Home Automation and LED Dimming

Flicker, the perceptible modulation of light output when a light source runs on AC power, has been known to cause physiological responses including headaches and in some cases seizures. Flicker is sometimes an issue with LED light sources, and when dimmed, flicker can be induced or made worse. Because most dimmers were designed for use with incandescent sources, LED lighting products face incompatibility issues, particularly with phase-cut dimmers. This incompatibility is both difficult to predict and there are no standard methods for measuring flicker in LED sources.

Lighting Control and LED dimming

NEMA (national electrical manufacturers association) and several other interested lighting control  associations have been working together to have a performance standard accepted and published for solid state dimming controls. They have also been pushing for a standard SSL 6-20104 which gives guidance to LED manufacturers. These guidance standards are directly related to the dimming of LED Solid state lamps. These standards are still in the development stage as is LED technology and will require several amendments to ensure total consistency between dimming devices and LED lamps.

Interestingly current UL standards UL 14725 specify an LED lamp as an "electronic ballast"and the main concern covered in this standard is the "in-rush" current which is generated at the start up of many LED lamps. High in-rush currents have the ability to damage the lamps as well as switch contacts, this results in a hazardous electrical installation where the switch is seen to be the means of disconnect. 

Home Automation & LED Dimming

Dimming of LED lamps is made more difficult due to the fact that any given lamp can be manufactured to  a particular arrangement of electronic and electrical specs, current, voltage, amperage and control signals, that vary considerably from any other manufacturers specifications.   So one of the lamps may be dimmed by a particular dimmer but the other, not.
Manufacturing a dimmer to match or suite a particular brand of lamp is ludicrous to say the least and not something that I feel should be pursued  Perhaps an in line controller or Puck that would allow all dimmers to dim all lamps, now thats a good way to go. I feel somewhat let down when I look at the cost of a decent LED lamp as well as the cost of a Puck , may as well stay with a standard 35w incandescent IRC lamp?

HOme Automation and LED dimming

Most LED lamp designs can be characterized by a diode-capacitor power supply feeding a constant current source. The diodes rectify the applied AC voltage, allowing it to charge the storage capacitor, whilst the LED elements draw constant current from the power supply that is related to the desired brightness.
In LEd loads the applied voltage and resulting current flow are not related by a simple linear relationship ie current flows from the applied voltage to the load only when the magnitude of the applied voltage exceeds the storage voltage on the power supply capacitor. The stored voltage on the power supply capacitor, in turn, depends on the current drawn by the LED elements themselves, which is a function of the LED brightness. The dimmer unit has to respond to these minute and plentiful, wave form shifts, hence the flickering of the lamp and an unstable dimming circuit.

LED Dimming

Although there is occasional compatibility between an LED lamp and an incandescent dimmer, more often than not there are problems with handshake and performance. The Incandescent dimmer will be inconsistent when dimming an LED. An incandescent lamp is simple in design and is ultimately a simple resistive load enclosed in a vacuum, this resistive load has a linear response to the dimmer as one adjusts the phase angle so the lamp burns more or less bright due to an altered wave form.
An LED lamp is far more complex in design with any number of technical and electronic differences between manufacturers, making it impossible to design a dimmer that can perform across the board.
LED technology is CONSTANT CURRENT technology, mess with the constant current and we have flickering or fluttering issues. This equates to a non linear relationship between the dimmer and Lamp.
Another factor creating confusion is that we may successfully dim one lamp whilst on the test bench and then have a totally different result when we connect to three, four or more lamps on the same bench.
My tip for the day , don't mess with Ohms law

LED dimming and Control

All phase controlled dimmers tregard;ess of circuit design or load need to be able to synchronize with the AC line and most importantly detect the AC Zero Crossing point. The reason why LEDs flicker when dimmed by conventional dimming technology is due to the dimmer trying to find the Zero Crossing which with LED technology is proving really challenging. There is a call internationally for Three wire electrical installations with an added neutral wire in the switch box to provide an essential return path for the dimmer.

Energy Management and home automation

A number problems arise when using a "dimmable" LED lamp with an incandescent dimmer, Typically a markedly reduced dimming range, preventing true ambiance settings. Constant flickering and depending on the level of dim ,can be a bright strobe like effect or just peripheral flutter causing immense discomfort. Inconsistency with some lamps firing up before others and Visa versa creating a disco type of effect, again totally unacceptable.
These phenomena's are posing some real challenges to lighting control systems and LED manufacturers. There is growing support and pressure on LED manufacturers to supply a product into the market that is more Dimmer tolerant and one that can be dimmed across the ranges by the majority of dimming technologies.

Energy Management and Lighting Control

While LED and CFL lamps are drawing market share from incandescent lamps due to their energy saving advantages, most consumers and end users require education about how these lamps will work with their existing dimming technology.
Dimmed lighting in itself is an energy saving process, dimming also allows for ambiance setting. 99% of the dimmers on the market allow for Incandescent dimming only.

LED Lighting Control and Dimming

Energy Efficiency requirements are forcing consumers to replace standard incandescent lamps with LED based technology. The big issue now is that most often the results are not what was expected, nor what was sold to them. There are performance issues which include actual light output, degree of light spread, colour variations, lamp failure and a BIG issue with dimming.

The Bottom line LED technology is NOT compatible with existing dimming technology. There are NO industry standards that guide performance requirements of Dimmers or LED's

Existing wiring infrastructure can negatively effect the capabilities of modern lighting controls. So retrofitting a home that has been fitted with an intelligent bus with Triac based dimming technology IS NOT AN OPTION.

It is also NOT A REQUIREMENT as the lighting control and automated system is in itself a massive contributor to reducing energy and far out performs the saving derived from lamp replacement.

As A consumer beginning a new build, rather invest in an energy management intelligent solution than on LED technology which in a residential application really has no ROI.

Automation and Lighting Control

Schneider Electric and Tridonic Announce Strategic Partnership

BY LIGHTING CONTROLS ASSOCIATION, ON MAY 9, 2012

Schneider Electric and Tridonic recently announced a strategic partnership. The corporate partnership represents collaboration around projects business, and will see the companies work together to promote energy efficient lighting control solutions to customers.

Schneider Electric operates in more than 100 countries and, through its diverse product and business portfolio, specialises in the design and implementation of lighting control systems. Tridonic, headquartered in Austria and part of the Zumtobel Group, enables customers around the world to develop innovative applications and solutions, through lighting components, lighting management systems, connection technology and LED solutions. Within the partnership there is a project with LEDON, a sister company of Tridonic, which develops and markets hi-tech LED retrofit lamps for private consumers.

The strategic partnership between the businesses will combine the product innovation and market pedigree from the companies to develop cutting-edge, energy efficient lighting control solutions for customers globally. The solutions will meet the needs of diverse market sectors, including airports, hospitals, infrastructure and high performance green buildings. Schneider Electric benefits from Tridonic’s deep know-how in electronic control gears as well as from the innovative Tridonic products. Tridonic benefits from Schneider Electric’s excellent customer relations in the project business where Tridonic takes the role as first choice partner for lighting management. In all cases customers will stand to benefit by receiving lighting systems with synchronised components from one hand and enjoying service and safe systems.

Home automation and Lighting Control

BY LIGHTING CONTROLS ASSOCIATION, ON JANUARY 4, 2012
by Jim Brodrick, Department of Energy

As more and more LED lighting products have come onto the market, one issue that has generated considerable confusion is dimmability. As discrete devices, LEDs are fully dimmable, and as a result the technology has long been touted as being more suitable for dimming than other lighting technologies. Many SSL products come with claims of dimmability, but in practice, many users have encountered problems when trying to dim them, resulting in no small degree of frustration. What’s more, LED sources exhibit other unfamiliar dimming behavior, as they typically do not lose efficacy or shift in color as much as incandescent sources do when they dim.

Why have there been dimming problems with LED lighting products? A big reason is that nearly the entire existing stock of dimmer controls – those already installed in residential, office, and commercial settings – was designed for incandescent lamps, and not for LEDs. That’s important, because the two technologies, in addition to being based on totally different principles, also interact with this installed base of controls quite differently. Electrically, an incandescent lamp is a simple resistor, whose light output is determined by the effective average of the voltage that feeds it, and responds predictably and consistently to the various circuitries used in traditional dimming controls. An LED lamp, on the other hand, consists of not only the chips, but also typically a driver. Separately, and especially together, they comprise something considerably more complicated than a simple resistor – something that is very much affected by nuances in circuit design used in traditional line-voltage dimming controls.

Making LED lighting products dimmable is not an easy task, and is further complicated by a lack of standards. For example, there are no performance standards for making dimmability claims about a product, and thus the term “dimmable” remains vague and undefined. This wasn’t much of a problem with incandescent lamps, which all behave pretty much the same way with dimmers. The National Electrical Manufacturers Association has formed multiple committees focused on improving LED dimming experiences. To date, they have produced an educational white paper, as well as guidance aimed at helping LED product developers improve their dimming compatibility with the installed base of dimmer controls. Additional efforts are still needed to define standard dimming performance evaluation and dimming compatibility testing.

Such efforts are sure to reduce dimming issues, but they likely won’t eliminate them. The bottom line is that successfully dimming an LED lighting product with a familiar line-voltage dimmer control depends on the driver and its compatibility with the dimmer and, for low-voltage circuits, the transformer, too.

The best way to know how or if a product will dim is to test it out – and this means the entire circuit, not just one lamp with one dimmer. That’s because there are minimum and maximum numbers of lamps that will work with a given dimmer, and this varies by the lamp and dimmer (and, for low-voltage systems, the transformer) combinations. But such testing is not always practical. To make it easier on buyers and specifiers, a number of manufacturers have started providing this kind of information in dimming compatibility tables for their SSL products, and the Lighting Facts® database will be adding links to such tables at some point in the near future. It should be noted that system variations can lead to performance variations, however, so even though a circuit with a specific combination of lamps and dimmer works today, if a different lamp (either a different make/model, or even a revision to an installed make/model) is swapped in for an existing lamp, all bets may be off.

Although dimming problems persist, and many product dimming claims are still unreliable, the prospects for dimming LED lighting are much better today than they were even a year ago – and will continue to improve. Not only are dimmable LED sources available, but new dimmers are also hitting the market. The new approaches to dimming may eliminate many compatibility concerns entirely. But for now, at least, successful dimming depends on buyers and users being well-informed and exercising due diligence.