In this circuit, switches should be connected to 24V DC and arduino pins should check whether switches are on or off to control led behaviour. I don't know how to use 24VDC for this situation. I would be glad if someone can help. Thanks.
- Where you currently have pull-down resistors, place a voltage divider with 2 resistors instead. For example something like 3k9 + 1k, to get close to 5V.
- In case you are worried about the quality/level of the 24V (raw battery voltage etc), then first place a 33V TVS on it, then after the voltage divider, use one diode from ground to signal and one from signal to 5V, as shown here: How would I design a protection clipper circuit for ADC input?. Keep the forward voltage of the diodes in mind - if you pick a standard one with 0.7V then it won't be effective until you go > 5.7V which might be more than the MCU can handle. When in doubt, add a 10k current limiting resistor to the MCU pin.
- All diodes in your schematic are drawn backwards. The triangle of a diode points to the cathode (-).