"Most 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."
For more information and documentation of the project.Click on the download button.