List of DIY Electronics Engineering Projects

POWER SUPPLY FAILURE ALARM CIRCUIT WITHOUT BATTERY BACKUP

This circuit alarms you whenever their is a power failure in your mains supply and the circuit doesn't use any additional Voltage Source.
It is simple to design and effective to construct.

Power failure alarm circuit monitor your supply line and trigger the buzzer to produce beep sound when their is a Voltage drop.
This circuit finds applications in Refrigerators, Fish Tank, air conditioner etc...

All the components used in this circuit is cheap to buy and easily Available in the market.


CIRCUIT DIAGRAM
COMPONENTS AND THEIR SPECIFICATION
WORKING PRINCIPLE:-
 The circuit mainly consisting of a stepdown transformer, a bridge rectifier, an PNP transistor and a buzzer.
The step down transformer step-down the high Voltage AC to a safer value for the circuit to work fine.
And this low voltage alternating current is now fed to a bridge rectifier to make it unidirectional.
The diode D2 and capacitor C2 forms a filter for this unidirectional alternating current and eliminate the available ripples from the voltage.

The first part of this circuit includes a stepdown Transformer, Bridge rectifier and a filter converts AC to almost DC, which is required for the operation of transistor Q1.

The second part of this circuit includes a PNP transistor BC558, a buzzer and a capacitor.

The rectified output from the first part is given to the base of a PNP transistor. This transistor remains OFF when their is a voltage at its input.

Whenever the power supply fails or drops below certain value the input voltage of the transistor reduces and triggers the buzzer connected across the collector terminal. The voltage required to beep the buzzer is delivered by an high value capacitor connected in parallel to the buzzer and transistor.

The diode D1 is used to avoid the discharge of c1 through there. And D2 is used to avoid the discharging path of C2.


PLEASE NOTE:-

  • The input to this circuit is 230V AC, so take extra care while designing and troubleshooting.

  • The Capacitor C1 act as a Voltage source in the absence of Main supply so choose the value of C1(Electrolyte Capacitor) as large as possible.

  • This circuit is not suitable for childrens below 13 years old.


  • Tittu Thomas

    Author & Editor

    I'm Tittu Thomas, An Electronics and Communication Engineer from India, Kerala. I love doing hobby electronics circuits, blogging, programming, etc. Started this blog while doing my B-Tech degree under CUSAT university.



    3 comments so far:

    1. Hello
      No components values in this article.

      ReplyDelete
    2. I am sorry.......
      And its updated.....

      ReplyDelete
    3. This comment has been removed by a blog administrator.

      ReplyDelete

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