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Designing a DALI application
DALI Manual | 08-2013 | en
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Current draw of the DALI circuit
Each device in the DALI circuit consumes current via the DALI circuit. The total current draw on the DALI circuit must
not exceed the maximum current of the DALI power supply.
To determine the current draw of a DALI circuit both the current draw of the DALI devices and the current draw of the
DALI controllers must be taken into consideration. The current draw of a DALI device is defined in the DALI standard
as 2 mA. The current draw of the individual DALI controllers (ComfortDIM devices) is shown in the relevant data
sheets.
It is important that the current draw of the DALI circuit does not exceed the maximum current of the power supply. In
the case of DALI-PS and DALI-PS1 this is 200 mA.
Example: DALI circuit with 24 dimmable ballasts (PCA EXCEL), 3 DALI-GC and 3 DALI-SC
Current draw of the individual DALI components (from the data sheet):
Total current = Σ Current draw of DALI devices + Σ Current draw of DALI controllers
Total current = 24 x ballasts + 3 x DALI GC + 3 x DALI SC
= 24 x 2 mA + 3 x 6 mA + 3 x 6 mA = 84 mATotal current
Maximum cable length
The maximum cable length depends on the maximum permitted voltage drop along the DALI cable; this is defined as 2
V max. Typically, this requirement is safely met for a cable length of 300 m and a cable cross-section of 1.5 mm².
Additional voltage drops at terminal points must be taken into consideration. For cross-sections smaller than 1.5 mm²
the maximum cable length is reduced accordingly.
...
Maximum of 16 DALI scenes per DALI circuit
The current on the DALI circuit must not exceed the maximum current of the power supply (DALI PS/PS1 =
200mA or DALI PS2 = 240mA).
The maximum cable length depends on the maximum permitted voltage drop along the DALI cable; this is
defined as 2 V max. This corresponds to a maximum cable length of 300 m for a line cross-section of 1.5 mm²;
contact resistance must also be taken into account. A voltage drop of 2V must not be exceeded.
The recommended minimum cable cross-section is 1.5 mm²
Dimmable ballasts (PCA EXCEL) = 2 mA
Group controllers (DALI-GC) = 6 mA
Scene controllers (DALI-SC) = 6 mA