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Thread: LED Question...

  1. #1
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    LED Question...

    Sorry if this is the wrong area? Didn't know... Best fit otherwise.

    I am looking to create a circuit board of some high intensity LED's, blue, to mount into my rear turn signals and front. I am a volunteer firefighter and use these when responding to calls or when my vehicle is on scene.

    I am looking for bright lights... But I am having a problem, what the heck is the difference between Luminous Flux and Luminous Intensity? Reading it didn't seem any difference, but they are seperated on a page with these titles on a table....

    500mcd vs 19lm or 255mW

    http://www.superbrightleds.com/leds.htm

    "XLamp 1 Watt LED" and "High Flux LED" Looking at the blue color.

    Any help would be appreciated!
    Jim
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  2. #2
    FLAC john1701's Avatar
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    it would be easier and cheaper to get the lights you need through the fire dept you are active with. Also according to Illinois law, pov cant use blue lights only red.
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  3. #3
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    Quote Originally Posted by john1701
    it would be easier and cheaper to get the lights you need through the fire dept you are active with. Also according to Illinois law, pov cant use blue lights only red.
    Actually, ILCS 625 states a volunteer firefighter can only use Blue ... And well, if my dept donated lights out, I wouldn't have gotten my dash light from an outside source.
    Jim
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  4. #4
    Constant Bitrate NiteMax Mark's Avatar
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    These are basically two different measures for closely related information like torque and horsepower. They are both telling you similar details that aren't exactly the same.

    Luminous Intensity is measured in mcd (milli-candles, or thousandths of a candle)

    This is a measure of the LEDs brightness at the brightest spot in the center of the beam. The "Viewing Angle" is the angle you need to move away from center for the brightness to drop to half. The highest mcd rating will usually come with a small viewing angle.

    Radiant Intensity is measured in mW (milli-Watts, or thousandths of a Watt)

    This is the total amount of light power the LED outputs in all directions.


    What's the difference?

    Many LEDs are made with the same LED guts and different lens shapes. Two different LEDs may have the same total output power but one is more focused than the other. A tightly focused LED will throw all of its light into a tight beam and the "mcd" rating will be very high -- as long as you look at it dead center. Off to the sides it will quickly look dim.

    A low mcd rating and a high Viewing Angle means that the light is dim at the center in exchange for light being cast in a much wider pattern.

  5. #5
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    Thankyou for the reply.

    Using the cost guess, I would say the $10.95 per LED lights are brighter
    Jim
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  6. #6
    Constant Bitrate NiteMax Mark's Avatar
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    The brightest LEDs really need some special handling to make sure they continue to work. All LEDs need proper current limiting, birght LEDs need this plus very good heat dissapation. If you are lucky enough to score some bright LEDs, you'll need to be very effective a building the right kind of curciut for them including good heat dissipation.

    There were some awsome LED flashlights at Target for 50% off. If I were doing this project, I'd adapt an existing product to make blue instead of building from scratch! The flashlights were $10 up until last week.

  7. #7
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    Well I have worked with LEDs before, I was just unsure about how these ones worked etc, I used standard 5mm lights, none of these.
    Jim
    2012 Honda Pilot (In Progress)
    2010 Honda Accord (After the Pilot)
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  8. #8
    Variable Bitrate kamikaze2112's Avatar
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    Maybe just look for some federal signal or whelen stuff on eBay. I've seen LED strobes on there before, i think that would work perfect for your application.


  9. #9
    Maximum Bitrate DJiK's Avatar
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    Quote Originally Posted by NiteMax Mark
    All LEDs need proper current limiting, birght LEDs need this plus very good heat dissapation.
    NiteMax is right.
    I used one 1 Watt 12V LED and a corresponding Resistor (sorry, forgot the value), to illuminate a gauge in my car. I left it on for about 20 mins, came back, turned it off, and tried to pulled the resistor out of the breadboard. I almost burned my fingers. The LED itself was resting on a 1"x1" heatsink, and was warm to the touch even after 5 mins.

    An mp3Car member, turbocad6, had to liquid-cool the backlight of his LCD because it used a couple dozen of those 1W LEDs. Check it out here.

    I suggest you to explore other alternatives for what you're trying to achieve.

    Good luck.
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  10. #10
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    Damn.. Maybe Ill just use strobes
    Jim
    2012 Honda Pilot (In Progress)
    2010 Honda Accord (After the Pilot)
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