Application of acousto-optic control delay switch
Acousto-optic controlled delay switch is used to replace the switch on the corridor of residential quarters. Only after dark, when someone walks through the stairs and makes footsteps or other sounds, the corridor lights will automatically light up to provide illumination. When people enter their homes or leave their apartments, the lights in the corridor will go out automatically after a delay of several minutes. In the daytime, even if there is sound, the corridor lights will not light up, which can achieve the purpose of energy saving. Acousto-optic controlled delay switch is not only suitable for corridors in residential areas, but also for public places such as factories, office buildings and teaching buildings. It has the advantages of small size, beautiful appearance, easy manufacture and reliable work, and is suitable for the majority of electronic enthusiasts to make their own.
How to design the acousto-optic controlled delay switch and what is its design principle?
The circuit schematic diagram of acousto-optic control delay switch is shown in the figure. The main component in the circuit is the digital integrated circuit cd40 1 1, which contains four independent NAND gates vd? 1 ~ VD4 makes the circuit structure simple and the working reliability high.
As the name implies, the acousto-optic controlled delay switch is "turned on" by sound control switch, and "automatically turned off" after a few minutes. So the function of the whole circuit is to turn the sound signal into the opening action of the electronic switch after processing. After the signal flow direction of the circuit is determined, the circuit can be divided into several units according to the main components, from which the block diagram shown in Figure 2 can be drawn.
Sound signals (footsteps, applause, etc.). ) is received by electret microphone bm and converted into an electrical signal, which is coupled to the base of vt through c 1 for voltage amplification, and the amplified signal is sent to two pins of NAND gate (vd 1), r4 and r7 are vt bias resistors, and c2 is power supply filter capacitor.
In order to turn off the acousto-optic switch in the daytime, that is, the light control circuit is composed of photoresistor rg and other components, and the series-connected voltage dividing circuit is composed of r5 and rg. When there is no light at night, the resistance of the photosensitive resistor is very large, and the voltage at both ends of rg is high, that is, t=2πr8c3 between high levels. Changing the value of r8 or c3 can change the delay time and meet different purposes. Vd3 and vd4 form a two-stage shaping circuit to shape the square wave signal. When c3 is charged to a certain level, the signal passes through NAND gates vd3 and vd4 and is output as a high level, so that the unidirectional thyristor is turned on and the electronic switch is closed. When c3 is fully charged, it only discharges r8. When it reaches a certain level, the output of NAND gates vd3 and vd4 is low, so that the unidirectional thyristor is turned off and the electronic switch is turned off, thus completing a complete process of the electronic switch from on to off.
Summary: Through the introduction of acousto-optic controlled delay switch, I believe that everyone has a certain understanding of the use and design principle of acousto-optic controlled delay switch, so as to know why this kind of acousto-optic controlled delay switch is used in some places. In fact, one of the biggest reasons is energy conservation, environmental protection and convenience for people. As for the design of acousto-optic controlled lighting, if you don't understand it, you don't need to study it. We amateurs just need to know the principle.
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