KNX Weather Station

KNX Weather Station – Overview :

The KNX Basic weather station records weather data, analyses these and can transmit them to the bus. The device has a wind sensor, precipitation sensor, temperature sensor and brightness sensors. -Self contained outdoor weather station. For measuring wind, rain, brightness and temperature.

For fully automatic blinds and sun protection control with automatic adjustment of blinds according to position of the sun. 

Rain sensor with integrated heating. The weather station can also be operated without mains supply. The heating of the rain sensor will not function then. Measurement and evaluation directly on device. Sun protection for up to three facades via  integrated brightness sensors. 

A KNX weather station includes a variety of sensors to measure different weather-related parameters, including:

• Temperature sensor: Measures air temperature.
• Humidity sensor: Measures humidity levels in the air.
• Wind speed sensor: Measures wind speed and direction.
• Rain sensor: Detects the presence and intensity of rainfall.
• Solar radiation sensor: Measures the intensity of sunlight.
• UV radiation sensor: Measures the level of ultraviolet (UV) radiation.
• Barometric pressure sensor: Monitors atmospheric pressure.
• Ambient light sensor: Measures the level of natural light.

sun protection channels. additional threshold channels for connection of external KNX sensors. And logic channels. Display of weather data on visualization. KNX software functions: Adjustment of slat position according to current position of the sun. Sun protection area both horizontal (azimuth) and vertical (elevation) can be set exactly. 

The ETS (Engineering Tool Software) enables application programs to be selected, specific parameters and addresses to be assigned and transferred to the device.

KNX Weather Station Available in brands:  Schneider, Theben, ABB, GIRA, eelectron, Jung, Elsner. 

Few Things to Remember

• Rain is only detected when the rain sensor is sufficiently wet. There can be a delay between the first raindrops in a shower to the point where rain is detected. 
• When the rain stops, and despite heating, it can take several minutes before the sensor is dry again and the device is able to detect that correctly. 
• When it is windy, awnings/blinds take time to retract. Configure the wind thresholds below the value provided by the awning/blinds manufacturer.

KNX Weather Station Technical Details

(A) Rain sensor & heating 

(B) 3 light sensors (front, right and left) 

(C) Programming push button and LED for the physical address 

(D) Rotor 

(E) Temperature sensor 

(F) Screws for aligning the weather station 

(G) Screw for fastening the weather station on the wall bracket

Weather Station Mounting Tips:

• Do not install the wind sensor in a sheltered position. 

• Avoid shadows (e.g. from masts etc.) and reflected light. 

• Pay attention to mounting position 

    – Rain sensor pointing up 

    – Rotor pointing down

* Fixing on MAST is recommended if wind is to be registered from all directions

Brightness sensors:

These are described in the ETS application software as Sensor front, Sensor left and Sensor right. These designations comply with frontal view of device, in accordance with the following diagram: 

Sun position adjustment:

The sun position adjustment controls the slats of the blinds or the shutter/awning height according to the actual position of the sun in the sky. The slats are always positioned so that the sunlight cannot shine through while the room is still kept as light as possible (no lighting required)
Date, time and the geographical location data are required for this function.

Azimuth and the course of the sun:

Azimuth: Here, horizontal angle of the sun in the sky at a specific point in time. 

Course of the sun: Path that the sun takes through the sky between sunrise and sunset.

 Example Stuttgart (approx. 48°47′ N, 9°11′ E):

Elevation:

Angle of elevation of the sun over the horizon at a certain point in time. 

Example of Stuttgart:

Calculation: The highest possible position of the sun (upper culmination) of the year is reached on the day of the summer solstice i.e. on 21 June (for a location north of the Tropic of Cancer). 

In simplified, this position of the sun can be calculated with the following formula: 

Maximum possible elevation ≈ 113.43° – latitude of location.

Example of Mumbai: 
Latitude approx. 19.08° N  
Maximum possible elevation = 113.43° – 19.08° = 94.35°

Façade Direction:

Alignment of the facade to be shaded, i.e the direction an observer is looking at if he looks straight out of the window.

 The direction can be read with a compass (point needle straight to the north) or consult an architect. 

Example: South east 135°.

KNX Weather Station ETS parameters:

Physical values:
Object 0“Brightness value at front” 
Sends the current brightness value at front brightness sensor. Only the value measured directly by the installed sensor is sent. Received external brightness values are not considered.

Object 1 “Brightness value left” 
Sends the current brightness value at the left brightness sensor (looking at device from the front). Received external brightness values are not considered.

Object 2 “Brightness value right” 
Sends the current brightness value at the left brightness sensor (looking at device from the front). Received external brightness values are not considered.

Object 4 “Temperature value” 
Depending on the configuration, sends the current temperature value either if there is a change and/or cyclically.

Object 5 “Wind speed” 
Depending on the configuration, sends the current wind speed if there is a change and/or cyclically. The unit used, i.e. m/s or km/h, Beaufort can be selected on the measured values parameter page.

Object 6 “Rain sensor” 
This 1-bit object sends the current rain status – “1” for “rain” and “0” for “no rain”. Depending on how it is configured, it can be sent only when the status has changed, after a change, or cyclically

Object 8 “Local time” As a transmission object: Sends the current time in DPT 10.001 format, depending on the configuration: only on request, cyclically or at specific times (see “Send time and date” parameter table). As a receive object: Used to set the time via the bus: 

Object 9 “Local date” 
As a transmission object (send time): Sends the current date in DPT 11.001 format, depending on the configuration: only on request, cyclically or at specific times. As a receive object (receive time): Used to set the date via the bus: 

Object 10″Time query”Object sends time query to bus clock to receive the current time

Object 12 “Elevation” Height of the sun over the horizon. 0° corresponds to sun at lowest point on horizon (sunrise or sunset). The actual elevation depends on the latitude and date and time. 

Object 13 “Azimuth” 
Horizontal angle of the sun in all directions. 0° = North 90° = East 180° = South 270° = West

Object 15 “Temperature sensor status”
 0 = Sensor OK. 1 = Error. 

Below Images is from KNX Home Lynk device of Schneider Electric which shows Weather Parameters from KNX Weather Station.

Courtesy: Schneider Electric

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