As there are too many powercuts in our country, i need to add backup power to the arduino...
as my project involves PIR sensors, once the power is lost the arduino does not keeptrack of the state of the buttons, and the sensor takes about 20-60 seconds to calibrate...
so i am thinking connect the 12v adapter to a battery and then from the battery to the arduino
so when power is there, the battery is simultaneously charging and powering the arduino and when power is not there the battery powers the arduino..
so which is the best and cheapest option, the battery can be a very low powered one even 500mah @ 12v could do the work.. since arduino uses very little power..