Dusk-to-Dawn and PIR Outdoor Lighting with KNX: Photocell, Motion Boost and Timer Logic
Combining a KNX photocell with PIR motion sensors gives exterior lighting a two-tier energy strategy: a low base level runs from dusk to dawn for safety, and a motion boost activates full brightness only when presence is detected — reducing energy consumption during no-motion periods by up to 80%.
Elsner P03-KNX-FLAT photocell: twilight and lux integration
The Elsner P03-KNX-FLAT is a wall or pole-mounted KNX weather station that provides both a twilight bit (DPT 1.001) and a calibrated lux value (DPT 9.004) on separate group addresses. The twilight bit is the primary trigger for dusk-to-dawn base lighting, while the lux value enables more precise threshold-based control.
Elsner P03 KNX group address configuration
ETS6 parameter settings for Elsner P03-KNX-FLAT: Twilight threshold: 50 lux (adjustable 1–200 lux) Twilight hysteresis: 10 lux (prevents rapid cycling at threshold) Group addresses (recommended scheme): GA 10/0/0 — Twilight bit DPT 1.001 (1=dark, 0=daylight) GA 10/0/1 — Brightness lux DPT 9.004 (0–100,000 lux) GA 10/0/2 — Wind speed m/s DPT 9.005 (optional, if P03-KNX-WS) GA 10/0/3 — Rain alarm DPT 1.001 (optional, if P03-KNX-WS) Twilight logic: Lux < 50 lux for > 30 seconds → GA 10/0/0 sends value 1 Lux > 60 lux for > 60 seconds → GA 10/0/0 sends value 0 (hysteresis window 50–60 lux prevents hunting at sunset/sunrise)
Mounting height and orientation: mount the P03 at 1.5–2.5 m height on the north-facing building façade or a freestanding pole. Avoid south-facing positions where direct afternoon sun will cause premature daylight readings. The sensor must not be shaded by eaves or trees — shade will trigger false twilight activation during the day.
Dusk-to-dawn base lighting logic: twilight ON to DALI dim
The dusk-to-dawn logic uses the twilight bit from the Elsner P03 as the master enable for outdoor lighting. When dark, the DALI group for exterior luminaires is dimmed to a 20% base level — sufficient for navigation and safety without wasting energy at full output throughout the night.
Dusk-to-dawn DALI base lighting logic block
Trigger: GA 10/0/0 (Twilight bit) = 1 (dark)
→ KNX DALI gateway: DALI Group 1 (Perimeter) → Scene 1
Scene 1 = 20% brightness (DALI value 51/255)
→ KNX DALI gateway: DALI Group 2 (Parking) → Scene 1
Scene 1 = 20% brightness (DALI value 51/255)
→ KNX DALI gateway: DALI Group 3 (Entrance) → Scene 2
Scene 2 = 40% brightness (DALI value 102/255)
(entrance requires higher base level for pedestrian safety)
Trigger: GA 10/0/0 (Twilight bit) = 0 (daylight)
→ DALI Group 1, 2, 3 → Off (DALI value 0)
Note: DALI scene commands are sent via KNX group addresses
to the KNX-DALI gateway (e.g. Tridonic DALI-2 Gateway or
ABB DALI Gateway DG/S 8.16.1) — not directly to luminaires.
Gateway group address: GA 10/1/0 = DALI Group 1 scene commandPIR outdoor sensor: dry contact to KNX binary input
Commercial-grade outdoor PIR sensors such as the Optex BX-80N (long-range curtain PIR) or Bosch LB1-APS-D (outdoor dual-technology) provide a volt-free relay output. This connects to a KNX binary input module mounted in the distribution board, converting the dry contact to a KNX telegram.
| Sensor | Detection range | Output type | IP rating |
|---|---|---|---|
| Optex BX-80N | Up to 24m curtain | Volt-free relay NO/NC | IP55 |
| Bosch LB1-APS-D | Up to 15m × 15m | Volt-free relay NO/NC | IP54 |
| Optex RLS-30VFM | Up to 30m long range | Volt-free relay NO/NC | IP55 |
| Paradox NV5MX | Up to 15m × 15m | Volt-free relay NO/NC | IP55 |
KNX binary input wiring for PIR dry contact
KNX binary input: MDT BE-04000.02 or ABB SA/S 2.16.2.1 Wiring: PIR relay NO contact → Binary input terminal I1 (+) Binary input COM terminal → PIR relay common PIR power supply: 12VDC from panel PSU (separate from KNX bus) ETS6 channel 1 parameters: Operating mode: Switch Contact type: Normally open Send on rising edge: value 1 (motion detected) Send on falling edge: value 0 (no motion) Group address: GA 10/2/0 — PIR Zone 1 motion Cyclic sending: disabled (edge-triggered only) Note: do NOT connect PIR 12VDC supply to KNX bus terminals. KNX bus is 29VDC with current limits for bus devices only.
Motion boost logic: base 20% to full brightness and timer return
The motion boost uses a KNX logic module to combine the twilight enable signal with the PIR motion input. The logic activates full brightness instantly on motion detection and starts a 5-minute hold timer — after which lighting returns to the 20% base level automatically.
MDT Logic Module motion boost configuration
Logic: AND gate (twilight AND motion) Input 1: GA 10/0/0 (Twilight bit = 1) Input 2: GA 10/2/0 (PIR Zone 1 motion = 1) Output: GA 10/3/0 (Motion boost enable) On GA 10/3/0 rising edge (motion boost trigger): → DALI Group 1 (Perimeter) → Scene 8 = 100% brightness → DALI Group 2 (Parking) → Scene 8 = 100% brightness → Start 5-minute timer block (300 seconds) On timer expiry (no new motion for 5 minutes): → DALI Group 1 → Scene 1 = 20% base level (return) → DALI Group 2 → Scene 1 = 20% base level (return) Timer retriggering: Any new motion within 5 minutes → timer resets to 300s → prevents lights cutting off mid-motion
MDT Logic Module (SCN-LOGM.01)
- AND gate: twilight × PIR → boost enable
- Timer block: 300s retriggerable staircase
- 16 channels cover all outdoor zones in one device
- ETS6 Logic Editor: drag-and-drop block programming
DALI scene assignments
- Scene 1 = 20% (base / economy night level)
- Scene 2 = 40% (entrance base — pedestrian safety)
- Scene 4 = 60% (business hours normal operation)
- Scene 8 = 100% (motion boost / alarm / maintenance)
KNX weekly time schedule: seasonal sunset adjustment
The twilight bit from the Elsner P03 handles automatic seasonal activation based on actual measured lux — no programming required as days lengthen or shorten. However, a KNX weekly time controller adds a configurable override for economic night-time off periods (e.g. 02:00–05:00 complete off) and a seasonal reduction in base level from November to January.
KNX time controller weekly schedule (example)
Device: MDT Timecontroller SCN-TC8.01 or Gira X1 time block
Monday–Sunday:
Dusk (via twilight GA) → base lighting ON at 20%
02:00 → GA 10/4/0 "Night economy" = 1
→ DALI perimeter + parking → Off
→ Entrance zone stays at 10% (safety only)
05:00 → GA 10/4/0 "Night economy" = 0
→ Restore base 20% on twilight groups
Dawn (via twilight GA) → All outdoor zones → Off
Winter seasonal override (Nov–Jan):
21:00 instead of dusk → avoid long energy-intensive winter nights
05:00 instead of dawn → consistent morning ON time
Reduce base level from 20% to 15% → Scene 5 (winter economy)
Note: twilight GA always takes priority over timer when
daylight arrives unexpectedly (e.g. full moon, streetlight
reflection) — use twilight bit as master enable, timer as
override or economy reduction only.DALI group structure for outdoor zones
Organising outdoor luminaires into DALI groups enables independent zone control within a single DALI segment. A typical perimeter installation uses three groups: perimeter pathways, parking area, and entrance canopy — each with different base levels and motion boost behaviour.
| DALI group | Zone | Base level | Boost level | Night-off |
|---|---|---|---|---|
| Group 1 | Perimeter pathways | 20% / Scene 1 | 100% / Scene 8 | 02:00–05:00 |
| Group 2 | Parking area | 20% / Scene 1 | 100% / Scene 8 | 02:00–05:00 |
| Group 3 | Entrance canopy | 40% / Scene 2 | 100% / Scene 8 | No off (24h safety) |
| Group 4 | Façade wash | 15% / Scene 5 | 60% / Scene 4 | 23:00–06:00 |
Energy saving quantification
The two-tier system delivers substantial energy savings compared to constant full-brightness night operation. A typical parking area with ten 50W luminaires running 3,500 hours per year illustrates the savings.
Annual energy saving calculation — 10 × 50W luminaires
Assumption: 3,500 night-hours per year, 10 × 50W luminaires
Constant 100% operation (no automation):
10 × 50W × 3,500h = 1,750 kWh/year
With dusk-to-dawn base + PIR boost (no night-off):
Base 20%: 10 × 10W × 3,500h × (1 − motion fraction)
Boost 100%: 10 × 50W × 3,500h × motion fraction
Assume 15% of night hours have active motion:
Base: 10 × 10W × 2,975h = 297.5 kWh
Boost: 10 × 50W × 525h = 262.5 kWh
Total: 560 kWh/year
With night-off 02:00–05:00 (3h per night):
Night hours reduced by 3h × 365 = 1,095h
Remaining: 3,500 − 1,095 = 2,405 hours base/boost
Approx total: 385 kWh/year
Saving vs constant 100%:
1,750 − 385 = 1,365 kWh/year (78% reduction)
At €0.25/kWh: €341 saving per year for one parking zoneCommissioning procedure
Outdoor lighting commissioning requires functional testing at dusk to verify the photocell twilight trigger, and simulation of motion in each PIR zone to confirm the boost logic and timer return. Test the night-off schedule by advancing the KNX time controller clock.
Commissioning test sequence
1. Photocell verification: ETS6 Group Monitor → watch GA 10/0/0 and GA 10/0/1 At natural dusk: confirm GA 10/0/0 changes from 0 to 1 Confirm lux value (GA 10/0/1) falls below 50 lux threshold Confirm DALI groups activate to base scene within 60s 2. PIR motion boost test (each zone): With twilight active (or write 1 to GA 10/0/0 via Group Monitor): Walk through each PIR detection zone Confirm GA 10/2/x sends value 1 on entry Confirm DALI group jumps to 100% Scene 8 Remain stationary for 5 minutes — confirm return to base 20% Re-enter zone — confirm timer resets (stays at 100%) 3. Night-off schedule test: Advance KNX time controller to 02:00 Confirm GA 10/4/0 sends value 1 Confirm DALI Group 1 and 2 switch off Confirm DALI Group 3 (entrance) remains at 10% Advance to 05:00 — confirm base level restores 4. Daylight override test: Write 0 to GA 10/0/0 (simulate daylight) Confirm all outdoor DALI groups switch off Confirm PIR motion inputs are ignored (AND gate output = 0)
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