Light control switch circuit in incandescent lamp

Under normal conditions, the alternating current forms a loop through the voltage dividing circuit composed of incandescent lamp, VD4~VD7 rectifier bridge, resistor R9 and the voltage stabilizing circuit composed of VD3 and C4. The loop current is less than 0.9mA, the power consumption is less than 0.2W, and the lighting does not light up. When the sound sensor receives the sound wave, the sound wave signal is converted into an electrical signal, which is amplified by IC1a and IC1b, and then passes through the coupling capacitor C1 to remove the interference signal generated by low-frequency vibration. When the ambient light is strong, the signal is bypassed by the photosensitive diode VD1 and is not output to the rear stage; when the ambient light is weak, VD1 is open circuit, and the acoustic signal output by the front stage is amplified by IC1c and 1C1d, and is composed of VD2, C2, and R4 The rectifier filter circuit rectifies the audio signal output by IC1d (which is quickly charged to C2 through VD2 in one direction) into a DC signal. At the same time, C2 and R4 also have a delay function, and the delay time is RC=22s. When the sound wave signal output by IC1d is a relatively short interference signal, the transition time from low to high level at the output terminal of C2 is shorter than the level transition time of the delay loop composed of R5 and C3. At this time, the output of C2 The signal cannot affect the change of C3 output level, and the interference signal is shielded; when the sound wave signal is normal, the level signal output by C2 passes through R5, C3, IC1f, R8, delays the connection of SCR, and the incandescent lamp lights up. Light control switch circuit in incandescent lamp: