I am trying to make a timer which will normally be plugged into the mains socket during normal operation. It has a 16F877A & one 16x2 LCD module. LCD module is powered by the PIC itself.
I would like to ask if someone has a good design or an idea to put PIC on backup battery power as soon as there is a mains powercut without resetting it. I will be using an smps delivering 12V to 7805 which will give 5 V to my PIC.
Through one resistance from 12V, PIC will know about the powercut and will switch OFF the LCD & turn it back on when power returns.
I have 3V backup plan (2 x AA) (NON-RECHARGEABLE). Can someone help me put it together so PIC can jump straightaway to 3V & back to 5V when power returns.