Refer to FIGURE 3.1 below and answer the questions that follow - NSC Electrical Technology Digital - Question 3 - 2021 - Paper 1
Question 3
Refer to FIGURE 3.1 below and answer the questions that follow.
### 3.1.1 State the function of resistor R1.
### 3.1.2 Write down the voltage across Pin 2 when swit... show full transcript
Worked Solution & Example Answer:Refer to FIGURE 3.1 below and answer the questions that follow - NSC Electrical Technology Digital - Question 3 - 2021 - Paper 1
Step 1
State the function of resistor R1.
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Answer
Resistor R1 serves as a pull-up resistor, ensuring that Pin 2 of the 555 timer is held high in its stable state when the switch is not pressed. This stabilizes the input and prevents any false triggering.
Step 2
Write down the voltage across Pin 2 when switch S is pressed.
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When switch S is pressed, the voltage across Pin 2 drops to 0 V, as the pin is connected to ground through switch S.
Step 3
State whether the LED will be ON or OFF when switch S is pressed.
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The LED will be ON when switch S is pressed, because the activation of the monostable multivibrator causes the output to go high, thereby powering the LED.
Step 4
Determine the typical threshold voltage of the circuit.
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The typical threshold voltage of the circuit is approximately ±6 V, indicating the voltage level at which the output state transitions occur.
Step 5
Explain why the switch bounce does not affect the output of the circuit.
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The switch bounce produces multiple rapid on-off signals; however, the capacitor C1 charges more slowly in comparison to the bounce frequency, thus filtering out the oscillations and yielding a single clean output transition.
Step 6
Draw the output on the ANSWER SHEET for QUESTION 3.1.6.
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[User should sketch the output waveform], which typically shows a single output pulse corresponding to the single press of the switch.
