I have two in voltage about equal power sources, a built in 12V and an external solar+battery backed up stable 12V source.
I looking for a simple solution to switch immediately to the other one because my circuit contains a raspberry pi 2 as well what I would not like to reboot.
There can be only 2 situations for my circuit:
1, Solar power source comes on (the main is force switched off)
2, Solar power goes out (the circuit is switching back to main)
Also I would like to completely turn off the main adapter with a relay when the device operates from solar not to waste power.
I realize this is possible by using a simple 12V relay in default close position connected to the solar input only and using 2 reverse current protections on both lines but would a big cap on the supply end be sufficient enough to keep the device operation for a second when the power switching happens?