I am building a home sentry system, but not just to detect unwanted visitors. Here in Florida, we have many snowbirds, i.e., folks who stay here for several months of winter, then go up North for the summer.
These folks could use a long term monitor that reports to them by email or text message if some parameters get out of range.
Besides monitoring for temperature, humidity, possible break ins, fire detection, I want to detect water leakage into the house. I've known of folks who came back in the fall to find that a window seal had failed, and a lot of water damage had occurred.
So a cheap way to build an area-coverage leak detector would be to twist together two insulated wires, provided they had a water-permeable insulation, and then string a length of it along the floor. The twisted wires would have near-infinite resistance, unless they gat wet. So a simple voltage divider and analog pin on an Uno would do the trick. (Long term corrosion might imply replacement of the wires now and then.)
I remember wire from when I was a kid ( a loooong time ago), which was insulated with some sort of wrapped cotton thread. That would be ideal, but I haven't found anything like that when searching the net.
Does anybody out there know of some type of wire with a water-permeable insulation? Thanks in advance for any suggestions.
Cotton covered wire was used for winding coils in radio circuits, so look for ham radio suppliers.
But yes corrosion will be a problem even in the absence of liquid water, so after a year or so it might not work. That applies to all sorts of resistive sensors. You could try a capacitive sensor and have a solder ion iron like sponge as the dialetric.
Paul__B:
Just run two bare stainless steel wires (Mig wire) under the carpet.
The easiest and cheapest would be to go to a farm store and get some white woven PVC fence wire with 4 or more stainless steel wires woven the length of the wire. Each wire is insulated from the other and the woven PVC makes it easy to handle.
jrdoner:
I remember wire from when I was a kid ( a loooong time ago), which was insulated with some sort of wrapped cotton thread. That would be ideal, but I haven't found anything like that when searching the net.
I had a 3 KM roll of 4 core TOW missile wire some years back like that.
4 Core steel cotton covered.
Humidity will change in the building. It would be far easier to add a temperature humidity sensor per room and monitor for any change. A broken or open window would alter that room paramters.
I believe you should be able to detect if a person is breathing base on accurate humidity readings.