Feature: LEDs


the promise of interoperability: compliant devices from different manufacturers can be commissioned using tools such as the Silvair platform to form a functional lighting control network. Te release of the Mesh Device Properties


v2 specification in September 2020 has unlocked more IoT capabilities beyond simple lighting control, enabling detailed diagnostics and reporting of maintenance events. Companies such as Silvair are already integrating these new capabilities into firmware, and commissioning applications. Silvair’s implementation of standalone scheduling requiring no gateway became available this year, an important development that will make it easier to design and deploy circadian lighting systems.


New appreciations Te hygiene lessons of the Sars-COV-2 pandemic will not be forgotten soon. Te increased attention paid in 2020 to disinfection and decontamination has helped stifle the transmission of viruses, including coronavirus, but also the common cold and other infectious diseases. Now there’s a very broad public understanding that regular


disinfection will stop the spread of any new strains or viruses that might emerge in the future. Optoelectronic products have their part


to play in the battle against transmission of infections: interest in the germicidal properties of ultraviolet (UV) light is rapidly increasing. We are expecting the development of LEDs in the UVC portion of the spectrum, with wavelengths between 100nm and 280nm to reach a tipping point this year. Established suppliers such as Nichia and


Seoul Viosys are vying with newcomers such as Luminus Devices to increase efficiency, lower the cost per UVC photon and scale up production capacity. Crucially, manufacturers are now producing UVC LED products with output power above 100mW. Luminus, for example, has released XFM-5050, a four-chip package with a nominal output of 240mW. At the same time, the cost of UVC LED


light has fallen below 20 US cents per mW and is edging closer to 10 cents per mW – seen as the tipping point by many equipment manufacturers. Efficiency in mass production has jumped from around


1.5% to over 3%, with experts forecasting rapid progress to efficiency of 10% . In parallel, manufacturers of optics for


LEDs have qualified new materials and released dedicated products that are both efficient and resist degradation by UVC light. Te increased power and efficiency of


UVC LED light sources is also leading manufacturers to explore applications for air and water purification. To date, UVC LEDs have been used primarily for surface disinfection. Tey are particularly suitable for disinfecting indoor air when placed at ceiling height (known as upper-room air disinfection): the very small light-emitting surface of a UVC LED enables tight beam control. For example, a Seoul Viosys linear UVC light module can be paired with the LEDiL VIOLET RS optic to make an ideal off-the-shelf light engine; see Figure 1a. Following the IES volumetric dosing guideline of 12mW/m3


engine would cover approximately 10m3


, such a UVC light ,


or 4m² in a room with a 2.5m-high ceiling, burning around 10W. Te LED unit is itself much smaller than a mercury tube, and what’s more, the mercury tube requires a large reflector to shape its 360° irradiation to


Figure 1 (left to right): The LEDiL VIOLET-12X1-RS combined with a linear UVC LED module such as the Seoul Viosys XMD-FBC-LLCA may be used in upper-room air- disinfection applications; The LEDiL VIOLET-RS optic for UVC LED linear configuration


www.electronicsworld.co.uk July/August 2021 31


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