Electronic circuits > Alarms/Indicators > Power supply failure alarm
Power supply failure alarmMost of the power supply failure indicator circuits need a separate power
supply for themselves. But the alarm circuit presented here needs no additional
supply source. It employs an electrolytic capacitor to store adequate charge, to
feed power to the alarm circuit which sounds an alarm for a reasonable duration
when the supply fails.
This circuit can be used as an alarm for power supplies in the range of 5V to
15V.
To calibrate the circuit, first connect the power supply (5 to 15V) then vary
the potentiometer VR1 until the buzzer goes from on to off.
Whenever the supply fails, resistor R2 pulls the base of transistor low and
saturates it, turning the buzzer ON.
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Published on: 2004-08-21 (4055 reads)
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