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 switch S is ... 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 functions as a pull-up resistor, which keeps Pin 2 of the 555 timer high and ensures that the circuit remains in its stable state when the switch S is not pressed.
Step 2
Write down the voltage across Pin 2 when switch S is pressed.
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Answer
When switch S is pressed, the voltage across Pin 2 is 0 V.
Step 3
State whether the LED will be ON or OFF when switch S is pressed.
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Answer
The LED will be ON when switch S is pressed.
Step 4
Determine the typical threshold voltage of the circuit.
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The typical threshold voltage of the circuit is ±6 V, which is approximately rac{1}{3} V_{cc}.
Step 5
Explain why the switch bounce does not affect the output of the circuit.
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The switch bounce creates brief fluctuations in the input signal; however, the capacitor C1 smooths these fluctuations. The circuit will only change states once the capacitor is charged past the threshold, hence preventing the switch bounce from affecting the output.
Step 6
Draw the output on the ANSWER SHEET for QUESTION 3.1.6.
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Answer
To draw the output, indicate a square wave with high and low segments corresponding to the timing of the circuit response to the switch being pressed. Ensure to label the time intervals correctly.
