The sound sensor adopts a high-sensitivity electret condenser microphone BM with an output impedance of 2kω. R 1 is the external load resistance of BM internal field effect transistor. Note that the solder joint connecting the BM metal shielding shell is the negative grounding terminal. The emitter follower driving circuit adopts a base bias voltage circuit. When the input voltage of VT2 base reaches a certain value, there is a voltage output on the emitter resistor R5, and VD 1 provides a path for VT2 base to charge reversely. Only when the signal voltage of R5 rises, the 1 pin is in a high level state, the ambient light is dark, and the photosensitive resistance value of RG is large (not less than 5kΩ), the input pin 2 can be in a high level state, and the condition that the output pin 3 of the AND gate circuit rises to a high level state can be satisfied. One-way thyristor VS is triggered by current limiting resistor R6, and its load small electric bead EL lights up. The power supply GB drops by 0.7v through the switching diode VD2 and is connected to the VCC pin of the integrated circuit. The experimental circuit of sound control lamp can control the opening of the lamp by high-five at 5m.

First, when the signal level at the input terminal reaches the door-opening level, the output terminal voltage starts to jump, the signal level at the input terminal rises to a certain extent, and the output voltage (4.5V) hardly changes, which can be regarded as the fluctuation at the top of the waveform is truncated. When the input signal is lower than the off level, the AND gate is "off" and the output voltage is almost zero (O. 15V), so the output signal is a pulse waveform, which is the shaping effect of the AND gate. Secondly, whether the sound signal can control the conduction of the unidirectional thyristor through the AND gate depends on the level of the control terminal of the other input terminal. When the ambient light is dark, the control terminal is in a high level state, and the light can be controlled by sound, which is the gating function of AND gate. When the ambient light intensity is low, the control terminal is in a low level state, and the voice control does not work, which is the prohibition of AND gate. Finally, the logic function of AND gate works, which completes the function of voice control not working during the day and light control with sound signal at night.

Second, the circuit diagram