In this four-part series, Charles Knuffke, Systems VP & Evangelist, Wattstopper/Legrand, North and Central America and past chair of the Lighting Controls Association provides a crash Lighting Controls 101 class for lighting practitioners. Originally published as the Controls Column in LD+A Magazine in 2023. Reprinted with permission.
In the last Controls Column, I discussed two key attributes of lighting control systems—specifically, the different architectures that manufacturers choose for their systems and the more common device-to-device communication methods that allow devices in a system to communicate with other devices and front-end equipment. From this foundation, we can move on to the devices that do the work inside a room. These are the components most easily recognized as the lighting control devices and specifically called out by various energy codes and project sequences of operations provided by electrical specifiers.
The best way to start is to divide up control devices into two camps, those that are considered system outputs, and those that act as inputs. In this column, we will focus on output devices.
Dimming methods
For lighting controls, the outputs are the components that control the luminaires. Originally, the only control that was available was the ability to turn luminaires On and Off based on the control of the electrical circuit that powered the luminaires, but that simple binary control has now been eclipsed by devices that can direct the luminaires to go to different light levels using any one of several different dimming methods:
Altering the AC Sine Wave: One simple way of controlling a load via the electrical circuit is to have a device with an internal relay that opens and closes to turn a circuit On or Off, and devices that do exactly that are still often used to control plug load circuits or decorative lighting.
After that, we should look at ways to dim luminaires rather than simply turn them On or Off. The oldest dimming method was to use circuit components that could alter the shape of the AC sine wave, either by keeping Off or “chopping” the initial part of the AC wave (referred to as forward phase or leading edge dimming) or latter part of the wave (referred to as reverse phase, or trailing edge, dimming).
Providing an Analog Signal: While an altered sine wave can easily control some lighting load types such as incandescent lamps, there are other lighting devices where they need the full sine wave of the circuit to operate properly, ballasts being a significant example. So rather than alter the circuit, methods such as using a 0-10VDC dimming signal to the ballast or impressing a secondary analog signal on top of the circuit’s sine wave (known as a powerline carrier signal), came to the market.
Of the analog signaling methods, 0-10VDC is more prevalent, likely due to the fact that it’s a non-proprietary signal that can easily be added to ballasts, drivers, or even devices outside the luminaire to provide raise/lower information to window shades or open/close baffles in a light pipe, or in addition to the signal that tells a driver to raise or lower a luminaire’s light output a secondary set of 0-10V wires can be added signal changes in tunable white luminaires.
Provide a Digital Signal: While analog signals were the first to come to market, they suffered from being unidirectional and not being very precise due to effects from other power lines or voltage drop. As a result, the lighting industry followed the digital path, and dimmers, ballasts and drivers were introduced that can listen to and respond to digital signals, with the two best known signals being DALI and DMX.
For a basic course discussion on lighting controls, there’s little time to get into the advantages and best applications for each, so for now, let’s just recognize that both protocols have a presence in today’s lighting market and provide capabilities for not only dimming lighting but also driving tunable white or tunable color lighting.
It’s worth remembering the purpose of all the above are methods of communication. We’re here to talk about lighting controls, however, so the takeaway, for any type of luminaire, is it’s imperative to understand the method required to properly control its lighting output and make sure that a matching load control device is included in the lighting control system. One generic term for any output device that provides uses any of the methods called out above that controls the output of a fixture or other device is “load controller.”
Control outputs
So now that we’ve got a list of different types of load controllers, what basic functions or parameters do we expect of them? Each manufacturer will decide on their own what to include, but it’s likely that they’ll include functions that are called out based on the key energy codes. Basic functions that should be expected are listed below, noting that a listed function may be implemented in the programming of the load or possibly another device in the space such as an occupancy sensor, time clock, or even a local override switch/dimmer.
Manual On or Automatic On: Current codes may require that to save the most possible energy, designers must ensure that spaces with occupancy sensors be set up so that someone must press a local override switch/dimmer to get the lights on when they enter a space. Another term that may be used to indicate a device is set for manual-On operation is vacancy mode.
Partial On: The same codes that call out manual On may allow the lights to turn On automatically to a specific level instead. Since the lights may have to turn On to an intermediate level like 50 percent, the term Partial On or Preset Level is often used.
Partial Off: Normally, when a space is vacant, an occupancy sensor is expected to turn the lighting Off. However, there are some spaces where the energy code may allow an unoccupied space to go to an intermediate level instead, such as in corridors, stairwells, and warehouse aisles where the lighting cannot be turned full Off for safety reasons.
Warning before Off: Again, in an effort to increase occupant comfort and safety for the occupants, manufacturers may find it beneficial to allow lights in their system to go to a lower level or “blink” before they go off. Either a pre-defined or adjustable time provides the occupant a grace period, allowing them to move or press an override switch to avoid them being put into darkness by the system.
Fade Rates: This isn’t something that’s an energy code consideration, but one that we’ve all likely experienced in restaurants when they change from say the afternoon lighting scene to the evening and the lights visibly drop to a lower level. Manufacturers may allow the startup technician or facility engineer to adjust the time or rate at which the lights will change based on various inputs to the system.
Moving on
Now that we’ve discussed the outputs and typical parameters that they may need to meet either the energy code needs and/or designer’s desired functionality for spaces on the project, next we can talk about typical devices and parameters for the input devices in a lighting control system: manual controls, occupancy sensors, timeclocks, and daylighting controls.
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