I have a system that sometimes generates a 12V signal to a DPDT relay coil, which switches on a 12V connection through the relay pins that can be used as a boolean signal to the arduino. I plan to do this by connecting a 5V L7805 regulator, followed by a 1n4007 diode to drop the voltage to approx 4.3V +-10% which should be safe.
My question is, should I be concerned about inductance from the relay coil? I know arduinos don't like inductive loads. Also, are any additional resistors necessary in this configuration, i.e. with the arduino i/o pins configured as inputs with pullup resistors?
If you can foresee any problems with this setup, please let me know.