Discrete component sound and light control stair delay switch circuit (6)

It is a sound and light controlled stairway delay lighting switch using piezoelectric ceramic H as
an acoustic transducer. The piezoelectric ceramic chip is less sensitive to sound signals than an electret condenser microphone, so the audio amplifier
uses VT4- VT6 I-level voltage amplification to improve the response sensitivity of Kai Zeng Lu Zhan.
    RL, R, and VT3 form a light control circuit, during the day, RI. Because the resistance is low, VT3 is turned on,
clamping the base potential of VT2 at a low level, so that VT2 always remains in a cut-off state, VT1 is turned on, the transistor VT7 is turned off because
the door panel is at a low level, and the light E is on. . night. R.I. Shows high resistance, VT3 is cut off, and
the blockade of VT2 is released. When there is no sound in the environment, VT2 is still in the off state, VT1 is on, VT7 is off, and the light is still
off. When someone walks on the stairs J, the piezoelectric ceramic piece B will pick up the sound of the person's footsteps and convert it into the corresponding electrical
signal, which will be amplified by the three-level voltage of VT4-VT6. pole,
the positive half-peak value of the sound signal can quickly turn on VT2 and cut off vri. VT7 is trapped in R. The gate trigger current can be obtained and
TF is turned on, and the lamp E is energized and emits light. At the same time, (1: The stored charge is quickly obtained through VT2 After a few seconds, the sound
disappears and VT2 returns to cut-off, but... the voltage at both ends of the capacitor cannot change suddenly. The level of VTl is still
low and cut-off, and V1I? is still open. Therefore, the lamp d: will go out on _Uj. At this time, the power supply is charged to f through R
, so that the voltage at both ends of G continues to rise. When it reaches O. (i5V, VT1 is turned on. VT7 loses the gate
trigger current , when the AC I Li crosses zero, the curse is cut off, and the light E is turned off.
    The delay time of l is called the main south R, and is determined by the value of C. The coin data is about imin. In order to improve the ability of JK electric
ceramics to sense sound waves Open a sound release hole in the sensitivity switch box, and use epoxy resin glue to
smear around the ceramic copper base plate, and then stick it to the sound release hole on the inner surface of the switch, so that the switch barrier can be activated.
The resonance cavity function effectively increases the output intensity of the sound signal. The sound release hole is appropriately small and can be in the shape of a fence
. It should not be too large to prevent human hands from contacting the copper bottom of the ceramic plate and suffering an electric shock.