2015 Technological Studies. Advanced Higher. Finalised Marking Instructions

Transcription

1 05 Technological Studies Advanced Higher Finalised Marking Instructions Scottish Qualifications Authority 05 The information in this publication may be reproduced to support SQA qualifications only on a non-commercial basis. If it is to be used for any other purposes written permission must be obtained from SQA s NQ Assessment team. Where the publication includes materials from sources other than SQA (secondary copyright), this material should only be reproduced for the purposes of examination or assessment. If it needs to be reproduced for any other purpose it is the centre s responsibility to obtain the necessary copyright clearance. SQA s NQ Assessment team may be able to direct you to the secondary sources. These Marking Instructions have been prepared by Examination Teams for use by SQA Appointed Markers when marking External Course Assessments. This publication must not be reproduced for commercial or trade purposes.

2 Part One: General Marking Principles for: Technological Studies Advanced Higher This information is provided to help you understand the general principles you must apply when marking candidate responses to questions in this Paper. These principles must be read in conjunction with the specific Marking Instructions for each question. (a) (b) Marks for each candidate response must always be assigned in line with these general marking principles and the specific Marking Instructions for the relevant question. If a specific candidate response does not seem to be covered by either the principles or detailed Marking Instructions, and you are uncertain how to assess it, you must seek guidance from your Team Leader/Principal Assessor. Marking should always be positive ie, marks should be awarded for what is correct and not deducted for errors or omissions. GENERAL MARKING ADVICE: Technological Studies Advanced Higher The marking schemes are written to assist in determining the minimal acceptable answer rather than listing every possible correct and incorrect answer. The following notes are offered to support Markers in making judgements on candidates evidence, and apply to marking both end of unit assessments and course assessments. Page

3 Part Two: Marking Instructions for each Question Section A Q (a) Marks (b) 6 (c) 04 = 0 = 0 (0) Page 3

4 Q (a) (i) Marks Slow Response () Offset () (ii) Oscillations () No offset () (iii) Fewer oscillations () Settles more quickly () (b) PID control adds extra functions to proportional control in ideal conditions. While proportional tries to minimise the error, PI eliminates it, but PID eliminates it with a faster response time. 3 (9) Page 4

5 Q3 (a) I = bd 3 / = / = mm 4 y = 50 mm M = σ I / y = / 50 3 M = Nmm Marks L M 8 L = [ 8M/ ] / = [ 8 36,666, / 7 65 ] / L = 6 9 m 0 (b) M/I = σ/y = E/R R = ( E y ) / σ = ( ) / 0 R = 44 5 m 3 (c) Reduced weight Increased strength/weight ratio Any one point per mark. (5) Page 5

6 Q4 (a) 0 digital inputs Analogue input ADC LCD output Flash/EEPROM Internal memory 4 outputs Internal clock Marks Any six points mark each 6 (b) Plan the program Write the code Assemble the code Download to PIC Test the program text editor assembler programmer Download cable Any six 6 () Q5 (a) Sub A = RC circuit, charges via K & M Sub B = voltage divider, provides /3 & /3 reference voltages Sub C = two comparators, comparing capacitor voltage with ref voltages Sub D = SR bistable, set and reset by comparators Sub E = DPDT relay, used to:- discharge capacitor when voltage > /3, charge up capacitor when voltage < /3, provide flashing switching for lamp (b) Limited frequency range due to being a mechanical device. Wear of components means it has a finite life (3) Page 6

7 Marks Q6 (a) main: bcf PORTB,3 ;mux measure left wheel call adcread movwf LEFTSPEED bsf PORTB,3 call adcread movwf RIGHTSPEED ;mux measure right wheel movfw RIGHTSPEED ;subtract subwf LEFTSPEED,W btfsc STATUS,Z ;zero error goto main btfss STATUS,C ;carry bit means + error (or zero) goto right call brakeleft goto main right: call brakeright goto main mark per line 4 (b) brakeleft: movwf ERROR rlf movfw movwf ERROR,F ERROR MARK comf movwf MARK,W SPACE Use twos complement of mark value as space value bsf PORTB,7 movfw MARK Apply left brake for MARK ms call pause bcf movfw call Double the error value (gain x) Use as mark value for PWM marks marks PORTB,7 Release left brake for SPACE ms SPACE pause marks brakeright: comf ERROR,F Do twos complement incf ERROR,F Add (correct negative value) marks () Page 7

8 Marks Q7 (a) Serial-In-Parallel-Out (b) Sub A -bit binary up counter plus AND gate; Sends pulse to Sub C when count = 3: this enables display Sub B 3-bit SIPO shift register; Stores a 3-bit binary value Sub C binary 7 seg decoder; 4 converts binary value to decimal; inputs blanked when BI low; preventing display of incomplete value Sub D 7-seg display, displays decimal of number in SIPO; 0 when binary-7seg decoder is enabled () Q8 (a) M = F L = = Nmm σ = M y / I = [ ] / = 50 5 N/mm 6 (b) E for aluminium alloy = N/mm δ = F L 3 / 3EI = / = / = 0 44 mm 4 (0) Page 8

9 Marks Q9 (a) V a = / ( ) 6 dt = 6t 4 (b) V out = / ( ) 6 dt = + 6/ t = 3 t 4 (c) Time V a V out (d) 3 (8) Page 9

10 Marks Q0 (a) When any LDR goes dark V across it increases Causes Schmitt inverting input to go higher When V reaches 3V Schmitt saturates low Triggers 555 in monostable mode Pin3 goes high for a time then low This clocks the 3-bit counter 6 (b) Rp 7 3 Rp = R/(0 + R) = R = R R = 46 7/5 33 R = (c) H = (A.B.C) + (A.B.C) + (A.B.C) 3 H = C.(A + B) (d) A B C Heater 4 Page 0

11 Q0 (e) pack: btfsc PORTB, goto weight btfsc PORTB, goto plastic goto pack weight: movlw d 0 movwf COUNT loop: bsf PORTB,7 movlw d 5 call pause bcf PORTB,7 movlw d 5 call pause decfsz COUNT goto loop return both return Marks plastic: movlw d 6 movwf COUNT loop: bsf PORTB,6 movfw MARK call pause bcf PORTB,6 movfw SPACE call pause rrf MARK,F rlf SPACE,F decfsz COUNT,F goto loop return (40) Page

12 Marks Q (a) M a = 0 CW+ + (0 350) (0 303) (V B 6500) = = V B V B = 80 / 6500 = 4 33 kn 3 H = 0 H B = 0kN 7 (b) M q = 0 CW+ (F 99) + ( ) = 0 99F = 0 F = + 5 kn (tie) M p = 0 CW+ +( ) (0 99) + (F 3 44) = F 3 = 0 F 3 = + 7kN TIE V = 0 + 7sin F sin60 = F = 0 F = kn ( TIE ) perp 73 9 sin73 9 = perp / 500 perp = 500 sin73 9 = 44 mm 7 Page

13 Marks Q (c) 555/5 = resolution ( / R 0 ) 5 = R 0 = ( 5 ) / R 0 = 000 R 0 = 000 R = 000 R = 500 R 3 = 50 R 4 = 5 R 5 = 6 5 R 6 = 3 3 R 7 = 5 6 R 8 = Q (d) toggle toggle toggle reset toggle 4 set set reset reset reset 8 (40) Page 3

14 Q (a) main: movlw d 5 movwf LOOPCOUNT loop: btfsc PORTB,0 incf PULSECOUNT,F movlw d call pause decfsz LOOPCOUNT goto loop movlw d 0 subwf PULSECOUNT,W btfss STATUS,C goto bleep movfw PULSECOUNT sublw d 3 btfss STATUS,C goto bleep bsf PORTB,7 movlw d 80 call pause bcf` PORTB,7 Marks bleep: bsf PORTB,6 movlw d 50 call pause bcf PORTB,6 movfw PULSECOUNT sublw d 3 btfsc STATUS,C goto main bsf PORTB,5 movlw d call pause bcf PORTB,5 goto main (b) I solid = BD 3 / = 0 3 / = 7333 I hole = / = 307 I xx = 46 mm 4 3 Page 4

15 Marks Q (c) M = 0 about R : 50 R R = 3 46 kn (d) 50: / = 4800 Nmm = 4 knmm 00: / = 00 Nmm = knmm 50: / = Nmm = 38 knmm 80: / = 7980 Nmm = 8 knmm 3 [END OF MARKING INSTRUCTIONS] 9 4 (40) Page 5