Electronic birthday candle circuit (2)

Circuit working principle: When switch s is closed, bulb H does not light up because VS1 is cut off
. When a match is lit to heat the Rt thermistor,
after the temperature of Rt rises rapidly to its Curie temperature point, its resistance value increases sharply and the partial pressure increases, so VS1 is triggered and conducts
, and the bulb H is energized and lit. At the same time, pin 2 of the trigger end of the music integrated circuit CW9310 obtains a positive level, CW9310 works, and the output signal is amplified by VT and drives speaker B to play music.