A few weeks ago I installed a sunshine intensity sensor at my house to shut down my roller shutters automatically when the sun shines too much. The sensor is part of the TaHoma system from Somfy. It allows to configuring a threshold and enable automatically the defined settings. The TaHoma system is powered by a local box which communicates wireless with the sensors and actors. Configuration and data processing is done on central systems at Somfy. That's a problem because the local box doesn't provide any data. But there is a Flash interface for configuration (speaks Adobe Flex to the backend) and an iPhone App which uses a API to communicate with the central servers. So I decided to build a script which calls the API and sends the sunshine intensity to Splunk Storm. On the first approach I called the backend once a minute, because I would like to know how often the value is read. After a few days I got an email from Somfy asking to shut down the requests because I triggered some alerts (if they would use Splunk, they had found the issue earlier g ). I discussed some details of my actions with Somfy but they didn't agree to open the API documentation yet.
Let's have a look to the data which I generated:
There were a few sunny days in May!
If we look for one day only we can see that the sun arrives at 11:30 AM:
Let's go deeper into the data:
Now we can see that the intensity value is updated every 3 minutes! That's a nice information which isn't documented somewhere. Now I could reduce the interval from one minute to three minutes. But I think Somfy would not accept this frequency as well.
The real interesting information is that I now new which threshold is useful, because there is a range from 0 to 100.000. On the docs to the system you don't find the information which value belongs to a high sunshine density. Now I am able to compare the values with my opinions and set up the right value. Next step is to measure to rooms temperature parallel to the sunshine density. Then it is possible to find the ideal value for closing the roller shutters before the room's heat up to much.