Temperature Sensors

About 10 RS485 temperature and humidity sensors have been installed around the house to monitor the environmental conditions. These were purchased from AliExpress (Search ‘RS485 Temperature Sensor’), but were modified slightly. Rather than using the enclosure that came with the device, they were hot glued to a standard Australian blank wall plate. This required that the RS485 connector be modified to sit on the other side of the PCB, and a small (6.5mm) hole be drilled into the wall plate. A significant amount of mineral wool insulation was also used in the wall cavity to ensure that the correct environmental conditions were being monitored.


The results are rather interesting. There is some noise on the sensors unfortunately, but some averaging has removed most of this. This graph is actually showing not the outside conditions, but the conditions in my garage as I am doing some testing. Note the temperature drop at 5am. This is when I left the house to go running, opening and then closing my garage door.


The Home Assistant GUI allows me to superimpose all the sensor results on one graph. The one below is interesting for a couple of reasons. First, the temperature in the dining room seems to drop more quickly than any other indoor sensor. The interesting thing here is that this sensor is the only one in the house that is near an internal brick wall rather than a gyprock wall. It would seem that the thermal mass of the wall causes the temperatures to drop more quickly than in other rooms.

The other thing to note is the blue line indicating the master bedroom. The temperature sensor in this room is able to determine when I get up from the temperature spike. I have yet to determine if this is an actual spike or is due to air flow. Testing this will be easy.

I also have a sensor in my laundry to monitor conditions there. The good news is, at least when I am not using the washing machine, that the humidity is fairly low.