Reno - Walls Open - Wiring Plan

[JDRoberts]

@Van-G

What about tripwire type sensor instead of motion or contact?

You mean a light beam like the ones used for garage door obstacle Detection? Or an actual physical tripwire?

Physical tripwires aren’t usually used in residential settings.

For discussion of the infrared option, see

In room detection of Occupancy

THE EXPENSIVE INFRARED DOUBLE BEAM OPTION BTW, if you are serious about this and you are the home owner (not just renting) it can be done very nicely with a double set of trip beams at about shoulder height. (Think of the alarm systems in movies like Mission Impossible. Or for that matter the “obstruction detected” sensor for a garage door.) By having two sets a few inches apart, you can detect whether someone is entering the room or leaving based on which one tripped first. However, people have to enter the room single file–if they break the beams at the same time, it will only count one person. And if you are carrying something shiny, you can confuse the detectors. Also, height can be tricky if you have large dogs and small children. Anyway…this can be done at a cost of about $800…