sound control circuit

For the voice-controlled lamp introduced in this section, during the day or when the light is bright, the power-saving switch is turned off and the lamp does not light up. At night or when the light is dark, the power-saving
switch is in the ready working state. When someone passes near the switch, the sound of footsteps, voices, clapping, etc. can activate the power-saving switch and the
light will turn on. After a delay of 40 to 50 seconds, the power-saving switch will automatically turn off and the light will go out. The voice-activated light is shown in Figure 16-14a, and the reference circuit is shown in Figure 16-14b.
    (1) Working principle The sound-controlled power-saving switch circuit is composed of 7 circuits: microphone BM, sound signal amplification, half-wave rectifier, light control, electronic switch, delay
and AC switch. The microphone and VT1, Ri~Ra, cI form a sound amplification circuit. In order to obtain higher sensitivity.
The Lu value of VT1 should be greater than 100, and the microphone should also be highly sensitive. The wind should not be too low, otherwise the circuit is prone to intermittent oscillation.
G, VD1 and VD2, G form a rectifier circuit to convert the sound signal into a DC control voltage . R, Rs and photoresistor RG form a light control circuit
. When light shines on RG, its resistance becomes smaller and the DC control voltage attenuates greatly. VTZ cutoff. VT2, VT3, R, and VD3 form
an electronic switch. Normally, that is, when there is light, VT2 and VT3 are cut off, there is no voltage on G, the unidirectional thyristor VTH is cut off, and the bulb EL does not light up.
When VTH is cut off, the DC high voltage is stepped down by VD4 and then applied to the upper end of G to charge G. When charged to 12V, vs breaks down to ensure that
the voltage on G does not exceed 15V.
    When no light shines on RG. The resistance of RG is very large, and the attenuation of the DC control voltage is very small. VT2 and VT3 are turned on, VD3 is also turned on,
C4 and G start to charge, and the voltage slowly rises. R8, G and unidirectional thyristor VTH form a delay and AC switch. G passes R. Add the DC trigger
voltage to the VTH control gate, VTH is turned on, the relay coil K is energized, the normally open contact K of the relay in the EL branch is turned on, and the bulb
EL lights up. The length of time the bulb lights up is determined by the parameters of C4 and island. According to the component values ​​​​given in the circuit diagram, about 40 seconds after the bulb lights up
, the VTH is cut off and the light goes out. G is an anti-interference capacitor, used to eliminate the light bulb jitter.
    (2) Component selection VT1 and VT2 both use 9014 transistors, VT3 uses 9012 transistors, and VTI should use p>ioo.
VTH uses 100-8 unidirectional thyristor. VD1-VD3 uses 1N4148 diodes, VD4 uses 1N4001 diodes, and VD5~VD8 uses
1N4004 diodes. The microphone should be selected with high sensitivity. Other components are shown in Figure 16-14.
    (3) Installation and debugging: All components are welded and installed on a printed circuit board, and then placed in an insulated small box. The photoresistor needs to be installed
on the housing where light can easily shine. As long as the components are selected correctly and the welding is correct, this device can generally work normally. If the switch
cannot be completely extinguished after starting, it can be eliminated by connecting a capacitor (capacity: 470pF) to the horse (this position should be left on the printed circuit board in advance)
. If intermittent oscillation occurs, cz can be replaced by o. 33vF capacitor, or reduce the wind to about 47kfl to eliminate it. Since the circuit is directly
connected to the mains, be careful when debugging and using it to prevent electric shock. Please note when using: Since the maximum load power of this switch is 100W,
it cannot be overloaded and the bulb cannot be short-circuited. When wiring, turn off the power or remove the bulb first. After connecting the switch, turn off the power or install the bulb .