555 ding-dong audio electronic doorbell circuit

Published:2011/6/1 4:04:00 Author:TaoXi | Keyword: 555, ding-dong, audio, electronic, doorbell | From:SeekIC

This two-tone bell circuit uses one piece of 555 time base circuit as the core. It sends out the beautiful and sweet sound of dingdong . The circuit is as shown in figure 15-46. The multivibrator is composed of the 555 and R1～R3，D1，D2，C2. SA is the button switch of the door, it is usually in the disconnect state. When SA is closing, pin-4 of 555 has the low electric potential to keep it in the mandatory reset state, pin-3 outputs the low electric potential. When someone presses the SA, the power supply VDD will charge the C1 through SA and D1, pin-4 of 555 has the high electric potential, the 555 starts working, the vibration frequency fc1=1.44/(RD+2R3)C2. RD is the DC resistance of D1 and D2.



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