battery backup plan

[MrDEB]

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.













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[aliarifat794]

Looks OK. However, it is better to simulate the circuit.

 

[Nigel Goodwin]

Jesus, all you need is a single diode, or at most two - but the second isn't usually needed (as the bridge rectifier usually serves that purpose).

 

[Diver300]

It doesn't look right that the relay needs to be energised to connect the backup battery.