4.31Display sensors
The gateway service that takes the temperature and humidity measured by a Veltnova wall display and writes them to KNX group addresses, so the display works as a room sensor.
Each Veltnova Android wall display has a temperature and humidity sensor built in. The Display Sensors service lets a display act as a room sensor on the KNX bus: the display tells the gateway what it measures, and the gateway writes it to the group addresses you choose. The readings are also published as System Values.
This is separate from showing a reading on a page. To show the display's own temperature on its own screen you need no service at all: see Veltnova wall displays.
#What it does
- Each listed display reports its temperature (degrees C) and humidity (percent) to the gateway while the app is open and signed in.
- The gateway writes the temperature as DPT 9.001 and the humidity as DPT 9.007 to the group addresses given for that display.
- The gateway publishes the readings as the System Values
display:<username>:temperatureanddisplay:<username>:humidity, named after the user the display signs in with.
#Before you enable it
- Each display needs its own gateway user (Gateway Properties > Users) and the Veltnova app on the display must be signed in as that user. The gateway recognises a display by the user.
- The KNX engine must be working.
- Needs gateway runtime 1.0.16 or later, and the app version that goes with it.
#Settings
Open Server > Internal services > Display Sensors. Enabled is Off by default.
| Setting | What it does |
|---|---|
| Label | The name of the service in the Server tree. Default Display Sensors. |
| Add Display | Adds a display to the list. |
Each display has:
| Field | What it does |
|---|---|
| Display User | The gateway user the display signs in with. |
| Temperature Group Address | Where the temperature is written (DPT 9.001). Leave empty to not write it. |
| Humidity Group Address | Where the humidity is written (DPT 9.007). Leave empty to not write it. |
The group address fields suggest your imported group addresses and have a browse button. The trash icon removes a display. A display with no user, or with no address, is not sent to the gateway.
#How it works on the gateway
- A value is written when it differs from the last written one by at least 0.2 degrees or 1 percent, and at least every 5 minutes even when it has not changed, so the bus never goes stale.
- The display checks its sensor every 30 seconds and reports it on the same rule, so the gateway hears from it at least every 5 minutes.
- A reading that is out of range (below -40 or above 125 degrees, or outside 0 to 100 percent) is ignored.
- The values are only written while the service is Enabled and the display's user is listed. Until then the gateway keeps the reading and does nothing with it.
- After a gateway restart the displays report again within a few minutes.
#Example
A living-room display that signs in as the user living.
- Add the user
livingunder Gateway Properties > Users, and sign the display's app in as it. - Open Server > Internal services > Display Sensors, turn Enabled on and click Add Display.
- Set Display User to
living, Temperature Group Address2/4/1and Humidity Group Address2/4/2. - Deploy.
The group address 2/4/1 now carries the temperature the display measures. An HVAC object or a thermostat can use it.
#Tips and common problems
- Nothing is written. Check that the service is enabled and deployed, the display's app is signed in as the listed user, and the KNX engine is running. A display with no sensor never reports.
- The value does not change often. That is on purpose: a small change is not written again until it reaches 0.2 degrees or 1 percent, or 5 minutes have passed.
- Two displays share one user. They report as the same display, and their readings overwrite each other. Give every display its own user.
- The temperature is a degree or two high. See the note above.