To interface it to arduino use a 7805 regulator.
No no no no no.
Never use a voltage regulator to reduce the voltage on a signal, that is just silly and causes you all sorts of problems.
It is like going out and buying a large book just to hold the door open.
It is the sort of thing beginners think of.
Use a two resistors in a potential dividor, or a transistor to get the signal to the right voltage.