Transcript
February 2014
Terry K. McGowan, FIES, LC ALA Director of Technology & Engineering
Newsletter Sponsor
LED Dimming/Controls And A "2-Knob" Theory One of the hallmarks of 2014 so far is the increasing technical activity involving LED dimming and controls. We have noticed this growing interest in controls during the Lighting for Tomorrow Competition for the last couple of years. New product entries are featuring dimmers that "learn" so as to better accommodate the kinds of lamp loads that they control. Some can automatically adjust themselves to different bulbs or fixture types; others are manually set. The load types can include incandescent, halogen incandescent, CFL or LED sources and even mixed loads of more than one lamp type. Testing Dimmers in Showrooms Lighting showrooms, which are, of course, designed to be places where lighting can be seen and experienced, are also ideal places for customers to see how dimmers or other controls work with the fixture and lamp products that they're buying. I especially applaud those showrooms that demonstrate controls in action or put together a test set-up with the customer's choice of a fixture and dimmer or other control so the system can be tried out before purchase and installation. Reasons to Use Dimmers Lists of reasons why LEDs should be used instead of older light sources usually include words like "dimmer friendly." The words are technically correct; but, from a practical standpoint and especially where existing dimmers are being used to dim LED products, an old rule also applies. To quote one of my lighting mentors: The big print giveth and the small print taketh away. For example, I'm used to adding up the wattage of incandescent bulbs on a dimmer circuit and then specifying a dimmer that will handle somewhat more than that total wattage. Easy. With an LED load, however, the dimmer may have to be de-rated by a factor of 3-4 times according to a 10/13 DOE Report, Dimming LEDs with Phase-Cut Dimmers: The Specifier's Process for Maximizing Success. The report quotes an example where a lamp manufacturer advised putting only 56 watts of LED bulb load on a phase-cut dimmer rated for 600 watts--which is more like a 10 times de-rating. My advice, therefore, is to take advantage of the dimmer manufacture's technical support, and design the product or installation using the manufacturer's recommendations. The DOE report is here: http://alturl.com/e3mnx. New Standards There is a new NEMA standard on LED dimming, NEMA SSL 7A-2013, titled, Phase Cut Dimming for Solid State Lighting: Basic Compatibility. It deals with the tricky subject of lamp/dimmer compatibility and sets up testing requirements for source combinations using both screw-in LED bulbs and LED fixtures with integrated light engines. There is a cost for the standard, but there's more information about it along with ordering information here: http://alturl.com/pn9kx. I should also add that the NEMA-affiliated, Lighting Controls Association, is also a good source of technical and educational information about lighting controls. The LCA is at: http://lightingcontrolsassociation.org. Check out their videos under "LCA TV." As you see above, the term "phase cut" is now part of the LED dimmer lexicon. It seems to be replacing an older term "phase control." The terms refer to the types of electronic circuits inside the dimmer and how they handle the incoming 60 Hertz voltage or current cycles. The circuits subtract or "cut" a piece out of the front or the back of the sine waves to lower the amount of power flowing to the LEDs, and that process is synchronized or "in phase" with the sine wave. The DOE Report mentioned above has some nice illustrations of how the process works in Sections 2.2.1 - 2.2.3. Thinking Like a Designer
LED dimmers are one thing; but, thinking more as a lighting designer than an engineer, what can be done now with controls to better respond to the needs of lighting users--what do they want? I have a "2-knob" theory, which is simply this: As electronic and digital controls become more integrated into LED fixtures, we shall find that users will increasingly prefer LED fixtures with controls, which can vary not only the light output, but also the color (chromaticity). Here's why: People love choices (retailers and manufacturers generally do too, of course) and choices that involve changing the color of the light from a fixture offer a chance for users to better tailor lighting to their preferred color, match the atmosphere of a room, coordinate the light from several fixtures in a space--and perhaps to change the color of light as desired from hour-to-hour or season-to-season-maybe even for entertainment. People, especially those with eye problems or older eyes, report that they can see better under some chromaticities than others. I've watched people turn the chromaticity knob on task lights and express delight as their vision improves. Remember that growing market for lighting for the elderly? Light and human health research indicates that people need strong circadian sleep/wake cycles. The color of light can affect that cycle. I'm not suggesting that the lighting industry get into the medical business of prescribing light for health; but adding a chromaticity knob lets lighting users choose what chromaticity they feel is best for them. Dimming and color controls add significant value to a lighting product. Color control is a feature that has not been practically possible with fixtures using incandescent light sources. Such features also give the trained lighting retailer an important selling advantage. It's not surprising that LED fixtures with these "2-knob" features are already on the market. Some of the best have been recognized by Lighting for Tomorrow , including the Prism LED Desk Lamp (2012) and, just last year, the Samjin LND Company's Circular Ceiling Light fixture which includes a portable remote control so someone waking from sleep in the morning can press a button and make the sun rise-at least from a chromaticity point-of-view. Let me know if you are aware of other "2-knob" LED fixtures--better yet, submit them to the 2014 Lighting for Tomorrow Competition. Submittal information is available at: www.lightingfortomorrow.com The intent-tosubmit deadline is April 18, 2014. Submissions can be easily done on line. Sincerely,
Sincerely, Terry McGowan, FIES, LC ALA Director of Engineering & Technology Issue: #
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