Practical voice-controlled music lantern (3)

The circuit of a practical voice-controlled music lantern is shown in Figure 1-49. The circuit principle is basically the same as Figure 1-46, except for
a few improvements: - The original half-wave rectifier circuit is changed to a bridge-type full-wave circuit. In this way, the current passing through the colorful light string is larger, and the brightness
is naturally improved: The second is to change the original resistors Rl and R2 to divide the voltage into two light-emitting diodes LED I and LED2.
The voltage obtained from both ends of the light-emitting diodes It is a stable DC voltage, and the luminous tube can also serve as a power indicator. Third, the
acoustic-electric transducer is changed from the original piezoelectric ceramic piece to an electret condenser microphone, so the sensitivity of acoustic wave control can be effectively improved.
          The power supply circuit of microphone B is stabilized by two light-emitting diodes LED1 and LED2 to obtain a DC voltage of approximately 3.2V
and supplied through resistor R4. The power supply circuit of the transistor VT is supplied with a regulated voltage by a light-emitting diode LED 2. By adjusting
the resistance of the potentiometer RP, the sound control sensitivity of the circuit can be adjusted. If the transistor VT is adjusted to the critical state where it is about to enter conduction
, the circuit can obtain the highest sound control sensitivity. If there is a slight sound in the indoor environment, the colored light string H can be made to sparkle with the indoor sound
.