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  • OT-LED Lights

    I bought led lamps from Costco a year or so back, a 20 pack I think 60 watt equivent. In my kitchen, I have 9 recessed fixtures that have been in there for about 5 years, used to have CPF bulbs. In the past couple months, the leds are doing weird things. One went out and I replaced it, but others, one at a time start flashing, or dim, for a while then they go back to proper function. Several bulbs are doing this, others aren't. So what causes this? Will these bulbs eventually burn out? The one that quit didn't do this.

  • #2
    LED if used with dimmers, require special led dimmers or they don't work right or may fail. That could be the problem or maybe you got a bunch of crap.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

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    • #3
      Feit Electric? cheapest brand... never been a fan. My Philips, Cree or Osram have been working perfectly.

      If not the dimmer discussed above (btw, some bulb can use "std" dimmers, but certainly not all), your issue is likely the built-in drivers. Is it hot (like an attic) where they are mounted?

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      • #4
        Originally posted by lakeside53 View Post
        . . . Is it hot (like an attic) where they are mounted?
        Sadly, it doesn't need to be hot. Most of the garbage out there will cook itself even in open-face fixtures (recessed), especially if covered above by insulation. If you want any kind of reliability, get the lamps specifically rated for 'totally enclosed fixtures', I personally use Phillips. Do not assume that just because the package does not say 'NOT for use in totally enclosed fixtures', they are. They are not.

        It isn't just LED's either. Most of the generic CFL lamps have the same issue, though they usually last a bit longer.

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        • #5
          Yep... amazing how hot 6-8 watts dissipation can make a fixture environment.

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          • #6
            Flashing, dimming, or simply not lighting anymore are all failure symptoms I've seen. I've seen CFLs fail in those ways too. First thing is how
            many hours did the package claim the bulbs should last? I've seen numbers ranging from 2,000 hours to 25,000 hours. If they were rated
            for 2,000 hours and you ran them 5 1/2 hours a day they should last at least a year.

            I use a Sharpie to write the date on the base of the bulb prior to installing it. While in some cases it only tells me when I last replaced that
            bulb, in other cases it allows me to calculate how many hours the bulb lasted because I'm consistent in when I turn those lights on and off.
            The bulbs I'm currently using are rated for 2,000 hours. I had 2 kitchen bulbs fail at ~2,300 and ~2,400 hours respectively. The bulb in the
            desk lamp in my den currently has 3,700 hours on it. The lamp in my dining room has 5,000 hours on it. Last December I installed one
            outside my back door, it failed after a month. I installed one outside my garage on the same day, it's still working.

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            • #7
              LED is the new magic phrase in the sales world. If it is LED, it must be great. Unfortunately, not all of them are. The LED itself may be more efficient and make less heat, but the rest of the circuitry that is needed to operate a two or three Volt DC device on 115 Volts AC is an engineering challenge. And that circuitry can be very inefficient and can get very hot. When I first saw big heat sinks on LED lamps I was flabbergasted. There is no real reason for that, but there they were. BAD DESIGN!

              When you shop for LED bulbs you need to look at the specs. The higher the efficiency, the less heat they make. That is a good thing.
              Paul A.

              Make it fit.
              You can't win and there is a penalty for trying!

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              • #8
                Feit, that's what the base says. I don't have dimmers on this, straight on and off. And yes, when I took the bulb out, it was hot. Not as hot as incandescent, but you wouldn't want to hang on to it for long.

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                • #9
                  Then it's too hot. One of the bulb types I buy has a tapered aluminum tube as the body, and it's covered in plastic. There are no fins, and there's no connection from the aluminum tube to the base so there's little there to conduct heat away. Leds are electronic components and do need to be kept from overheating- and the heat dissipation scheme is usually barely adequate from what I've seen. A recessed fixture has no where to dissipate heat to as it's usually covered by attic insulation. This makes the marginally adequate led bulb even less so in its ability to run cool enough to have any kind of lifetime.

                  I just bought another led bulb today from a dollar store. It actually has heat sink fins, so I'm hoping it will run cool enough for continuous operation in normal summer ambient temperatures. I'm in the process of hacking it to find out how well connected the led deck is to the finned body. I've hacked many types of bulbs and I'm not really happy with how poorly the led deck is connected to the heat sink.

                  It appears to me that the construction of the led deck itself is ok in any of the bulbs that I've hacked. All they need is to be kept from getting too hot
                  Last edited by darryl; 08-06-2017, 05:50 PM.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    Of course, they should be designed not to make that much heat in the first place. Modern, switching techniques can help this a lot. But yes, if they are so poorly designed in the first place, they do need to be kept from getting too hot. There is an old rule of thumb that the temperature rises 10 degrees for every level of assembly or packaging. A bare silicon chip is placed in a standard package: it's 10 degrees hotter in there. That package is assembled on a circuit board: another 10 degrees. The board is in a device: another 10 degrees. Or perhaps more if the device is large and complicated with sub-assemblies. In the case of your LED light bulbs, the bulb goes in a fixture: another 10 degrees. If that fixture is not in free air: another 10 degrees. Seems like the chips doing the work are around 40 or 50 to as much as 100 degrees hotter than the surrounding air.

                    The good news is this rule of thumb is probably a bit on the pessimistic side. The bad news is the folks who made it up were technical types and probably using Celsius degrees which are almost twice as large as Fahrenheit ones. So a predicted 50 degrees above ambient temperature by this rule translates to a 90 degree difference measured in the Fahrenheit scale. Along with all the other concerns about Voltage and current and power, electric and electronic devices really need to be designed with heat dissipation in mind.

                    I fear that all too many manufacturers are rushing to get LED products into the market at a cheap price. They are taking too many shortcuts to keep the price down and are putting LEDs, which should last 20 years, into lamps that are doomed to burn out in a year or two. This will negate much of the savings that the LED lamps should be giving us and will give the public a bad taste for them. The chip manufacturers are making some amazing chips today. With better engineering I can see no reason why a properly engineered and manufactured LED bulb should cost more than a high grade incandescent one. And it should last 20 times longer.

                    So I take issue with the statement, "... that the construction of the led deck itself is ok ...". If you change the word "construction" to "design", I fear that it is the main problem with the life of LED bulbs.



                    Originally posted by darryl View Post
                    Then it's too hot.

                    ...<snip>...

                    It appears to me that the construction of the led deck itself is ok in any of the bulbs that I've hacked. All they need is to be kept from getting too hot
                    Paul A.

                    Make it fit.
                    You can't win and there is a penalty for trying!

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                    • #11
                      Originally posted by Paul Alciatore View Post
                      Of course, they should be designed not to make that much heat in the first place. Modern, switching techniques can help this a lot. But yes, if they are so poorly designed in the first place, they do need to be kept from getting too hot. There is an old rule of thumb that the temperature rises 10 degrees for every level of assembly or packaging. A bare silicon chip is placed in a standard package: it's 10 degrees hotter in there. That package is assembled on a circuit board: another 10 degrees. The board is in a device: another 10 degrees. Or perhaps more if the device is large and complicated with sub-assemblies. In the case of your LED light bulbs, the bulb goes in a fixture: another 10 degrees. If that fixture is not in free air: another 10 degrees. Seems like the chips doing the work are around 40 or 50 to as much as 100 degrees hotter than the surrounding air.
                      .......
                      I can see no reason why a properly engineered and manufactured LED bulb should cost more than a high grade incandescent one. And it should last 20 times longer.

                      So I take issue with the statement, "... that the construction of the led deck itself is ok ...". If you change the word "construction" to "design", I fear that it is the main problem with the life of LED bulbs.
                      Maybe you need to review basic physics....

                      You have white LEDs, which seem to take 3 volts to run them. Now, the LED may take a few hundred milliamps or up to an amp. I just looked up some on Digikey, and that popped out as an example about 3V and an amp. Don't recall the exact lumens, but it was reasonably high.

                      It seems to be very difficult to get actual energy numbers for LED efficiency. It is all converted to lumens per watt, which has to be translated to energy output as light vs energy input. But incandescent may emit 2 or 3% of the input energy as light. If LEDs are 6 x more efficient, then they would have 18% efficiency.

                      Using that as the base you have 3 W going into an LED, and of that, you may have 2.5W of losses (1/6 of the total power is used for light). The losses have to be sent somewhere, so they go into a heatsink, which is the finned or smooth thing you see. There will be several LEDs in a bulb, so there will be more watts of dissipation in the LED.

                      The switchmode supply running the bulb is generally quite efficient, at 90 to 95%. If the bulb takes 10W, maybe a half a watt or a bit more is lost to the SMPS. Some very cheap ones might be only 80% efficient, and use up to perhaps 2 watts.

                      With an incandescent, heat is no issue, the filament gets extremely hot, but is not adversely affected by that for a fairly good lifetime.. With a CFL, again the heat is in a component (the tube) that is not overly affected by heat, even if it is affected more than the filaments are. Although the power conversion devices must dissipate some heat, it is usually not very much of the total.

                      With the LED, assuming the 18% efficiency of available, practical LEDS (not special laboratory creations), most of the input energy is still dissipated (all but the 18%), however the parts doing the dissipation are all heat-sensitive solid-state devices. They must be kept cool, and the heatsinks you are complaining about are what does that.

                      They are necessary because a similar amount of heat to a CFL is being dissipated, but instead of it being in a glass tube and the vapor inside it, which are not very sensitive and have lots of surface area, the heat is in a solid state device with a max junction temperature under 200C, and hardly any surface area.

                      You need to EXPECT that there will be a heatsink. It is just basic physics, follow the energy, and check temperature limits.
                      Last edited by J Tiers; 08-06-2017, 07:35 PM.
                      1601

                      Keep eye on ball.
                      Hashim Khan

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                      • #12
                        Darryl wrote:

                        "I just bought another led bulb today from a dollar store. It actually has heat sink fins, so I'm hoping it will run cool enough for continuous operation in normal summer ambient temperatures. I'm in the process of hacking it to find out how well connected the led deck is to the finned body. I've hacked many types of bulbs and I'm not really happy with how poorly the led deck is connected to the heat sink."

                        I just bought an LED light at Dollar Tree, 60 watt rated light output, 9 watt rated electricity use. Funny thing, when I took it out of the package, something "clunked" inside the enclosure, sounded like something on a thin wire swinging in the bulb. I screwed it into the overhead fixture in the garage (which no one EVER turns off) and we'll see how long it lasts. I intend to go back to the store and shake some to see if this is typical.

                        Steve

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                        • #13
                          Ok, that makes sense- design rather than construction.

                          This was a pretty easy hack- on this bulb I got today- I snapped off the front cover, which was secured on with a couple wisps of silicon rubber, but also has tabs. Under that is the led deck of course, two screws and two feed wires. Whole thing came apart nicely and can be put back together without problem. I pulled the led deck off and cleaned up the heat sink compound, which I was happy to see there. The deck itself is thicker than most, being about 60 thou at least. It did have some flashing on the bottom of it, so presumably that would keep the deck from sitting totally flush to the heat sink surface. This is an important detail in that would want to maximize the area of contact to most efficiently remove the heat from the leds. At any rate the finned structure is in full contact with the led deck, so I can't fault that- and more to the point for me, I'm more able to rely on it to remain working for years.

                          An interesting thing, for me anyway, is that the led deck runs from 26.4 volts as shown by my meter and at full line voltage. At that point the chip array draws 300 ma. The 16 leds are arranged in two strings of 8 leds, so the current through each string is 150 ma, and what they call 'low voltage' operation becomes possible. This particular bulb has about the largest physically sized power supply that I've seen in these things lately. The output cap alone is about the size of the smallest power supply I've seen. None of this makes it any more or less likely to fail, but I like to think that larger is usually longer-lived.

                          Anyway, this has been a review of this finned decorative led 'bulb' from a dollar store. There is no maker, no model number, and it's likely that none of you will ever see this particular one anywhere.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #14
                            That's probably the power supply- sometimes they just dangle there from the wiring. There's usually a slot of some kind that the pc board is supposed to be inserted into. It appears that sometimes the assembly process leaves something to be desired-
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                            • #15
                              Originally posted by darryl View Post
                              .....

                              Anyway, this has been a review of this finned decorative led 'bulb' from a dollar store. There is no maker, no model number, and it's likely that none of you will ever see this particular one anywhere.
                              Does it have a UL or similar mark on it or its packaging?

                              Dollar store goods are commonly "under the radar" and are not tested or safety agency rated in any way.

                              If they are ever cited on it, there is no chain to follow back to a supplier. Just like computer boards were 25+ years ago...
                              Last edited by J Tiers; 08-06-2017, 09:32 PM.
                              1601

                              Keep eye on ball.
                              Hashim Khan

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