Once the goal of controlling our building automation system with an easily modifiable software has been achieved, just the imagination can limit the range of the possible applications.

In addition to the first obvious application to remotely control the devices with PCs, tablets, smart-phones or whatever browser enabled device, many further operations can be performed directly on the server side by the controller board, both using external sensors connected to the board or just by software algorithm.

The rolling shutters can be activated at a scheduled time for a gentle wake up with sunlight, or driven by rain or wind sensors in case of storms.
The room lights for children scared by darkness can be switched on or off automatically at a given time.
Lights and/or rolling shutters can be randomly activated to discourage possible burglars in an uninhabited house.
And so on.

A standard twilight switch works measuring the environment light and acting consequently.
A simpler, bust less efficient, way is with a timer switch, but it must be periodically corrected with season changing.
Anyway, the most classic light automation is activation of lamps in stairs, entrances, parks or yards during the night.
A more precise system can be obtained switching on light at the exact sunset time and switching them off at sunrise at that location.
Knowing the location latitude, the dawn and dusk time for each day of the year can be calculated, enabling an automatic correction without the needs of external sensors.
update on 27-08-2016

Twilight Switch

Control lights or rolling shutters according to the daylight

The original software has been written in Javascript for an HTML page by Renato Rizzi and republished with further explanation by Ellegi software. See at both sites for all the details about usage.

It has been ported with no effort on the node.js application server to just display the dawn and dusk time on the control page, updated at midnight. This information can be used to control the required devices according to the personal needs.