Steven Keeping writes:
As high brightness LEDs become practical alternatives to incandescent and fluorescent light sources, manufacturers are under pressure from a skeptical public to publish realistic operational lifetime figures.
Accurate lifetime estimates for LEDs operating in specified conditions would help designers select the best device for their product, manufacturers set warranty periods, and consumers compare cost-of-life of LEDs with conventional light sources (an important justification given LEDs’ higher initial purchase price).
Consumers understand that an incandescent bulb may last 1000 hours and a compact fluorescent light (CFL) perhaps five times that before catastrophic failure, but are less familiar with solid state lighting sources.
The problem for the manufacturers is that properly driven and thermally managed LEDs can last for years, so sitting around and waiting for an LED to fail is not a practical test regime. Secondly, an LED can either fail catastrophically or, more likely, suffer from a slowly diminishing output. At what point should such a fading LED be considered as ‘failed’?
This article discusses the standardized test method for determining approximately how long a high brightness LED will remain “fit for use.” The article then goes on to describe the latest improvement to this test which increases the accuracy of the result, then discusses why this is still not an equivalent of the “lifetimes” cited for conventional light sources – and whether that really matters.
Determining LED Rated Life: A Tricky Challenge - [Link]
I have recently stumbled upon some LED strip at my local electronics shop and decided to give them a try. I bought some which I used to replace the spot lights in the kitchen. It is cold white, which is surprisingly good, especially for night time illumination (think moonlight like hue). It works at 12V and consumes about 0.25A per meter.
After installing the strip, some automation proved to be necessary, and so the following circuits were built. The goal in mind was to keep things as simple as possible and use only parts I had at hand, which is why the solution might not be the best.
The hallway spotlights got new white LEDs as well and a light sensor. Tiny PIR sensors will turn on the lights in the kitchen and bathroom when someone comes in range. The sensors are rather popular modules using a BISS0001 IC; they provide a 3.3V level for an adjustable time when motion is detected.
Overall the results are great. The hallway is lit at night, the there is a small automatic light for the bathroom and the automatic kitchen light is bright enough even for day time illumination of the sink and counter. The slow turn off provides both a visually pleasing effect and a warning in case someone stood still long enough to make the light go off. I am still looking for a simple solution to produce the same effect on turn on, but without the delay.
Fun with LEDs - [Link]
Kristin Lewotsky writes:
LEDs have a well-deserved reputation for high-efficiency operation, not to mention high reliability. Properly specified and implemented, LEDs should and do satisfy virtually every lighting application. Still, there are times when actual device lifetimes fall short of the specified ideal. LEDs are wide-bandgap semiconductor devices. As a result, they have far more complex and varied failure modes than the incumbent technologies. Unlike an incandescent lamp, where failure is fairly simple (the bulb produces light until the filament breaks), with an LED, the failure modes range from mechanical and electrical to material.
Understanding and Preventing LED Failure - [Link]
Paul Dietz, William Yerazunis, Darren Leigh write:
A novel microprocessor interface circuit is described which can alternately emit and detect light using only an LED, two digital I/O pins and a single current limiting resistor. This technique is first applied to create a smart illumination system that uses a single LED as both light source and sensor. We then present several devices that use an LED as a generic wireless serial data port. An important implication of this work is that every LED connected to a microprocessor can be thought of as a wireless two-way communication port. We present this technology as a solution to the “last centimeter problem”, because it permits disparate devices to communicate with each other simply and cheaply with minimal design modification.
LEDComm: Bidirectional Communications using LEDs - [Link]
Mini RGB LED video wall using a Netduino and an Adafruit LED strips… [via]
16×10 RGB LED display built with an Adafruit LPD8806 LED strip and a Netduino mini as the controller. The display is capable of showing over 2 million colors. What’s not to like about RGB LEDs? With their bright, mesmerizing glow, often capable of displaying millions of colors, they’re a great to way to catch the attention of the viewer. Now, what if you had a 5 meter long RGB LED strip, loaded with 160 RGB LEDs to play with? Oh, the possibilities… It so happens that Adafruit, in their infinite wisdom, carries a very nice RGB LED strip, powered by a LPD8806 driver and encased in a waterproof sleeve. What about turning it into a mini video wall for instance? Think ‘Times Square’, just smaller
Mini RGB LED video wall using a Netduino - [Link]
ColorNode » DigitalMisery.com – [via]
ColorNode is a wireless Arduino-compatible microcontroller board designed to replace the stock controller board on GE Color Effects light strings.
ColorNode was inspired by the original controller protocol reverse-engineering effort featured here: Hacking Christmas Lights. That work enabled simple control of each individual bulb of these light strings using just one pin on a microcontroller. The stock controller works nice and the patterns are good, however being able to have full control of the color and brightness of each bulb unlocks the potential for awesome holiday light displays. Hacking these lights is also relatively inexpensive, compared to using other addressable strings or light sequencers on the market.
ColorNode – OSHW LED string controllers - [Link]
TRIAC Dimmable LED Driver
LT3799 isolated LED controller with active power factor correction (PFC) is specifically designed for driving LEDs over a wide input range of 24V to 480V+. It is ideal for LED applications requiring 4W to over 100W of LED power and is compatible with standard TRIAC in-wall dimmers. The LT3799’s unique current sensing scheme delivers a well regulated current to the secondary side with no opto-coupler, enabling it to provide ±5% LED current accuracy. It also offers low harmonic distortion while delivering efficiencies as high as 90%. Open and short LED protection ensures long term reliability and a simple, compact solution footprint addresses a wide range of applications.
TRIAC Dimmable LED Driver - [Link]
Now, you can experience the energy-saving benefits of LEDs combined with Sharp’s true-to-life color rendering in applications previously limited to a 50W incandescent, halogen, or compact fluorescent equivalent. Meet Sharp’s new 10W Mini Zenigata.
This new module utilizes a 6 (series) x 10 (parallel) LED matrix that delivers a luminous flux between 610 and 690 lm. Sharp’s entire Mini Zenigata product line delivers an impressive CRI value of 87, exceeding ENERGY STAR requirements (minimum of 80 CRI).
The new 10W Mini Zenigata joins Sharp’s existing 3.6W, 4W, 6.7W and 7W Mini Zenigata products to offer chromaticity performance tighter than that defined by existing ANSI CCT standards (under 3 Macadam ellipse). Be sure to review our specification table below on this page to view updated features to many of our 3.6W, 4W, 6.7W, 7W and 10W products.
The Mini Zenigata product family gives a new meaning to “compact,” with approximately half (56%) the surface area of previous models and a significant reduction in the emissive area when compared to our Zenigata offering. Mini Zenigata modules provide an operating life exceeding 50,000 hours at a service temperatures of 80°C.
Mini Zenigata Leds - [Link]
16×24 LED Matrix – Easy to use, chainable displays. These LED panels take care of all the work of making a big matrix display. Each panel has six 8×8 red matrix modules, for a 16×24 matrix. The panel has a HT1632C chip on the back with does all the multiplexing work for you and has a 3-pin SPI-like serial interface to talk to it and set LEDs on or off. There’s a few extras as well, such as being able to change the brightness of the entire display, or blink the entire display at 1 Hz.
16×24 LED Matrix – Easy to use, chainable displays - [Link]
Thanks to an increasing interest about LEDs OSRAM from our offer, we can now offer you selected types for lower prices.
As we all see, LED light sources experience a global „boom“. Their usage thereby also their sale grows. Thanks to it, we are taking on stock still bigger ammount and we managed to gain notably lower prices. And as your those, for which we do our work, we automatically reflected these lower purchase prices to your favour – into sale prices. Namely, we decreased prices at selected types of Advanced Power Topled Plus, Golden Dragon oval Plus and Golden DRAGON Plus series, listed in the product list under this article.
LEDs OSRAM have a very quality and thin luminophor layer. Also thanks to this, LEDs OSRAM provide a very colour-uniform luminous flux even in corner angles of the radiation pattern – unlike various no-name power LEDs, which often provide significantly more yellowish light at the corners of the radiation pattern.
Detailed description of all types you can find on the OSRAM website.
Save costs at selected OSRAM LED types! - [Link]