I tend to buy LED light bulbs, not to use but because I like gadgets. I noticed some interesting ones from Cree in the big orange store, so I bought one.
It does appear to be an improvement over other ones, so I’d suggest other people try it. Here’s how I’d rank the three I have:
Dimability: Does it dim like an incandescent (0-100%, full range of the dimmer, etc
Sylvania: Poor
Phillips: Poor
Cree: Poor
Light Throw: Does it throw light in the same directions as an incandescent:
Sylvania: Poor
Phillip: Fair
Cree: Good
Does it look like an incandescent in a fixture (I have some mica nightstand lamps where the bulb is really close to the shade:
Sylvania: Poor
Phillips: Poor
Cree: Fair
Light Quality, does the light look like incandescent light, does it pass a blind A/B test (screw into one of a pair of lamps, ask sister to come in and tell which is real and which is Memorex)
Sylvania: Fair
Phillips: Good
Cree: Good
Light color rendering: I put colored lenses in front of the bulbs to see how well they produce that spectrum of color. LEDs have a notoriously hard time rendering red well.
Sylvania: Poor
Phillips: Poor
Cree: Fair
In short, I’m not running out to replace all my incandescents yet, but it does look like the technology is getting closer.
I am puzzled-I believe that Cree actually makes the LED chips-the other vendors buy them and package them. I find LED bulbs a little dim-but they are great for outside operation when they stay on a long time. Wait a few more years-there will be dramatic improvements-the stuff on the market now will be obsolete
I still can’t justify the price. I looked at some 25w equivalent candelabra-base bulbs for a chandelier in my kitchen, and they want $16.00 a piece for them.
For specialty shapes and sizes, LEDs might be too expensive. But for something like a ceiling light, last year I calculated that the savings in lower electrical use alone would pay back the extra cost of an LED in about five years. That’s not including the savings from the longer lifetime of an LED.
Mdcastle– Are these all-directions table-lamp bulb-shaped bulbs you’re looking at? Because I didn’t think all-directions LED bulbs were really there yet (as opposed to spot/track/ceiling/reading light bulbs, where good LEDs really are there yet).
The Philips and Cree really are better than all the other LEDs I’ve seen as far as being useable in a typical light fixture that throws light all direction. (The Sylvania is kind of OK, but a lot of the other brands just shoot a lot of light whichever direction the bulb is “pointed”) The Philips uses blue LED that excite yellow phosphors on a globe, the Cree uses white LEDs that point towards the sides and are further dispersed by a frosted glass globe. The Cree looks a lot like a “normal” light bulb and can be used in enclosed fixtures are two advantages it has over the Philips if those are considerations.
For the OP…model numbers are a critical difference to know, those within one manufacturer is not enough.
For example, Phillips makes several substantially different “Edison” replacement bulbs with different lumen output, color temp, distribution pattern…
I’ve played a bunch with Phillips and Sylvania bulbs. My favorites so far, as a household incandescent replacement, are the Phillips “funky yellow robocop style” line of bulbs.
Well, they tend not to slap “Model Z80” in big letters on the bulb, they’re all marketed as replacements for standard A19 60 watt bulbs . The Sylvania the packaging says “Ultra High Performance” and it’s kind of flaired rather than round, and it is the Philips Robocop bulb I have. I have noticed the Philips have changed form orange to yellow. I have the older orange version and I’m not sure what the significance is.
I guess in conclusion the two areas to work on are dimming performance and being able to render the color red. Others have noticed that a red sweater seems dull under LED light, and if you put a red lens over an LED you get a really sick, pale color instead of a normal red, I haven’t compared them side by side yet but the Cree did seem to do a bit better.
The enclosed fixtures part got me all excited. I know the geek.com article says it, but unfortunately the FAQ at cree.com says:
Also, the user comments at homedepot.com say that people have had trouble using them in enclosed fixtures. (User comments should, of course, be taken with a grain of salt.)
I picked up an LED bulb at the orange store the other day, for $9.95. I have it in my bedside lamp for the moment, and I have to say it seems to be just fine. It is instant-on, gives a nice quality light, has no flicker or other visual oddities, and generally seems to be a plausible replacement for the incandescent bulb. I’d like to see the price come down a bit before jumping into them wholesale, but it definitely is way better than CFLs.
I will probably pick up a few for specific locations - a very hard to change bulb in the kitchen, the outside lights (CFLs really suck in cold temperatures), a cellarway bulb that is always on. That sort of thing.
I bought one of the cree’s today at the orange store. Bought the warm white 60w version. The color’s a little warmer than I’d like, but as it’s a nightstand lamp I don’t think it’ll be an issue. I might buy one of the daylight versions next trip.
I bought a bunch of the Feit lamps at Costco a while back and am very happy with those.
Anyone interested can check out candlepowerforums.com for lots of additional information.
LED Christmas lights pretty much run off of straight AC. Trouble is that it requires a bunch of LEDs in series to reduce the voltage, and you get nasty 60 Hz flicker. Anyway, it’s not really a problem; the driver circuits aren’t the obstacle in getting cheap LED bulbs (it’s not significantly more complicated than the guts of a CFL, and look how cheap those are).
I bought a bunch of the Cree lamps a week or so ago and have been happy with them. The glass bulbs are fragile, though; as I was walking out of the store, one of my bags slipped and dropped maybe a foot; when I got home, I realized I had cracked the globe. No matter–I peeled it away and used the bare bulb in my closet, where I don’t care about the aesthetics. I am pleased that the glass was safe and crumbly with the rubbery coating.
My only remaining wishes are for higher-wattage lamps (100W would be nice) and small-diameter Edison bases (required by my overhead fan).
They exist.
I have used these to make a couple of always-on fixtures around the house. They are not an ideal light source, though. They have a small (but noticeable) flicker (especially if you look for it), and they still require substantial heatsinking. Still, I’m very happy with the results - I replaced a 30W “bright stick” fluorescent fixture with 12W of LED, and I like how it looks.
If I remember correctly you design LED lights. Can you stack a bunch of LED’s together and stagger them so the flicker overlaps? Is it possible to coat a lens so it fluoresces and acts as a buffer for the flicker?
Why are the AC versions heating up? are they using resistors or SCR’s?
Nope. At least not unless you have 3-phase power. Traditional switch-mode power supplies (like those used by Cree and Philips) have big capacitors to smooth things out.
White LEDs already use a yellow phosphor with a longer lifetime than the LED itself, but the time constant is still very short. I suspect it would be hard to find a phosphorescent material that put out suitable white light.
LEDs are nowhere close to perfectly efficient–somewhere on the order of 25-30% (lab units approach 50%). All of the waste turns to local heat (unlike incandescents, where much of the waste heat gets beamed away in the form of IR).
I didn’t see anything on the packaging about not using in enclosed fixtures, I must have missed it (I think the packaging got tossed during a housecleaning binge so I can’t check)
LED manufacturers need to figure out how to deal with enclosed fixtures if the next phase of the incandescent bulb ban that also bans the halogens goes through.
Here’s the “deal” with LEDs - they are very non-linear devices. As opposed to the filament of an incandescent lamp, which draws current in a more-or-less linearly-proportional rate vs. the voltage impressed across it, LEDs draw essentially zero current when the voltage is below their forward voltage, and then huge amounts of current as the voltage increases (so much that if the voltage is even 2v higher than the rated forward voltage, the LED will draw so much current that it will be destroyed). This presents real issues when trying to design an AC line-powered LED.
The way it’s done right now is to make the device with lots of individual LEDs wired in series, so that the sum of the forward voltage drops is very close to the peak value of the AC voltage. Then, a current-limiting resistor is used to prevent the device from burning up. The problem is that this device will draw zero current for the majority of the AC cycle, and then a lot of current at the peak.
Because of this, you get the LED emitting light in very short bursts, leading to flicker. Also, it has lousy power factor, but that’s more of an issue for the power company than you. The only way to stagger LEDs to reduce flicker would be to shift the voltage peaks. It might be possible to do this with inductors, but one you start getting into that type of circuity, you might as well just use an LED driver, and get all the other benefits it provides (better power factor, dimmability, better efficiency, no flicker, etc.).
It might be possible to create a long-persistance phosphor which would reduce the flicker, but that’s a job for the rare-earth gurus.
I do like these ACriche LEDs, but only for applications that are very cost-sensitive and can tolerate some flicker.