Recent content by Oznog

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  1. O

    How can LEDs be used in sealed recessed-can lighting?

    Wow then a 13.5W light under the same design would get up to 110C... the caps aren't likely even rated for >105C. If your cap lifespan drops by 1/2 every +10C, that'd be less than 1000 hrs.
  2. O

    Hand dryer UV

    "UV" covers a WIDE range of wavelengths. For understanding, 3 subranges are relevant to this situation: UV-A is 400 – 315 nm. It includes plain ol' visible purple colors. It's "blacklight". It causes fluorescence of blacklight posters. Almost ALL "UV LEDs" are UV-A- most are 395 nm, some...
  3. O

    How can LEDs be used in sealed recessed-can lighting?

    Hmm, Cree's "65W equivalent" only uses 10.5W because they've got a much better lumen/W figure. The Utilitechs are I think 63 lumens/W, and 13.5W. The temp will be higher than the Cree due to wattage alone.
  4. O

    Best solution for lighting in warehouse/factory environment

    mds82 is right. The F54T5/HO type is REALLY the way to go. If you go with the High Efficiency type, it's ~4900 lumens on 49 watts (standard T5/HO type is 54W). That is both a tremendous output, AND a virtually unbeatable efficiency. Cost-effectiveness is unbeatable. The tube is INTENSE...
  5. O

    How can LEDs be used in sealed recessed-can lighting?

    The funny thing is, there's a pretty big finned heatsink (doesn't show up in the pic) in back that is wholly inside the sealed can. None of this heat conducts to the bezel.
  6. O

    5mm LED Christmas Lights

    You may notice a "flicker"... to say the least. The thing is, most strings are NOTHING but a BUNCH in series and a resistor. It's not just that it rises and falls 120 times a sec like fluorescent- no, it has no bridge rectifier. It actually turns on and off at 60 cycles/sec and is completely...
  7. O

    How can LEDs be used in sealed recessed-can lighting?

    I'm looking at some of the Utilitech 13.5W model 0113539 recessed lighting Lowes has: http://www.lowes.com/pd_113539-59179-DLS02-627D-WH-F1_0__?productId=4176973 How does that even work? There's a large heatsink on back, but it's supposed to retrofit into a recessed-lighting can. Since...
  8. O

    High temp thermal grease?

    Not actually for an LED, but I thought I'd ask here because someone may know... I'm in need of a thermal grease which would work at high temps, like 250C-350C continuous. For all its glory, Arctic Silver is only rated for 180C peak and 130C continuous. What are the options for thermal...
  9. O

    Are most LED grow lights a ripoff? Why do they need so many LED's?

    delete, double post
  10. O

    Are most LED grow lights a ripoff? Why do they need so many LED's?

    It depends on your goals. LEDs won't be cheaper than MH. That stuff is VERY efficient, and it can probably make some gains, but not remarkable gains. It'd be hard to justify the power savings of a well-designed system versus the purchase cost. If you're building a moon base, or want to grow...
  11. O

    100,000+ Lumen

    But HID (metal halide) isn't actually less efficient than LED (yet they get no press in the "green" market at all). Metal halide's supposed to be 65-115 lumens/watt. Sure, there are SOME big LEDs on the market which exceed 100 lumens/W. But that's not yet accounting derating for operation at...
  12. O

    Need help designing custom copper MCPCB for an XML

    I did some playing around with the aluminum flux. It most certainly DOES stay tinned! However, there did seem to be complexities and problems. It seems that the flux activates as a specific temp, at which point the solder must be in contact with the aluminum to alloy into it. The problem is...
  13. O

    question about LED street light design

    Yeah, there's a huge cooling problem. Other light sources don't require cooling. In fact, AFAIK, an incan LOSES efficiency as heat escapes through the bulb wall. Streetlights can't employ cooling holes, as stated. Insects will quickly move in and clog the fins or jam fans stuck. Road dust...
  14. O

    Need help designing custom copper MCPCB for an XML

    Neat... but were these heatsinked or what? How would you compensate for the difference in thermal mass? Copper's about 40% greater thermal mass than aluminum, for the same volume. In actual installed usage, it is not significant in helping performance. In short-term off-the-sink tests, a...
  15. O

    Need help designing custom copper MCPCB for an XML

    You'd think, being an alloy of 65% copper, it would be a good heat conductor, but yellow brass (common type) is only HALF the thermal conductivity of pure aluminum. The alloy is important- well, ALL the copper and aluminum alloys take big hits...
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