555 ambulance audio circuit

Published:2011/4/25 1:41:00 Author:May | Keyword: 555, ambulance audio | From:SeekIC

As shown in diagram 21-1, this circuit consists of two ambipolar 555, and it all works at multivbrator state. It is not hard to equate frequency of two oscillators by parameter in the diagram. f1=1/T=1.44/[(R2+Rp)C1] When resistance of potentiometer RP changes in the range of 0~75kΩ, corresponding frequency is 14.4Hz~0.9Hz. f2=1.44/[(R2+2R5)C2]≈700Hz IC2 is controlled by low frequency square wave of IC1. When output square wave of IC1 is low level, oscillating frequency of IC2 is low; and when output of IC1 is high level, oscillating frequency of IC2 is high ,so the loudspeaker can send out rhythm sound of di-da, di-da . Output sound frequency can change by changing the time constant of R4, R5 and C2.



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