DALI feedback telegrams

Feedback for DALI short-circuit

The gateway detects short-circuits on the DALI cable, as may occur in the case of an installation error.
If the DALI system is overloaded, e.g. because too many DALI sensors are used, a short circuit is also detected.

As soon as a short-circuit is identified on the DALI cable with the mains power supply switched on, the gateway transmits a status to the KNX when the status function for DALI short-circuits is enabled.

The gateway uses the 1-bit communication object "Status - DALI short-circuit" for the status of a DALI short-circuit. The telegram polarity of this object is fixed: No short-circuit = 0. Short-circuit = 1.

Setting feedback for DALI short-circuit

In the ETS, it can be defined whether the status for a DALI short circuit is to be transmitted to the KNX. When enabled, telegram transmission is always actively transmitting. As soon as a short-circuit has been detected and eliminated, the gateway transmits a status telegram without a delay. The parameter "DALI short circuit" on the parameter page "DALI system... -> General" defines the behaviour of the short-circuit monitoring.

The connected DALI operating devices also react to a short-circuit in the DALI cable. The devices set themselves to the specified "System Failure Level". This brightness value is defined by the behaviour "in case of bus voltage failure" parameter of a group or single device.

The status of a DALI short-circuit can be transmitted only if the bus voltage is connected and switched on at the time of the short-circuit. If no bus voltage is connected and switched on at the time of the short-circuit, no status is transmitted either. Feedback is saved, however, which means that it is transmitted later when the bus voltage is switched on.

The gateway initialises after switching on the mains power supply or after an ETS programming operation. If a short circuit is detected on the DALI line in this state, the gateway also transmits a corresponding status. After the bus voltage returns (mains voltage switched on permanently at the gateway during bus failure), the feedback is not automatically sent on the bus.

Feedback for mains voltage supply at the gateway

The gateway can monitor its supply voltage at the mains voltage connection. If there is a failure, the gateway is able to transmit a status telegram to the KNX before stopping operation, provided the bus voltage is uninterrupted. Optionally, the switch-on of the mains voltage supply can also be fed back.

If the mains voltage supply of the gateway and the connected DALI operating devices are connected to the same circuit, the operating state of an entire DALI system can be monitored on the KNX side by evaluating the mains voltage status.

For the status of a power failure or mains voltage return, the 1-bit communication object "Status - Supply voltage" is used at the gateway. The telegram polarity of this object is fixed: Mains voltage available = 0. Mains voltage failure = 1.

Setting feedback for mains voltage supply

In the ETS, it is possible to define whether only a failure of the mains voltage supply of the gateway is reported to the KNX or additionally also a mains voltage return. Telegram transmission is always actively transmitting. As soon as there is a change of state in the mains voltage, a feedback telegram is transmitted once. The parameter "Supply voltage" on the parameter page "DALI system... -> General" defines the behaviour of the mains voltage monitoring.

The status of a mains voltage failure can be transmitted only if also the bus voltage is connected and switched on at the time of the failure. If no bus voltage is connected and switched on when the mains voltage returns, no status is transmitted either. Feedback is saved, however, which means that it is subsequently transmitted when the bus voltage is switched on later.

The status is not transmitted automatically to the KNX after the bus voltage returns or after an ETS programming operation.

DALI busy

During operation of the gateway, it is possible for the telegram load of the DALI system concerned to increase, especially if a number of control functions of the groups and single devices are running simultaneously. The gateway signals "DALI busy" if the load reaches or exceeds a defined limit with the effect that trouble-free operation of the DALI system is no longer guaranteed. This signalling takes place if the parameter is activated on the 7-segment display of the device ("db" indication) and optionally also to the KNX by means of a 1-bit communication object "Status - DALI busy".

A DALI busy can occur, for example, if several colour wheel sequences run simultaneously in different groups or single devices. This can lead to continuous or intermittent overloading of the DALI system, which means that hues cannot always be safely transmitted to the operating devices. To identify such disturbed operation, the DALI busy status can be used.

With the "2-gang" product variant, the DALI system (1 or 2) affected by the load is additionally signalled by the corresponding status LED. If both DALI systems are affected, signalling takes place simultaneously with both status LEDs.

A DALI system is considered to have a maximum load if a DALI telegram is sent approx. every 35 ms. This corresponds to approx. 28 DALI telegrams per second. The limit value for detecting a DALI busy is set to a load of approx. 75%.

If the gateway detects a heavily loaded DALI system, it indicates this overload for a duration of 10 seconds on the 7-segment display and also via the KNX status object. If the load continues beyond this time, the gateway automatically extends the indication for at least ten more seconds. The status in the KNX object is then also retained. The gateway revokes the status only when the load of the DALI system falls below the defined limit value again.
Optionally, an acknowledgement can be used. In this case, the gateway resets the status in the DALI busy object only when confirmation has been received by the separate 1-bit acknowledgement object.

In the event of a DALI busy, the gateway attempts to send out all the necessary control commands in sequence and completely on the DALI line. Commands received via KNX (e. g. switching, dimming, values) or specifications regarding internal functions of groups and single devices (e.g. colour wheel sequence, HCL or CTM matrices) are transferred to the DALI side as quickly as possible. However, this can lead to noticeable delays or even telegram losses due to the high load of the DALI system!

Setting DALI busy

The status for the indication of a DALI busy can be configured separately in each DALI system on the parameter page "DALI system... -> General" configurable.

No DALI busy is generated during ongoing DALI commissioning or device initialisation after an ETS programming operation.

The gateway does not automatically transmit the DALI busy status after a device reset (ETS programming operation, bus/mains voltage return) even if the status was active before the reset. The status is only reported when a high load occurs after initialisation of the gateway.