Do you think LEDs are a good idea?

You do realize that LEDs driven from AC also flicker? In fact AC driven LEDs flicker at line frequency. CFLs use high frequency ballasts, so any flicker is at a much higher frequency.

Despite my defense of CFLs, I like LEDs. LEDs, when properly designed, are currently the best light for many purposes, although they tend to be expensive.

I'm uncertain as to your motivation, but the tone of the post sounds a bit hysterical.

Tom

 

http://en.wikipedia.org/wiki/Mercury_(element)

1) More mercury is released into the air if you use an Incandescent bulb, as Coal Fired Power Plants are the major source of mercury. CFLs contain Mercury, but in small amounts, compared to the amount used to make electricity over the life of the bulb.

2) Mercury is indeed toxic, so toxic there is no hint it causes cancer in the long term, as everyone exposed to large amounts dies of heavy metal poisoning in the short term.

 

Although, I haven't read everything about CFL vs LED. I use mostly CFLs, because they are easily available. From what I understand, the Mercury is very small, less then a thermometer. I actually would like to go from CFL to LED, but the wattage equivalent on the LEDs that I have seen only go up to 40 watts. And for most of my lights need 60W or more in an LED equivalent. But I have been very please with the light quality of CFLs

 

LED technology will take over eventually, when the time and price and functionality are all good to go. They may come up with some sort of a circuit for alternating refresh rates with multiple led applications. I think if you get different fixtures on different phases it might help, but I'm not 100% sure on that.

 

Perhaps I misread the above as I'm having trouble focusing, and I am nearly too weak to type a response, but I'm pretty certain those claims are untrue.

[FONT=&quot]

[/FONT]
Quit eating the bulbs and you will be fine. I've been trying to cut back and am down to a bulb a year now. I was consuming 3 bulbs a month with incandescents which is pretty tough on the digestive tract.

Take solace in this: If you are ingesting mercury you won't need to worry much about cancer.

However, after researching this I learned that "Mercury in Cancer suggests that your mind is greatly influenced by emotional and subconscious patterns - thoughts will affect your emotional state and visa-versa." Don't you just love astrology? Wow, thoughts might affect my emotional state...never would have guessed that.

[FONT=&quot]

[/FONT]

Sounds great! Got any LED's that give a an even, soft white hue at 40, 60, and 100W equivalent for $1.50/bulb? $5/bulb?

LED's have some good uses and tremendous potential, but they still have quite a ways to go.

 

That's an interesting idea, and it might work in commercial buildings, where 3 phases are generally available. But typical residences are wired with only a single phase available.

The better way to do it right now is to power an LED lighting circuit with a DC power source, supplied by an AC/DC converter. This can be done economically if a whole array of LED fixtures are used. But the cost is driven up when each LED fixture needs its own step-down transformer and AC/DC converter. That is why LED "retrofit" bulbs are so expensive right now. It's not the little LEDs, its the power adaptation circuitry embedded in the bulb.

 

Welcome to PC !
It's obvious you've never purchased LED's if you think they'd do fine for 100% of your lighting. BTW, did you know that MANY cfl's contain less mercury than the amalgam in your fillings? Guess its time for us to replace teeth with caps.

 

Is the amalgam going to give me cancer or will I die of heavy metal poisoning first? :madgrin:

 

Is LED flickering true for all AC powered LEDs, or just some?

I initially thought the mercury concerns were the worry of the poster not understanding the amounts involved, but then I wondered if Indian made CFLs might have a lot more mercury than US products.

 

Yes, all AC-powered LEDs should flicker, though you generally don't notice it unless the LED or your center of vision are in motion. Kind of like not noticing the flicker of a CRT unless you wave an object in front of it.

 

Many DC powered LEDs also flicker if they have control circuits. Most of the dimmer circuits and some driver circuits use pulse width modulation (PWM) to control the duty cycle of the LED. The flicker from this can be seen when the LED or your eyes are in motion. I notice it with some car tail light LEDs. When I turn my eyes I see a string of dots.

Tom

 

Really, really crude LED lamps would just stick the LED across an AC source and act as a half-wave rectifier. That would flicker at the AC frequency. It would be worse than a conventional lightbulb because it would only illuminate once every cycle, while the conventional lamp glows twice per cycle. (It operates in both the positive and negative swings of the AC cycle.)

A much more sensible thing to do would be to use a full-wave rectifier, e.g. a bridge configuration, and a capacitor to smooth the output. You'd get some ripple. Or possibly a switched-mode power supply would be more compact. Either way you'd get a pretty clean DC supply, which wouldn't flicker.

 

We just did a CFL giveaway at my church, and I got motivated to get my statistics in order. There is enough methyl mercury in albacore tuna that US guidelines set an upper limit of one 5 to 6 ounce can per week for pregnant women or nursing mothers. Typical US albacore canned tuna is about 0.4 PPM mercury. Whereas a typical CFL contains 3 - 4 mg (~0.0001 ounces) of mercury.

Do the arithmetic, and, if you are pregnant or nursing, you are allowed to eat one CFL per year. But no more than that.

We have one LED bulb in service, in one candelabra-type fixture where CFLs would not strike consistently (for reasons I have yet to track down). Works beautifully in that application, as sort of a super-bright night-light for a stairwell. Lovely bluish-white color to the light, very decorative. And for 5 watts, I can't complain.

But the typical LED bulb is not, at present, as efficient as the typical CLF, in terms of lumens per watt. (Though there is every indication that they will eventually be better.) And, golly, CFLs have gotten so cheap here ($2.90 for four 60-watt-equivalent, at the Home Depot) that it's tough to swallow the additional cost of the LED. (Not that lightbulbs are a big item in my budget, but that's human nature.)

So, at present, LEDs are more expensive and (typically) less efficient than CFLs. But you can put them some places where standard CFLs can't go. And the color of the cheap ones (in-your-face-white) is a nice change. So it's a niche market at best right now.

The mercury, as noted by several, is very close to a non-issue. In terms of mercury, the US is definitely coming ahead by switching from incandescents to CFLs due to the reduction in coal-fired electricity. (Power plants, btw, are now under an EPA-mandated cap-and-trade system for mercury emissions, because they were the last large unregulated source of US mercury emissions, accounting for about 50 tons emitted per year.) Fluorescents have always contained mercury, so fluorescents ought to be tossed out with the toxics not the regular trash. And should have been all along.

The weirdest thing I've found in pushing CFLs is that people somehow manage to forget that this is not a new technology. Pretty much every commercial establishment and school has fluorescent lighting. The only difference between a CFL and a tube fluorescent is that you toss the electronics when you toss the bulb. The bulb itself is made of the same stuff that traditional straight-tube fluorescent lights are made from.

Traditional 100-watt incandescents are going to be banned from sale in the US starting 2012. Everything from 40 to 100 watt will be banned by 2014. Courtesy of the 2007 energy security act. Much of the rest of the world is doing the same. There will be halogen substitutes, at least in the near term. But if you have a pathological fear of anything but 19th century lighting (essentially unchanged since Edison's 1880s model), you'd best plan on stocking up.

 

Typical incandescent bulbs operate at about 12-17 lumens/watt. Typical CFLs operate at about 40-70 lumens/watt. LEDs cover a huge efficiency range, anywhere from 10-150 lumens/watt. Most common commercially available LEDs are 50-100 lumens/watt. Laboratory experiments achieve better results. A company recently set a record, demonstrating an LED at 161 lumens/watt. The biggest variable in LED efficiency is choosing the proper voltage to drive the LED, which affects the current. LED efficiency also seems to vary based on color.

So, it looks like LED fixtures are available that are more efficient than CFLs, you just need to do a little research and read the fine print. Right now the biggest advantage with LEDs is that they last several times longer than CFLs, provided that they are driven with the optimum voltage. You can burn an LED out in seconds if you apply too much voltage.

 

In the soft white color range the LED's are presently less efficient than CFL's. That is what I've gathered from looking at specs. If you like glacier blue then the LED's are higher efficiency in the bluer color range. The color is okay for night lights. It's fair in the flashlights without batteries (the ones you shake), but the softer white hues are easier to see with.

chogan2, $2.90/bulb is too much for a 60 W CFL at Home Depot. The n:visions have been about $1.50/bulb in the standard 4 bulb blister pack for at least the past year. (Lucky for me they are also consistently instant on, something the GE's are incapable of.) I've noticed they now have some sort of "Eco options" name being applied to the same bulb model numbers as the n:visions. Four or five years ago they were branded "Commercial Electric" with the exact same model number and the same base--I still have quite a few of these installed in the 100W variant, they are on their 3rd home. n:vision's website claims 2.3 - 3.5 mg of mercury in their bulbs.

 

There is more than one way to get white from LEDs. Most white LEDs are blue or UV LEDs with a coating of white phosphor in the tip. The photons from the LED excite the phosphor, which in turn glows white. The phosphor generally wears out before the LED.

A more efficient, longer lasting, and elegant method of producing white involves combining red, green, and blue LEDs in one device. The three primary colors combine to produce white, or any other color desired. Obviously this method is more expensive, takes more space, and involves three times the driver circuitry.

LEDs have two big problems: 1) They are directional, and 2) Heat. The directional nature of LEDs is good for some applications, but not good for general 360° illumination. As for heat, LEDs run cooler than most light sources, due to their inherent efficiency, but the heat is concentrated at the die, not radiated into space. This makes heat dissipation a problem, generally requiring special fixtures and intelligent driver circuitry.

Tom

 

Sorry, I was not clear -- that's for a four-pack, or ~70 cents per bulb. One of the guys at my church, who installs solar setups, says VA Power subsidizes these. That seems so unlike my local power company to do anything that reasonable, but I have no reason to doubt him. Anyway, 70 cents per bulb or so.

What I learned mostly from the bulb giveaway is that people around here were not aware of the major ongoing drop in CFL prices.

I heard people solemnly advising (e.g.) don't put them in the bathroom because they'll burn out too soon from all the off-and-on. (In fact, they have to do 5000 on-off cycles to pass the rated 10,000 hour life test -- one cycle for every 2 hours rated life.) Whereas at the current price here, you need ... 36 hours for payback of the 20 cent cost differential relative to incandescents.

Anyway, so I'd hand out the bulbs, then I'd tell them 70 cents a bulb at the Home Depot. The 100s are more, but they've set up the 60s to be cheap.

The other major discovery was that nobody knew Home Depot now sells 40 watt candelabra-base bulbs designed to replace those "flame shaped" incandescents in candelabras. Last check they only had 15Ws. Now they have 40Wers. Three pack for <$10. Those evaporated off the tables before just about anything else.