medium DALI-2 exam questions

Medium level questions

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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3. Q03

   DALI bus power supplies are typically available at 100, 120, 150 or 250 mA depending on the vendor (ABB BCO/S, Tridonic DALI-PS, Lunatone PS5), and should be sized for the cumulative current of control gear plus input devices, with a 30 percent margin.

   TrueFalse

   7. Best practices· Bus-Netzteil· Medium

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   Correct answer

   True

   Learning tip

   Standard DALI PSU ratings give roughly the following gear budgets: 100 mA for about 15 gear, 150 mA for about 25 gear, and 250 mA for about 40 gear plus input devices. A 30 percent margin is recommended for inrush peaks and future extension. The PSU is often integrated into the KNX/DALI gateway itself to save components. Always verify the exact draw of every gear (some still draw 10 mA).

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4. Q04

   The DALI DT1 'Inhibit' (or 'Rest Mode') temporarily disables an emergency luminaire during planned building maintenance, avoiding spurious tests during the intervention; the gear returns automatically to normal mode after a timeout.

   TrueFalse

   13. Emergency DT1· Inhibit Mode· Medium

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   Correct answer

   True

   Learning tip

   Inhibit / Rest Mode is used for planned electrical maintenance with scheduled mains outages. Without it, every outage triggers the emergency luminaires, discharging their batteries ten times faster than usual and raising false alarms. Activation is either manual (by a technician) or automatic (via schedule). A safety timeout returns the gear to normal mode after N hours (typically 8 h max) to prevent forgotten inhibits, and the audit log records every inhibit event.

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5. Q05

   The DALI-2 standard is codified as IEC 62386, split into several parts: 62386-101 (general requirements / system), 62386-102 (control gear), 62386-103 (control devices), 62386-2xx (lamps and device types) and 62386-3xx (input devices).

   TrueFalse

   18. Standards· IEC 62386· Medium

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   Correct answer

   True

   Learning tip

   IEC 62386 is organised in layers: Part 101 defines the overall system requirements, Part 102 covers the general behaviour of control gear (the ballasts and LED drivers), and Part 103 specifies the control devices such as application controllers. The 2xx series defines device types for control gear, including DT1 for emergency lighting, DT6 for LED modules and DT8 for colour control, while the 3xx series covers input device types such as DT301 push buttons and DT303 occupancy / light sensors. This is the official reference document; the full set is published by IEC and is a paid acquisition (around 600 EUR for the complete bundle).

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