Two (2) questions re: 12V to 5V, if I may…

Hello DFRobot,

I am interested in 752 for use with an Arduino or RaspberryPi to detect an automotive key on.  Would this work or should I use a 2 channel (1 of the 2 channels) signal input to detect existence of 12V (key ON)?

I know an opto coupler circuit will work,  and like the DIN rail type level converter.

Other question relates to 752, and VIN shown on signal input side.  Where does that VIN originate from?  I ask because I have a sensor with 7 inputs which by default are 12V (inactive) and ground (0V) when 1 of the signals are active/ON.  I assumed I only needed the 1 signal on the left hand side and the output would be a converted Arduini compatible output (5V OFF, 0V ON).

Thank you,

Brian.