Environment: Arduino MEGA 2560 R3
My project is quite simple, The board is in sleep state all the time. It wakes up only when a low voltage is detected on the interrupt pin and writes a value to EEPROM.
The circuit is connected to a PC via USB. At any point, the PC can ask Arduino for the stored value.
The PC will be turned on only during daytime but my circuit has to work even when the PC is off. Therefore, I need an external battery power supply.
From https://www.open-electronics.org/the-power-of-arduino-this-unknown/, it appears Arduino can work fine if 6V is applied to VIN pin.
Q1. Can I use a 9V battery instead? Q2. If I use 4 1.5V batteries in series, do you see any problem with that? Q3. Is there a way to make Arduino draw power from USB source if it is available? Otherwise, it can fall back to battery pack. I am thinking this will increase the battery life.
Your help is truly appreciated.