I ran into a problem for an extention on a existing product.
The problem is that this needs to work even when the AVR is in reset :(
(It's some times hold in reset and that can't change).
I need at signal to a PLC (dry set of contacts) to tell when a voltage get's below about 1.8V (and release above 2-3V not critical ).
I plan on using a reed relay for the signal.
The system is powered with 12V.
I have not done this kind of work for many years, so I would try to get it working with a LM339 or perhaps a NE555
But perhaps there is a better way ?