The battle is on to create an LED light source that replicates the dimming characteristics of halogen. Ben Cronin asks if Lucent's Ambience WarmDim comes close
It would be an understatement to say there are parts of the?lighting market that have grown quite attached to the halogen?lamp. This is especially the case in the hospitality sector where?the warm glow of this ubiquitous light source, particularly when?dimmed to lower levels, is prized for its ability to improve the?customer experience. But as the worst offending versions of?the product have been cast into obsolescence by the EcoDesign?regulations, and hotels and restaurants look to improve their?sustainability credentials and reduce their energy bills, a gap in?the market has clearly emerged for an LED product that mimics?its halogen antecedents.?
Lucent Lighting's international business development manager?James Morris-Jones, who is at Lighting's offices to demonstrate?the capabilities of the company's Ambiance WarmDim light?engine, argues it would be foolish for an LED light source to copy?all of the characteristics of halogen technology. But he thinks his?product comes close in the most important respects.?
"We've tried to imitate halogen but what we're saying is that?it's not an exact representation of a halogen lamp," he says. "We?know how difficult that is. As we see it, this is a standard that we've?designed and it's not going to be able to achieve all of the colours?in the spectrum that other products can achieve but it can achieve?the look and feel that customers require."
Six plus one?
The LED array in the Ambiance WarmDim module consists of?six 3,000K Cree XP-E LEDs in a circular format that surround?one 2,200K Cree XT-E LED. The idea is that the 3,000K LEDs?provide the cooler ambient light for when the power is at?100 per cent and these then gradually go out and the warmer?2,200K chip increases in brightness as the product is dimmed.?
The overall effect, as Morris-Jones dims the product using a?potted potentiometer, is surprisingly smooth, especially given?the complexity of what it is trying to achieve. The 2,200K chip?only appears to come on as the peripheral LEDs are at their?lowest levels and the effect of the warmer coloured chip is subtle?rather than the gaudy yellow associated with some 'warm' LED?products.
This inevitably gives rise to questions about which parts of the?spectrum are missed and how the light engine stacks up in terms?of colour rendering. Lucent has provided a graph that compares?the product with a generic halogen lamp; Morris-Jones remarks?that the average colour rendering figure of 80Ra for the product?is a vast improvement on some of the prototypes.?
"We originally had six 3,000K LEDs and an amber LED in?the middle of the LED array but we changed it after we had a lot?of feedback about the product," he says. "The thing is that the?amber was far too orange, so when it dimmed all the way down,?eventually it was just a horrible CRI. It was 16Ra and only just on?the actual chart. We thought that's not really going to help when?you put it in a hotel bar or restaurant – people wouldn't thank?you for making hands, faces and food look awful."?
Morris-Jones clarifies that the 80Ra is an average across?both types of LEDs in the updated version of the product.?"Sometimes it's more, but even when it's dimmed down it?achieves that figure as an average," he says. "Although the LEDs?we're using are not regarded as high CRI, it's still comparatively?high compared with the coloured chip we originally used."?
Partners?
Lucent has designed the engine to be 50mm in diameter so it?can be incorporated into a number of its own luminaires, (see image) but the plan is to also work with other OEM partners.?"The way we attach them to our fixtures is always in a simple?format. I'm not saying this is a retrofit solution but there is an?option there for that to be retrofitted into other luminaires –?only on consultation with us, however" says Morris-Jones.?
It is a similar story when it comes to using the product with?different control systems. "We test for compatibility and make?a recommendation," he says. "It works across all dimming?platforms although phase dimming doesn't work as well for?this type of product. We'll always try and recommend DALI or?1–10, especially if someone is very keen on having a nice curve –?which is obviously the lighting designer's preference."?
Similarly, Lucent says the module would work with any?reputable branded 700mA driver on the market but gives?guidelines on the wattage of that driver.?
Applications?
Table lighting in restaurants would appear to be the most?obvious application for the technology, but the company is keen?to stress that the fixture could also be used for other, more?ambient, applications.?
"We've developed a standard beam angle of 19 degrees, which?is quite specific, but at its top end it's a 3,000K fixture. It's only?when you dim it that it turns into a different luminaire. In the?daytime you've got a standard fitting; it's in the evening that it?really comes into its own," he says.
Ambiance WarmDim will be displayed for the first time at Light + Building in Frankfurt.
