Digital Addressable Lighting Interface (DALI) is a protocol for digital lighting control that allows a robust, scalable and flexible lighting network to be connected and configured. DALI is currently the most widely used digital protocol. Lately, when talking about DALI control, in addition to DALI 2, DALI DT6 and DALI DT8 are often mentioned and discussed. But what is meant by these definitions?

Types of DALI devices

The DALI protocol is supported and advanced by the Digital Lighting Interface Alliance (DiiA), a group of global lighting companies aiming to develop the market for DALI-based control solutions.

The original development aim of the protocol was to allow digital control, configuration and interrogation of fluorescent lamp ballasts to replace the simple one-way, broadcast-like application of 0/1-10V dimming. With the DALI protocol, basic broadcast options are available and, through simple configuration, each DALI device can be assigned a separate address, allowing digital control of a single device.

DALI is a two-way communication protocol. The DALI protocol has been extended many times since its inception, and today it is possible to determine whether lamps are working properly and their level of luminous intensity, each new device being assigned a new unique number. The latest important updates concern emergency lighting (DT1), white light control (DT6) and RGB/TunableWhite (DT8). The following figure shows the components of IEC 62386. DALI DT8 and DALI DT6 are essentially the control systems of the DALI protocol. The former relates to lamps with colour temperature control, the latter defines the scope of control systems and intelligent drivers.

dali dt6 dt8

But how are their respective systems designed to handle their individual controls?
Despite their disparities, are they similar in some respects?

What are the control options?

Control options involve control systems, and a control system is responsible for managing commands and regulating the behaviour of other devices in an electronic system. And this is how DALI drivers work, integrating microprocessors for protocol management.

With DALI, the relevant control functions are already integrated in the ballasts. These control gear units enable luminaires to emit saturated light colours in accent lighting, for example. These light emissions take the form of colour temperature control (RGB/Tunable White).

How do the DT6 and DT8 control options apply? DT6 devices are the control systems and LED luminaires, while DT8 devices are the luminaires with the colour control function. A DALI control line allows individual devices and control units to be configured, after which functions such as addressing and grouping are achieved.

Four types of colour

The LED modules will always emit a colour of light according to four types of colour modes. The DALI DT8 protocol must support at least one of these modes. Not all DALI masters are similar, so it is not certain that all DT8-compatible master devices control all four colour types:

  • X-Y coordinates
  • Primary colour N
  • TC colour temperature with 2 colour channels
  • Colour RGBWAF

The Tunable White control concept

Tunable White lighting is a flexible control that allows you to control the output (intensity and colour appearance) of white light. Depending on your preference, DALI allows you to manually and dynamically change the light level and hue of the white light produced by your LEDs.

a1 3 DALI DT8 vs DALI DT6: the differences

The four colour types mentioned above define adjustable white lighting. The three colours red, green and blue can be combined to form a white colour. The combination of these three colours must be expressed in a correlated colour temperature (CCT). This combination allows us to perceive a white colour from red, green and blue. The CCT is expressed in Kelvin.

Both the DALI DT6 and the DALI DT8 can be used to achieve adjustable white control. The difference is that the DT8 requires only one address while the DT6 requires two addresses to produce adjustable white lighting.

What does a two-channel DALI DT6 system consist of?

DT6 refers to item 207 of IEC 62386. This part refers to the power supply or LED driver. The designation of a DALI DT6 LED driver should use a separate DALI-2 address for each channel in each product or ensure that an SSL system operates according to a predetermined colour intensity curve.

The IEC requirements for this part specify a control system using digital signals for electronic lighting that is in line with the requirements of IEC 61347, including DC power supplies.

To function effectively, a DT6 2-channel system includes:

  • Two independent DALI channels
  • Variably settable output currents via DALI for each channel
  • A single interface for flexibility

What does a DALI DT8 system consist of?

The DALI DT8 controller allows the colour temperature to be changed using an address. DALI DT8 commands can include the command to adjust the brightness intensity of a luminaire with regard to Tunable White, RGB and RGBW.

The DT8 LED driver refers to point 209 of the IEC standard and uses a single address for dual channels. A DALI DT8 system comprises:

  • 1 DALI address
  • Output currents adjustable via DALI
  • A single interface for flexible control

The difference between DALI DT6 and DALI DT8

The differences between these two types of DALI control are summarised below:

DALI DT6

DALI DT8

Type of device

LED control systems and luminaires are assigned to DT6

It is for luminaires with colour control

Addresses and Channels

It requires only one address for a single channel. For example, it would use one address to dim colour temperature and another address to dim light intensity. It can also use multiple addresses, e.g. Y number of addresses for Y number of channels.

It can use one address for two channels. For example, a single-address DT8 controller can dim the colour temperature and control the light intensity.

Protocols

Complies with IEC 62386 requirements of 101, 102 and 207

Complies with IEC 62386 requirements of 101, 102, 207 and 209

Conclusions

In conclusion, we can safely admit that DALI DT8 control saves time, labour, space, complexity and cost because:

  • The DALI DT8 uses a single DALI address to control two or more outputs on a special DALI DT8 LED driver. It therefore significantly reduces the number of such addresses and LED drivers for colour change control.
  • For Tunable white control, DALI DT8 requires only one address, whereas DALI DT6 requires two addresses.

DALI products from Universal Science

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