On my long list of things to get around to (which I'm going to try and be better at tackling from now on) is some temperature and humidity monitoring in my flat.
This is a bit of a brain dump as I'm still in the thinking/planning stage.
We have no tumble dryer so we dry clothes inside[1] (usually the spare room which doubles as my office). We need a dehumidifier anyway as the airflow in the flat isn't great (it's a 4 storey house chopped up into flats so any original concepts of airflow are long gone, no air-bricks above the ground floor, etc). This got me thinking about monitoring temperature and humidity.
Anyway, my ideal solution would have (in preference/implementation order):-
* office / spare bedroom (temp, humidity, radiator temp by ziptie-ing a sensor to the copper inlet pipe to allow me to tell how often the heating is on)
* lounge (temperature/humidity)
* main bedroom (temp)
* hall (temp)
* bathroom (temp, humidity)
* kitchen (temp, humidity)
* MiniGB's bedroom (temp)
I have a soldering iron, dangerously minimal knowledge of DS18B20 Dallas 1-wire stuff (and associated 1-wire humidity sensors), raspberry pis and good linux/scripting/DB/web knowledge to hack something together to do this.
Ideally I'd have one/two/three separate 1-wire networks with minimal spurs, but the wiring plan is the main problem.
The office/spare bedroom and lounge are easy as both have computers in, so an extra bit of RPi stuff behind the scenes won't be a problem, but getting stuff to other parts of the house is tricky as I don't want to be drilling through walls or laying my own ugly cabling anywhere (I suppose I could hide some thin cabling along the edge of carpet/skirting board but this would be a considerable faff.
On a run earlier I remembered that there's a load of wiring already in place in the form of an alarm system with passive IR sensors. We've never used the alarm (mainly because we've got good security anyway, and we're a first floor flat so way less likely to be burgled than a ground floor, and for insurance reasons[2]). I've been meaning to get rid of the alarm system for ages (I put it into maintenance mode long ago and so the control panel by the front door has been blinking a spanner at me for years). The siren has been disconnected but the main alarm box is still wired into the mains (with it's own fuse in a white socket-sized box so hopefully easy to isolate). I was hoping to unhook it from the mains and then use the existing wiring (to the passive IR sensors and the outside alarm box) for the 1-wire stuff. I could then minimise the number of RPis I'd need to deploy around the flat.
The office/spare-bedroom and lounge would still be done by the existing computers (or Pi zeros).
The main bedroom has a panic button wired to the alarm that I could hopefully borrow the cable from.
The hall has the main alarm box in a cupboard so that's an easy location for the central RPi.
The bathroom, kitchen and daughter's bedroom would require some cabling as there's nothing going that way (although the kitchen has a phone extension that doesn't seem to work, it's probably connected to the phone socket in the spare bedroom that also doesn't work (I'm pretty sure the previous occupants had a second line put in at some point). I could hopefully borrow the cabling from that phone extension to connect the kitchen to the spare bedroom.
The other useful thing about using the alarm wiring is that I'd be able to stick a temperature sensor and humidity sensor outside in the existing alarm box (where it will be nicely sheltered from the rain) since there will be a cable from the main alarm box inside to the branded alarm box on the wall outside. (And it'd be nice to have outside temperature and humidity, ideally air pressure too.)
I was also thinking of using the wires between the main alarm box and the keypad by the front door to run USB power there to run a Raspberry Pi that shows the local bus times (
https://yacf.co.uk/forum/index.php?topic=71021.msg2077623#msg2077623) as that project has sat doing nothing for two years (and would still be useful).
Eventually I'd like to run an ethernet cable down to where my bike is kept so I can put a RPi/camera/arduino in there and also capture the blinky light on the electricity meter to monitor our usage. Should check again but last time I did it I couldn't get wifi working reliably, too many walls, otherwise this RPi could also get the outside temp/humidity for me.
I'd really like to keep the number of RPis to a minimum (the above plan calls for 4 or even 5 depending on how I do things) and each extra USB wall wart just adds to the fire risk.
[ If/when I ever get the flat rewired I'd get them to put in some proper 3-core cabling everywhere (along with cat 6 networking and aerial coax) so I could do this all properly. ]
Anyway, initial brain dump done, will come back and add to this when I've thought about it some more, would be interesting to hear of anyone else's solutions to this kind of thing.
1. Except for the two weeks in the summer it's nice enough to do this outside, although our patch of garden is a bit of a schlep. In the summer it's just easier to dry clothes inside with the windows open.
2. Home insurance company said declaring the alarm would only take £10 or so off the bill and we'd have to remember to set it every time we went out.
