Architecture DALI-2: exam questions with worked answers

Questions for the "Architecture" topic

1. Q01

   DALI-2 (IEC 62386 Edition 2, 2014+) is the major evolution of DALI v1, adding native support for input devices (sensors, push-buttons) directly on the DALI bus itself, together with a product certification programme administered by the DALI Alliance (DiiA).

   TrueFalse

   1. Architecture· DALI vs DALI-2· Medium

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   Correct answer

   True

   Learning tip

   DALI-2 differs from DALI v1 in several ways: input devices (presence sensor, lux meter, push-button) now sit on the bus, whereas v1 supported only control gear; application controllers are standardised (Types 75-79); multi-master operation is allowed; device discovery is automatic; memory banks (manufacturer info) are standardised; and product certification is performed by DiiA-accredited test laboratories. The practical consequence is that fully autonomous DALI-2 installations can be commissioned without a central KNX or BACnet controller, with auto-configuration handled on the bus itself.

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2. Q02

   The DALI bus uses a polarity-free twisted pair (no + / - orientation), with Manchester coding at 1 200 baud over a nominal 22.5 V DC supply, and is allowed to share the same multi-core cable as the 230 V mains feeding the luminaires.

   TrueFalse

   1. Architecture· Physikalische Schicht· Medium

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   Correct answer

   True

   Learning tip

   The DALI physical layer is polarity-free (unlike KNX TP1, which is polarised), uses Manchester coding with one bit equal to 833 microseconds, runs at 1 200 bit/s (slow but ample for lighting), and operates at a nominal 22.5 V DC (16-22.5 V usable). It may share a multi-core cable with 230 V mains, in contrast to KNX, which mandates 4 kV separation. The maximum bus length is 300 m with a conductor cross-section of at least 1.5 mm squared.

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