Building a clock and decided to include a battery backup.
I wanted a MOSFET, but a small DPDT relay is perhaps easier.
here is my schematic that I am consifering.
Why not just backup the timekeeping circuit like most normal people do. Your battery will go flat very quickly (assuming it's powering the LEDs) and you won't realise your power has gone off - or will you?
Why not just backup the timekeeping circuit like most normal people do. Your battery will go flat very quickly (assuming it's powering the LEDs) and you won't realise your power has gone off - or will you?
If you think way back to the start of this project (which has spanned several threads), the use of an RTC chip is somewhat beyond MrDEB's abilities. He's counting clock cycles in the micro, which makes battery backup somewhat more complex.
It looks like MrDEB is planning on using a 9 volt battery. An alkaline 9 volt battery supplying 33mA will last less than 24 hours a day based on an hour use each day.