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Thread: Totally OT, LED lighting question

  1. #16
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    Quote Originally Posted by Tom Stenzel View Post
    ...I've never seen a LED that needed 25 volts for the forward junction to conduct. But then I haven't paid much attention to the illumination LED market.
    ...
    25 volts! That's a new one for me too. Decades ago I bought some expensive LEDs with internal current limiting resisters - with the huge lighting market maybe it is now cheaper to build in some circuitry.

  2. #17
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    Quote Originally Posted by John K Jordan View Post
    I understand that may depend on the electronics in the bulb. Have you tried with others? Apparently the electronics in the bulb itself must sense the output from the dimmer and reinterpret it to drive the LED appropriately, with either current reduction or pulse width modulation. It seems that some dimmers and some bulbs don't communicate or work together well.

    A search found several tips. Perhaps this one is useful: http://luxreview.com/article/2016/02...-dim-led-lamps

    JKJ
    I haven't really spent time on it. The dimmer does 'go dimmer' with an incandescent lamp so I'm sure the LED lamp is the issue rather than the dimmer. This application doesn't require low light output and I expect LED lamps will get better at variable output as R&D continues.

  3. #18
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    Quote Originally Posted by Curt Harms View Post
    I haven't really spent time on it. The dimmer does 'go dimmer' with an incandescent lamp so I'm sure the LED lamp is the issue rather than the dimmer. This application doesn't require low light output and I expect LED lamps will get better at variable output as R&D continues.
    Are these LED's made for a dimmer.

  4. #19
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    The LED fixture/lamp power supply must be dimmable and the dimmer switch must be designed to support LED. Older dimmers cannot work properly with LED (and CFL in many cases, too)
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #20
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    Quote Originally Posted by Jim Becker View Post
    The LED fixture/lamp power supply must be dimmable and the dimmer switch must be designed to support LED. Older dimmers cannot work properly with LED (and CFL in many cases, too)
    Some older dimmers do work with dimmable LED bulbs. It can be a crapshoot, though. At work, I have hundreds of LED bulbs on some commercial Lutron dimmers that came out long before LEDs, but they're pricey dimmers to begin with ($130+ per).
    Jason

    "Don't get stuck on stupid." --Lt. Gen. Russel Honore


  6. #21
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    The ~2002 vintage light/fan controllers we have in several rooms in our house dim the Costco LEDs we have. We've had one failure, very early and the replacement in that spot has continued so it was a fluke I'm sure. We converted 90% to LED, the rest being 4' florescents I'll eventually convert and some flood lights on the second story soffits that I can't reach and we rarely turn on anyway. Open fixtures, closed fixtures, ceiling fans, recessed cans, bulbs facing up, down, sideways. Most of ours came from Costco but some from Lowes too, usually the Utilitech ones.

    My mom has had some more trouble with those jelly-jar style fixtures. I might buy the plastic globes for her and drill a few holes top and bottom for airflow. The bugs get in anyway so not going to make a difference there.


  7. #22
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    I am coming a little late to the party, but I have been responsible for life testing LEDs for the automotive industry, both interior and exterior. The first thing you have to deal with is what we called infant mortality. It isn't possible to test LEDs, or any other electronic element for that matter, adequately enough to strain out all manufacturing failures. If you install a whole lot of assemblies, some will die quite soon due to this phenomenon. After that, LEDs tend to last a very, very long time. We have switched LED tail and brake lights on and off hundreds of thousands of times and they seldom fail. The same is true of instrument clusters. As John pointed out, LEDs are dimmend with pulse width modulation and they are cycled on and off millions of times in just seconds. The single biggest root cause of failure is heat. All automotive electronic designs are life cycle tested to failure in the lab over a wide variety of environmental conditions. The big killer of LEDs is heat.

    In the automotive world, most of the testing is done at 14VDC. There is very little active electronics involved. In many cases, there is only a single current limit resistor and those almost never fail. House hold lighting requires some type of power supply and that is probably where most of the failures will occur, as many have already mentioned.

  8. #23
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    LEDs are here to stay. They may take on a few different configurations before it all shakes out.

    As to the pulse width driving of lights, it is interesting when driving at night to see the flashing streams of a taillight when my eyes move back and forth to check the side mirrors. Some people do not notice this effect.

    On the other side of things when incandescent lamps were on the way out one of my purchases was boxes of 60W bulbs. Hopefully enough were purchased to last a long time in the one place they are needed, our well shed. During the cold months when freezing temps are expected a 60W light in the well house is enough to keep things from freezing.

    With LEDs possibly appearing in appliances an old problem will likely go unnoticed. If the door switch on a refrigerator failed stuck on, the system couldn't keep up with the heat produced by an incandescent lamp and the refrigerator wouldn't get cold. It would also run all the time.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  9. #24
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    Quote Originally Posted by Jim Koepke View Post
    ...when incandescent lamps were on the way out one of my purchases was boxes of 60W bulbs. ...
    There are a couple of places I want to use incandescants so I bought a stock a few years back from Amazon. I like to purchase 130v bulbs instead of 120v.

  10. #25
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    Quote Originally Posted by Art Mann View Post
    If you install a whole lot of assemblies, some will die quite soon due to this phenomenon. After that, LEDs tend to last a very, very long time. We have switched LED tail and brake lights on and off hundreds of thousands of times and they seldom fail.
    Well, not everyone has this down, or at least not 7 years ago. We had an LED taillight fail on a 2011 model. I paid $350 for the assembly despite numerous online reports of the failure. A few months later the manufacturer agreed to pay for any that failed and we got a rebate. Ironically in between we got rear-ended and both assemblies were destroyed. Adjuster and I made a deal to use a "recycled" rear bumper, including all the reverse sensors and such, and trunk lid the shop found at a local junkyard, err recycling operation, in a matching color (one of those tri-coat paints that's hard to match) in trade for replacing both taillight assemblies with new parts. I probably won on both accounts.


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