>> http://www.edn.com/blog/PowerSource/39582-Home_Depot_s_20_EcoSmart_LED_l= ight_What_s_inside_.php That's a better than many tear-down. Recommended that people interested in LED replacement lighting look at it. BUT I think they were fooled by the LEDs' I'd suspect that what they describe as LEDs are in fact integrated arrays of LEDs - a bit of prying of those packages is in order. Use of LM3445 as dimmable controller is worth noting LM3445 data sheet http://www.national.com/ds/LM/LM3445.pdf Overview page http://www.national.com/pf/LM/LM3445.html#Overview Note that this IC needs 10+ LEds for reasonable efficiency and preferably 1= 4+ Another reason to think the "LEDs" are Nx LED 's ___________________________ > I keep seeing this argument from the LED fanatics ("LEDs will have > higher delivered efficiency because they're directional emitters"), > and I'm not convinced. =C2=A0Lamp design is pretty entrenched; even after= a > couple decades it is nearly impossible to find lamps designed for > CFLs, for example. =C2=A0And all that ergonomic data on indirect lighting > and what not isn't going to disappear either; there are reasons beyond > efficiency that lighting is designed the way it is. =C2=A0Except for > special applications (Walmart installing LED lights in the frozen food > cases was brilliant!), I foresee LED bulbs being stuck into the same > old inefficient fixtures for a long time. I'm pleased to say that I disagree :-). I'm not an LED fanatic (despite possible indications au contraire). I calls em as I sees em. Incandescent filaments are close to 360 degree radiators with some obvious non-symmetries and when placed in a bulb envelope cover most of a sphere at varying output levels. Some people put reflectors inside the bulbs but this is not overly common. CFLs tend to be mainly cylindrical radiators unless care is taken to maximise the glass surface in horizontal directions - which is very seldom done. There is a substantial % of light down and up but less than sideways when the bulb is mounted cap up. Tube fluorescents tend to be cylindrical radiators with the high L:D ratio making end radiation minimal and the end caps making this even less so [tm]. LEDs in SMD packages have radiation angles of less than 180 degrees due to basic necessity and half power points are usually in the 120-160 degree range. With modest lensing angles around 80-12- are easy and lower radiation angles are easy with more lensing. Few higher power SMD LEDs bother unless there is a niche application - it is easy to reduce angle with reflectors and this is expected to be needed if desired. Look at the tear down on the page referenced above - both the example bulbs use LEDs as I've noted with the "glass" being used to create some dispersion. This is actually poor use of the LED - a clear or absent :glass" allows greater efficiency- with light distribution being shaped by the LED characteristics which can be tailored to suit. Diffusers more often than not substitute smudging and light loss for good optical design. ie WHY absorb light instead of sending it where you want it. All the above makes a cap-up radiation face down LED inherently more efficient at lighting horizontal surfaces directly below it - and this is equally applicable for lighting any plane surface that the LED is "pointed at. Tube fluros tend to cover 180 degrees directly and 180 with reflectors (if fitted) Incandescent similar but in a spherical arrangement. CFL depends on tube shape but a substantial percentage goes out or up and needs reflectors for efficient use. None of the above is "bad" - it just has to be properly accounted for. BUT for lighting horizontal plane surfaces such as tables, floors etc, the LED natural pattern has an advantage. The other factor is LED efficiency which is now for better quality LEDs above CFL, pushing tune fluro and still far from sensible maximum. Full power LED lumen/Watt is typically 100+ l/W and if under run can be 120-130 l/W at medium powers and 150+ l/W at a low % of rated output. Efficiencies of 200 l/W seems entire;ly feasible and the absolute maximum is ~~~ 350-400 lumen Watt - when you will not need any heat sink as all input energy is radiated as light :-). Even if an LED "bulb" is placed in a more traditional; CFL or incandescent downlight fiitting it will provide greater efficiency of % light emitted actually used than the original bulbs as there will be less use of reflectors and more direct downwards radiation. Russell McMahon --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .