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PhotonStar SmartNemesis LED

Issue 54 Apr / May 2010

One of the products that created a lot of interest at this year’s ARC Show was PhotonStar’s new SmartNemesis LED downlight. David Morgan puts it through its paces.

PhotonStar is a new LED luminaire company started by former directors of the high tech LED chip design company, Mesophotonics. The LED division of Mesophotonics was sold to Luxtaltek, a Taiwanese LED manufacturer in 2007 and PhotonStar was formed soon afterwards.

The founders of PhotonStar, Dr James Mckenzie and Dr Majd Zoorob, are both physicists with long experience in photonics optics and LED design. They were joined by a number of other highly qualified scientists from Southampton University to complete the development team. With this highly qualified technical capability in place, the company has concentrated on the performance and efficiency aspects of LED lighting, developing a range of downlights and accent lights. These incorporate PhotonStar’s LED light engine and control design.

It would appear that the initial PhotonStar products utilised industry standard LV halogen luminaire components into which their LED light engine and thermal management components were fitted. The company has now taken over Architectural Lighting and Controls, another Southampton-based lighting firm, enabling them to widen the product range to include specials and other products better suited to the lighting design market.

The latest PhotonStar product - which was launched at London’s ARC 2010 Show - is the high-power SmartNemesis downlight that incorporates a variety of clever technical innovations to optimise efficiency and performance.

SmartNemesis is designed as a replacement for commercial twin lamp compact fluorescent downlights. The bezel diameter of 183mm is typical for this category of downlight and is much larger than the MR16 replacement LED downlights now available from many suppliers. The highest power version (56 watts) delivers over 3,200 lumens in a very cool, 6500K colour temperature. In warm white, 2700K, it provides 2,600 lumens. The light engine developed for the SmartNemesis utilises 32 top flux bin Cree LEDs for the 56W version and 24 top flux bin Cree LEDs for the 42W version.

This LED light engine incorporates a diffusing screen but no individual collimating lenses. Optical control is achieved via the specular vacuum metalised moulded reflector and a wide distribution is produced with this combination.

To maximise energy savings and improve sustainability each SmartNemesis incorporates a light sensor that monitors the light level on the working plane and maintains a pre-set level by dimming down to take advantage of available daylight via a micro processor controlled dimmer in the driver. The dimmer can reduce light levels to below 1% in 0.5% steps and is also used to maintain a safe LED operating temperature if the ambient temperature rises above a pre-set limit. The target light level is set with the aid of a hand held controller so that each downlight can be set to maintain an individual lighting level. The driver includes dimming control via DALI, DMX or 0 – 10V.

PhotonStar claims an efficiency level of up to 73 lumens per watt for this product when the daylight sensor is activated. When used with occupancy sensors this, they claim, enables energy savings of up to 70% when compared to standard CFL downlights.

The test sample I was shown for this review was unfortunately not left with me for direct comparison with CFL or other LED downlights so I cannot comment on the relative energy performance of the SmartNemesis. My impression of the light output and light pattern was that the light output was powerful but that the light pattern on the floor was not completely uniform with some darker areas visible. This may have been an issue with this pre-production sample or a more fundamental design issue.

Although PhotonStar claim that the optics provide glare-free illumination, this is only true when viewed from normal viewing angles. When on full power, a direct view of the LED light engine is a painful experience for the eyes. With the increasing output from ever smaller LED emitters, glare is becoming more of an issue and the traditional reflector cone downlight may need to evolve to reduce this hazard. The surface brightness of a CFL lamp is much lower than that for a high power LED light engine so a direct view of the light source is not a significant problem. Some useful luminous intensity figures provided by PhotonStar compares CDM and CFL downlights from Zumtobel and Philips with the PhotonStar LED downlight. This shows the levels to be roughly three times higher for their LED downlight than for the CFL equivalent. As a comparison the CDM figures are around eight times higher than the CFL levels but reflectors for these lamps often incorporate a two cone design to reduce this problem.

As would be expected given PhotonStar’s technical capability, thermal management of the LED light engine has been given a high priority. The LED Light engine is cooled with the aid of a large passive die-cast aluminium heat sink that extends sideways for optimum cooling. The same size heat sink is used for both wattages so that in the 56 watt version the recommended safe ambient temperature in the ceiling drops to only 35ºC and the L70 lifespan falls to 45,000 hours. As previously mentioned, the downlight incorporates an onboard thermal sensor in the light engine so that if the ambient temperature rises above a pre-set limit the light output is reduced to keep the LED array working at a safe level. PhotonStar’s markets include a number of countries in the Middle East so an effective and sophisticated thermal management system is essential for these applications.

To remove any additional heat sources from the LED array, the driver and power supply are remote which allows the separate 24 volt DC power supply to run a number of downlights.

The overall quality and attention to detail in the design of the SmartNemesis should appeal to the target specification market. However, the indicated price seems quite high when compared to downlights from some of the major brands incorporating the Philips Fortimo light engine, which some may say has a higher perceived brand value in the market. The LED downlight market is clearly going to be a highly competitive and volatile one over the next few years as the increasing number of players try to gain volume sales on the basis of their performance figures and ever lower prices.

PhotonStar has followed a logical path in defining the performance of this range around that of existing CFL products but there seems to be an unresolved issue with the potential for glare and the rather harsh quality of light created from most high power LED downlights. Their focus on achieving high efficiency and high reliability is certainly to be commended but it is a pity that a more creative use of LED technology and optical control has not been considered in the development of this range.

I look forward to seeing future PhotonStar products that may combine high levels of efficiency with a more mellow, softer lighting effect.


© David Morgan Associates 2010. David Morgan runs David Morgan Associates, a London-based international design consultancy specialising in luminaire design and development.
Web: Tel: +44 (0)20 8340 4009
The views expressed in this article are entirely those of David Morgan and not necessarily those of mondo*arc.


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