Electrical Technology Grade 12 Eastern Cape Mock 2022 QP

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 12 SEPTEMBER 2022 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS MARKS: 200 TIME: 3 hours This question paper consists of 19 pages, including a 1-page formula sheet and 5 answer sheets.

Downloaded from hlayiso.com 2 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) INSTRUCTIONS AND INFORMATION 1. This question paper consists of SIX questions. 2. Sketches and diagrams must be large, neat and FULLY LABELLED. 3. Show ALL calculations and round off answers to TWO decimal places. 4. Number the answers correctly according to the numbering system used in this question paper. 5. You may use a non-programmable calculator. 6. Show the units for ALL answers of calculations. 7. A formula sheet is provided at the end of this question paper. 8. Answer the following questions on the attached ANSWER SHEETS: QUESTION 5.3.2 QUESTION 5.4 QUESTION 5.5 QUESTION 6.8 9. Write neatly and legible. Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 3 QUESTION 1: MULTIPLE-CHOICE QUESTIONS Various options are given as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.15) in the ANSWER BOOK, for example 1.16 D. 1.1 The purpose of the Occupational Health and Safety Act is to … A provide for the health and safety of persons at work. B provide for the health and safety of persons at home. C prevent wear and tear on machinery. D prevent workers from using machinery. (1) 1.2 With reference to a monostable multivibrator, select the correct option: A It is a free running oscillator B It has ONE input C The magnitude of the supply voltage determines the length the output is high D It will stay high indefinitely (1) 1.3 An astable multivibrator has the following characteristics: A Free running with NO external inputs B Free running with TWO inputs C TWO stable states with TWO inputs D NO stable states with ONE input (1) 1.4 What will happen to the value of a light dependant resistor (LDR) if the light shining on it increases? A It will remain the same. B It will first increase and then decrease. C It will increase. D It will decrease. (1) 1.5 A Schmitt trigger circuit works on the principle of: A Inverting signals B Amplifying signals C Hysteresis D Adding the signals together (1) Copyright reserved Please turn over

Downloaded from hlayiso.com 4 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) 1.6 Pin 3 of a 555 Integrated Circuit (IC) is called: A Vcc. B Ground C Output D Input (1) 1.7 The maximum supply voltage for a 555 IC is: A +15 V B +12 V C -12 V D +5 V (1) 1.8 With reference to the LED seven segment display, common cathode refers to: A The anodes of all eight LED’s are connected to a common ground rail. B The cathodes of all eight LED’s are connected to a common positive rail. C The anodes of all eight LED’s are connected to a common positive rail. D The cathodes of all eight LED’s are connected to a common ground rail. (1) 1.9 The function of an encoder is to … A convert an analogue signal to a digital signal. B convert a digital signal to an analogue signal. C convert a binary code into a recognisable decimal form. D convert a decimal code into a recognisable binary form. (1) 1.10 Active low latch flip-flop is also referred to as a … A Master/Slave Latch. B D Latch. C ̅S̅ Latch. R D RS Latch. (1) 1.11 The ILLEGAL mode of operation for an Active High Latch (RS Latch) flip- flop occurs when: A Both inputs are high B Set input is high and Reset input is low C Reset input is high and Set input is low D Both inputs are low (1) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 5 1.12 With reference to microcontrollers, a LED display would be an example of a(n) … A output. B input. C controller. D process. (1) 1.13 With reference to microcontrollers, the term RAM means: A Read All Memory B Random Allocation Memory C Read and Memorise memory D Random Access Memory (1) 1.14 With reference to microcontrollers, identify which ONE is NOT part of the microcontroller: A Control Unit B Serial Port C Memory D Arithmetic Logic Unit (1) 1.15 The term I2C stands for: A Inter-Integrated Circuit B Integrated 2 Circuits C Internal Inter Circuit D Interconnected 2 Circuits (1) [15] QUESTION 2: OCCUPATIONAL HEALTH AND SAFETY 2.1 Define major incident with reference to the Occupational Health and Safety Act 1993. (2) 2.2 State ONE cause of unsafe acts in a workshop. (1) 2.3 Describe why the following are unsafe acts or unsafe conditions. 2.3.1 Running in the workshop (2) 2.3.2 Overloading electrical outlets with too many appliances (2) 2.4 Explain how you would conduct a qualitative risk analysis in your workshop at school. (3) [10] Copyright reserved Please turn over

Downloaded from hlayiso.com 6 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) QUESTION 3: SWITCHING CIRCUITS 3.1 With reference to FIGURE 3.1 below, answer the following questions. FIGURE 3.1: BI-STABLE MULTIVIBRATOR 3.1.1 Name TWO characteristics of the bi-stable multivibrator circuit in FIGURE 3.1 above. (2) 3.1.2 Explain what would happen in the circuit if R3 were to be removed. (1) 3.1.3 Explain the importance (function) of R3 in the circuit shown in FIGURE 3.1. (2) 3.1.4 Describe what happens when the SET switch, S1 is pressed. (3) 3.1.5 Explain the function of R1 and R2 in the circuit. (2) 3.2 Draw a fully labelled circuit diagram for an astable multivibrator op amp circuit. (6) 3.3 With reference to the astable multivibrator op amp circuit, explain the term feedback. (3) 3.4 Name ONE application of a monostable multivibrator. (1) 3.5 Explain the principle of operation of a day/night switching circuit. (6) 3.6 Draw a fully labelled diagram of a typical hysteresis curve. (6) 3.7 Draw the output waveform of a 555 timer IC used as a Schmitt Trigger. Show at least TWO full cycles. (4) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 7 3.8 FIGURE 3.8 and TABLE 3.8 below show the resistor values, output voltages and gain of a summing amplifier. Refer to FIGURE 3.8 and study TABLE 3.8 below to answer the following questions. R1 RF V1 = + 0,5 V R2 V2 = + 1,2 V VOUT R3 V3 = + 0,9 V FIGURE 3.8: SUMMING AMPLIFIER RESISTOR VALUES OUTPUT GAIN R1 R2 R3 RF VOUT β (AV) 20 kΩ 20 kΩ 20 kΩ 20 kΩ B 1 20 kΩ 20 kΩ 20 kΩ 40 kΩ + 5,2 V D 5 kΩ 10 kΩ 20 kΩ 40 kΩ C 4,08 20 kΩ 20 kΩ 20 kΩ A + 10,4 V 4 TABLE 3.8 3.8.1 State the function of a summing amplifier. (2) 3.8.2 Calculate the output voltage at B. (3) 3.8.3 Calculate the output voltage at C. (3) 3.8.4 Calculate the value of the feedback at A. (3) 3.8.5 Calculate the total gain at D. (3) [50] Copyright reserved Please turn over

Downloaded from hlayiso.com 8 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) QUESTION 4: SEMICONDUCTOR DEVICES 4.1 Name FOUR characteristics of an ideal operational amplifier. (4) 4.2 FIGURE 4.2 below shows the op amp as a non-inverting amplifier. Answer the questions that follow. +V VIN = 1,5 V VOUT -V RF = 50 kΩ RIN = 10 kΩ 0V FIGURE 4.2: NON-INVERTING AMPLIFIER Given: VIN = 1,5 V RF = 50 kΩ RIN = 10 kΩ 4.2.1 Calculate the voltage gain in FIGURE 4.2. (3) 4.2.2 Calculate the output voltage. (3) 4.2.3 Describe the effects of decreasing the feedback resistor. (2) 4.3 With reference to the 555 timer IC, answer the questions below. 4.3.1 Explain the function of pin 6 (threshold) on a 555 IC. (3) 4.3.2 State the voltage parameters between which a 555 timer can operate. (2) 4.3.3 Explain the astable mode of operation of a 555 timer. (2) 4.3.4 Name ONE method to identify pin 1. (1) [20] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 9 QUESTION 5: DIGITAL AND SEQUENTIAL DEVICES 5.1 Name TWO methods to display information in digital systems. (2) 5.2 Refer to transistor coupling as used in LED seven-segment displays and identify the circuit in FIGURE 5.2 below. (2) V+ FIGURE 5.2 5.3 Refer to FIGURE 5.3 below and answer the questions that follow. A B B 0 OUTPUT 0 B 1 OUTPUT 1 2 OUTPUT 2 3 OUTPUT 3 FIGURE 5.3 5.3.1 Identify the circuit in FIGURE 5.3. (1) 5.3.2 Complete the truth table of FIGURE 5.3 on the ANSWER SHEET for QUESTION 5.3.2. (3) Copyright reserved Please turn over

Downloaded from hlayiso.com 10 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) 5.4 On the ANSWER SHEET for QUESTION 5.4, draw the logic circuit of a full adder using AND gates, exclusive OR gates and an OR gate. (8) 5.5 FIGURE 5.5 below shows a clocked RS flip-flop. Complete the output waveforms on the ANSWER SHEET for QUESTION 5.5. S Q CLK 𝑄̅ R S Q CLK R 𝑄̅ FIGURE 5.5: CLOCKED RS FLIP-FLOP (4) 5.6 FIGURE 5.6 below represents the logic symbol of a flip-flop. SET D Q CLK CLR Q FIGURE 5.6: FLIP-FLOP 5.6.1 Identify the flip-flop in FIGURE 5.6. (1) 5.6.2 Explain how the circuit is designed to eliminate any illegal states in the operation of this flip-flop. (4) 5.6.3 Name TWO applications of this type of flip-flop. (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 11 5.7 FIGURE 5.7 below shows a three-stage asynchronous ripple counter. Answer the questions that follow. 1 A B C SET SET SET J Q J Q J Q Input clock pulses K CLR Q K CLR Q K CLR Q FIGURE 5.7: ASYNCHRONOUS RIPPLE COUNTER 5.7.1 Explain the principle of operation of the circuit in FIGURE 5.7. (8) 5.7.2 Explain why this counter in FIGURE 5.7 is referred to as an asynchronous counter. (2) 5.7.3 State the maximum number, in decimal numbers, that this counter in FIGURE 5.7 can count to. (3) 5.7.4 Explain why this counter in FIGURE 5.7 is referred to as a ripple counter. (2) 5.8 Refer to FIGURE 5.8 below which is a block diagram of a serial-in: serial- out shift register and answer the questions that follow. SET SET SET SET Serial D Q D Q D Q D Q Data out CLR Q CLR Q CLR Q CLR Q B FIGURE 5.8 5.8.1 Label A and B. (2) 5.8.2 Explain the principle of operation of this register. (5) 5.9 Explain the difference between combinational logic circuits and sequential logic circuits with regards to their basic building elements. (2) Copyright reserved Please turn over

Downloaded from hlayiso.com 12 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) 5.10 Name TWO types of shift registers, other than the serial-in: serial-out shift register, that are used in digital electronic circuits. (2) 5.11 Explain the term truncated counter. (2) [55] QUESTION 6: MICROCONTROLLERS 6.1 Refer to the block diagram in FIGURE 6.1 below and answer the questions that follow. CPU X I/O ROM FIGURE 6.1 6.1.1 Identify the block diagram in FIGURE 6.1. (1) 6.1.2 Identify component X. (1) 6.1.3 Write out the abbreviation ROM in full. (1) 6.1.4 Explain the function of the RAM. (2) 6.2 Answer the questions with reference to the hardware of a microcontroller. 6.2.1 Explain the term discreet logic. (2) 6.2.2 Explain the term integrated logic. (2) 6.3 Answer the questions with refence to the registers of a CPU. 6.3.1 Name ONE type of special-purpose register. (1) 6.3.2 Describe the function of an accumulator. (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 13 6.4 Answer the following questions with reference to communication in a microcontroller. 6.4.1 Explain the function of the system bus. (3) 6.4.2 Name the THREE busses in a microcontroller. (3) 6.4.3 State TWO advantages of synchronous communication when compared to asynchronous communication. (2) 6.4.4 State TWO disadvantages of parallel communication when compared to serial communication. (2) 6.5 Answer the following questions with reference to RS-485 communication protocol. 6.5.1 State the logic operating values which is represented by -200 mV and 200 mV. (2) 6.5.2 State THREE applications of the RS-485. (3) 6.5.3 Explain the differences between simplex communication and half duplex communication. (4) 6.6 Answer the following questions with reference to the software of microcontrollers. 6.6.1 Explain the difference between an algorithm and a program. (4) 6.6.2 Explain the term looping (repetition). (2) 6.7 Answer the following questions with reference to data flow diagram symbols in PICAXE. 6.7.1 Explain the function of the symbol referred to in FIGURE 6.7.1. (2) FIGURE 6.7.1 6.7.2 Explain where a terminator symbol will be used in a flowchart. (1) Copyright reserved Please turn over

Downloaded from hlayiso.com 14 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) 6.8 Study the PICAXE circuit in FIGURE 6.8 below and design a flow diagram for the circuit. Complete your answer on the ANSWER SHEET for QUESTION 6.8. SCENARIO: When the on/off switch is activated, the program must execute as follows: a S3 must be pushed to activate the OUTPUT LED (the LED will come on for either 5 or 2 seconds). S3 is a push-button. b S2 must be used to select one of TWO timers (one set to 5 seconds and the other to 2 seconds). S2 is a toggle switch. c S1 must allow the user to repeat the program or to stop it. S1 is a toggle switch. On/Off R1 6V S1 PicAXE 08M S2 Output S3 S1: Repeat the program (Yes = On/No = Off) S2: Timer selector (5 seconds = On/2 seconds = Off) S3: Activate the LED (Push On = Activate) FIGURE 6.8: PICAXE CIRCUIT (10) [50] TOTAL: 200 Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 15 FORMULA SHEET SWITCHING CIRCUITS 𝑉 𝑅 1. Gain A𝑉 = 𝑉𝑂𝑈𝑇 = − (𝑅 𝑓 ) inverting operational amplifier 𝐼𝑁 𝑖𝑛 𝑉 𝑅 2. Gain A𝑉 = 𝑉𝑂𝑈𝑇 = 1 + (𝑅 𝑓 ) non-inverting operational amplifier 𝐼𝑁 𝑖𝑛 𝑅 3. 𝑉𝑂𝑈𝑇 = 𝑉𝐼𝑁 × (− 𝑅 𝑓 ) inverting amplifier 𝑖𝑛 4. 𝑉𝑂𝑈𝑇 = −(𝑉1 + 𝑉2 + 𝑉3 ) summing up op amp 1 5. 𝑓𝑟 = 2𝜋√𝐿𝐶 1 6. 𝑓 = 2𝜋√6𝑅𝐶 Copyright reserved Please turn over

Downloaded from hlayiso.com 16 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) ANSWER SHEET 5.3.2 SEPTEMBER 2022 CENTRE NUMBER EXAMINATION NUMBER QUESTION 5: DIGITAL AND SEQUENTIAL DEVICES 5.3.2 Inputs Outputs A B 0 1 2 3 0 0 1 0 0 0 0 1 0 1 0 1 0 0 0 1 1 1 0 0 0 Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 17 ANSWER SHEET 5.4 SEPTEMBER 2022 CENTRE NUMBER EXAMINATION NUMBER QUESTION 5.4 C1 SUM A CO B FIGURE 5.4 Copyright reserved Please turn over

Downloaded from hlayiso.com 18 ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS (EC/SEPTEMBER 2022) ANSWER SHEET 5.5 SEPTEMBER 2022 CENTRE NUMBER EXAMINATION NUMBER QUESTION 5.5 S 0 1 1 0 R Q FIGURE 5.5 Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2022) ELECTRICAL TECHNOLOGY: DIGITAL ELECTRONICS 19 ANSWER SHEET 6.8 SEPTEMBER 2022 CENTRE NUMBER EXAMINATION NUMBER QUESTION 6.8 START STOP Copyright reserved Please turn over