Lighting Control KNX Advanced: exam questions with worked answers

Questions for the "Lighting Control" topic

1. Q01

   What is the principle of Constant Light Control regulation in KNX?

   • A.Maintain a fixed illuminance (e.g. 500 lux) by varying the artificial lighting in response to the natural daylight contribution
   • B.Switch every lamp to full power as soon as a presence sensor detects occupancy
   • C.Dim linearly from 0 to 100% over the course of the day (sunrise to sunset)
   • D.Switch lighting off automatically after X minutes of inactivity

   5. Lighting Control· Constant Light Control· Hard

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   Correct answer

   A — Maintain a fixed illuminance (e.g. 500 lux) by varying the artificial lighting in response to the natural daylight contribution

   Learning tip

   (A) is correct: Constant Light Control is a closed-loop combination of a lux meter and a dimming actuator. The controller compares the measured illuminance to the setpoint (e.g. 500 lux) and adjusts the artificial output to cover the gap left by natural daylight from the windows. Energy savings are typically 30-60% versus simple on/off switching, and the function is usually paired with presence detection to avoid lighting unoccupied zones. (B) describes a brute-force presence-on-full strategy with no light regulation. (C) describes a time-based daylight curve, not closed-loop regulation. (D) describes an absence time-out, which is a separate function.

   Source: ABB i-bus KNX Lighting Application Manual (public)

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2. Q02

   Tunable White control (variable colour temperature, e.g. 2700 K warm to 6500 K cool) over KNX typically uses two distinct DPTs: one for the overall intensity (DPT 5.001, %) and one for the colour temperature (DPT 7.600, K).

   TrueFalse

   5. Lighting Control· Tunable White· Medium

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   Correct answer

   True

   Learning tip

   DPT 7.600 is Absolute Colour Temperature in Kelvin (16 bits, technical range 0-65535 but usable range 2000-10000 K). Combined with DPT 5.001 for intensity, it allows independent control of the two dimensions. This is the standard binding for Tunable White luminaires using a warm-white plus cool-white dual-channel LED.

   Source: KNX Specifications V3.0.0 (public) — DPT 7.600 Absolute Color Temperature

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3. Q03

   A KNX presence detector configured with a 15-minute timeout keeps the lighting on for that duration after the last detection, then automatically switches it off.

   TrueFalse

   5. Lighting Control· Präsenzerkennung· Medium

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   Correct answer

   True

   Learning tip

   Off-delay values typically range from 5 to 30 minutes depending on usage: around 15 minutes for offices, 3 minutes for corridors, 5 minutes for restrooms. The detector sends DPT 1.001 = 1 on detection and DPT 1.001 = 0 once the off-delay elapses. It is commonly combined with a lux sensor so the light is not switched on when daylight is already sufficient.

   Source: Theben PIR detector application

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4. Q04

   The emergency lighting of a building CANNOT be driven by KNX alone: it must comply with dedicated standards (NF EN 1838, EN 50172) that require a self-contained system with a backup battery.

   TrueFalse

   5. Lighting Control· Sicherheitsbeleuchtung· Hard

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   Correct answer

   True

   Learning tip

   A self-contained emergency luminaire is a regulatory obligation: it has a local battery and operates without either mains supply or bus communication. KNX can supplement it with test/diagnostic functions or with the normal switching command (self-contained luminaires light up when the 230 V supply fails), but it must NEVER replace the autonomous emergency system. This is a classic exam topic for tertiary projects.

   Source: NF EN 1838 / EN 50172, ABB lighting AM

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5. Q05

   DALI devices can be commissioned through the KNX/DALI gateway, typically using ETS apps or manufacturer-specific tools.

   TrueFalse

   5. Lighting Control· Beleuchtung & Beschattung· Medium

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   Correct answer

   True

   Learning tip

   Modern KNX/DALI gateways embed a DALI master controller that performs short-address assignment, group setup and scene programming on behalf of the installer. Many manufacturers ship a dedicated ETS App that exposes this DALI commissioning inside the ETS user interface, while others rely on a separate web tool or USB application. In either case the gateway is the interface between the KNX project and the DALI bus state.

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6. Q06

   RGB control via KNX is typically performed with 3-byte colour telegrams (DPT 232.600).

   TrueFalse

   5. Lighting Control· Beleuchtung & Beschattung· Medium

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   Correct answer

   True

   Learning tip

   DPT 232.600 packs the red, green and blue components into a single 3-byte structure, each component scaled from 0 to 255. A single Group Address therefore carries the complete colour setpoint, which keeps the three channels synchronised and avoids the colour drift that occurs when R, G and B are updated independently. KNX visualisations and colour pickers natively serialise their output into this DPT.

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