Hello, I built an home alarm and it works OK in the protoboard and mounted on a work table. Now to put it operational the PIR sensor along with an on / off switch is at the entrance of the house and about 15 meters, on the second floor, I plan to put the arduino. Is there any limitation with the distance ??
In my home alarm distance = 3 m I don't think it's a problem (until first lightning)
assuming the PIR is a digital HI/LO, and it needs some power, I think the only limit is on the resistance introduced by the cabling. 15M should not be an issue.
Make sure you use pullup/down for the PIR connection.