A transformerless power supply module is used to power the circuit safely. It typically includes capacitors and resistors for voltage reduction and filtering.
NPN Transistor (BC547):
The NPN transistor is used as a switch. When an AC voltage is detected, the transistor allows current to flow, turning on the indicator LED.
LED (Indicator):
An LED is connected to the collector of the NPN transistor. When the transistor is turned on, the LED lights up, indicating the presence of AC voltage.
Phototransistor or Photodiode:
A phototransistor or photodiode is used as an optical sensor. It is placed near the live wire but without direct contact. The presence of AC voltage induces a small current in the phototransistor or photodiode, activating the transistor.
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