I'm a newby to electronics.
I have an Arduino Leostick that I need to be able to trigger off both 9 and 12 volt nominal from batteries. The 9 volt battery currently gives 9.3 Volts but that voltage may drop over time. I have no way of knowing what the real voltage from the 12 Volt battery is, it could be giving 12.6 or even 13.5 volts or more for all I know, it's the size of a car battery. The Leostick must NOT trigger at 3.4 volt input, or anywhere near that voltage.
Which resistors are suitable for a voltage divider? Should I be using analog or digital input?
What happens to an Arduino if the input is, say, 5.3 volts on an analog input for a period of no more than 10 seconds? Would it register as 0.3 volts or 5 volts or fry the circuits? Does the digital input switch from LOW to HIGH at 2.5 V?