Non-two-wire sound and light control stair delay switch circuit (4)

It is a sound and light controlled stair delay call switch circuit composed of 充cr)401l digital integrated circuit and several discrete components . It is characterized by strong anti-interference ability and stable and reliable operation.
    Microphone B, three-switch tube VT1, etc. constitute a voice control circuit. J picks up the environmental sound wave signal and then outputs the corresponding electrical
signal, and VT1 amplifies it and is coupled to the input terminal pin ① of NAND flI by VT1, making pin ① high level. "l".
If it is night, the photoresistor RI. Is a high resistance, the other input terminal pin ② of the NAND gate I is also high level
"I". According to the logical relationship of the NAND gate "all l out.", pin ③ is low power +. VDI conduction, C. That is,
charging. At the same time, NAND gate II is inverted, pin ④ outputs high level, transistor VT2 is turned on, gate tube VTH
is turned on, and lamp E is powered on and emits light. After the sound signal, the ③ pin of the NAND gate T returns to high level, and VD] is cut off.
At this time, the stored charge is discharged through I<, and the input A terminal of the NAND gate H can continue to be maintained at the low level, inverting
After that, it was the island level, and Dianzhou still kept shining. When (,;; the input terminal of NAND gate II jumps to high level after the discharge is completed
, and then outputs low level , VT2 is cut off. When VtI¨彳E AC power crosses zero, it will be turned off, spider 1: goes out.
    The power supply of this machine It is composed of C, capacitor step-down, VD2, VD3 rectifier, vs stabilized voltage supply, and VT3 forms an electronic
filter, so it can effectively eliminate interference in the circuit and ensure the reliability of the circuit. Adjust R.
Resistance The sound sensitivity of the circuit can be adjusted. The smaller the R. resistance, the easier it is to be triggered by sound control, but the small resistance of R should be lower than 680kfl, otherwise the light will easily stay on. Adjust the R. Light control
of the adjustable circuit. Sensitivity, increase or decrease the value of R. and G , you can adjust the duration of the electric lamp E. Fine-tune R., n'_ to change the brightness of the lamp. When VT2 is required to be turned on, adjust R; make VTH in the fully open state. , that is, the light F is the brightest. At this time, you need to pay attention to safety, because the circuit board is live!