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.