555 "happy birthday to you" electronic candle circuit

Published:2011/5/22 3:09:00 Author:TaoXi | Keyword: happy birthday to you, electronic candle | From:SeekIC

As the figure 17-47 shows, the whole circuit is composed of four parts: the optical electronic switch, the timing circuit, the voice circuit and the audio circuit, and it can be used in applications of birthday congratulation or celebration. The optical switch is composed of the optical fiber, the light sensitive tube and the IC1.etc. When you light up the birthday candle, the light beam which is transmitted by the optical fiber reduces the interelectrode resistance of the phototransistor 3DU3 lower than dozens of ohms, 555 starts up, J1 closes, J1-1 turns off and J1-2 closes, the circulation path is connected. The timing circuit is composed of the IC2，IC3，R2，RP2，C3,R4,RP3,C5. The timing time td=1.1（R+RP)C.



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