welcome to this lighting control series exploring the digital addressable lighting interface
protocol shortened to DALI to get started we're going back to basics for electricians who may
be experiencing a DALI based lighting control system for the first time now if you're working
in new or refurbished commercial buildings you'll struggle to avoid lighting controls
as they are increasingly required to achieve energy performance requirements we know that
when it comes to controlling lights traditional systems rely on switches and wiring cables from
one switch to each lighting circuit that you want to control now this system has worked
well for hundreds of years that is until the number of light points increases then there
are more switches and more cabling making it more difficult for anybody using the space especially
if the switches aren't clearly labeled plus if you want to change things up with your lighting
it becomes a major job since you have to alter all of those fixed wires so the first reason to
move away from the light switch is to enable flexibility and simplicity of wiring which is
especially important in commercial applications where the layout is likely to change so think
of open plan offices where walls move desks move around which may need some different arrangements
when it comes to lighting however the main reason to use a lighting control system is to
save energy and the problem with the traditional light switch is that people are often very good
at turning lights on especially when it's dark but they often forget to switch them off when
they leave so using a lighting control system we can automatically turn lights off when no
one's using the space remembering the most energy efficient lights are the ones that aren't being
used lighting controls can also help us to save energy by adjusting the lighting in response to
the amount of daylight entering a space you don't need as much artificial light when a room is being
flooded with daylight from windows or skylights this is often known as daylight linking or if
you really want to sound like an expert daylight harvesting and we'll return to this later in the
series another advantage of using lightning controls is the ability to implement scene
setting which is changing the lightning levels to reflect the activity that the room is being used
for so you'll often see this used in places like restaurants where the light levels are typically
higher during the day but then turned down low to create a more relaxed atmosphere in the evening
you'll often see them as well in conference rooms where you might want the general lighting up high
when you're having a a meeting situation and then reducing the lighting level when there's a screen
based presentation so everyone can fall asleep of course you could use a combination of traditional
switches occupancy sensors and dimmer switches to create a lightning control system but the wiring
will quickly become a nightmare and the biggest nightmare in that is the dimming element when we
used incandescent and halogen lamps dimming was easy we connect a dimmer in series with the power
supply to a lamp and chop the AC waveform to effectively reduce the amount of power
flowing into the lamp which in turn reduces its light output however historically it was almost
impossible to dim fluorescent and discharge lamps using a traditional dimmer switch the situation
has improved with LED light sources but trying to match a traditional dimmer with an LED lamp or
fixture remains a significant challenge so much so that we created a whole series of video just
on dimming LED lamps and the troubleshooting that goes along with them the need to ensure
consistent reliable and flicker free dimming was one of the main drivers behind the creation of
the DALI protocol over 20 years ago this brings us neatly to the letter I in DALI or interphase
a DALI lighting power supply or ballast has two sets of terminals The Familiar Mains
connection to power the actual light source and an additional set of control terminals the interface
the interface input or DALI connection allows a dedicated control signal to communicate with
electronics inside the ballast or LED power supply this allows the power output of the device to be
accurately controlled enabling smooth dimming the DALI control signal is also known as a DALI
bus and electricians will be very familiar with the term bus bar as it's used to distribute power
to circuit breakers and switch gear and the same applies to the DALI bus it's a common set of wires
used to send a control signal to lighting fixtures which are all connected to the same bus the DALI
standard allows you to control up to 64 individual lighting fixtures on one DALI bus now electricians
are usually taught to keep power and data wiring separate with DALI you don't have to and in most
installations the data bus is contained within the same cable as the power itself it's a robust
protocol which is immune to disturbances on the Main's power supply the cable's typically
used to wire DALI systems a regular Mains cable you don't need to use Twisted pairs or screened
cable the DALI bus can be wired as Loop in and loop out from one fixture to the next as a star
configuration or combinations of both you can even integrate the DALI bus into track lighting systems
the only wiring configuration to avoid is the ring so you don't want to create a ring final circuit
and that will be music to the ears of most UK electricians the DALI Bus itself is an extra low
voltage signal but can't generally be regarded as safety or protected low voltage sources therefore
the DALI cable should be installed to the same standard as regular Main's wiring you should also
use the same respect as Main's voltages when it comes to Safe isolation as with the combined data
and power cable there is the chance that somebody could have connected what you think are the data
cables to the mains a lot of the terminals on some DALI devices are labeled da plus and da
minus the bus wiring isn't polarity sensitive now let's explore the digital and addressable elements
or the D and the A of the DALI protocol the DALI signal can be configured to talk to an individual
light fixture groups of fixtures or all of the fixtures connected to the bus think of that as a
floor of a building you could talk to One fixture or perhaps a whole rooms worth of fixtures or all
of the fixtures on that particular floor that's what makes this system really powerful however to
implement a DALI system we need some additional elements the DALI bus needs a power supply which
is typically 16 Volts DC with a current of up to 250 milliamps I always said earlier that
the DALI bus was not polarity sensitive there is one case in which you would need to observe the
correct polarity that's if you have two devices providing power to the bus power supply provides
power to control devices which could be push buttons for scene setting occupancy sensors or
light level sensors the clever thing about DALI is that the control devices share the same bus
as the lighting fixtures and you can have up to 64 control devices connected along with the lighting
fixtures the last piece of the jigsaw is called the application controller or the systems brains
this device is programmed to decide which lights respond to the various sensors and the inputs
to the system whilst at first this may sound complicated in reality control devices often
combine the functions of application controller power supply and the sensors into a single device
here's an example from Flex 7 which integrates application control Power and sensors into a
single package and it's been preconfigured for a typical office lighting application DALI is
really flexible and can be used for whole building lighting control or just controlling a few lights
in one room of course not all functions of DALI have to be implemented in every single device you
can produce some simplified versions so check this out this looks like a normal Main's dimmer but
it's actually a DALI dimmer capable of controlling up to 25 DALI fixtures the dimmer provides power
to the DALI bus and a control signal for all of the fixtures connected to it the dimmer operates
in what was termed broadcast mode where all of the fixtures on the DALI Bus receive the same
dimming signal so the lights dim up and down at the the same time in response to the dial turning
up or down with this entry level device it's not possible to address individual fixtures in our
next video we'll take this simple installation a step further and look at practical implementation
of a DALI control system and how this is combined with a prefabricated wiring system which are used
extensively within commercial buildings I hope this introduction to DALI has helped
you understand what's going on the next time you pop a ceiling tile in an office if you have
any questions or like to share your experiences implementing lightning controls drop us a comment
below it'll help the community and can help shape the future of this lightning control series