Automatisation of Basement Windows

Our basement was generally too humid. The 6 windows were open in summer and closed in winter time.

When the windows are open, the outside air gets inside, but because the temperature of the incoming air takes on the inside temperature, also the relative humidity changes (mainly in summer, when windows are open, the relative humidity inside gets very high).

Solution: Measure the temperature and the relative humidity inside and outside and calculate the absolute humidity for both, inside and outside. If inside absolute humidity is higher than outside, windows will open, the other way round (with a certain hysteresis) windows will close. [Second condition for opening the windows: the temperature inside is not allowed to fall below 12 degrees Celsius (because of the stored food) - in winter time, the absolute humidity inside is nevertheless very low.]

Because the sensors are in relative big distances (ca. 20 m), we use the RS 485 communication protocol.