DALI Sensors
Introduction to DALI sensors
DALI-2 sensors are devices that send control commands to the DALI bus. These can, for example, be push-button sensors, rotary sensors or brightness sensors.
The DALI specification distinguishes between two types of DALI sensors:
- “Application controllers” are devices that send DALI control commands directly to DALI operating devices.
A short press on a DALI push-button, for example, sends a switching telegram to all connected DALI operating devices. - “Input devices” are devices that send operating commands to a higher-level controller via the DALI bus. This higher-level controller, e.g. the DALI gateway, analyses the operating commands and then sends control commands to the corresponding DALI operating devices.
However, there are also DALI sensors that can operate either as “application controllers” or as “input devices” in instance mode. This requires the devices to be reprogrammed using DALI commands. If a higher-level controller is used, reprogramming is carried out automatically during commissioning. This is also the case with the DALI Gateway.
Application Controller
In a DALI system, there must always be at least one device that sends control commands to DALI operating devices, i.e. works as an application controller.
A distinction is made here as to whether it is a single-master device or a multi-master device. With single-master devices, there may only be one transmitting device in the DALI system. With a multi-master device, several devices can send control commands to DALI operating devices. The non-transmitting devices read the control commands and track the status internally so that there are no light jumps or status errors when operated by another device.
Input devices (instance mode)
A sensor that works as an input device requires a higher-level controller that can analyse the operating commands transmitted. In this case, this higher-level controller is the KNX DALI Gateway.
The DALI specification defines instances that ensure correct command evaluation and application between the sensor and the higher-level controller. The sensor and the DALI Gateway must understand the same command set, i.e. support the same instance.
Each functional unit of a DALI sensor can be an instance of the device.
Examples:
- DALI-2 rotary control device. The push and rotary operation can each be a separate instance.
- DALI-2 motion detector with integrated brightness evaluation. Both functions can be independent instances.
The following instance types are specified in the DALI-2 standard:
- Instance type 1: push-button (62386-301)
- Instance type 2: analog input, (62386-302) (used, among other things, for: sliders, rotary knobs, temperature sensors, etc.)
- Instance type 3: motion detection measurement (62386-303)
- Instance type 4: light intensity measurement (62386-304)
- Instance type 0: instance type that is not defined in the DALI standard, but is specified by the sensor manufacturer (general purpose, 62386-103)
DALI sensors and KNX DALI Gateway
In addition to controlling DALI operating devices via KNX components, the gateway also offers the option of using DALI sensors to control the DALI operating devices. To do this, the DALI sensors are linked to the DALI gateway via DALI sensor commissioning. The individual functions of the DALI sensors can then be assigned to the DALI groups or individual devices via KNX group addresses as if they were KNX sensors.
KNX actuators can also be controlled via the DALI sensors.
Since the DALI Gateway is a multi-master device, DALI sensors can also be integrated as application controllers that directly control DALI operating devices. The DALI Gateway receives the control commands for the operating devices and tracks the status so that, for example, a KNX visualisation always displays the correct status of the luminaires.
Number of DALI sensors
The number of sensors that may be operated in a DALI system depends on how great the energy consumption of the sensors is and how many DALI operating devices are available.
Up to 32 sensors can be addressed per DALI system. There are also 32 sensor channels available per DALI system. The maximum current consumption limit of 2 mA does not apply to sensors. Sensors often require a significantly higher current consumption.
No more than 148 mA may be used per DALI system to supply all DALI devices. It is thus necessary to add up the current consumption of the individual sensors and the operating devices in order not to exceed the maximum permissible current consumption for the planned project.
DALI system with DALI sensors
The gateway functions as a master control component (master controller) within a system, which also guarantees the power supply of the DALI interface. The DALI operating devices, e.g. electronic ballasts, work as command receivers (slaves), which only return states or status messages to the master on request. It is the task of the gateway to transmit control commands received from the KNX onto the DALI line and to check the operating devices. The use of other DALI control components in multi-master operation, for example, DALI sensors as application controllers, is possible.
Communication between the KNX system and the DALI interface takes place bidirectionally via the gateway. On the one hand, the gateway receives telegrams from the KNX, which either directly influence the brightness state of a DALI group or of individual operating devices (e.g. by switching, dimming, brightness value specification or scene recall) or adjust it indirectly (e.g. with time, disabling or forced position functions). The gateway always determines the current brightness states of the groups and single devices internally and forwards brightness commands to the DALI operating devices, which then adjust themselves to the appropriate brightness. On the other hand, the internally-tracked switching or brightness states of the groups and single devices can be fed back to the KNX. It is also possible to transmit the status information of the DALI operating devices (lamp error, electronic ballast error) or gateway (mains voltage failure, DALI short-circuit) to the KNX.
DALI-2 sensors as application controllers
The DALI Gateway is a DALI-2 multi-master device that allows the use of additional DALI control components in multi-master operation. The DALI Gateway reads the telegrams from connected DALI-2 sensors and tracks the status of the individual groups or individual devices so that a KNX visualisation displays the correct status of the DALI operating devices.
A DALI-2 rotary control device can, for example, be integrated into a DALI system (Principle overview of a KNX-DALI system integration with DALI sensors (example)) as an additional control point. This DALI sensor must fulfil the following requirements:
- It must be a certified DALI-2 sensor.
- The application controller must be activated in the respective sensor.
- If the DALI sensor has its own DALI power supply, this must not be connected.
- The following control commands are supported:
- control of the absolute brightness (arc power level),
- absolute colour temperature values (Color Temperature Tc),
- absolute RGB colour values (SET TEMPORARY RGB DIMLEVEL)
- absolute white values WAF (SET TEMPORARY WAF DIMLEVEL)
The DALI sensors as application controllers are not taken into account during ETS project design and commissioning.
