Photo AI
FIGURE 3.2 below shows the circuit of a multivibrator - NSC Electrical Technology Digital - Question 3 - 2023 - Paper 1
Question 3
FIGURE 3.2 below shows the circuit of a multivibrator. Answer the questions that follow. 3.2.1 State the purpose of the variable resistor R2. 3.2.2 Explain how the... show full transcript
Worked Solution & Example Answer:FIGURE 3.2 below shows the circuit of a multivibrator - NSC Electrical Technology Digital - Question 3 - 2023 - Paper 1
Step 1
State the purpose of the variable resistor R2.
Answer
The variable resistor R2 is used to adjust the frequency of the output signal by changing the time constant of the connected capacitor C1. This allows for variation in the duty cycle and frequency of the square wave output generated by the multivibrator.
Step 2
Explain how the LED will be affected if it is directly connected to pin 3 without resistor Rs.
Answer
If the LED is directly connected to pin 3 without the current-limiting resistor Rs, the LED would likely be damaged due to excessive current flow. The output from the 555 timer can produce a high output voltage, which can exceed the rated current for the LED, leading to overheating and failure of the LED.
Step 3
Explain how this circuit operates.
Answer
This astable multivibrator circuit operates using a 555 timer in an oscillation mode. In this configuration, the capacitor C1 charges and discharges through the resistors R1 and R2, which sets the frequency of the output signal. When the capacitor charges to a specific threshold, it triggers the output to switch states, generating a continuous square wave output. The cycling continues as the capacitor discharges through R2 when the threshold is crossed.
Step 4