Technical data

QUICKTRONIC
®
Intelligent DALI DIM | Overview of dimmable control gears
14
2.4.13 DALI data transmission
For DALI, the data line is supplied by a voltage source with
current limiter. This source can be separately executed or
integrated into another control unit. Typical characteristic
values of the source are an open-circuit voltage of approx.
16 V and a short-circuit current of 250 mA.
A transmitter can modulate the data telegram on the line by
periodically short-circuiting and releasing the line. All con-
nected participants receive the data telegram by evaluating
the voltage on the data line.
For DALI, the data is transferred using the Manchester
code (two-phase code). In doing so, each bit receives an
edge in the middle, which the receiver uses to reconstruct
the transmission clock. The direction of the edge indicates
whether the data bit has a value of 0 or 1. A falling edge
means a logical 0 and a rising edge a logical 1. Access to
the data line is regulated through the defi ned waiting times
between the individual data packets.
2.4.14 Behavior in the event of failure
When there is no supply voltage at the DALI interface
(control unit defective or switched off), the ECG activates
the “system failure level”. The “system failure level” can be
confi gured. Upon delivery, the “system failure level” is set to
100 %. After a mains voltage failure, the ECG sets the
“power-on level”. The “power-on level” can be confi gured.
The “power-on level” is set to 100 % when delivered. The
“system failure level” takes priority over the “power-on level”.
The “system failure level” and “power-on level” can be con-
fi gured, for example, with the OSRAM DALI Wizard or DALI
magic.
2.5 The DALI dimming curve
2.5.1 Logarithmic dimming curve
The IEC 62386 defi nes the dimming range of a DALI control
gear from 0.1 to 100 %. The dimming curve is shown in the
following graph. To the eye, this gradation corresponds to
the linear behavior according to the Weber-Fechner Law
4)
.
The dependance of the relative luminous fl ux
on the digital 8-bit value is described through the
following correlation:
This results in the following graphic correlation:
Because not all DALI control gears begin at 0.1 % luminous
fl ux, the smallest value for DALI ECGs with a 1 % minimum
dimming level is, for example, 85 (equals 1 %). All values
under 85 (except 0 = off) are interpreted as a minimum level
of light. So that no transitions between the individual digital
levels can be seen when dimming, the DALI ECGs from
OSRAM have a digital “smoothing” (additional function QTi
to increase the light comfort, not part of the DALI Standard).
2.5.2 Linear dimming curve
In addition to logarithmic dimming, a linear dimming curve
is also possible with the QTi DALI/DIM.
You can change from a logarithmic dimming curve (factory
setting) to a linear dimming curve with the OSRAM DALI
Wizard and DALI magic.
4) The Weber-Fechner Law states that the subjective strength of
sensations behaves logarithmically relative to the objective intensity
of the physical stimulus.
100 150 200 250
Digital light value
50
DALI dimming curve
Luminous fl ux [%]
0
10
20
40
30
60
70
80
90
100
50
Short overview of the most important dimming values
Percentage luminous fl ux Digital dimming value
00
0.1 1
0.5 60
1.0 85
3126
5144
10 170
20 195
30 210
40 220
50 229
60 235
70 241
80 246
90 250
100 254