DALI (Digital Addressable Lighting Interface) enables individual control of luminaires over a standardized low-voltage bus. DALI-2 extends this with native sensor integration and improved interoperability. This guide covers DALI fundamentals, system architecture, BACnet gateway integration, and practical commissioning for building management systems.
DALI is a digital communication protocol operating on 16-24V DC (typically 24V) with daisy-chain topology. Each device has unique short address (0-63) or group address (0-15). Two-way communication enables devices to acknowledge commands and report status.
| Aspect | DALI | DALI-2 |
|---|---|---|
| Release | 1990 (IEC 60929) | 2022 (IEC 62386) |
| Dimming Control | Yes (0-100%) | Yes, enhanced |
| Integrated Sensors | No (via gateways) | Native support |
| Device Standardization | Variable | Improved |
| Backward Compatibility | N/A | Full DALI compatible |
DALI-2 provides better occupancy/temperature integration while maintaining compatibility with legacy DALI devices.
Components:
Wiring Topology: Single twisted-pair carries both power (24V DC) and data (1200 baud). Devices daisy-chain in series (no star topology). Maximum 300m total cable length; typical segment 50m.
| Gateway | BACnet | Max Devices | Sensors | Cost | Best For |
|---|---|---|---|---|---|
| Helvar Digidim Pro | Yes (native) | 128/zone | Integrated | $8-12k | Institutional |
| Encelium (Osram) | Yes (native) | 254 | Yes | $6-10k | Corporate |
| Philips Hue Professional | Yes (gateway) | 250+ | Integrated | $5-15k | Scalable |
| Dacapo DALI Gateway | Yes (MSTP/IP) | 254 | Via gateways | $2-3k | Cost-sensitive |
DALI zones expose as BACnet objects:
DALI Zone 3 (Conference Room)
├─ Light_Level (AV) → Present_Value: 0-100% dimming
├─ Scene (AV) → 1-254 scene selection
├─ Occupancy (BI) → 0/1 occupancy status
├─ Daylight (AV) → 0-100% ambient light %
├─ Energy (AV) → kWh consumption
└─ Fault (BI) → 0/1 lamp failure status
Integration Mapping Table:
| BACnet Object | Purpose | Read/Write | Unit |
|---|---|---|---|
| Zone_01_Level | Lighting dimming | RW | % |
| Zone_01_Scene | Scene selection | RW | Scene# |
| Zone_01_Occupancy | Presence status | R | Boolean |
| Zone_01_Daylight | Ambient light | R | % |
| Zone_01_Energy | Power usage | R | kWh |
| Zone_01_Fault | Lamp/ballast status | R | Boolean |
Niagara DALI Module:
IF Manual_Override THEN
Zone_Level = Override_Value
ELSE IF Occupancy THEN
Base = Setpoint
Daylight_Reduction = (Daylight_% / 100) x 50
Zone_Level = Base - Daylight_Reduction (minimum 30%)
ELSE
Zone_Level = 5% (nightlight)
ENDIF
Occupancy-Based Switching: Motion detector → 15-min timeout → Lights to nightlight (5%)
Daylight Harvesting:
Ambient Light (lux) → Lighting Level
0-200 lux → 100% (no daylight)
200-400 lux → 70% + 30% natural
400-600 lux → 40% artificial
600-800 lux → 20% artificial
>800 lux → 0-5% (natural only)
Energy savings: 40-60% in perimeter zones; ROI typically 3-5 years.
Standard Lighting Scenes:
| Scene | Level | Use Case | Timing |
|---|---|---|---|
| Occupied Day | 100% | Low daylight (winter) | 8am-12pm |
| Occupied Evening | 60% | High daylight (summer) | 12pm-5pm |
| Unoccupied | 20% | Occupied traffic expected | 5pm-10pm |
| Cleaning | 80% | Maintenance operations | Ad-hoc |
| Emergency Exit | 5% | Nightlight/backup | 24/7 |
| Off | 0% | Late night shutdown | 10pm-6am |
Site Survey:
Device Addressing:
Sensor Configuration:
Niagara Integration Testing:
Devices Offline/Not Responding:
Sensor Not Triggering:
Scene Selection Not Working:
Daylight Harvesting Not Engaging:
Calculation Example: 5,000 m2 Office
DALI with BACnet gateways enables sophisticated lighting control integrated with building management. Proper commissioning, sensor calibration, and control logic design deliver 40-60% energy savings in optimized buildings.