This is a good example of two interesting trends. One is the use of multiphysics in engineering analysis. The other is the trend toward smart sensors. As mentioned, thermal issues are a major cause of failure in LEDs and large scale integrated curcuits. This is something the EE did not have to spend a lot of time dealing with in the past. It is good to see Mentor Graphics addressing the issue and taking advantage of new sensor capabilities. It makes life easier for all of us.
That's a very surprising statistic, TJ. At the rate of 75 percent, I would think the city would reconsider either its supplier or the use of LEDs period. Given the difficulty of fixing and replacing traffic lights, I would imagine a more reliable source -- even if more expensive -- would pay for itself.
Interesting point about some LEDs being better than others in terms of quality. I suppose that's true with any component. Any rough guidelines engineers need to consider to help them spec the proper LED supplier?
The alterantives to consider for the heavy LED failure rate in the traffic light failure is that teh LEDs themselves may not have been quality LEDs from a reputable supplier. There are a considerable amount of low quality LEDs that do not perform as well as the more expensive offerings. Also, it may be the substrate that they are mounted on, the solder joint and several other failure modes. I worked in the automive industry on LED headlights and tail lights. I am sure you have noticed the dead LEDs in the tail lights of the truck ahead of you. The quality and durability of these LEDs and the assembly as a whole where not very good. They have improved and so will the LEDs and sub-assemblies in the street lights. Unfortunately early adopters are the guinea pigs for QC.
Call me obsessive, but I’ve always thought an LED should last longer than a human if treated correctly.A continuous light at 80K hours is around 9 years.If we kept the junction under 80C or some other less severe level, could we get a lifetime (>100 years) from them?Could they not be “the light that just does not burn out”?
Cost savings has driven the change to LED lighting; they use less electricity and while expensive on the initial purchase will last much, much longer than conventional lights.
I'm in North Charleston, SC commissioning several projects. North Charleston uses LED traffic signals. Almost every single red and green LED array in the city has at least five LEDs that don't function. In some cases, more than 75% of the LEDs do not turn on. While LEDs do eliminate the single-point failure of incandescent bulbs, 75% failure is unacceptable.
I don't know if it's thermal problems of the LEDs or their circuit boards, environmental aspects of high heat and humidity of this region, or something else. but driving around North Charleston makes me think LED lighting still has bugs to stomped out.
Fantastic synthesis of Theory and Experiment. This interplay between experimentalists and theorists is just what is needed to get an accurate snapshot of the actual system. The theoretical modeling provided by CFD brings us very close to visualizing the system under study, but only when actual measurements are used to carefully calibrate and verify the CFD models. Calculating overall system performance using component values measured in isolation runs counter to the systems reality that the integrated system is often greater than the sum of the parts. Especially when it comes to energy efficiency, I hope we continue to see more stories like this one.
Advertised as the "Most Powerful Tablet Under $100," the Kindle Fire HD 6 was too tempting for the team at iFixit to pass up. Join us to find out if inexpensive means cheap, irreparable, or just down right economical. It's teardown time!
The first photos made with a 3D-printed telescope are here and they're not as fuzzy as you might expect. A team from the University of Sheffield beat NASA to the goal. The photos of the Moon were made with a reflecting telescope that cost the research team £100 to make (about $161 US).
The increased adoption of wireless technology for mission-critical applications has revved up the global market for dynamic electronic general purpose (GP) test equipment. As the link between cloud networks and devices -- smartphones, tablets, and notebooks -- results in more complex devices under test, the demand for radio frequency test equipment is starting to intensify.
Much of the research on lithium-ion batteries is focused on how to make the batteries charge more quickly and last longer than they currently do, work that would significantly improve the experience of mobile device users, as well EV and hybrid car drivers. Researchers in Singapore have come up with what seems like the best solution so far -- a battery that can recharge itself in mere minutes and has a potential lifespan of 20 years.
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