tag 标签: lighting

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  • 热度 1
    2016-3-14 18:39
    486 次阅读|
    0 个评论
    Do you remember the original role of the USB port? It was to replace the many diverse and incompatible ports used for the personal computer's keyboard, mouse, printer, and other basic peripherals. Now look at where USB is today – it's fair to think "hey, USB, you really have grown up."   The same scenario may be happening with power over Ethernet (PoE), as it extends from a basic power-delivery standard to a much more impressive one. The PoE specification is now in its third version and the power level it supports, with the right cabling, is impressive at nearly 100 W. The original intent of PoE was to power small peripherals already connected via Ethernet and eliminate the need for an AC source or embedded battery. These devices included VoIP desk phones, surveillance cameras (including pan-zoom-tilt), and door-entry card scanners, but the latest power levels open PoE to a wide range of new applications.   A recent post by Jean Picard at the Texas Instruments Power House blog, PoE lighting is coming , not only gave technical specifics, but was also tight-provoking in how it potentially takes PoE to a new applications arena—one which may change how we think about a basic function such as area illumination.   One prominent technical issues is that the IEEE802.3bt standard created two new types, called type 3 and type 4, which allow the PSE (Power Sourcing Equipment) to provide up to 60 W and 90 W (at 52 to 57 V), respectively. Then step back and think about the earlier versions of the PoE standard: the original IEEE 802.3af-2003 PoE standard provided for up to 15.4 W of DC power (minimum 44 V DC and 350 mA) to each device, with only 12.95 W is guaranteed to be available at the PD (Powered Device). The updated IEEE 802.3at-2009 PoE standard (also known as PoE+ or PoE plus), provided for up to 25.5 W of power. We're looking at up to a six-fold increase in capability – that's definitely very impressive.   We've always associated most area lighting with AC power. Many new and retrofit installations skip incandescent bulbs and go with LEDs, but still there's that AC line in the picture. Even standard AC-based dimming circuits, which are now trivial using standard TRIAC-dimmers for incandescents, have been the subject of major IC-design efforts for LEDs. The objective is to provide an IC which can implement the same ubiquitous dimming function but for LED drivers.   But what happens when the primary power source is DC at around 50 V, and the source can only deliver a modest number of watts? All the conventional wisdom associated with lighting power has to be rethought, which is an opportunity for new ways to solve ongoing problems. A moderate-voltage DC line – often below regulatory requirements for a licensed electrician or inspection – means that may routine assumptions about powering area lighting need to be reexamined.   This is not the first time that basic power-distribution and topology has seen a possible paradigm shift. A similar situation occurred when providing low-voltage DC rails for ICs migrated from direct AC/DC converters to use of an AC/DC intermediate bus converter, followed by multiple low-voltage DC/DC point-of-load (PoL) units. Doing so changed how power was distributed, planning for multiple rails, allocation of IR losses, and much more.   That's why it's a good idea to keep an eye on how PoE for lighting develops, if it does. One way to do this is by following Cabling Installation and Maintenance which gives detailed insight into the in-the-field reality of the copper and optical-fiber cabling issues, which you can’t get in a lab or test-bench setting. They have already looked at how PoE may be included in the 2017 revision National Electrical Code (NEC) published by the National Fire Protection Association (NFPA), which governs installations throughout most of the US, see here and here ; it's a sobering dose of reality.   PoE for lighting may turn out to be a non-starter for many reasons related to cost, practicality, or basic capacity overload. One of the issues I see with PoE here is that everyone will want to hop on the "PoE as power source" bus (sorry about the pun) since it offers many advantages in theory. Soon, the PoE PSE will be overloaded and have no more power to give. If that happens, I am pretty sure lighting will stay with or revert to AC-line as the source, while the original PoE peripherals get priority.   Do you see PoE for LED-based lighting becoming a viable mainstream technique? Or will it only be practical for niche lighting situations?
  • 热度 1
    2014-9-17 18:25
    987 次阅读|
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    Until now, my mind was set on using vacuum tubes augmented with tri-colored LEDs to enhance the look and feel of my hobby projects. However, I may have to take a look at those reproductions of vintage-style light bulbs known as Edison Bulbs. You can see all sorts of these little beauties by performing a search for "Edison Bulbs" on eBay, Google, and YouTube.   The reason I'm waffling on about this here is that I just heard from my old chum Alan Winstanley in the UK. One interesting item of news he had to impart was the fact that the hard-copy version of his Basic Soldering Guide Handbook has just gone on sale for $14.99 at Createspace . Another interesting nugget of knowledge Alan conveyed is that he's been photographing Edison Bulbs. He doesn't get out much.   As Alan says: "For fun, I photographed a whole bunch of vintage light bulbs (or, rather, modern facsimiles thereof) as I was fascinated by the reflections the incandescent filaments made around the glass envelope."     "I also aimed the macro lens at the filament supports, where I saw a new world of engineering open up."     "I soldered up a triac dimmer to tone the filaments down to a warm orange glow -- I had various bulbs to play with, including coiled, spirals, squirrel-caged and more besides."     "All these light bulbs are a modern pastiche (today's word) on vintage lighting. They were pretty hard to shoot using a macro lens. The depth of field is a few mm and the tiniest vibration (e.g., from passing traffic or me coughing) caused the glowing filaments -- suspended on their support wires -- to 'ring' or go out of focus. Most of all, I enjoyed exploring the reflections within the envelope."   Well, I have to say that I am very impressed, both by Alan's photographic skills and by the Steampunk-esqueness (sometimes it's hard to know where to stop with a word like this) of these little scamps. As I mentioned earlier, I may have to consider using these little beauties to enhance the look and feel of my hobby projects. Meanwhile, if anyone is interested in using Alan's images for any reason, they are available for purchase from BigStockPhoto.com .
  • 热度 3
    2014-9-17 18:23
    555 次阅读|
    1 个评论
    Originally, I have been focused on using vacuum tubes augmented with tri-colored LEDs to enhance the look and feel of my hobby projects. However, I may have to take a look at those reproductions of vintage-style light bulbs known as Edison Bulbs. You can see all sorts of these little beauties by performing a search for "Edison Bulbs" on eBay, Google, and YouTube.   The reason I'm waffling on about this here is that I just heard from my old chum Alan Winstanley in the UK. One interesting item of news he had to impart was the fact that the hard-copy version of his Basic Soldering Guide Handbook has just gone on sale for $14.99 at Createspace . Another interesting nugget of knowledge Alan conveyed is that he's been photographing Edison Bulbs. He doesn't get out much.   As Alan says: "For fun, I photographed a whole bunch of vintage light bulbs (or, rather, modern facsimiles thereof) as I was fascinated by the reflections the incandescent filaments made around the glass envelope."     "I also aimed the macro lens at the filament supports, where I saw a new world of engineering open up."     "I soldered up a triac dimmer to tone the filaments down to a warm orange glow -- I had various bulbs to play with, including coiled, spirals, squirrel-caged and more besides."     "All these light bulbs are a modern pastiche (today's word) on vintage lighting. They were pretty hard to shoot using a macro lens. The depth of field is a few mm and the tiniest vibration (e.g., from passing traffic or me coughing) caused the glowing filaments -- suspended on their support wires -- to 'ring' or go out of focus. Most of all, I enjoyed exploring the reflections within the envelope."   Well, I have to say that I am very impressed, both by Alan's photographic skills and by the Steampunk-esqueness (sometimes it's hard to know where to stop with a word like this) of these little scamps. As I mentioned earlier, I may have to consider using these little beauties to enhance the look and feel of my hobby projects. Meanwhile, if anyone is interested in using Alan's images for any reason, they are available for purchase from BigStockPhoto.com .
  • 热度 1
    2013-5-8 23:24
    506 次阅读|
    0 个评论
    We are usually being told that using WLEDs (White Light-Emitting Diodes) for lighting purpose has many advantages. For example, high efficiency, high brightness and much longer lifetime than fluorescent lights. However, since many manufacturers wish to reduce the cost of production and to increase the light intensity, the WLEDs are being 'pushed' to the maximum power they can affort... As a result, the lifetime of those WLEDs will be shortened (or more precisely saying, the light intensity and efficiency decreases significantly) in a period of time. More importantly, the driver / controller will be burnt due to the excess loading or temperature due to the heat generated. Fig. A burnt controller in a MR16 (4x1W) WLED bulb   Although the controller PCB which is very cheap (RMB$2) can be replaced easily, many people may throw those LED bulbs which are out of order away, even if only the controller is burnt.... The result contradicts the original intention that using WLEDs for lightening up the environment.
  • 2012-2-7 15:18
    170 次阅读|
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     LED Lighting (LS2516, JN2297AZ) ??LED Lighting系统规格: -15V/1.5A电源输入. -镍氢或镍镉电池(2000mAh) 8节串联. -充电电流720mA. -2颗LED显示充电状态. -自動充飽時間保護3.7hr, 自动停止充电 -可一边充电, 一边使用. ??LS2516充电控制功能: -自动依镍氢电池电压状态, 作相对充电 控制流程:激活/预充/快充/涓流. -依照规格需求, 可由电阻调整充电电流. -合乎工业界高标准的精准-delta V = 5mV充饱判别. -多重电池保护:过放或老旧电池脉波激活, 过高电池电压停止充电保护, 完整可设定的时间保护. -充电状态双色LED显示:无电池/充电中/ 充饱/异常. -封装SOP-8.   
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