J-M-L:
Yes, but if you tilt the sensor to face the inside of the car then you can limit undesired triggering. The lens is often fixed to a certain sweep and distance and you can usually set the sensitivity through a potentiometer on the board. you can hack the fresnel lens as well by putting some electric masking tapes to avoid "shooting too large" and only bring in radiation that are happening in a limited range.--> Experimentation is key!
Well I would only have the sensors armed when I'm not in the vehicle or anything. I want it to activate if someone reaches into my jeep when I have the top and doors off. Id find the best spot to cover the area in the jeep. Id like to maybe use 2 or 3 sensors. Can these be run in series or do they all need to be hooked up to the arduino board separately
I do see what you mean though with the masking tape, being if it can reach 10 meters, I dont want it shooting to far.
Is it possible to wire in a remote to the arduino board to arm and disarm it like you would a regular car alarm?