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Discussion in 'Electronic Design' started by Jennie, Oct 5, 2004.

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  1. Jennie

    Jennie Guest

    I have a FR200 radio with a light bulb attached. I am looking to hook up a
    LED that is the best energy miser.

    I am using a 5mm LED that is rated 20mA and 3.6 Volts - radio shack

    FR200 = 4.5 Volts 3 AA Batteries at 1.5 each...Volts is series Volts
    increase and Amps stays the same.

    R = (Vs - Vr) / I

    R = (4.5 - 3.6) / .020 = 45 ohms

    What is the most energy miser bright LED out there? One to give me lots of
    light time?
     
  2. Jennie

    Jennie Guest

    Is this the right newsgroup to ask this type of ?
     
  3. Jennie

    Jennie Guest

    Where are the high efficiency leds?
     
  4. You can operate any LED at a current well below its specified maximum,
    with an almost proportional decrease in light output. Experiment with
    the ones you have with current at .01 and .005 amp and see if the
    light is bright enough. The only way yo make the battery last longer
    is to find one that has high efficiency, so you can run at the lowest
    possible current.
     
  5. sci.electronics.basics would be better.
     
  6. Rich Webb

    Rich Webb Guest

    Google knows...
     
  7. LEDs are sold many places. Where did you get the last one? The key
    specification is the luminous intensity (usually specified in mcd or
    millicandelas). Divide that number by the specified current and you
    get millicandelas per milliamp. This is the conversion from current
    to light efficiency.

    For example, these LEDs sold through Digikey have the following specs:

    http://rocky.digikey.com/WebLib/Fairchild/Web Data/MV8W00.pdf
    typical 2500 mcd at 20 ma, 125 mcd/ma.

    http://rocky.digikey.com/WebLib/Lumex/Web Data/SSL-LX5093XUWC-TR.pdf
    typical 2300 mcd at 20 ma, 115 mcd/ma.

    Whatever kind you get, run it at the lowest current that gives enough
    light.
     
  8. Jennie

    Jennie Guest

    Radio Shack...

    MCD 1100 at 20mA, 55mcd/ma Is the lower the number, mcd/ma, a more
    efficient LED?
     
  9. No. Millicandela is about 1/1000 of the light of a candle. More MCD
    is more light (what you want) for the same current (what you have to
    pay). The same way higher miles (what you want) per gallon (what you
    have to pay) is a more efficient automobile.
     
  10. Jennie

    Jennie Guest

    Thanks, where is a good explanation of how a led works, etc....
     
  11. HP's 2nd edition of "Optoelectronics/Fiber Optics Applications Manual." (If you
    can find them after I sucked up a dozen of them from various sellers on the web
    last year and sent them to people I knew would be interested.)

    Jon
     
  12. Clarence

    Clarence Guest


    Here is somethings to start with

    http://csm.jmu.edu/physics/hughes/APL_66_115.pdf

    OR

    http://www.engineering.vcu.edu/fac/morkoc/learning/science.pdf

    AND

    http://www.lumileds.com/pdfs/protected/AB12.PDF


    OR if you really need it and will pay for it.

    http://ao.osa.org/abstract.cfm?id=25107
     
  13. Clarence

    Clarence Guest

  14. Rich Grise

    Rich Grise Guest

    Some time ago, there was a thread about letting a big cap discharge
    through a LED, and "does it dim continuously, or wink out at the end",
    so I did the experiment. From 20 mA down to 10 I didn't see any
    noticeable change in brightness (probably would have if I'd had 2),
    and it gave light "smoothly", all the way down to 0.

    So do some experiments. I wouldn't be surprised if there's a LED
    that would give you a usable indicator at just a couple of mA.

    Good Luck!
    Rich
     
  15. My super-greens are usefully bright (under room lighting, narrow
    angle) at just 250uA.


    Best regards,
    Spehro Pefhany
     
  16. Jennie

    Jennie Guest

    Some LED's glass is so distorted the light has to be distorted too..
     
  17. Jennie

    Jennie Guest

    Where do u get the LED's?
     
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