I used a PJRC AVR Teensy 1.0 to make a bike light controller. Basically it keeps the headlight and front and rear flashers on for two minutes unless it gets an interrupt from a reed switch on the spokes and magnet on the wheel, which resets the two minute countdown.
I used a 4.5 volt phone charger for building and testing and got it working perfectly.
The problem is when I use 3 AAA batteries. It only works for a few minutes and not when it is cold.
So, apparently, 4.5 volts is right at the edge of margin of error of the 5 volts the board is supposed to need.
Shit, they don't make 5 volt batteries or batteries that can be combined to give me 5 volts.
It doesn't have an off switch, just sleep mode.
I thought of using a regulator and 4 AAA batteries, but I don't know how much current will be drained by the regulator when it is in sleep mode.
Maybe I can just get away with 6 volts.