Not so easy to run an LED ”bulb” off of a dimmer switch – but here’s how

Had dinner with a colleague the other night -- complaining that he's now had 3 Verizon FIOS set top boxes for his home entertainment system -- each and everyone skips channels after a few minutes. Recalling the EDN Mag comments, I asked him if he had CFL's in his den -- and the answer was "yes".

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My home light is all 12V MR16 but now I replace them with LED's they are dimmable and getting more powerful and I don't mind leave it on, long life low consumption the only problem is the price. this is the product of our centuries I love it

Re: Engineer & LED power supply In addition to the series capacitor ballast, it is probably a good idea to also add a shunt capacitor across the output of the rectifier bridge. This should be a small value ceramic with a low ESR. Remember to use 120 Hz when figuring the value. This should protect that LED from line noise. A choke in series with the rectifier bridge input would also do the job but it would be larger and would dissipate some power.

'Engineer' said that all that's needed is a bridge rectifier and current-limiting capacitor. This is true for a sine wave, but real power lines are loaded with sharp transient spikes (especially if used with a phase-control dimmer), resulting in extremely high peak currents through the LED. This kind of treatment drastically shortens life. A much better solution would be a current limiting inductor, if we were willing to pay for it.

I read that engineering students at Kettering U are working on ways to dim LEDs. I hope they figure something out because a dimmable LED bulb would be so much more versatile to use. Also, I heard that if you dim a non-dimmable bulb, you can burn out the LED. Is that right? I bought some nice LEDs from eaglelight (Thanks Sandy). The LED lights are worth the money but they''re expensive and I would hate to ruin them by putting them on a dimmer.

ELECOSN announces its 5W dimmable LED Bulb with features: ?The users can use inncandescent lamp dimming controller and halogen lamp electronic transformer to do the dimming, not need to have the specific LED dimming controller ?The dimming functions are integrated into the LED driver, not need additional Signal Pins (PWM Dimming Controller) for dimming. The bulb can keep only two pins that is exactly the same as traditional halogen bulbs. ?What the users should do is just to connect the bulb to traditional electronic transformer, which is used by halogen lamp, and incandescent bulb controller ?NO lower lifecycle Liquid Electrolyte Capacitors applied in the drivers, so the lifecycle of the LED Driver is the same with the LEDs, that guaranteed the extremely long use life of the bulb ?Our 4.2W EverBright is the only LED Lamp that can replace 50W Halogen MR-16 Lamps with similar brightness, and the payback from the saving power bill is only 6 months in condition that the bulb are 24hrs turned on. Most of other LED Lamps from other providers are not able to replace the 50W halogen lamps because of the insufficient brightness Its website is elecosn.com

To Butch and ABC123, Butch is partially right about the 100nf capacitor, but the real culprit is the power the motion detector logic is designed to steal through the controlled load. The motion detector is in series with the lamp, just like a switch is. The CFL (and probably the LED types as well are each presenting a fairly high load impedance (input) in series with a fairly high load impedance, (but nonetheless a current source through the motion detector), dividing the AC such that each sees a good portion of it. As the motion detector (or dimmer, electronic timer, etc.) is used to seeing the entire line voltage, this makes little difference to it. However, it''s ideal for the CFL inverter/ballast. The flicker is the bridge rectifier and capacitor in the CFL input circuit charging until the starting circuits can start the mercury vapor arc, whereupon the much lower impedance arc draws the capacitor-stored voltage down extinguishing itself, over and over.

My experience with CFL's has been that they don't like heat. After opening several up, it is not surprising given the number of general purpose components stuffed into the base along with a circuit board that did not seem very heat tolerant. One of the first things noticed were several overheated (cold solder) connections. Unless high temperature circuits are incorporated the CFL will have to remain the choice for table lamps and open air fixtures.

My experience with CFL's has been that they don't like heat. After opening several up, it is not surprising given the number of general purpose components stuffed into the base along with a circuit board that did not seem very heat tolerant. One of the first things noticed were several overheated (cold solder) connections. Unless high temperature circuits are incorporated the CFL will have to remain the choice for table lamps and open air fixtures.

Does anyone know why if I put a CFL in a socket controlled by a motion detector it flickers in the off position and works correctly in the on position?

Did they find a way to remove mercury from the CFLs yet? Think LEDs were just flagged because of Cadmium usage or some other nasty! Fix one thing and break another!!!

I bought some incandescent lamps a few years back that were sold as "cryptonite" bulbs. They sold for $2.12 ea. and were advertised to last for 10,000 hours. They lasted for over 2 years in my porch light sockets. I had previously put regular namebrand incandesent lamps in those sockets and they burned out in less than 2 months. I have been unable to locate those light bulbs for purchase since that time. Has anyone else hear of or used that lamps? I think maybe they work so well that they quit manufacturing them. I tryed the CFLs in the same application and they lasted less than 6 months.

I recently swapped out all my incandescent bulbs with both CFL's and LED's. Here's my real world experience: Whereas most of my CFL's have lasted for several years, I did have a couple that surprised me by failing after a couple months. Those were definitely the odd ones. I suspect that as new manufacturers are getting in on the game, some are not manufacturing to the highest standard. I'll admit that I bought a mix of "big name" CFL's as well as some from names I've never heard of. I don't remember which ones made the bulbs that failed quickly. But in my experience, over all the CFL's I bought, they seem to last several years. I can't tell you exactly how long, because it's been about 3 years for a few of them and 1 year for most of them. As for LED's, I didn't do as much research as I thought I needed before I bought them, and I paid the price. 1st off, you must be VERY careful about the warmth of the light. The warmer lights are dimmer than the same powered bright white bulbs. I wasted some money because the seller wasn't clear on how warm the light was... my wife hated them, they were too cool. That was wasted money. 2nd, this is probably more important, get the "high discharge" or "high brightness" LED's. For these bulbs, a 3W would have a cluster of 3 x 1W HD LED's, a 7W would have a cluster of 7 x 1W HD LED's, etc... Do not get the other LED bulbs, no matter how cheap!!! they are a waste of money. I bought several of those, and sadly, I can't find a use for them. So when comparing a bulb with 120 LED's or 7 of the 1W HD LED's, the 7 LED bulb is superior. I know, you'd think more LED's is better, but not so, the quality of the LED is more important. Lastly, most sellers of the HD LED bulbs over estimate the incandescent equivalent. However many lumens they say it has, subtract 50 because you will be buying a warm light, then compare it to your own chart of lumens/incandescent wattage. The HD LED light bulbs, in my opinion are acceptable and will take the place of CFL's in time, but unless you buy the right bulb, you will make an expensive mistake. Having bought a few of these HD LED bulbs, I can tell you that I like them, and none have burnt out in the past year. Whether they last the 50,000 hours they promise, will take a few more years for me to figure out.

Joseph wrote: "the woman who is in charge for the energy program in California [said] the level of mercury that goes from the coal power station is significantly larger than possible environment contamination from CCFL thrown out." Good point perhaps, but the real issue is not that one offsets the other. The real problem will be the localized contamination from landfills that slowly leach into our ground water system along with rivers and streams. The coal power plant is very localized and can take steps to reduce or eliminate leakage. Landfills are much more of a problem.

I imagine it maybe a better option to redesign the dimmer switch, won't be quite as mass produced will it.

In the future we may all be genetically engineered to see a far broader spectrum than we do today, so there will be no need for artificial lighting at all.

I have been using some CFL's in my house for nearly NINE years, in applications where they are turned on-off two-three times a day, and in two CONTINUOUSLY on applications (outdoor light). I have no idea what is wrong with your power, or your bulbs or both.

Incandescent light bulbs can last for a very long time. At least one in my house seems to be 30 years old. On the other hand, I have had to replace many CFLs. Many CFLs are still going. I am willing to replace IL with CFLs where there is no dimmer involved, and am looking forward to the day that leds can handle the required level of illumination required- as opposed to mere brightness. But they need to work with dimmers.

Wallplug efficiencies aside, the unfortunate truth is that CFLs give out a terrible quality light that's no good for reading, working, or being in an environment where one wishes to distinguish colours. They're not as bright as they're claimed as well (a 60 W incandescent looks much brighter than a 60 W-equivalent CFL). And they interfere with my FM radio. I'll be stocking up on low-voltage halogens then... CFLs are great in principle, deeply flawed in practice.

There is a modified dimmer technique - so called "Mark-X". The dimmer is limited to 50%-100% (plus off) and the electronic ballast measures the input's dim level and doubles it. This way, the ballast stills gets enough power for it to work.

Funny that happens in your household Ms. Conners. I bought my house 3 years ago and the first thing I did was replace all incandescents with CFL lights. The only place where I have replaced 1 bulb after 2 years of use is in my laundry room, because of frequent on/off cycling. I'm still running all the others for 3 years, and these are all cheap Costco bundles. And for those worried about candelabras, I have one at the main entrance of my house, and they also make CFLs for that. Granted they are not everywhere, but I ordered from a specialty store. Big difference in power consumption (and heat generated) and I get the same light output.

W17053 wrote: "they don't last long when used on-and-off. They won't work long in a closet, but will run 'forever' if left on." Another one I don't believe! I've tried it, and the BEST life I've achieved - left on all the time, never switched off - is 5000 hours NOT the 8000 to 10,000 claimed!.

Joseph wrote: "the woman who is in charge for the energy program in California [said] the level of mercury that goes from the coal power station is significantly larger than possible environment contamination from CCFL thrown out." Surely no-one ever believes anything claimed by officials any more? I admit that living for 10 years under a government of blatant liars (UK) may have coloured my views, but I now always start with the assumption that they are lying to me until proven otherwise!

I have to comment about CFLs, I have found that the 40 watt replacements are the fastest and first to blow. Typical for my household in on/off site such as a bathroom, maybe 4 to 5 months. However in the bedroom nightstand where these bulbs are on longer than an hour at a time, so far about 18months and still going. But it's not the electronics that dies it's the filaments, YES there are 2 filaments, that usually burns out. I have taken many of these CFTs apart, disassemble the eletronics and hook them up to as much as a 40 watt long fluorescent and be able to run that bulb for months on end. The problem is the surge currents in the filaments that burn the filaments out. I don't see this as a problem on the higher wattage lamps though?

It is not true that LEDs need a DC supply. They can be simply driven using a bridge rectifier and capacitor as the current limiter. Of course this only works for a fixed frequency supply, but it will work with dimmers, since they are a form of PWM, but controlling the amount of the sine wave during which they are on.

Invest in Gallium stocks. Gallium is a rare and expensive metal. I can''t wait to see what happens to the cost of LEDs when we start to use Gallium for general lighting. Even if they aren''t as efficient as LEDS, OLEDs will probably end up far less expensive, especially since they don''t need complex optics and heatsinking.

I have replaced GU10 20W spots in my home office with LED (in the UK our mains is 240v). However, out of 6 bought less than 2 years ago, 2 have failed and one has grown dim - less than half the brightness of a new one. I expect that they will improve over the next couple of years, but LED bulbs are not yet ready for the mainstream, in my experience.

Time to install 150W bulbs throughout the house (with dimmers of course :) True, try to find a CFL that is the size of a small mains powered teardrop bulb - good luck!

It seems that longevity of CFLs has decreased over the last three years, probably as the volume increases and the manufacturers cut more corners. But the real problem with CFLs is that they''re full of mercury, so I''m eager to see them replaced by LEDs.

Ms. Conner, please get your facts straight before printing something quite wrong. You say that the incandescent bulb sales will end 2011. That's wrong. I did a little searching and a phase out of incandescents begins 2012 and is complete by 2014 in the US except for some applications. Taken from Wikipedia: "Many of these state efforts became moot when the federal Clean Energy Act of 2007[5] was signed into law on December 19, 2007. This legislation effectively banned (by January 2014) incandescent bulbs that produce 310 - 2600 lumens of light. Bulbs outside this range (roughly, light bulbs currently less than 40 Watts or more than 150 Watts) are exempt from the ban. Also exempt are several classes of specialty lights, including appliance lamps, "rough service" bulbs, 3-way, colored lamps, and plant lights." The [5] footnote refers to the information taken from a U.S. News and World Report article on the subject, the Dec. 17, 2007 issue. I found the article and that's where they indeed sourced the information. So please, to the "conservatives" out there that are always being victimized by those "liberals", take solace that you won't be thrown in the klink until 2014. Between now and then you can look for other ways to be frightened and abused.

Has anyone experienced very high base temperatures when a CFL fails? I had one fail in a range hood while I was out of the room. I did not realize the lamp had failed until my wife smelled it burning. It got so hot the base insulation bubbled and melted. If this had occurred in a normal lamp socket I believe it would have started a fire. Since then I have refused to use any more CFLs.

I liked the comment about Chandeliers, I imagine the candle people talking about new-fangled electricity the same way. 1. LEDs are no where near the brightness limits, it is only efficiency that is limiting. We have been experimenting with 100 watt LEDs that are dangerously bright. Say goodbye to your night vision for a few days if you aren''t careful. The goal is to make them more efficient than alternatives, which is pretty close to happening now, but efficiency is the limiting factor. 2. As quantities increase to a few billion units a year, you will see the prices plummet. That will in turn increase the demand. Amazing how technology isn''t in that equation except peripherally. 3. I personally will welcome a three color LED lamp for my Cheap Chandelier which seems to burn out right before I actually plan on inviting people over. Having a lamp that simulates flickering flames or bright lights when needed will be great and having it last 40,000 hours (to half brightness, not burn out!) will be even better.

The isssue with short lived CFL's and LED bulbs can usually be traced to temperature issues. Incandescent bulbs are just glass and metal and can handle a huge temperature range. But CFL's and LED's have tiny switch mode power supplies in the base. These sensitive electronics begin to age quickly at 50 Deg C or so. They simply cannot be expected to last in unventilated can housings or other places where no air can flow past the bulb. It's worst when the bulb is installed base-up. I have used them in ordinary table lamps and ceiling fans for years with excellent life. (Lacking a filament, they are tolerant of vibration, making them really attractive for undimmed ceiling fan lights.) The low temperature start issues can also be traced to the electronics in the base...

The cheap no-name CFLs I bought lasted about as long as the dollar-store incandescents. But, the 2 cases of Sylvania CFLs I found at Lowes are still going strong. My electric use is about half of what it was a year ago.

With my experience, CFLs don't want to start when they get cold - you probably can't use them as a porch light in cold weather, or in the 'fridge (you need an incandescent, or maybe LED). What about the oven light? As another commenter mentioned, they don't last long when used on-and-off. They won't work long in a closet, but will run 'forever' if left on.

What are we supposed to do with our expensive chandeliers, throw them in the dumpster? I hope the govt is not really serious about this phase out idea!

Get 'incandescents on the black market'! The 'liberals' and 'environment-Nazis' will turn us all into 'criminals'. Maybe the Feds need to install an incandescent lamp sensor 'wall' at the south border along with the people wall! (for those who might miss it: all sarcasm)

LED lamps will need to get a lot better before I will buy another one. I paid ~$50 for a "70 LED" bulb, it wasn't even bright enough for reading. I found a use for it in my porch, as low level mood lighting. It failed less than a year after I got it. Has anyone spouting LED even tried one out? They will have to get MUCH better than that, or I'll get my incandescents on the black market (which is guaranteed to start up.)

I?ve had CFLs running here for 18 years. I?ve even got high efficiency ballasted CFL pool lights UL approved running since 1991. Reliability is fine. Color has improved and if you want to spend the money they can even look acceptable.

Bruce, I have spoken at LED show in SF two weeks ago with the woman who is in charge for the energy program in California and asked her exactly this question. Her answer: the level of mercury that goes from the coal power station is significantly larger than possible environment contamination from CCFL thrown out.

The first CFL I had in my house just failed on me 2 months ago. But, it was working since 1991, as a kitchen lamp, that gets used every day. So, over 16 years of use saved me money so many times over already.

I bought 12 Philips CFL's over 10 years ago and have used them in standard settings, and 9 still work fine...however, they cost ~$10 each at the time and so we may presume they were made with greater quality. The cheap generic versions out today may die soon. You still get what you pay for.