Since I have a very well insulated house, the heat inside the house dissipates very difficult once heated up. My aim is to keep the heat out of the house by means of automatically working sunscreens at every window facing the sun. I have been struggling for a long time to get it working properly.
First I tried to determine whether the sun is shining be means of LUX sensors. (Fibaro Multisensor). Apart from the fact that they didn’t work as trustworthy as I hoped, they solely measure sunlight intensity, which is something different than sun warmth. Furthermore the multisensor is not meant to be mounted outside, requiring a protection enclosure, which affected the LUX readings. This also rendered the temperature sensor of the Fibaro Multisensor useless, since it is mounted in direct sunlight inside a box. So I concluded a separate temperature sensor would be required.
While trying to combine the LUX sensor with a Temperature sensor, I came to the idea to simply look at the difference between the temperature of direct sunlight and the ‘standard’ outside temperature (shadow). I found out that this is a trustworthy way to determine whether the sun is shining, and at the same time it provides me with proper temperature data. The Fibaro Binairy sensor I use can handle 4 temperature sensors simultaneously. Currently it measures temperatures of sunlight, shadow (outside temperature), inside living room and cellar.
It all resulted in the following flows:
- One flow calculating the average shadow temperature, using the last 18 raw data readings
- One flow calculating the average sunlight temperature, using the last 18 raw data readings
- One flow calculating the temperature difference and set a Boolean at a certain value
- One flow measuring the shadow temperature and set a Boolean at a certain value
These flows are closing the sunscreens:
- One flow setting above mentioned Boolean TRUE when temperature difference is more than 7ºC
- One flow setting above mentioned Boolean TRUE when shadow temperature reaches 20ºC
- One flow checking if both booleans become TRUE and if so, lower the sunscreens (also depending on the time).
These flows are opening the sunscreens:
- One flow setting above mentioned Boolean FALSE when temperature difference is less than 5ºC
- One flow setting above mentioned Boolean FALSE when shadow temperature is less than 20ºC
- One flow checking if Boolean for temperature difference becomes FALSE and if so, open the sunscreens.
The result as shown in Insights over the course of two days:
If somebody is interested in the actual flows, please let me know here. I could post these too.