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Shown for the multi- time call circuit . The circuit consists of step-down converter circuit, monostable delay circuit , music, integrated circuits, relay control circuit , speakers and other components. One buck rectifier to provide DC voltage for the entire circuit . The circuit will switch K2, K3 placed in different locations may be different functions . The K3 placed in the ” bell “position . Press the button and AN, music can release a music -signal integrated circuits to drive loudspeakers stereo music . Achieve ” bell ” function .
The K3 placed in the ” call “position , K2 placed in the ” herald the break of day “position , then after dawn , as light by the photosensitive resistor RG showed low resistance to BG1 end , C. 1 over R1, W1 charging , when charging the potential to reach 2/3VDD , the 555 reset occurs , the output pin low to pull J1 , J2 release , and trigger audio circuit , sound issued herald the break of day , Achieve ” herald the break of day “function . The time interval from dawn to be a harbinger of dawn can be changed by adjusting the W1 , that by changing the charging time constant of the circuit to achieve the ” delay be a harbinger of dawn . ” The K3 placed in the ” Call “, K2 placed in the ” regular “position , then closed at this time BG1 . When turned on , C1 through W1, R4 charging , the charging time td = 1.1 (Rw1 R4) C1, the regular time , the icon corresponding parameter is about 150 minutes . Time to time , 5,553 feet to low to pull J1 , J2 release , cut off the power supply equipment , so that “the time to open , shut down “feature.