LOW power HALT, battery and supplys.

i have heard can put arduino "sleep mode makes low power consumption.

being am, thought have power saving mode , have small battery keep alive.

the rtc has alarm output pin can use "wake up" arduino, , turn on main power.

then output of power supply go through 7805 re-charge battery , power arduino, , rest of circuit.

well, battery on output of 7805, need have diode on output stop battery feeding 7805.

alas there problem there 5 v become 3.8 volts (or ever is.)

thinking back, around problem put diode (same 1 after output) between gnd pin of 7805 , gnd offset drop.

right?

quote

..have small battery keep alive..
alas there problem there 5 v become 3.8 volts (or ever is.)
thinking back, around problem put diode (same 1 after output) between gnd pin of 7805 , gnd offset drop.

not good.  you drop voltage more, 5v - 2x diode_drop.
the best way put small battery (what mean small?) @ 7805 input (btw, there better voltage regulators today) of 2 diodes.

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