i used a relay logic to give a back up power to my microcontroller when the main supply is removed. Now it is moving smoothly when the main supply is gone, as it provides the back up, but when the supply comes back the relay is vibrating instead of cutting off. what is the reason for this ? how can i solve it ?

 

Attach your schematic. Then the members can assist you.

 

i'll be sending the shematic soon

 

Wild guess: lack of a protection diode so the back emf generated by the coil when the relay shuts down triggers the driving IC again (if applicable). Happened to me with a 555 timer. After I removed the diode, the relay connected to the timer output started behaving like that.