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High Efficiency LEDs?

Discussion in 'Electronic Design' started by Shannon H., Aug 25, 2004.

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  1. Shannon H.

    Shannon H. Guest

    My apologies if the following question is a dumb one, but could someone
    please explain to me if there is any difference between the standard
    LEDs that one might expect to find at Radio Shack and those installed in
    certain newer-model, long-lasting LED-style flashlights, garden lights
    and lanterns?

    I have seen several products in catalogs in recent months which specify
    that because of new technology, their LEDs not only last 1000,000 hours,
    but that they draw less power than other, older LEDs. Is that the case?
    And if so, could someone tell me specifically where I might be able to
    purchase them and exactly what I should ask for?

    I'm looking for amber-colored LEDs as opposed to the white ones-- if
    that makes any difference. I'm hoping to replace the LEDs in my solar
    powered lamp posts which currently yield approximately seven hours of
    run time on one day's charge. I'm afraid that switching to another brand
    of LED would eat up too much power and make the light last fewer hours
    during the night.

    Please feel free to email me with any information or advice that you
    think may be helpful-- it would be greatly appreciated.

    Thank you,

    Shannon
     
  2. Radio Shack has a white one that is definitely fairly high efficiency -
    the 276-320. It has a wide beam, unlike the narrow beam of ones used in
    flashlights. The one most used in flashlights is Nichia's NSPW-500BS.
    Most white LEDs at full power fade with a "halflife" of usually 20,000
    to 50,000 hours. I have even sometimes heard 6,000 hours and some junkers
    do less than that!
    They last longer at reduced power. Most LEDs other than white, pink,
    purple, violet and UV last 100,000 hours if not overpowered or overheated.
    New and old LEDs, and high eff. and low eff. LEDs have similar
    current/power input (among those with similar case styles). The highest
    efficiency ones of recent years can produce 25-50 (maybe more) times as
    much light as those that were the standard in the mid 1970's.
    Radio Shack 276-320 is a good white LED for experimenters needing only
    one or two and not needing a narrow beam.

    For more, have a look at:

    http://www.nichia.com - go to "products" - they also have an online
    ordering system that can deal with fairly small quantities.

    http://www.hosfelt.com - look at their LED page, then give them a call if
    you want to place an order.

    http://www.misty.com/~don/led.html - my bright and efficient LED page -

    I am not a supplier but I mention some good ones.
    Amber ones have a lower voltage drop than white ones, tend to have
    similar efficiency, and tend to have less "dark condition illumination
    power" than white, green and blue due to being less favorable to night
    vision. (Orange and red are even worse than amber for stimulating night
    vision.)

    Also note that amber, orange, red and yellow-green have a voltage drop
    about 60% of that of white, blue and non-yellowish green. You may have to
    rework things if using amber LEDs in an application that works with white
    ones. Amber LEDs have a typical voltage drop of 2.1 volts while white
    ones have a typical voltage drop of 3.5 volts.
    If you replace white LEDs with amber ones with no other rework, expect
    runtime of even less than with white LEDs. You may also have excessive
    current through the LEDs.

    - Don Klipstein ()
     
  3. Yes, the efficency of LEDs varies greatly.
    The newer "high efficency" LEDs use more exotic materials and new
    manufacturing processes etc to get greater efficency, i.e. light
    output vs current.
    To make any decent comparisons you will need the datasheet for the LED
    you are using now, or at least the datasheets for the various ones you
    plan on buying so that you can make comparisons.
    Note however that there is a HUGE amount of variability in the specs
    for LEDs. The output intensity in mCd or Lumens, viewing angle etc.
    It's ain't easy to just compare LEDs on their mCd rating for instance,
    but it's a starting point.

    A place to start might be here:
    http://www.superbrightleds.com

    Regards,
    Dave :)
     
  4. I cannot attest to the long life, but as far as power goes, I am
    definitely convinced there is a big improvement over standard LEDs. I
    have a bright white LED flashlight that I bought with a mountain bike
    two and a half years ago, and I have been using it as a flashlight for
    night jogging regularly with no perceivable degration in power output
    on 2 Duracell AA batteries! Every now and then I will run into a deer
    (or black bull), which, at 11:00 P.M, is just as startling to me as it
    is to the animal, at which point I check it to be sure, and I am
    always impressed.

    -Chaud Lapin-
     
  5. Look at:
    http://www.pressbox.co.uk/Detailed/4882.html
    In this case, the life extension, is not in the LED itself, but in changes
    to the encapsulating plastic, to stop it darkening, and reducing the
    light.
    In the UK, the place to go, is:
    http://www.ultraleds.co.uk/
    Who do everythin from single LED's, to complete assemblies and lamps.

    Best Wishes
     
  6. Don

    Don Guest

    If you want a really bright led look up "Luxeon Star LED"

    These are the brightest of them all.
     
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