Digital Addressable Lighting Interface
Digital Addressable Lighting Interface (DALI) is a trademark for network-based systems that control lighting in building automation. The underlying technology was established by a consortium of lighting equipment manufacturers as a successor for 0–10 V lighting control systems, and as an open standard alternative to Digital Signal Interface (DSI), on which it is based.
|International standard||IEC 60929 and IEC 62386|
|Developed by||Activity Group DALI, since 2017: Digital Illumination Interface Alliance|
|Superseded||0–10 V lighting control|
|Cable||mains-rated, with 600 V isolation, separate or part of power cable|
|Signal||16 V DC|
|Max. voltage||22 V DC|
|Max. current||250 mA|
|Protocol||asynchronous, half-duplex, serial protocol over a two-wire bus|
|Pin 1||+DALI bus|
|Pin 2||−DALI bus|
DALI is specified by technical standards IEC 62386 and IEC 60929. Standards conformance ensures that equipment from different manufacturers will interoperate. The DALI trademark is allowed on devices that comply with the current standards when manufactured.
Members of the AG DALI (founded by Philips lighting in 1984) were freely allowed to use the DALI trademark until DALI working party was dissolved on 30 March 2017. Since 9 June 2017, Digital Illumination Interface Alliance (DiiA) certifies DALI equipment. DiiA is a Partner Program of IEEE-ISTO.
A DALI network consists of a controller, a power supply (which may be built into the controller) and one or more slave devices (e.g., electrical ballasts, LED drivers and dimmers) that have DALI interfaces. The controller can monitor and control each device by means of a bi-directional data exchange. The DALI protocol permits devices to be individually addressed and it also allows multiple devices to be addressed simultaneously via multicast and broadcast messages.
Each device is assigned a unique short address in the numeric range 0 to 63, making possible up to 64 devices in a basic system. Address assignment is performed over the bus using a "commissioning" protocol after all hardware is installed. DALI gateways can be used to implement systems that have more than 64 devices. Data is transferred between controller and devices by means of an asynchronous, half-duplex, serial protocol over a two-wire bus, with a fixed data transfer rate of 1200 bit/s.
A single pair of wires comprise the bus used for communication to all devices on a DALI network. The network can be arranged in a bus or star topology, or a combination of these. Each device on a DALI network can be individually addressed, unlike DSI and 0–10V devices. Consequently, DALI networks use fewer wires than DSI or 0–10V systems.
The bus is used for both signal and power. A power supply provides ≤ 250 mA at 16 V DC; each device may draw up to 2 mA.:20,35 While many devices are line-powered, low-power devices such as motion detectors may be powered directly from the DALI bus. Each device has a bridge rectifier on its input so it is polarity-insensitive. The bus is a wired-AND configuration where signals are sent by briefly shorting the bus to a low voltage level. (The power supply is required to tolerate this, without supplying more than 250 mA.)
Although the DALI control cable operates at ELV potential, it is not classified as SELV (Safety Extra Low Voltage) and must be treated as if it were at mains potential. This has the disadvantage that the network cable is required to be mains-rated, with 600 V isolation, but has the advantage that it may be run next to mains cables or within a multi-core cable which includes mains power. Also, mains-powered devices (e.g., HF ballasts) need only provide functional insulation between the mains and the DALI control wires.
The network cable is required to provide a maximum drop of 2 volts along the cable.:19 At 250 mA of supply current, that requires a resistance of ≤ 4 Ω per wire. This wire size needed to achieve this depends on the length of the bus, up to a maximum of 16 AWG (1.3 mm2) at 300 m.
The speed is kept low so no termination resistors are required,:21 and data is transmitted using relatively high voltages (0±4.5 V for low and 16±6.5 V for high:19) enabling reliable communications in the presence of significant electrical noise. (This also allows plenty of headroom for a bridge rectifier in each slave.)
Each bit is sent Manchester coded (a "1" bit is low for the first half of the bit time, and high for the second, while "0" is the reverse), so that power is present for half of each bit time. When the bus is idle, it is high voltage all the time (which is not the same as a data bit). Frames begin with a "1" start bit, then 8 to 24 data bits in msbit-first order (standard RS-232 is lsbit-first), followed by a minimum two bit times of idle.
A DALI device, such as a HF fluorescent ballast, can be controlled individually via its short address. In addition to this method of control, DALI devices can be arranged into groups in which all devices of the same Group can interact with each other. For example, a room with 4 ballasts can be changed from off to on in three common ways:
Using the Short Address, e.g. sending the following DALI messages:
- DALI Short Address 1 go to 100%
- DALI Short Address 2 go to 100%
- DALI Short Address 3 go to 100%
- DALI Short Address 4 go to 100%
This method has the advantage of not relying on the limited number of scenes available in each ballast, or having programmed each ballast with the required group numbers and scene information. The fade rate of the transition can be chosen on the fly. This method can have an undesirable side effect called "Mexican Wave" when a single large room such as an auditorium contains many ballasts, due to network latency of the comparatively slow 1200 baud rate of DALI. For example, a transition from all on to all off may result in a visible delay between the first and last ballasts switching off. This issue is normally not a problem in rooms with smaller numbers of ballasts.
Using the DALI Group previously defined for the ballasts in the room, e.g.:
- DALI Group address 1 go to 100%
This method has the advantage of being immune to the "Mexican Wave" effect as described above. This method has the disadvantage of requiring each ballast to be programmed with the required group numbers and scene information, and has a fixed fade rate which is preset at the time of commissioning.
Using the DALI Broadcast command all, every ballasts will change to that level, e.g.:
- DALI Broadcast go to 50%
DALI lighting levels are specified by an 8-bit value, where 0 means off, 1 means 0.1% of full brightness, 254 means full brightness, and other values are logarithmically interpolated between, giving a 2.77% increase per step. That is, a (non-zero) control byte x denotes a power level of 103(x−254)/253.
(A value of 255 is reserved for freezing the current lighting level without changing it. In a response, it indicates a lamp failure.)
This is designed to match human eye sensitivity so that perceived brightness steps will have uniform brightness change, and to achieve a uniform brightness between units from different manufacturers.:21
Devices store 16 programmable output levels as "scenes". A single broadcast command causes each device to change to the configured level, e.g. dim lights over the audience and bright lights over the stage. (A programmed output level of 255 causes a device not to respond to a given scene.)
A 17th "system failure" scene is triggered by a loss of power (sustained low level) on the DALI bus, to provide a safe fallback if control is lost.
DALI commands are 16 bits long, an address byte followed by a data byte. The address byte specifies a target device or a special command addressed to all devices.
When addressing a device, the least significant bit of the address byte specifies the interpretation of the data byte, with "0" meaning a lighting level byte follows, and "1" meaning a command follows.
When sending a special command, the data byte is a parameter. An important special command saves the data byte to a "data transfer register" which is then used as a parameter by subsequent addressed commands.
Address byte forms:
0AAAAAAS: Target device 0 ≤ A < 64.
100AAAAS: Target group 0 ≤ A < 16. Each device may be a member of any or all groups.
101CCCC1: Special commands 256–271
110CCCC1: Special commands 272–287
111xxxx1: Reserved (x ≠ 15)
1111111S: Broadcast to all devices.
|Set Value||Broadcast / Groups / Channels||Send direct level values||R/W|
|Off||Broadcast / Groups / Channels||Send the off command||R/W|
|Up||Broadcast / Groups / Channels||Increase value by 1 until Max Level, honouring the fade time||W|
|Down||Broadcast / Groups / Channels||Decrease value by 1 until Min Level, honouring the fade time||W|
|Step Up||Broadcast / Groups / Channels||Increase value by 1 until Max Level, ignoring the fade time||W|
|Step Down||Broadcast / Groups / Channels||Decrease value by 1 until Min Level, ignoring the fade time||W|
|Recall Max Level||Broadcast / Groups / Channels||Output Max Value||R/W|
|Recall Min Level||Broadcast / Groups / Channels||Output Min Value||R/W|
|Step Down and Off||Broadcast / Groups / Channels||Decrease value by 1 /Turn off||W|
|On and Step Up||Broadcast / Groups / Channels||Turn on / Increase by 1||W|
|Go to Scene x||Broadcast / Groups / Channels||Go to scene 1–16||W|
"OK, Lamp Failure"
"Off, Lamp Power On"
"Off, Limit Error"
"No, Reset State"
"Missing Short Address"
|Device||Channels||Status of the Device||R|
|Lamp Power On||Channels||Is the Lamp on?||R|
|Version Number||Channels||Replies: Current Version||R|
|Device Type||Channels||Replies with the device type||R|
|Actual Level||Channels||Query Current Level||R|
|Max Level||Channels||The Max level the Device can go to||R/W|
|Min Level||Channels||The Min level the Device can go to||R/W|
|Power On Level||Channels||Lamp output with voltage recovery||R/W|
|System Failure Level||Channels||Lamp output in the event of system malfunction (e.g. interrupted DALI line)||R/W|
|Scene Levels||Channels||Sets the levels for Scene.||R/W|
|Fade time||Channels||Time in seconds for fading from the current brightness value to the new brightness value||R/W|
|Fade rate||Channels||Fade steps per second that are performed in response to an indirect fade command (Up and Down commands)||R/W|
A "DALI 2" extension adds support for "controls": inputs such as daylight sensors, passive infrared room occupancy sensors, or manual lighting controls. These are commanded with 24-bit commands, which are ignored by DALI lighting devices, so up to 64 controls may share the bus with up to 64 lighting devices.
DALI and Bluetooth
On 2017-02-16 the Mesh Professional Lighting Subgroup was created as a forum to discuss and develop Bluetooth mesh technology as a foundation for the wireless lighting standard.
- "DALI - a working party of ZVEI". www.dali-ag.org. 30 March 2017. Retrieved 23 July 2017.
- "DiiA acquires DALI trademarks" (PDF). Digital Illumination Interface Alliance - IEEE Industry Standards and Technology Organization. 9 June 2017. Retrieved 23 July 2017.
- "Communication in building automation". Siemens Building Technologies. Siemens Building Technologies. 2013. Retrieved 12 July 2013.
- "Digital Addressable Lighting Interface" (PDF). DALI. DALI AG, Activity Group, ZVEI-Division Luminaires. September 2001. Archived from the original (PDF) on 27 June 2013. Retrieved 12 July 2013.
- Artistic Licence. "The DALI Guide" (PDF). Artistic Licence. Retrieved 1 March 2016.
- Wago. "DALI/DSI Master Module 750-641 manual" (PDF). Wago. Wago. Retrieved 1 March 2016.
- "WAGO-Software WAGO DALI Configurator" (PDF). Wago. Wago. Retrieved 1 March 2016.
- "Digital Addressable Lighting Interface (DALI) Control Devices Protocol PART 1-2004" (PDF). Draft Version 1.13. National Electrical Manufacturers Association. 20 October 2004. NEMA STANDARD PUBLICATION 243-2004.
- "Wireless extension for DALI". Virtual Extension. Virtual Extension. 2014. Retrieved 3 August 2014.
- "Mesh Professional Lighting Subgroup (mesh-lighting)". The Official Bluetooth SIG Member Website. Bluetooth Special Interest Group. 2017. Retrieved 29 April 2017.
- DALI at ZVEI - Zentralverband Elektrotechnik- und Elektronikindustrie e.V.
- Digital Illumination Interface Alliance