thank you all !
I need to detect 0Vdc or >60Vdc (system on).
You say using a optocoupler I only need one resistor in series? I guess just like you would light up a led right? great ! I need to build 10 of this in a board so the fewer the parts the better.
so how can I choose the optocoupler? as I say, the system should have 0 V when OFF and around 60 or more Vdc when it is ON. I just need to dectect if its ON or OFF.
I will need for each subcircuit:
1 x 1N400x diode (to protect reverse voltage)
1 x Resistor to feed the optocoupler. Dont know which one as I dont know the optocoupler
1 x Optocoupler
Any additional help on selecting one for this particular use, bearing in mind the input voltage can go from 60 to 80Vdc and with surges.
once again, thanks a lot, this is a really important proyect.