i wanna put a motion sensor in my grill so when people walk by the front of my car at night my lights turn red. Lights are already wired with leds. now it's a 2 part sensor. the eye is 1 part that runs off of a 9 volt battery. the other part with the speaker that makes noise runs of 4 c batteries or a 4.5 volt dc plug. what resistors or what not do i need to make these be able to run off the cars 12v system?