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Thread: Do LED lights go dim?????

  1. #1
    Boolit Master
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    Do LED lights go dim?????

    Reason I'm asking is at the store, they have some LED light displays.
    When they were first put up, it was a little to bright to me.
    Now they seem to be about the right brightness.
    I don't know if it's from being on for a while, or they dimmed it.
    Display has been up for about a year.
    I'm guessing it's on all the time.

  2. #2
    Boolit Buddy
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    The lady at the local home improvement store told me to stay away from the cheaper brands. She said that they did get dimmer over time. Maybe she was just trying to get me to spend more money. Lol
    NRA Life Member

  3. #3
    Boolit Master sawinredneck's Avatar
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    They all dim over time, the better ones at a much slower rate than the cheaper ones. The rated average is 10k hours, give or take a lot!
    Quote Originally Posted by sniper View Post
    Irish Proverb: Never approach a Bull from the front, a horse from the rear, or an Idiot from any direction!

  4. #4
    Boolit Master popper's Avatar
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    The LEDs do dim but it is a long term slow event. Many LED lights use phosphor coating and it does get dim faster - used up.
    Whatever!

  5. #5
    Boolit Master JBinMN's Avatar
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    If it wasn't said in the OP that it was some "Store displays", I would have thought, "Maybe check the batteries?".

    LOL Sometimes I have a odd sense of humor...
    "If ya don't like my gate, ya don't have to swing on the hinges..." - L. Ackerman ( RIP)
    *------*
    "A man ought ta do what he thinks is best" - "Hondo" Lane.(John Wayne)

  6. #6
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    MaryB's Avatar
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    Cheap LED's lose about 20% brightness in the first year then stabilize for quite awhile. One in my bathroom has been in constant use(that room is dark no matter what) for 6 years and is getting pretty dim, I need to replace it.

  7. #7
    Boolit Master
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    Thanks guys. Now I know.
    Never thought the display might be run by batteries. It is a display. Good point.
    I thought LED lights last a long time. I'm guessing cheap one's don't.
    I used to buy those cheap china LED flashlights. They didn't last long.
    Noticed after a while, some bulbs would go dim or not work at all.
    Never seemed to work when you really need them.
    At least with a bulb, you could change it and the light would work again.
    My Mag Lite had a spare bulb in the end cap. Had to replace it a few times.

  8. #8
    Boolit Master
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    It's all about thermal management (and the better builds costs more $).

    The often-quoted 50k hours spec for LED's has historically cited associated junction tests of 25 degrees Celcius IIRC.
    (To their credit, Cree has updated their rated junction temperatures considerably, 85 C - again IIRC).

    With poor thermal management, junction temperatures are almost always /considerably higher/ than spec, drastically shortening life (i.e. dimming to 50%).

    I have seen LED lifetimes as low as 500 hours of actual use before considerable dimming due to insufficient thermal management resulting in junction temperatures considerably over manufacturer spec.

    Hope this helps,

  9. #9
    Boolit Master

    gwpercle's Avatar
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    Buy the better bulbs. I bought two "store brand" LED's to test, that started flickering after only a short time use . Replaced them with two "name brand" LED's . Not only did they seem just a bit brighter , they were cooler to the touch. After being on 4 hours you could touch the bulb, it was warm but not hot. They haven't started flickering yet either .

    I'm sure this cooler "better thermal management" is going to help with the life span.
    Kestrel says it so much better than I .... "thermal management" sounds so much more educated than " the bulb is cooler ". Cajuns were never known for a great command of the English language...... " Choot 'Em!!! Elidabet!" is about par for the course.
    Gary
    Certified Cajun
    Proud Member of The Basket of Deplorables

  10. #10
    Boolit Master
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    Thx, but not exactly the same however; sometimes poor thermal design will keep the heat inside an assembly, not permitting it to conduct to the surface where it can be removed via convection/radiation.

    For example, the exterior of a high-output LED flashlight with good thermal design will get _HOT_, but can keep the electronics inside from frying.
    Have seen this directly with IR images of flashlight designs; improving the thermal path can yield some interesting & sometimes counterintuitive results.

    Or for you Cajuns,
    Hot = lots of heat leaving
    Cool = either a low thermal load or a poor thermal path ... darn it, the engineer hat fell back on, lol.

  11. #11
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    MaryB's Avatar
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    I have solar and use DC lights as backup around the house. 24 volt light fixtures are stupid expensive so I build my own. I use old CPU heatsinks with fans to keep them barely above room temp and they last forever. Super bright too! Last power outage neighbor across the street asked me how I had lights told her that is what the solar panels are for!

    This is equal to a 150 watt bulb



    Huge slow speed cooling fan so it is fairly quiet



    Cost me about $20 to make total and I made a red oak frame it rides in so it looks nice in the kitchen
    Last edited by MaryB; 10-11-2017 at 11:14 PM.

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