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Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

High Brightness LED Technologies

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Thanks to the many benefits of LED based light sources (long life, low power consumption, wavelength choices, vibration/shock tolerance, design flexibility and a decreasing cost factor), LED lighting has become the preferred technology for machine vision applications. Until recently though, the light intensity available from the more mature LED technologies had limited applications to those with relatively small fields of view and where the LEDs lower light intensity could be compensated for by relatively close positioning of light to subject. But things are changing with newer “High Brightness” (HB) LED technologies that are now available in packages capable of delivering much higher light intensity. This performance increase is enabling new machine vision applications with subjects that require high intensity lighting, and installations that require remote light placement capable of illuminating large areas. The challenge for machine vision lighting companies is to develop new light designs capable of managing the increased thermal loads of the new HB LEDs, and, at the same time, to provide new lighting power and control products to meet HB LEDs’ unique power characteristics.

The NERLITE® LALL™—Large Area LED Light product line from Siemens was developed to address the new machine vision lighting market opportunities opened up by HB LED technology. LALL’s employ housings made from custom aluminum extrusions and machined components. These housings provide the thermal mass and area required for “fan-free” passive cooling that contributes to low maintenance and keeps HB LEDS operating within manufacturer specified operating temperature safe zones. The LALL housings also deliver rigid and durable foundations for the larger, high intensity lighting units that are key in solving applications such as high speed web inspection and large area illumination for robotic pick-and-place environments. Additionally, LALL’s have been designed to comply with NEMA 4X and IP-64 to enable applications in food and beverage or anywhere that production conditions require wash down tolerant line equipment.

In addition to the new lighting designs, HB LEDs also posed new challenges for the power and control aspects of the lighting system. LEDs by design are current driven devices. While voltage regulation proved to be an economical and effective means to drive earlier generation LEDs, the new HB LEDs do not respond uniformly to voltage regulation. The LED-to-LED light output of HB LEDs may vary significantly, and their life expectancy may be shortened when driven by voltage. But when HB LEDs are supplied with a constant current, they deliver stable, uniform and predictable light output over useful lives of 50K hours or more. To provide current regulating power and control products to complement the LALL product line, NERLITE partnered with Gardasoft Vision, a leading designer and supplier of constant current drivers and controllers for machine vision illumination. The resulting line of drivers and controllers encompasses cost-effective single channel constant current drivers with both fixed and variable output models, and a range of multi-channel programmable controllers. The programmable controllers provide users with multiple lighting modes including continuous, strobe and selectable. In selectable mode, digital signal inputs from a PC or PLC enable remote selection of multiple lighting programs that the user has stored on the controller.

The lighting systems created with NERLITE LALL’s and Gardasoft Constant Current Drivers and Controllers deliver stable and repeatable light output, even under conditions of varying supply voltage, temperature and LED ageing.

Siemens Nerlite
15 Twin Bridge Rd.
Weare, NH 03281
Phone: (603) 529-2385
Fax: (603) 529-2406
www.NERLITE.com



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