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More  Beepers & Buzzers;    Piezoelectric

Very Loud Pulsating Beeper Keeps Average DC Current Draw Low

Many battery powered alarms draw excessive current when operating.  Some of the most attention-getting noise makers, such as the unit shown below, use piezoelectric sound generators with a frequency sweeping tone.  When operating with a 9v battery, these units can often draw 100ma or more. In many applications, a continuous alarm sound is not needed.  Locating a balloon or a rocket are examples where you want a loud sound but a low average power drain.  To lower the average current, the device can be pulsed with short 0.05 second chirps, once every two or three seconds.  This lowers the average current by a factor of 60.  So, instead of drawing 100ma, by chirping the alarm, the current is lowered to just 2ma.  The circuit below generates the pulse train needed for these short but very loud chirp sounds.
  Pulsating Beeper  


Click on Drawing Below to view PDF version of Schematic

More  Beepers & Buzzers;    Piezoelectric

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