This was a simple power failure alarm circuit and it can be widely used where indication during power failure was required.Most of the power supply failure alarm circuits requires a power supply for themselves in order to make the alarm work.But there is no need of additional supply source to the alarm and this feature holds the advantage than other power failure alarm circuits.Lets see the working of this circuit.
WORKING:
The supply for this circuit can be derived from regular AC power supply and then it can be rectified to feed this circuit.The supply range of this circuit varies from (5 to 15V).To calibrate the circuit, first connect the power supply and then vary the potentiometer VR1 until the Piezo sounder goes from ON to OFF.
The electrolytic capacitor C1 was employed in this circuit to store adequate charge, to feed power to alarm circuit which sounds an alarm for a reasonable duration when the supply fails.This supports the circuit to work after the power failure without any external supply source.Whenever the supply fails Resistor R2 pulls the base of the Transistor Q1 low and saturates it, turning the sounder ON.The alarm sounds for reasonable time,until the stored charge in the capacitor discharges completely.
WORKING:
The supply for this circuit can be derived from regular AC power supply and then it can be rectified to feed this circuit.The supply range of this circuit varies from (5 to 15V).To calibrate the circuit, first connect the power supply and then vary the potentiometer VR1 until the Piezo sounder goes from ON to OFF.
The electrolytic capacitor C1 was employed in this circuit to store adequate charge, to feed power to alarm circuit which sounds an alarm for a reasonable duration when the supply fails.This supports the circuit to work after the power failure without any external supply source.Whenever the supply fails Resistor R2 pulls the base of the Transistor Q1 low and saturates it, turning the sounder ON.The alarm sounds for reasonable time,until the stored charge in the capacitor discharges completely.
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Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Clik here to view.
