DALI Helps & Troubleshooting – Introduction to MOONS' DALI LED Driver

DALI is a digital protocol. Signal levels are defined as:

1. Logic "0" corresponds to a bus voltage between −4.5 V and +4.5 V (typically 0 V), while logic "1" corresponds to a bus voltage between +9.5 V and +22.5 V (typically 16 V).

2. The maximum DALI bus current for each system or subnet is 250 mA, and the maximum current consumption of each load interface is 2 mA.

3. Network cables should provide basic insulation with a voltage rating of at least 250 V. In practice, 600 V-rated cables are commonly used to provide additional safety margin. For a cable length of up to 300 m, the maximum permissible voltage drop between the bus power supply and the furthest device is 2 V.

When planning and wiring a DALI (Digital Addressable Lighting Interface) system, several basic rules should be observed to ensure stable and reliable operation:

It is recommended to use no more than 63 addresses per DALI subnet. Although the DALI standard supports up to 64 addresses, reserving one free address simplifies system maintenance, such as temporarily replacing faulty devices, performing automatic addressing, or adding new devices without re-addressing the entire subnet.

In general, DALI connections are not polarity-sensitive, as the bus receiver typically includes an internal bridge rectifier that automatically handles either polarity. However, certain devices, such as sensors with auxiliary power supplies, D4i drivers, or legacy products, may require correct polarity to be observed. Therefore, the manufacturer's instructions should always be checked during wiring to avoid improper operation.

The maximum supply current of a DALI bus is 250 mA. The total current consumed by all DALI devices on a subnet must not exceed this limit. Exceeding 250 mA may result in unstable communication or improper device operation. If additional current capacity is required, the system should be divided into multiple subnets with separate DALI bus power supplies.

DALI cabling and connections should be treated in the same way as mains wiring. Although the signal level is only 16 V, the hardware is not SELV-rated (Safety Extra-Low Voltage). Therefore, wiring practices and protective measures equivalent to those used for mains wiring should be applied during installation.

A 2-conductor, mains-rated cable must be used for DALI wiring. A conductor cross-sectional area of at least 1.5 mm² is recommended, for example by using two conductors from an RVV 2×1.5 mm² or NYM 3×1.5 mm² cable. Shielding is generally not required, but the cable should meet the required insulation specifications.

Check the number of addresses: Ensure that no more than 63 device addresses are used on each DALI subnet. Although the DALI standard supports up to 64 addresses, reserving one free address simplifies maintenance.

Check the total current consumption of connected devices: The total current consumed by all DALI devices on the bus must not exceed 250 mA. Standard DALI devices typically consume 2 mA each, while special devices may require additional current; refer to the manufacturer's documentation where necessary.

Check the cable length: The total cable length between the bus power supply and the furthest device should not exceed 300 m. A conductor cross-sectional area of at least 1.5 mm² is also recommended.

Check the DALI bus voltage: Use a suitable multimeter to measure the DC voltage across the DALI bus. Under normal conditions, the measured voltage should ideally be between 16 V DC and 22.5 V DC, and should never fall below 9.5 V DC.

Check the voltage drop: The voltage drop between the bus power supply and the furthest device should not exceed 2 V. A measured voltage below 14 V DC may indicate excessive voltage drop and can result in unstable communication.