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High-performance LEDs and MCUs are key ingredients in tunable lighting: energy saving, LED-based bulbs are remote controllable via smart phone or tablet.

It doesn't seem all that long ago - late twentieth century to be exact - when the most automated lighting fixture in our home was the light timer that plugged into the wall outlet. My parents would set it prior to each vacation to give the appearance that we were home. Sometimes the "set it and forget it" novelty of the timers created awkward on/off events well before or well after sundown. In those days, the family phone was plugged into the wall.

Today there's a steady stream of products that allow consumers to control their appliances and devices with far more precision than those light timers of yesteryear, even from far away using phones that can be carried in your pocket. Thermostats, for instance, are programmable and in the case of the Nest Learning Thermostat, can learn the user's habits and set itself accordingly. It is also WiFi capable and can be controlled via an iPhone or Android app from a smart phone. House temperature is only the beginning of the devices homeowners can control online. IP cameras for home security, power switching devices and even lawn sprinklers can be controlled remotely thanks to wireless technology.

Consumers create and control their own lighting

The second half of 2012 brought innovative additions to the way we even see the smart, connected home. Electronic companies are offering energy saving, LED-based bulbs that are remote controllable via smart phone or tablet. These smart, connected LED bulbs can glow as brightly as an incandescent bulb, utilize a wireless "hub" or base station to establish a network connection (Insteon offers a bulb that also includes a hand held remote), and they allow the user to control the LED bulbs from virtually anywhere via apps on their iOS or Android devices. Depending on the manufacturer, signals are transmitted over radio frequency, powerline, or both, giving the user additional flexibility.

These products promise easy setup, and they tout a feature that will potentially change the way we look at home lighting: users are able to customize the lighting for their rooms for any specific need or desire by creating different "scenes", known as "LightRecipe" in the Philips Hue system. LightRecipe, for instance includes soothing scenes as presets with names like "relaxation", "sunsets", "deep sea" and "beach" while allowing users to upload photos and letting the app sample the colors and integrate them into the scene or even create their own, new scene.

Behind the scenes: LEDs and MCUs

Controllable LED bulbs require high-quality light and colors. Smart LED bulbs are capable of producing over ten million colors and shades of white. With such a wide spectrum of colors, consistency and a high CRI are highly desirable goals for engineers. LEDs used in today's smart LED bulbs have to be efficient and typically offer high lumens per Watt efficacy, very low forward voltage, and industry-standard (ANSI) color binning.

The Philips Hue system uses the LUXEON Rebel ES lime green LEDs. Philips Lumiled's phosphor technology offers desirable control over color temperatures to provide a broad spectrum of light while achieving over 90 CRI in some white points. Still, LEDs can change their color points at higher temperatures, so the Philips team built the LED models into the lamp and made sure the lamp dynamically compensates for age and temperature of the LEDs. Therefore, the same color is always reproduced. These characteristics, and the design team's attention to uniformity, ensure the consumer can select the right color or produce the right scene to create the ambiance they desire in their home.

Smart LED bulbs take lighting into the twenty-first century by freeing users from manually flipping or turning a switch. Wireless control is one of the main features of this technology, so a bridge or hub is needed to set up the system and communicate with the application (or remote control). Microcontrollers (MCUs) run the communications stack to between bulb and base station, and they give the bulbs their "smarts" by running the algorithms to produce the high-quality light.

MCUs optimized for smart energy applications with bridges integrate high-performance transceivers and should exhibit desirable receiver sensitivity while addressing interference, as well as low standby power. These applications require generous Flash memory, but vendors such as Philips include additional Flash memory with their Hue bulbs for software updates that will continually add new and improved features. To run the Hue bridge application and all its features, the company also chose a powerful Cortex M3-based microcontroller that includes up to 1 MB of Flash and up to 128 KB of system SRAM.

Not surprisingly, LED bulb system designers are presented with a number of RF-related issues. Heavy in-channel WiFi use causes interference issues, so designers of connected LED bulbs must carefully tune the RF and tolerance characteristics of their products especially for those lamps that reach the thermal limits of their components. In addition, the heat sinks and associated potting materials' proximity to the bulbs can make PCB antenna positioning difficult - wrong antenna placement could dampen rather than boost the signal.

A smarter, brighter future for the home

The end user, however, just wants the smart bulbs to work, so ease or use is still the primary goal for the designers. Philips' Hue makes user-setup easy because the team chose Ethernet for its bridge instead of WiFi, which spares the consumer from transferring WiFi keys. "Just plug it into your router and it works," said George Yianni, Architect, Connected Lamps for Philips. The light bulbs screw right in, and the user simply plugs in the bridge and downloads the app. Yianni adds, "The wireless protocol we use, ZigBee LightLink, can automatically set itself up finding the most reliable path between the bridge and the light bulbs, even using other light bulbs as repeaters as necessary."

Once consumers become aware of the benefits connected LED bulbs can offer, greater adoption will follow. These bulbs offer substantial energy savings over conventional bulbs, and their easy controllability allows users to get just the amount of light and ambience out of them while still reducing their energy bill.

Yianni also points to the biological benefits. He explains Hue's "scientifically proven" light recipes can be set to improve, when the user desires, concentration, relaxation, or even provide an energy boost. Along with integration of other smart devices in the home network, "smart," connected LED bulbs will help make the home a more pleasant place.

Once consumers become aware of the benefits connected LED bulbs can offer, greater adoption will follow.

By Chris Warner, Executive Editor
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Author:Warner, Chris
Publication:ECN-Electronic Component News
Date:Mar 1, 2013
Words:1088
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