Detecting car ignition lock state

Other Hardware General Electronics
1

Did someone try to connect arduino to standard car ignition lock ?
I just want to check if the car is turned on or not.

Would some step down converter + one GPIO do the trick or do i need do use relay ?

Regards !
A.

2

Voltage divider of 47k from either ignition or accessories line in car to input pin and 27k from that input to ground.

Also 1N4148 or similar diode from input pin pointing to Vcc

Also 1 µF capacitor from same input pin to ground.

Input pin reads HIGH when more than 7 V on ignition or accessories line.