Last week, Lutron, a leading provider of wireless lighting controls and home automation systems, filed a patent for powerline-carrier (PLC) technology. The two-way communication system works over a building’s existing powerlines, much the same way as the popular X10 did in the 1990s, but is now infused with modern day smart technology.
PLC technology essentially carries data on a conductor that is also used simultaneously for DC electric power transmission. It operates by adding a modulated carrier signal to the wiring system.
In a summary of the invention, Lutron describes “a two-way load control system for controlling an electrical load receiving power from an alternating-current (AC) power source comprises a power device (e.g., a load control device for controlling the electrical load or an input device) and a controller that is adapted to be coupled in series electrical connection between the AC power source and the power device. The load control system may be installed without requiring any additional wires to be run. The power device receives both power and communication from the controller over two wires (e.g., the pre-existing wiring).”
The Lutron PLC controller generates a phase-control voltage having a variable timing edge, rather than the standard modulating of high-frequency digital messages or pulses onto the AC mains line voltage to communicate with the power devices. Specifically, the controller transmits "forward" digital messages to the power devices by modulating the timing edges of the phase-control voltage relative to a reference edge.
Practically speaking, this means the timing of the edges of the phase-control voltage can be controlled precisely by the controller and detected reliably by each power device. In addition, Lutron’s system does not require a zero-crossing detector to detect the timing edges of the phase-control voltage, as you might expect of standard PLC technology.
Since the controller generates a phase-control voltage for communicating digital information to the power device, the electrical hardware of the controller is very similar to that of a standard dimmer switch. Furthermore, the controller is able to "swallow" the phase-control signal, such that the phase-control signal only exists on the power wiring between the controller and the power device, and does not generate noise that interferes with other control devices coupled to the power wiring.
In other words, the phase-control signal only travels downstream from the controller to the power device, and not upstream from the controller to the AC power source. Since the controller and the power devices do not modulate high-frequency digital messages onto the AC mains line voltage, large reactive elements coupled across the AC power source do not degrade the quality of the digital messages transmitted by the controller to the power device.
In the patent application (#20160295670) entitled, “Digital load control system providing power and communication via existing power wiring” Lutron underlined the new technology’s unique qualities. The key element being that the majority of comparable technologies require a neutral wire in order to deliver data over the same wires that power a load. Lutron’s technology, however, requires no neutral wire at all, representing a great leap forward.
In another significant component of the patent application, Lutron describes the ease with which a non-dimmable lighting ballast can be replaced with a dimmable model, with no need to run additional wires for control:
“Despite decades of attempts to develop practical power line carrier lighting control systems, there continues to be a need for apparatus that can reliably communicate data over a single power line between a dimmer switch and an electronic dimming ballast in a low-cost lighting control system. There also continues to be a need for low cost apparatus that can reliably and selectively control a plurality of fluorescent or light-emitting diode (LED) lighting fixtures connected to a single controller by a single power line,” the application reads.
On this topic, Lutron also points out that there remains a need for an inexpensive PLC system that allows upgrading from a simple, non-dim lighting system to a dimmed lighting system without the need for additional wiring or a complex commissioning process.
“The transition to LEDs for lighting has come at the same time as the development of the Internet of Things, which is about to disrupt the building automation systems (BAS) industry and opens up the possibility for lighting control to play a much more important role,” explains our last lighting report.
Lutron’s lengthy patent application also goes into some depth on the technology’s implications for home automation, referring to smart bulbs, thermostats, pool pumps, motorized shades, audio systems and other devices that could be controlled via the powerlines.
Positioning the new technology well within the exciting Internet of Things in smart buildings space and specifically the smart home market.
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