The following
control technologies refer to the signal and wiring between th
e control on the wall and the fixture or lamp. L
ED retrofit lamps generally only use
forward or reverse phase control technologies.
LED fixtures may use any method, and it is independent of the
driver type (constant current or constant voltage).
The compatibility of a
dimmer with a particular
LED fixture begins with making sure they both use the same
control method. These control technologies are used in standalone applications and control systems as well as in wired and wireless lighting control systems. Controls that use
phase control to control a
lamp may also use a
wireless technology to communicate between loads or within an entire
home lighting control system.
Forward Phase Control:
Typically used for
incandescent and magnetic low-voltage (MLV) light sources, this is the most common method of
dimming control. The National Electrical Manufacturers Association (NEMA) estimates that there are approximately 150 million
forward phase control dimmers installed residentially, and many of these are likely to control
LED replacement lamps in the future.
Working well with
forward phase control is critical to the success of
LED bulbs because of the huge existing installed base. Unfortunately, these
controls were never designed for
LED lights and are not UL listed to operate
LED lights, so the performance is hit or miss and in many cases will cause
LEDs to flicker, drop out, pop on or not dim very low. These
dimming controls may also require multiple
lamps per control in order to meet the
minimum load requirements of the control.
New
forward phase control dimmers have recently entered the market that have been specially designed to reduce or eliminate the problems seen with
controlling LED loads on existing incandescent dimmers. These
dimmers are UL listed with specific LED loads, ensuring an acceptable application.
Reverse Phase Control:
Typically used to
control electronic low-voltage (ELV) light sources, reverse phase control is best for capacitive loads such as
LED drivers. While it does not have the installed base that
incandescent dimmers have, this
control type is often more successful at high performance
LED dimming without flicker.
Reverse phase dimmers were designed for the l
ower power “electronic loads” of electronic low-voltage transformers, so they tend to work better with the
drivers required for
LED loads.
Unfortunately, these controls nearly always require a neutral wire to power the internal electronics, and not every electrical back box has a neutral present. Installing
reverse phase dimmers in older buildings may require that a neutral wire is pulled to the box. Furthermore, these types of controls are not as widely available in the marketplace and are generally more costly.
Three Wire Control:
This standard
fluorescent control type is used by
dimmers that were created for
fluorescent dimming.
Three-wire controls have a separate line voltage wire that carries the
phase control signal separate from the power wires.
Three-wire is more precise than forward or reverse and the control signal is much more
immune to electrical noise. There are over 30 years of history in the industry of using
3-wire controls to
dim fluorescent ballasts to 1% without flicker, drop out, or pop on. Of course, to get this performance, a third line voltage control wire must be pulled to the fixture.
0-10V Control:
This a
nalog control standard has been used in energy management controls such as
occupancy and daylight sensors and is now becoming popular with many
LED products. This control type is isolated and considered low voltage class 2, enabling it to be safe to the touch and allowing for simplified wiring.
One of the benefits of
0-10V controls is that it is defined in the
IEC standard number 60929 Annex E. Unfortunately, some manufacturers don’t follow this standard. This leads to
drivers and lamps that claim to be
0-10V compatible but drop out or pop on, or that
dim backwards with the
lowest light at the top of the control and the
brightest light at the bottom. Some
0-10V products do not work at all with controls designed for
0-10V ballasts, which are the majority of installed
0-10V controls. Since the control signal is a small analog voltage, long wire runs can produce a significant drop in the signal level resulting in different light levels from different drivers controlled by the same control device.
DALI :
The
DALI digital standard originated in Europe for control of
fluorescent ballasts, but is now commonplace in
commercial buildings in the United States.
DALI is also defined in IEC standard 60929 Annex E. It allows for
digital control of individual fixtures, maximizing the user’s control and productivity.
DALI provide
addressing of individual fixtures and
status feedback from the drivers. This makes it easy to digitally assign
occupancy sensors, daylight sensors, time clocks, manual controls and other
controls to one or many fixtures without complicated wiring. This opens up an entire suite of
energy-saving and system-monitoring control schemes where the design and setup is all done within software, making designing with them simple.
DMX:
Typically used in
theatrical applications,
DMX remains popular with
RGB LED applications where
multiple channels are necessary for individual color control. Some manufacturers are using DMX as the control type for white light in general illumination applications, which can often be complicated in terms of wiring, addressing, and interacting with other controls in the space.
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