Practical voice-controlled music lantern (2)

The thyristor VS constitutes the main circuit of the lantern , and VTl-VT3 constitute the control circuit. The 220V AC power is rectified by VDI,
step-down by R5, stabilized by VD2 and filtered by C2 to output a stable DC voltage of about 12V for the control circuit. The piezoelectric ceramic piece B
constitutes an acoustic-electric transducer, which picks up the acoustic signal of the indoor environment and converts it into an electrical signal. It is amplified by the transistor VT1 and VT2
in two stages, and finally flows through the base of the VT3 through the capacitor C3, VT3 It is connected as an unbiased emitter follower. The music signal
is rectified by the VT3 emitter as its bias voltage, thereby changing the size of the VT3 emitter output current. This current
is injected into the gate of the thyristor VS through the light emitting diode LED. , change the conduction angle of vs, so that the colored light string H connected in series in its anode circuit
flashes with the rhythm of indoor music. The LED can also flash, and it doubles as a power indicator.