Realtime Clock in Arduino
Jump to navigation
Jump to search
Internal
Arduino has an internal clock. Is shut down if Arduino loses power. Can use 3.7 battery for power. Library is RTC.h.
https://www.arduino.cc/en/Reference/RTC
Power draw for Arduino on standby on 3.7V is about 20ma. So uses about 1.5Whr every 24 hours.
See more about Relay#Power Draw
External
Module is cheap - [1]