# Define Trigger

The **trigger** determines when the automation is executed. This can be initiated by various events or conditions, such as reaching a specific time, a sensor event, or a change in the weather.

**Steps to Select a Trigger:**

1. **Add Trigger:**
   * Click on "**Add your first trigger**" A dialog window will open where you can select the platform or event that should trigger the automation.
2. **Select Platform:**
   * In the "**Platform**" dropdown menu, choose the appropriate platform or category that provides the trigger.
   * Examples of platforms:
     * **KNX**: Access KNX group addresses to use devices or scenes on this platform as triggers.
     * **OpenWeather**: Set weather conditions as triggers (e.g., rain, sunset, temperature change).
     * **System**: System events like restart or shutdown can also be used as triggers.
     * **Variables:** Changes in defined system variables can also serve as triggers.
3. **Multiple Selection (Optional):**
   * If you want to select multiple triggers simultaneously, you can activate the "**Multiple selection**" option. This allows you to define several events as potential triggers that are monitored in parallel.
4. **Search for Triggers:**
   * Use the search field to find specific triggers more quickly, especially in larger installations or when many group addresses are present.
5. **Confirm:**
   * After selecting the desired trigger, close the window to add the trigger to the automation.

{% hint style="info" %}
**Note:**

* Triggers are the first step of every automation. They define when and under what circumstances an action is executed. By using different platforms, you can utilize a wide range of events as triggers to optimally automate the system.
  {% endhint %}

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