AC-DC, switch to glow LED and BUZZER

GENERAL DESCRIPTION:

Ø In this project , LED glows when AC supply  is on and as soon as AC cuts off circuit switch to DC supply and then  LED and BUZZER is turn on which is controlled by a switch. In this circuit we use a Relay for switching

COMPONENTS USED:   

 Step-Down transformer (240V to 12V).

  Bridge-Rectifier(w04M).
  
   LEDs (3mm x2).

 

                  Buzzer (6V).

     

   Relay (12V DC-SPDT).

   General purpose PCB sheet

  

         DC source (9V battery).

WORKING:

Ø First of all 220V is step-down to 12V by a step-down transformer.

Ø Bridge Rectifier then convert this 12V AC into DC.

Ø Then a resistance and a LED is attached in parallel to the rectifier.

Ø After this a 12V Relay is attached parallel with this circuit.

Ø A 9V battery with a switch, LED and a BUZZER is attached with the second pole of the Relay.