Month: October 2020

LEDs are the answer. Now just tell me what the question is. That’s what it seems like, doesn’t it? Nobody doubts the promise of LED technology, and certainly the unprecedented design flexibility is very exciting. It seems, however, that anyone with any LED experience has a disappointing one among their forays.  So what’s the matter with all of us?

It’s become clear to me that some of these problems stem from familiar metrics and guidelines that are no longer sufficient.  We roll our eyes at naïve consumers who quantify their needs in terms of a “60 watt light bulb,” but perhaps it’s time we reconsider some of the other metrics that have been convenient, handy and “good enough.” For today, let’s pick on color quality.

For the most part, if it is important to have objects look attractive, we seek light sources with a color rendering index (CRI) in the 80s or higher.  Perfect, we reason, would be a CRI of 100.  We rely very heavily on that number, but will that really get us what we need?

The CRI scale was developed to measure color fidelity compared to a reference light source – at most color temperatures, an incandescent type source.  If we believe that incandescent light quality is the ultimate goal, then a CRI of 100 would represent perfection.  Those who have ever left the house with a navy blue sock on one foot and a black one on the other, however, may not agree with that assessment.  As guidelines for legislation and financial incentives are set, we should remember that CRI was never intended to indicate fitness for an application, nor does it say anything about preference by any population.

Averaging the appearance of eight pastel colors for what is reported as the CRI (Ra) metric is a compromise of convenience, but there are six additional reference indices that can hold more information.  But is higher always better?  Many highlight the R9 (deep red) index, since people generally want to look healthier and better rested than they may actually be, but does even that tell the whole story?  Many people prefer neodymium lamps in their homes, which transform standard incandescent lamps from 100 CRI and R9 of 100 to a CRI of 77 and an R9 of 15.  There are CFL lamps that are nearly indistinguishable from incandescent lamps at the same 82 CRI of their disdained cousins, but with an R9 value of 20 rather than zero (or lower).

It turns out that we don’t actually like to see all colors.  We tend to prefer red tones (ruddy complexion, toasty fireplaces).  We don’t like yellow so much (jaundice, sickly appearance).  So maybe we don’t actually want all indices to score 100?  This logic may be great for residential applications, but perhaps not for healthcare settings.  I would certainly want my pediatrician to readily recognize jaundice in my baby.

While there are new scales being developed, like the color quality scale (CQS) and gamut area index (GAI), the issue still remains – is our goal color fidelity (versus what as a reference) or preference (whose preference)?  The answer is likely “it depends on the application.”  As an example, the DOE’s Retailer Energy Alliance has recognized that in their performance specification for refrigerated display cases, where they include minimum values for saturated color indices R9 through R12.  So maybe the metrics are actually fine.  Maybe we need to remind ourselves what they actually were intended to measure, and consider identifying additional complementary metrics to define exactly what we are trying to characterize.

When building an LED luminaire or lamp, total price of components in the bill of materials is a critical to the commercial success and adoption of a product in the market.  Another factor that is truly important in the long run of manufacturing LED products is the total cost for such components and the ability to meet the expected lifetime demanded by the market.  The LED lighting market is demanding high reliability and long expected lifetimes of products in excess of 50,000 hours.  Total cost not only takes into account the price of components, but also the costs associated with issues such as manufacturing quality, warranty claims, and brand reputation due to reliability issues.

The industry has already started to see some of these associated costs in instances related to failures of electrolytic capacitors in drivers and optical performance degradation due to lens material complexities in LED systems.  Connectivity products for LED systems are also important components that are not immune to such concerns and need to be carefully evaluated for quality and reliability when selected during the design process.  While the price is important, selecting the right connectivity solution may prove to be less expensive to a manufacturer over time.

Understanding the basics of the connector design and test process helps a fixture designer make a confident component selection to meet market demands.  The basic connector consists of a housing and contacts used to create the electromechanical interface. The interface can be used for wire?to?wire, board?to?board, and wire?to-device/board connections. The purpose of the connector is to establish and maintain a reliable, yet separable low?resistance connection. The contacts used in a connector system are at the heart of what makes a connector work.  Correct material selection is critical to ensure adequate normal force is retained at the interface during the life of the connector.  The connector housing provides a number of very important functions. Fundamentally, the housing provides electrical isolation between adjacent contacts and between the contact and the outside world.

In high?intensity LED applications, the LEDs themselves generate enough heat to require careful consideration of thermal management and material selections. Choosing the right connector is critical to ensure it meets the intended application and environmental conditions just as with the LED, optics, thermal management and driver electronics.

Connectivity solutions should to be designed or evaluated for LED environments to minimize common failure modes such as fretting corrosion of contacts and other issues due to the effects of plastic relaxation that lead to catastrophic failures.  At TE Connectivity, we have developed design processes and testing procedures along with robust material selection guidelines to design high quality connector performance and field reliability.  Years of innovation and experience is embedded in TE’s design and manufacturing practices providing the market with the confidence it needs to build products with high demands for useful life at competitive prices.

In today’s solid?state lighting systems, LEDs, thermal solution, optics and packaging comprise a considerable part of the overall cost of the lighting system. The connector is usually a small part of the overall cost and is often specified without adequate consideration and balancing of cost versus performance. It makes little sense to scrimp on the one component that your entire fixture relies on for power. Without a reliable and appropriate connector system, the lighting fixture, however well designed and esthetically pleasing it is, becomes a dull, static (and unlit) non?functional object d’art. Spend some time and consideration selecting the appropriate proven connector system for the application even if it costs a little more. It will pay dividends in the long run.

The bitterness of poor quality lasts much longer than the sweetness of the lowest price.