555 household earthquake sound and light alarm circuit

Published:2011/6/2 19:10:00 Author:TaoXi | Keyword: 555, household, earthquake, sound, light, alarm circuit | From:SeekIC

This circuit is composed of the impact sensor, the monostable trigger timing circuit, the multivibrator and the sound & light alarm circuit.etc, as the figure 15-50 shows. The IC2 uses the time base circuit 555, the controllable multivibrator is composed of the IC2, R3, R4 and C3.etc, in peacetime the IC1 outputs the low electrical level to make the IC2 in the mandatory reset state; when the earthquake happens, the IC1 outputs the high electrical level to make the IC2 to start working, the oscillation frequency fc=1.44/(R3+2R4)C3. The oscillation frequency of the figure parameters are 100Hz. IC2's output oscillation pulse makes the light-emitting diode LED1 to light, at the same time the pulse is amplified by VT1 to drive the speaker to send out the low-frequency alarm sound.



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