Sch. for Sensing 16-12 VDC using a I/O on arduino

Hey guys... I ran across this schematic, and it looks plausable that I could use this to sense whether I see 16-12 VDC on a vehicles starter wire using a standard Arduino 5v I/O and just reading if its high or not.

Basicly I just want to sense if the starter relay coil is energized or not. Instead of using a voltage divider, or 5V regulator like others have mentioned, I thought this circuit was interesting, as it looks like the voltage can fluctuate some and still have a somewhat consistent output.

Let me know your thoughts.

The links to the diodes are here: D1 = D2 =

Too complex for your need. All you require is the 5.1volt zener and the 1k resistor feeding it. I'd suggest you go for a 4.7volt zener to ensure you remain below the 5volt requirement. This will produce a maximum of 10ma through the zener, 47mw of dissipation, so no problem with component heating jack

Thank you so much for this valuable feedback! I’ll try it out!