Sound and light dual control delay energy-saving lamp (2)

The circuit of the sound and light dual control delay energy-saving lamp is shown in Figure 1-51. The right part of the dotted line in the circle is the ordinary lighting circuit, and the left part is
the sound and light dual control delay energy-saving lamp control circuit. As can be seen from the figure, it has only two external terminals like the ordinary switch, that is, a single line
in and out, so it can directly replace the ordinary switch. Switch without changing the original lighting circuit in the room.
VD3～VD6 form a bridge rectifier circuit. After R8 reduces the voltage and limits the current, VD2 stabilizes the voltage and C3 filters and outputs about 9V DC
voltage for the transistors VT1～VT4. During the day, the photoresistor RO shows low resistance under indoor natural light, VT3 is in
the conductive state, and VT4 is cut off. At this time, there is no voltage on 04, VT5 is cut off, VT6 is on, and the gate and cathode of the thyristor vs
are short-circuited by VT6, so vs is turned off and the lamp H will not light up. At night, RO has a high resistance due to no light exposure, but due to
the bias effect of R2, V TI is turned on, and the VT1 emitter current flows into the base of VT3, so that rr'3 is still in the on state,
so in the quiet state, The lamp still won't light up.
    When someone walks on the stairs, and their footsteps or conversations are picked up by microphone B, the corresponding electrical signal is
output and sent to vri for amplification through Cl. The amplified audio signal is injected into the base of VT3 from the VTI emitter on the one hand, and the base of VT3 on the other hand. The collector output of V TI
is coupled to the base of r[2 via C2. The signal is amplified by VT2 and sent to the base of VT1 again from its collector output
. It can be seen that VT1 and VT2 form a positive feedback audio amplifier, which has extremely high circuit gain. Therefore, the
circuit has high sound control sensitivity, which is the ingenuity of this circuit design. Since the base of VT3 has a strong audio signal
input, the negative half cycle of its signal causes VT3 to exit the conduction state and enter the amplification state or even the cut-off state. The collector potential of VT3
rises, VT4 is turned on, and the 9V DC voltage is quickly charged to C4 through VT4 and VDI, and VT5 is turned on and VT6
is turned off through R9, releasing the blockade of the thyristor vs gate, and the vs gate is obtained by Rll When the current is triggered in the forward direction, vs is turned on, the lamp will
light up and shine. After the lamp is lit, although its own light makes RG become a low resistance, causing VT3 to be turned on and blocked, because C4 is
full of charge, C4 emits junction discharge to VT5 through R9, so that VT5 can still maintain the conductive state, so the lamp can Keep
lighting. When C4 is discharged, VT5 is cut off, VT6 is turned on, vs is turned off, and the light goes out. If there is another sound, the light
will turn on again. The delay time for each lighting of the lamp is mainly determined by the discharge time constant of R9 and C4. The data shown in the figure is about 30s.
During the day, due to the VT3 blockade, no matter how loud the sound is, the lights will not light up.