Old-school IoT sensing with absolutely no AI

Winter is coming, as one might say. Actually it is here, with freezing temperatures and inches of snow. Time to turn on the heater in the garage. However, if someone leaves a door open it will heat the atmosphere in general and burn through all of the propane. Yes, it would be absolutely trivial to put magnetic sensors on the doors that turn off the heater if the door is open but that is no fun at all. This has actually been a long-running project with all kinds of interesting solutions, some even including Apache NiFi and other big data things. One solution used Insteon and actually allowed the system to automatically close doors. However, various disasters could occur and I turned this system off. In any case, the Insteon door sensors were not reliable.

The root of the problem is that the system really has to understand what is happening in the space, not just the states of various parts of it. Someone could be just about to back a car out when the system decides to shut a door. Not good. Seemingly, a perfect and autonomous solution is still a little way down the road. A short term hack seems in order, however!

Since I am working on rt-ai Edge right now, it was natural to think about how to use rt-ai Edge to solve this problem. I have some ZeroSensors around so I put one of them in the garage. I realized that, when the doors are shut, the garage is very dark and the temperature stable at the thermostat setting (allowing for hysteresis). If a door is open, the garage gets illuminated in one way or another (garage door motor lights, ambient light, outside lights at night etc) and is a somewhat reliable, albeit indirect, indicator of door status. Also, the temperature will drop pretty quickly, giving an indication that either a door is open or the heater has failed.

Given how simple this is, I put together a quick filter SPE to process the light and temperature data from a ZeroSensor and send me an email if the doors are seemingly open for more than a preset time. The screen capture above shows what is going on. There are actually a couple of stream processing networks (SPNs) in action in this space, mainly running on the rtai0 node. One of them is the YOLO-based driveway vehicle detection system while the other is the garage environmental sensing network. A node can be running multiple SPNs at the same time – they are ships in the night and can be managed totally independently.


This screen capture shows the configuration dialog for the SensorFilter SPE. I currently also have it set to confirm when the garage doors have been shut so that I know if someone else has taken care of the problem.

Another step would be to turn the heater off if a door is open and the temperature is dropping – right now, I am not planning to allow the door to be shut remotely for the reasons mentioned earlier. At least turning the heater off avoids wasting a load of energy. I can control the heater via Insteon. I would just need another SPE to provide the interface between the filtered alerts and my Insteon server.

Still, one day it would be nice to do this properly. This entails understanding the state of the space – things like are there any people in it? This is not completely trivial as the system can’t always see someone inside a car. However, it can assume (until I get an autonomous vehicle) that if a car is moving or has moved, there must be someone driving and, until the system detects that person leaving the space, it must also assume that it should take no autonomous action. However, it needs to maintain state in order to be sure that there’s nobody in the space (or in a car just outside the space) so that it can take control. I have a feeling that there may be quite a few corner cases with this but it would be fun to try, even if it only simulates trying to close doors.

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