC, genie, 4017, decade counter, 4026, op. amp, latch, counter or similar suitable process component. Output components to give a visible output: LED, lamp, bulb, flashing LED, EL material or similar. 3 Marks 4 of 19

5 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Discussing the component s suitability for the safety product up to 4 marks Candidates could make references to any of the named components in the system diagram in 1(b)(i). Award 1 mark for each simple, unexplained statement made. Award 2 marks for an explained or justified statement. Note: Candidates can gain all 4 marks by making 4 simple statements. Examples of simple statements worth one mark: 1(b)(ii) the switch turns the circuit off when it is not being used. an LDR will automatically turn the circuit on in the dark. an astable will create a flashing output. a counter will make the outputs more noticeable. an LED is bright. an LED is very small. a flashing LED is clearly visible. a bulb can be very bright. 4 Marks Examples of justified points worth two marks: the switch will turn the product off when it is not being used so the battery will last longer. the LDR will turn the product on automatically so the user is much safer as he/she might forget to switch it on. an astable will make the LED flash which will more noticeable in the dark. an LED is very bright and can be seen from a long distance. an LED is a long-lasting component compared to a bulb. LEDs are lightweight, so the product will be light and easy to carry. Bulbs are easy to replace if the break as they simply screw into a holder. Bulbs are easier to replace than an LED which would need re-soldering. 5 of 19

6 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Generating two ideas for the safety product up to 8 marks Mark both designs holistically, giving credit for best features. 7-8 marks Two well-communicated and distinctly different ideas meeting the brief. It is clear how the product is firmly secured to the user, and how visibility is improved. The sketches are good quality, and the notes and labels enable the ideas to be easily interpreted. 1(c) 1(d) 5-6 marks Two different ideas that still meet the brief, with clear evidence of how visibility is generated. The means of attaching the product is discussed, but may lack clarity, and the sketches are harder to interpret. The sketches contain brief notes. 3-4 marks Only 1 idea has been drawn, but is of a standard comparable to the top band criteria. Or 2 ideas which are quite similar. The means of attachment is not very clear, and it may not be obvious what the product is being attached to. It is still clear how the product improves visibility. The sketches are of a basic level of quality with limited annotation. 1-2 marks A very basic attempt with poor clarity of communication. 0 marks Nothing worthy of credit. Details of case construction up to 6 marks Materials up to 2 marks. Award 1 mark for a generic material such as wood, metal, plastic. Award 2 marks for a specific material such as acrylic, HIPS, polystyrene, aluminium, steel. Securing of output components up to 2 marks. Award 1 mark for basic detail, including drilled hole, fixed to PCB, glued in place. Award 2 marks for detailed response, including use of LED clip or bezel, interference fit hole, soldered to PCB and use of opaque case, MES bulb holder or similar suitable response. Award 1 mark for an indication, through a drawn feature or notes, of how the product is powered. 8 Marks 6 Marks 6 of 19

7 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Award 1 mark for a feature, either drawn or annotated, which enables the product to be weatherproof. Accept a reference that a named material is waterproof or weatherproof. 7 of 19

8 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Testing and evaluating a product up to 4 marks For each method: 1 mark for simple reference to one method. 2 marks for a justified or explained method. 1(e) 1(f) 2(a)(i) Testing and evaluating methods include: Checking the visibility of the user from various distances. Checking the visibility of the user in various light conditions. Giving the product to a user and asking for their opinions and feedback. Testing the battery life of the product. Conducting a drop test to check for sturdiness and reliability. Testing the reliability in harsh weather conditions. Similar suitable responses. Describing methods of disposing of the safety product when it is no longer needed up to 4 marks 1 mark for each simple reference to one method. 2 marks for a justified or explained method. Disposal methods include: recycling of the case. passed on to another user. the battery is to be placed in a recycling bin. the battery is taken to a recycling facility. the materials can be reused in another product. integrated chips or other components can be taken out and used in another circuit. similar relevant points. Component identity up to 3 marks N.B. The words do not need to be spelled totally correctly to gain a mark e.g. accept capaciter or capacito. Image 1: Electrolytic capacitor, or polarised capacitor, or just capacitor 1 mark Image 2: 7 segment display or LED display 1 mark Image 3: Accept: Piezo transducer piezo sounder piezo sounder transducer piezo electric transducer piezo 4 Marks 4 Marks 3 Marks 8 of 19

9 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 piezo crystal oscillator all worth 1 mark 9 of 19

10 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Question Marking Guidance Marks Symbols up to 3 marks Symbols drawn as per the specification N.B. Orientation is not important. The symbols can be drawn facing in any direction. Bell 1 mark 2(a)(ii) NOT gate 1 mark 3 Marks Motor 1 mark N.B. the circle must have the 2 lines coming out of it. SPST switches in series and parallel up to 2 marks Award 1 mark for a correct SPST symbol. Note: accept any recognisable symbol for an SPST e.g. 2(b)(i) Award 1 mark if the switches are connected in series such that the lamp is lit when both are thrown. (if the switch symbol is incorrect, still award the mark if the switches are in series). 2 Marks 10 of 19

11 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Award 1 mark if the switches are connected in parallel such that the lamp is lit when either is thrown. Accept PTM symbol in this question. 2(b)(ii) 1 Mark 2(b)(iii) Identifying the OR function circuit 1 mark Award 1 mark for ticking circuit B. Labelling a diode and showing current flow up to 2 marks. Award 1 mark for correctly labelling the anode and cathode leads. Award 1 mark for correctly showing the direction of current flow. 1 Mark 2(c) 2 Marks 2(d)(i) 2(d)(ii) Purpose of the dot on a SIL network 1 mark Shows the orientation of the network. Identifies the common pin. Shows which way around to place the SIL. Shows pin 1 Any suitable, similar response. Using SIL networks in circuits up to 2 marks. 1 mark for a simple, unjustified response. 2 marks for a justified or explained point. Advantages: Faster circuit assembly Smaller circuit boards 1 Mark 2 Marks 11 of 19

12 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Easier assembly of a circuit Fewer holes need to be drilled The network can be re-used/re-cycled Note: Award no marks for unqualified, one-word responses such as quick, easy, cheap, small 12 of 19

13 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Question Marking Guidance Marks Stating in which block the following would be found up to 3 marks 3(a) 3(b)(i) Award 1 mark for each correct response. LEDs - Output Monostable Timer A 4017 I.C. - Counter Drawing the symbol of a 2 input AND gate 1 mark N.B. Orientation is not important. The symbol can be drawn facing in any direction. The vertical line on the left hand side must be a straight line. There must be 2 input leads and 1 output lead shown. 3 Marks 1 Mark 3(b)(ii) Completing the truth table for a two input AND gate up to 3 marks Award 1 mark for each correct line. B A Q Marks 13 of 19

14 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Showing how the resistance of an LDR varies up to 2 marks 1 mark for a descending straight line 3(c) 2 Marks 2 marks for a descending curved line as shown 3(d) Award 1 mark for ticking Rises. 1 Mark 14 of 19

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16 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Question Marking Guidance Marks Completing the breadboard up to 6 marks Award 1 mark for each correct connection. Pin 1 to 0V Pin 2 to junction of R and C Buzzer connected to pin 3 Pin 4 to +V Pin 6 to junction of R and C, or to pin 2 Pin 7 to junction of the 2 resistors Note: if wires share a hole with a pin or connection, do not award mark for the first instance only. 4(a) 6 Marks Reasons for using a breadboard up to 4 marks Award 1 mark for each simple response. 4(b) No soldering required. Components can be changed easily. The circuit can be tested or prototyped A computer or software is not needed. A good way of learning about, and understanding of, circuits. Components can be re-used. Similar suitable responses. 16 of 19

17 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Award 2 marks for an explained reason. 4(b) continued No soldering needed so fewer tools and less equipment needed. Components like resistors can be changed to test different designs. Computers and software are not needed to test a circuit so less expensive. Components can be removed and re-used. It is testing in the real-world so you know a circuit would actually work. A wide range of circuits can be made provided you have the components. Low start-up costs compared to using CAD. Similar suitable responses. 4 Marks 4(c) 4(d) Astable frequency calculation up to 5 marks Calculate the frequency of the output pin 3 if R1 = 10k, R2= 56k and C= is 10µF. 1 mark for the formula 1 mark for correct substitution of both resistor values, and demonstrating an understanding of k. [ ( 10, x 56,000) or, if using MΩ x μf, ( )] 1 mark for correct substitution of cap. value [ 10/1,000,000 or , or 10 x10-6, or if using MΩ, x 10] 1 mark for correct answer 1.18 (accept if rounded-up to 1.2) 1 mark for units Hertz Suggest two modifications that would improve the quality of soldering and ease assembly of the PCB up to 2 marks Award 1 mark for each simple response. Modifications include: Thicker copper tracks. Addition of text or labelling. Larger solder pads. Spreading the components out. Make the gaps between the tracks bigger. Addition of hole(s) for use of PCB pillars or screws. Addition of strain relief holes. Accept responses that don t specifically improve quality of soldering or ease of assembly, but are sensible modifications that can be made to improve the overall quality of the circuit, and demonstrate good practice. Do not accept rotating the IC or re-designing the layout without some 5 Marks 2 Marks 17 of 19

18 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 justification. Modifications include; Describe a safety hazard of an etching process, and a precaution that should be taken. Award 1 mark for a relevant hazard. Hazards include: 4(e) 4(f) Chemicals, or acid, or ferric chloride in the eye. Damage to eyes caused by UV light. Chemicals, or acid, or ferric chloride splashing onto skin. Clothes or aprons could get splashed or stained. The fumes from etchant are not good for you. Award 1 mark for a suitable precaution relevant to the named hazard. Precautions include: Wearing of glasses/goggles. Working in a well-ventilated area. Wearing an apron to cover clothing. Wearing of gloves. Wearing a dust mask or breathing mask. Give three advantages of using stripboard when constructing a circuit up to 3 marks Award 1 mark for each simple response Note: an unqualified cheaper or quicker is not worthy of a mark. Advantages include: No chemicals needed to make the board No need for PCB design software Less equipment needed No need to drill holes in the board UV light box and etching equipment not needed A cheaper process as less equipment needed A more permanent prototype than a breadboard. 2 Marks 3 Marks 18 of 19

19 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE of 19

20 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Question Marking Guidance Marks Calculate the time constant for the monostable if R1 is 33k C1 is 100µF up to 4 marks. 1 mark for formula T= R x C 5(a) 1 mark for demonstrating that 33,000 has been used 1 mark for demonstrating that 100/1 million, or , or 100x 10-6 has been used. 1 mark for 3.3 seconds or 3,300 milliseconds. ( unit needed for mark) [note: x 100 is also correct ( 0.033MΩ x 100µF)] Explain the function of resistor A and resistor B in the circuit up to 4 marks Resistor A up to 2 marks Award 1 mark for each simple response, or 2 marks for an explained response, where some further detail has been added. Responses include: 4 Marks 5(b) It is a pull-up resistor Keeps pin 2 high Prevents the monostable from accidental triggering Prevents pin float Limits current going through the PTM to prevent a short circuit. 4 Marks Resistor B up to 2 marks Award 1 mark for each simple response, or 2 marks for an explained response, where some further detail has been added. Responses include: It is a current limiting resistor Prevents damage/provides protection for the transistor Stops too much current going to the transistor 5(c) Explain why a relay is used in the circuit up to 2 marks Award 1 mark for each simple response, or 2 marks for an explained response that contains further technical detail.. Responses include: 2 Marks Connects the 2 circuits together A 555 will not drive a solenoid 20 of 19

21 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 There is a low voltage and high voltage circuit Prevents damage to components or the circuit. 5(d) Discuss the social, moral and cultural issues of using CCTV cameras in and around a school up to 8 marks Issues that can be discussed include: Helping to improve the safety of pupils and staff. Helping to improve the behaviour of pupils. Helping to prevent vandalism, damage, littering. Helping in the identification of pupils who may have done something wrong. Helping to prevent un-authorised visitors entering the site. Discussion of negative effects are worthy of equal merit. For example: Invasion of privacy. Cost to the school for installation and monitoring. Pupils feeling that they are not trusted or treated with respect. Cameras are sometimes found in inappropriate or private areas like toilets of changing rooms. Concerns along cultural or religious grounds. Consider the content and quality of communication. Marks awarded as follows: 8 Marks Note: a wholly bullet-point response can gain a maximum of 6 marks. To gain 7-8 marks, both positive and negative effects of the use of CCTV need to be included in the discussion. 0 marks no answer worthy of credit. 1-2 marks Limited coverage. Just one issue discussed. Many spelling and punctuation mistakes. Limited use of technical vocabulary. 3-4 marks Discussion of advantages and disadvantages of two issues. Some spelling, punctuation or grammar errors. Poor structure of answer, and repetition made. 5-6 marks Good coverage and a well-structured response. Advantages and/or disadvantages for at least two issues discussed using specific terms and 21 of 19

22 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 vocabulary. There may be one or two spelling or punctuation mistakes, or minor grammatical errors. 7-8 marks Excellent coverage and depth of answer, and a well-structured response. Several issues discussed in good detail. Excellent spelling, grammar and punctuation. Avoidance of repetition. A top band response must include both positive and negative effects. Question Marking Guidance Marks Give two properties of steel that make it suitable for the casing up to 2 marks Award 1 mark for each suitable property: Properties include: 6(a) Strong Hard Durable Hard-wearing Long component life Can be welded, riveted or other means of joining A low cost material Readily available Can be painted, or have other different finishes applied. It is fire or heat resistant 2 Marks Note: Do not accept won t rust or corrosion resistant or similar unless a surface finish has been mentioned. 6(b) Explaining two reasons for using a laser cutter up to 4 marks Award 1 mark for a simple, unexplained point. Award 2 marks if a point is explained or justified. Advantages include: 4 Marks The part can be batch produced Many identical items can be made More accurate than cutting by hand 22 of 19

23 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 The edges of the acrylic have a smooth finish A design can be modified if there is an error A laser can be used to cut and engrave A prototype can be quickly made The laser cutter may be quicker than cutting the front by hand Similar suitable responses. State two advantages of using lamps and LEDs up to 4 marks Award 1 mark for each correct response. This question is not asking candidates to compare bulbs and LEDs, but to say why a bulb or LED would be used in a product. Comparison is valid, but not necessary. Also, a one-word bright is not sufficient for a mark. If a candidate states that a bulb or LED is very bright and easily seen, or similar clarification, award a mark. Other advantages of a lamp include: 6(c) Emits light all around Available in many sizes and power ratings Easy to replace if broken Readily available if justified e.g. easily available in shops. Low weight Low cost 4 Marks Advantages of LEDs include: Small size Very low weight Available in many colours Don t get hot Low current devices Last a long time Low cost Durable; resist damage if knocked or dropped. 7(a) Comparing the use of a melody generator IC and a microcontroller up to 4 marks Award 1 mark for each simple statement. Statements could include: A melody generator IC is much smaller. Requires less soldering. Can only play one tune. Microcontroller circuits can play different tunes. A melody generator circuit could be much smaller. Microcontrollers can also switch other outputs at the same time. Similar suitable and relevant point. Microcontrollers can be used for other functions. 4 Marks 23 of 19

24 MARK SCHEME GCSE DESIGN AND TECHNOLOGY: ELECTRONIC PRODUCTS JUNE 2017 Award 2 marks for each justified statement. Statements could include: A melody generator is a smaller component so the circuit board could be smaller/cheaper. A melody generator has fewer leads so less soldering is needed. Microcontrollers can play or be programmed to create different tunes so the toy could be more interesting. A microcontroller can also be programmed to perform other functions and play tunes in response to various inputs. 7(b) Microcontroller program up to 6 marks Award: 1 mark for LED on at the start 1 mark for decision with yes/no routes for input switch A / input1 1 mark for decision with yes/no routes for input switch B / input2 1 mark for both tune routines correctly called-up 1 mark for a return from both routines to a correct part of the program 1 mark for return to a correct part of the program if neither switch is pressed. Flowchart, Basic programs or other programming systems acceptable. Example of a flowchart program solution: 6 Marks 24 of 19

25 MARK SCHEME GCSE DESIGN AND TECHNOLOGY ELECTRONIC PRODUCTS JUNE 2017 Example of a basic program solution: start label_1: out %xxxxx1xx if input 1 = 1 then goto label_2 if input 3 = 0 then goto label_1 tune 4, ' Play tune B goto label_1 label_2: tune 4, ' Play tune A goto label_1 25 of 19