From a user perspective, the goals of lighting control are three-fold: (1) flexibility: control lighting in accordance with the user's desires; (2) ease of use: control lighting in a way that is straightforward and intuitive for the user; and (3) control lighting in a way that optimizes resource (energy) consumption. Current technologies enable control that satisfies those goals to a modest degree.
Control of lighting (illumination) and other building systems today is largely dominated by three approaches: (1) hardwired local control, such as conventional toggle light switches and dimmers; (2) hardwired local control augmented by hardwired sensors, such as motion sensing light switches; and (3) hardwired centralized control, such as systems incorporating a control computer that explicitly commands individual lights or lighting circuits to turn on, turn off, and dim. Such local controls directly accomplish the intent of the human operator who activates them. Such centralized controls allow for programmed behaviors but exercise very explicit control over operation of the individual lights. Such centralized controls also typically require detailed and explicit “commissioning” activities to program the desired operations for individual lights. Often, centralized control systems utilize protocols such as DMX512 and DALI (digital addressable lighting interface) to issue commands to individual lights.
Some technologies separate control activation (e.g., the light switch) from the controlled light or other device. An early example of this control is the X10 system, a one-way control system relying on transmission of low-frequency signals over the AC power line. A more recent example of similar technology is the Insteon system, which uses an AC signaling system like X10, but uses acknowledgments to make the protocol more reliable. Wireless systems are also used, including both proprietary wireless and industry-standard initiatives such as the Home Automation Profile of the ZigBee wireless mesh network standard, or lower-level protocols relying on the IEEE 802.15.4 standard (which also underlies ZigBee). These systems, particularly the wireless ones, can be easier to install than hardwired systems. Like the hardwired local and centralized controls that they replace, these systems typically require explicit “commissioning” activities to achieve the desired results.
Illumination produced by light-emitting diodes (LEDs) is particularly desirable both from an energy consumption standpoint (since current laboratory LEDs are the most efficient general-purpose light emitters in existence today, and they are following a clear path to further improvement) and from a control flexibility standpoint. LEDs also have significant other advantages in packaging flexibility, lifetime, size, and durability. Most current LED-based light sources for general illumination are relatively primitive, in that they incorporate no built-in control mechanisms, and simply supply the constant DC current needed to operate the LEDs, sometimes using pulse-width modulation (PWM) to adjust brightness. Some LED sources are more sophisticated, allowing dynamic adjustment of color. Such sources typically are controlled in a centralized fashion, in part because the complexity of control required for such adjustments can be difficult to express with a simple locally actuated control.
Although illumination by LEDs is advantageous from a technology and lifetime standpoint, the cost of LED illumination devices is significantly greater than conventional light sources such as incandescent or fluorescent bulbs. The very long inherent lifetime of LED sources is also at odds with the traditional distinction between permanently installed lighting fixtures and replaceable light bulbs. LED lighting is likely to be packaged as complete units, combining the fixture and light source without any intent that the source be easily replaceable. Although LED light sources can fail, such a failure can be treated as a repair, rather than as an expected and regular intervention.
Inasmuch as existing technologies for control of lighting and/or other building systems rely on localized controls or centralized controls, those technologies do not provide the degree of flexibility and ease of use that is desirable for taking full advantage of the capabilities and attributes of LED lighting.