Practical Voice Delay Switch: Traditional Chinese Circuit Design Guide

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Voice activated delay switchCommon voice-activated switches are mostly composed of discrete components. The disadvantage is that there are many components, and assembly and debugging are more troublesome. If a voice control special integrated circuit is used, the structure is simple and the operation is stable and reliable. This is because the internal structure of the integrated circuit is cleverly used to give it a delay function. As long as you clap your hands or shout, the light will light up immediately. After a period of time, the light will go out on its own. It is suitable for installation in stairs, aisles, etc., and is conducive to saving electricity.1． How the circuit worksThe voice-activated delay switch circuit is shown in Figure 45-1. It is composed of an electret crystal microphone, a voice-activated dedicated integrated circuit and an execution circuit. Figure 45-1After the power supply is stepped down by capacitor C5, bridge rectified by diodes D2~D5, stabilized by DW and filtered by capacitor C4, it is added to the voice-activated delay switching circuit. When there is no voice control signal input to the MIC electret microphone, there is no input signal voltage at pin ① of the IC, and there is no voltage output at pin (12) of the IC. The BG tube is turned off, the relay J does not operate, and its normally open contact J1 disconnects the power supply of the bulb ZD; when a sound wave signal is sent to the MIC, the electret microphone The sound wave signal is converted into an electrical signal, and is coupled to the ① pin of the sound control integrated circuit IC via the capacitor C1. At the IC pin (12), the secondary amplified output voltage inside the IC is obtained, causing the BG tube to conduct, the relay J to close, the normally open contact on it closes, and the power supply of the bulb ZD is connected, and the bulb lights up. At the same time, the capacitor C3 connected to the IC's ④ and ⑤ pins can make the ⑤ pin output a positive pulse about 50 seconds after receiving the signal, and send it to the IC's (13) pin. After inversion, amplification and shaping, the IC's (12) pin goes low, causing BG to cut off, the relay J to release, the normally open contact J1 to disconnect the power of the bulb, and the bulb goes out. That is to say, if you clap your palm or blow a whistle, relay J will immediately close and the light will turn on; after about 50 seconds, J will release and the light will go off.It can be seen that changing the capacity of C2 can change the length of time the light is on.If the circuit shown in Figure 45-2 is used instead, it is a multi-functional plug-type voice-activated switch, which can control the opening and closing of household appliances such as TVs, electric fans, and radio recorders. Since only one stage of the two-stage inverting amplifier in the integrated circuit is used, when the IC pin ① inputs the signal voltage, the IC pin ⑨ outputs a high level. Only when the IC pin ① inputs the signal voltage again, the IC pin ⑨ returns to the low level. Therefore, when turning on the power of an electrical appliance, clap your palms and the power will be turned on; when you need to turn off the power of the electrical appliance, clap your palms again and the power will be off. Figure 45-22. Component selectionThe sound-activated integrated circuit block is BHKI type.MIC is an electret crystal microphone, and any type can be selected.Components in Figure 45-1:R11．5MΩR21MΩR31kΩR4500kΩC10.022μ …

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