555 Timekeeping audio circuit

Published:2011/4/25 22:18:00 Author:Ecco | Keyword: 555 , Timekeeping , audio circuit | From:SeekIC

The circuit is shown in Figure 14-31, it is a timing signal controlled multivibrator composed of 555. Pin 4 of 555 is the force reset terminal, when the pin voltage drops below 0.4V, the circuit will go to non-trigger state. Using the foot control to external timing signals, usually it shows a low potential, while the voltage of time signal being higher than 1V, the circuit turns and issues an audio time signal with about 400Hz. Pin 4 of 555 is connected to the output clock timing, or connected to the security and other sensing devices deflection point by a 10kΩ resistor. Once there is a high mutation, the speaker will issue a hasty sound, the parameters of oscillator can be changed by the R1, R2, C1.



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