Check for 12V with Arduino (Two resistors and a diode)
No the schematic is incorrect, there will be a constant 5 V on ARDUINO_PIN because you've connected it straight to +5V.

Also, general convention for drawing schematics is to have the input on the left and output on the right.

The diodes are not doing anything either.

If the Arduino board is working on that +5V supply then all you need is a resistor divider that makes about 5 V from the 12 V, like so:







simulate this circuit &ndash; Schematic created using CircuitLab

There is no need for additional diodes.
When an Arduino is operating on 5 V then an input voltage above about 5V/2 = 2.5 V is considered a "1" so 4.8 V is more than enough.