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Timer for a buzzer

Discussion in 'General Electronics Discussion' started by Melkor6000, Mar 12, 2012.

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  1. Melkor6000


    Mar 12, 2012
    As part of a recent electronics project, I included a piezo buzzer, which I want to have buzz for about a second, and then stop.

    I have tried using a 555 timer in monostable mode, but that doesn't work, since the voltage that triggers the buzz is continuous (I gather from other reading that a monostable oscillator only works when the lifetime of the trigger voltage is shorter than the discharge time.)

    Is there a way to put something in-line with the buzzer, which causes a continuous voltage to become a ~1 second pulse? It would need to be able to do this time after time (a reset button is an option, since I have space for it on the console).

    Thanks, and please respond if something is unclear in my question.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Place a capacitor between the "continuous voltage" and the trigger pin of the 555.

    That way, whenever the voltage turns off, a brief pulse will set off the monostable.

    See here. Note that you need a negative going transition to trigger the 555.
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