102 TECHNOLOGY / BENCHTEST IDENTITY CRISIS...
The shapes, formats and types of LED modules submitted to the bench test by the leading manufacturers demonstrate how much choice there is for lighting manufacturers to consider and evaluate when starting a new product development.
Figure 2: One definition of an LED light engine as proposed by the Zharga Consortium
Figure 3: Two types of LED Light Module
Figure 1: Organisational structure of the Zharga Consortium
On one hand the choice is excellent from a product designer’s perspective because they are able to choose the most appropriate module for the task at hand. However, one of the potential downsides is that once you have selected a module the fixture design will be fixed around the unit. Although this isn’t a revelation - many traditional fixtures in the past were designed around the par- ticular lamp sources so interchanging was not very possible across lamp types - it does reduce the attractiveness of LED modules (as in theory the light source shouldn’t need to be replaced). Hence, one could argue, why not just build a complete LED fixture without using modules! Fortunately, there is a group of compa- nies attempting to rationalise and define modules within the lighting industry that may make it easier to interchange modules from different manufacturers in the future. The Zharga Consortium is a cooperation of independent companies and was created in February 2010 to help define specifications for the standardisation of LED modules. The consortium now boasts 146 different mem- ber companies - from LED manufacturers to heatsink and connector organisations - and has an organisational structure as shown in figure 1.
The Zharga Consortium has attempted to define what is meant by an LED module as shown in figures 2 and 3. The Zharga defini- tion is the combination of an LED module and the associated control gear only. The definition treats LED light engines as a black box, with defined interfaces that do not depend on the type of LED technology used inside the light engine. By defining the light engine in such a way it is possible to enable future “unknown” advances in LED technol- ogy to be incorporated without the need for redefining the standard. This is a sensible approach as there are numerous different mechanical and optical formats for LEDs which would be difficult to cover otherwise. It also enables the LED manufacturers to include built in sensors such as thermistors, photodiodes and colour monitors to provide automatic control without the need for the fixture manufacturer to understand the technicalities.
It is also important to note that the Zharga specifications only define the outside of LED light engines and not the fixture the modules will be placed in, thus allowing a degree of product design freedom. The five interfaces considered within the specifications include:
1) Dimensional / Mechanical including the
socket) 2) Power, insulation and earthing 3) Controls 4) Photometric (lumen output, colour, light distribution) 5) Thermal
An LED module is able to be developed in two ways as shown in figure 2: 1) Type 1: Integrated control gear within the module housing. Typical for lower power modules. 2) Type 2: Separate control gear in a separate housing. Typical for high power modules.
For type two LED light engines, the LED module and control gear housings will be connected with a cable and, as this cable is considered inside the light engine, it is considered a part of the black box and therefore will not be specified. In February and June 2011, the Zharga Consortium approved the first light engine specifications so let’s hope the consortium member manufacturers will be attempting to launch products that adhere to the speci- fications. I believe none of the products tested in this issue are fully compatible with each other and therefore it is still early days.
The two LED light engines specified cur-
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