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Light Emitting Diodes; Ready for prime time?

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  • Light Emitting Diodes; Ready for prime time?

    I use almost exclusively compact fluorescent bulbs for lighting around the house and shop. They work well but have some drawbacks. They don't like cold and start slowly or not at all if too cold. They don't last long at all in service where they are switched on and off a lot as the service life is determined by the number of starts more than the number of hours operating. They also have a poor power factor and that will erase some of the savings when the utilities start charging to compensate power factor losses.

    LEDs on the other hand have very long service life, they run at unity power factor as they are DC devices and will operate at any temperature that matters. As a bonus they start instantly and don't flicker when run on DC (absent pulse width modulation dimming). They also have high quantum efficiency turning more power into visible light than other methods.

    The two main problems have been low total output and cost.

    Both of those problems are fast disappearing. I have recently been experimenting with LEDs for use as ordinary lighting. I already use them for photographic lighting and spot task lighting but I want to move them into the general lighting arena.

    I recently found some cheap flashlights at our local surplus/import dealer that boast 32 "ultra bright white LEDs". The flashlights cost $7 and are quite well made (machined aluminum) but like most of these devices use 3 AAA batteries. Three AAA batteries can't supply enough current to run 32 LEDS at full output. I tried running the flashlight on "shore power" and found that they can be run at least twice as bright if given sufficient current, 20 milliamps per LED being somewhat of a standard.

    The attractive thing about these particular flashlights is that the head of the unit is a near drop in replacement physically in a standard fixture. PAR 20 LED bulbs are available now with 36 LEDs but cost around $40-$50. That's much too expensive but $7 is a different story.

    Here is a relamped fixture using the head of one of these flashlights shown beside the fixture. The fixture has been rewired to take as input a standard 6 volt wall wart supply with a ballast resistor. This removes it from code scrutiny as it becomes essentially a flashlight. The lamp is using about 2 watts of power. It puts out about the same apparent brightness as a 10 watt 12 volt halogen bulb.

    I'm pretty happy with this but it isn't going to replace my 50 watt track lighting bulbs yet which are just about the only incandescents left in my house. I think I will make another as I have another spare fixture and using just the gimbals and lamp put them on my mill for task lighting.

    Playing with this gave me an idea. I have (had) a 60 LED battery operated trouble light that I bought maybe a year ago for $30. It quit working after a few months and I set it aside for future use. Well, I used it yesterday to make a "real" lamp for my living room workstation. I machined up a fixture for it that hopefully doesn't look like a trouble light and does I hope look "store bought". It's one of the things I like about this hobby of machining. I enjoy it when somebody asks me where I bought such and such and I then have the pleasure of informing them that I made it.

    Here is what I came up with. It consumes about 6 watts and is very bright. I am running the LEDs at about 23 ma each which has stepped up the light output of the array far above what it was producing on batteries. Another thing I really like about the white LEDs is the color temperature of the light. I hate warm white lighting. I much prefer high blue color temperature especially in the winter when it is dark so much of the day. Having this lamp at my work station will help fend off SAD (Seasonal Affective Disorder).

    Here are some more pics. In the next montage the bottom image shows looking directly at the lamp which is not recommended since it is bright enough to be very uncomfortable. The bottom right shows the far side of the living room illuminated only by the LED lamp. I used no fancy camera exposure tricks, that is the apparent subjective brightness.

    This next montage is closeups of the fixture I made. It was some pretty fiddly machining on the lathe and mill, especially the mill portion of it. I used parts from a standard pole lamp for the support. The cooling fins are entirely functional since the lamp dissipates about 6 watts. Besides, there are two things that just plain look cool on a project, fins and lightening holes. This lamp also runs from a 7.5 volt wall wart rated at 1.5 amps.

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  • #2
    Evan, The only problem with those lamps is the "color temp". I'd
    like a little warmer color. It's too bad there arent some high intensity
    red ones to mix in to do so. Do you have any ideas? I prefer WW
    in convential flourscent tubes.


    • #3
      1) What you like is exactly what I hate....... That BLUUUUUUE light.

      To be quite blunt, it sucks. Sucks the eyes right out of your head, or feels like it.

      because of the physics of LEDS, that is NOT going to change any time soon. OTOH, a fluorescent can be "tweaked" far more easily as to color temp, and it is done on a routine basis.

      Yes, some twiddling can be done by adding other colors to "fool the eye", but it isn't a wide spectrum, just a few peaks.

      2) The "efficiency" of LEDS is still somewhat of a myth. At least half of the "efficiency" has come from reflecting the entire light output to a "spot" beam. If that is what you want, as with a traffic light, it is fine. If you want general illumination, it's not very good.

      If you reflect the entire output of a CF you get a LOT of light, much more than a typical LED available now. Even if the meter says LED is similar, the eye sez NO!

      The bright LEDS can draw up to 1A+ at 4-5V. That is 5w. A 15W CF puts out more usable light than 3 bright LEDs, which are spotlights.

      Of course if you LIKE staggering through the dark from intense blue "light pool" to intense blue "light pool" . LEDS are fine.

      3) The poor power factor of CF fluorescents is a myth. The power factor of a CF is completely determined by the input circuit, and it is perfectly possible to make a CF with a PF of 0.999.

      If I can make a 2500W audio amp with a PF of 0.999 (I did at the last job), a 15W CF is a chump job. Demand it, and the ICs to do the job will appear in weeks...... Just as they did for CF bulbs.

      Keep eye on ball.
      Hashim Khan


      • #4
        They do make high intensity warm white leds.

        I considered bending the leds to spread the light more and changing the design of the housing to accommodate that but I need as much high intensity high color temperature light as possible. That is the first line way to stave off the "winter blues" otherwise known as SAD and it is a proven treatment that works.

        The quantum efficiency of LEDs is no myth anymore. The latest are putting out over 100 lumens per watt, an efficiency nearly ten times better than incandescents and better than the best fluorescents.

        While they can make high power factor CF bulbs most of the ones on the market aren't.
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        • #5
          I've not seen them, but I've read that it is possible to produce "white" light from LEDs by using a mix of colored LEDs, much the same way a color television tube can produce the appearance of white with a combination or red, blue and green.

          If that is so, it would seem as though it would be possible to create the illusion of any color warmth a person would want.

          Any opinions on that?

          I wouldn't care to get into any arguments about the myths surrounding LEDs, but I can share what I've experienced.

          For a couple of years, now, I have some Streamlight flash lights that have the option of using LED illumination or an incandescent lamp. With almost daily usage I've never had to replace the batteries, yet; however, long ago the incandescent bulbs have faded to uselessness because of low battery voltage. I almost have to light a match to see if they are on; but, the LEDs continue to provide all the light that I need for my purposes.

          I also use an LED book light and LED "hockey puck" lights. The hockey pucks get heavy usage in our travel trailer and spice pantry shelves. I don't even bother putting new dry cells in them. Instead, I use the discards from my pocket radio. After a couple of years of use, I've only had to change out the battery in one hocky puck light. The discards provide plenty of illumination from my book light awith bout a half hour of daily "after-lights-out reading" and will last about six months.

          Those are the kind of myths that are hard to argue with. I'm a fan.


          So many projects. So little time.


          • #6
            On my Lathe, I replaced the guts of my Halogen Lamp with LED's.
            NO MORE HEAT! NO MORE BURNS from touching the lens.
            And I swear that I can see much better. Not sure why.

            Tom M.


            • #7
              Evan, I salute your efforts. I also believe LEDs are the future of lighting. And it is perhaps not too far off.

              One slight correction on the CF bulbs. They are no better in constant service. Three or four months is all you will get if you leave them on. No where near the five years they claim. There must be some magical use factor, perhaps two or three hours a day with only one on/off cycle, that produces the magical long life. I have never seen one last over 18 months. And I would suggest that they be purchased individually and the receipt be taped to the fixture where they are used for future refunds. In this manner you might actually see some savings.
              Paul A.
              SE Texas

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


              • #8
                If that is so, it would seem as though it would be possible to create the illusion of any color warmth a person would want.

                Any opinions on that?
                Notwithstanding what Jerry said the white LEDs produce warm white the same way that a fluorescent does. White LEDs are really ultraviolet LEDs with a phosphor conversion coating that downconverts the UV to visible light. By changing the mix of phosphors the color of the light can be manipulated.
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                • #9
                  This is going to sound stupid and I know there is a reason ,,, but why cant they make an LED like a regular size bulb? even if it takes a matrix of little branches inside of a flat internal disc or something, why do we have to fiddle Fuqe with all these little bulbs and put them together? would there be an internal overheat in the center or something?


                  • #10
                    Try the luxeon star, warm white. 3300°K
                    Just got my head together
                    now my body's falling apart


                    • #11
                      but why cant they make an LED like a regular size bulb?
                      They do. This site was just linked on my laser thread by batt-man.


                      I may order some.
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                      • #12
                        A politician claimed that if compact flourescents replaced all incandescent bulbs in the US we could shut down "...80 that's: eight zero coal fired power plants..." (his words). That sounds extravagent so call it an exaggerated truth. Compact flourescents are about four times as efficient in terms of usable light output per unit of power consumed. LED's are about three times more efficient than flourescents.

                        An economist who specializes in power distribution proposed that since about 30% of the power consumed in the US was used for induction motors and the majority of those were used inefficiently at part load that VFD's and other solid state motor controllers have the potential if universally used to save about 30% of the power consumed.

                        I've noted myself that large consumers of energy for process heat simply waste it to the environment. I refer to glass manufacturers, air reduction plants, peak load power generation, etc - clean industries that could be co-located in urban areas. If their waste heat could be recuperated and used for habitable space heating yet more savings could be realized.

                        We are a wasteful society. I'm quite sure if we could apply a little political will we'd discover ways to reduce our aggregate energy consumption by - well - half out present usage.

                        Evan's exploration of the use of LEd is but the tip of the iceberg.


                        • #13
                          So far the record for a production led is about 400 lumens from a 7 watt led. Fluorescent is still more efficient. Plus having to heat sink them kind limits the design.

                          Most small leds actually run at about 50ma at 3.6v voltage drop.


                          • #14
                            My current employer just spun-off a company with the aim to produce LED units to directly replace fluorescent tubes. I think the idea is to target the commercial sector which would be more likely to use fluorescent replacements than incandescent replacements.


                            I have nothing to do with this company or its products, just thought I'd mention it. As far as I can tell from the website, nothing is in production yet.


                            • #15
                              Evan, not to sound ignorant, but what exactly is a " wall-wart "
                              I'm thinking you're referring to a power adapter that cuts 120 ac down to whatever it is in tended to?
                              I have an assortment of these in all sizes in my never throw away box.
                              everything from 4.5 volt dc to 24volt dc.
                              Also, I don't know about the other 49 US states but here in California, there are alot of LED traffic lights and the number grows every year.
                              grumpy old fart