"Good light costs so little."
September 26, 2014 12:19 PM   Subscribe

In 1924 a consortium of lightbulb manufacturers formed the Phoebus cartel. Its goal: planned obsolescence. The Great Lightbulb Conspiracy.

The Phoebus cartel is a plot point in Thomas Pynchon's novel Gravity's Rainbow: The Story Behind the Story Behind "The Great Lightbulb Conspiracy".
posted by We had a deal, Kyle (50 comments total) 35 users marked this as a favorite
 
(Post title is a slogan from this 1935 GE/Mazda advertisement.)
posted by We had a deal, Kyle at 12:20 PM on September 26, 2014 [2 favorites]


Are Compact Fluorescent Lightbulbs Really Cheaper Over Time?
To estimate your particular savings, the Energy Star program has published a spreadsheet [.XLS] where you can enter the price you’re paying for electricity, the average number of hours your household uses the lamp each day, the price you paid for the bulb, and its wattage. The sheet also includes the assumptions used to calculate the comparison between compact fluorescent and incandescent bulbs. Playing with the default assumptions given in the sheet, we reduced the CFL’s lifetime by 60 percent to account for frequent switching, doubled the initial price to make up for dead bulbs, deleted the assumed labor costs for changing bulbs, and increased the CFL’s wattage to give us a bit more light. The compact fluorescent won.
posted by bonehead at 12:29 PM on September 26, 2014 [2 favorites]


Related: The Story of Byron the Bulb from Thomas Pynchon's Gravity's Rainbow.
posted by chavenet at 12:34 PM on September 26, 2014 [7 favorites]


oh good. i finally understand something GR. i think.
posted by sio42 at 12:44 PM on September 26, 2014 [4 favorites]


But surely the Market magically solved this?
posted by signal at 12:46 PM on September 26, 2014 [4 favorites]


Can't access the main links above right now, but I once interviewed for a job with a company that made LED lights for the wing and tail lights on commercial aircraft (those red & green lights that indicate which way it's headed).

Diodes (the "D" in "LED") can be run at any spot along their power curves, up until they overheat and self-destruct. LEDs basically give off light power in a shape like the I-V diagram of diodes; without going into detail, as the voltage gets closer to TOO-HIGH, the incremental increases in light output become less significant, anyway, so there's not much you gain for the added risk.

Also, the lifetime curve of a diode (in use-hours) looks rather hyperbolic: at extremely low voltages, they will work continuously for centuries; in the middle voltages they will operate for years; in the high end of their output they will burn out in a couple years/months/days/milliseconds (as you reach the TOO-HIGH voltage).

Naturally, I was informed they purposefully design their lights to burn out in a couple years, even though doubling their lifespan would create almost no change in the brightness. The lifetime was picked to be noticeably higher than standard (incandescent) bulbs, but not too high.

I loathe design like that.
posted by IAmBroom at 12:55 PM on September 26, 2014 [38 favorites]


But surely the Market magically solved this?

According to the article it was war that solved it, since the cartel broke up in 1940.
posted by Kevin Street at 12:59 PM on September 26, 2014 [2 favorites]


Solved it? Did light bulbs start lasting longer?
posted by MtDewd at 1:02 PM on September 26, 2014


Well, maybe Byron's still out there...
posted by You Can't Tip a Buick at 1:02 PM on September 26, 2014 [2 favorites]


The Centennial Light (previously) has been burning almost continuously since the McKinley administration.
posted by ricochet biscuit at 1:12 PM on September 26, 2014 [3 favorites]


This sounds like the plot of Ayn Rand's lost novel, Atlas Blinked.

Also, I wonder what all the wingnuts who were up in arms a couple of years ago about having to switch to CFLs and LEDs would say if they knew their beloved incandescent bulbs were the real product of a shadowy conspiracy.
posted by TedW at 1:17 PM on September 26, 2014 [2 favorites]


Last week, having awoken and deciding I needed to embark on a nocturnal tinkling expedition, I turned on the bathroom light and it - charmingly - exploded, showering both me and the tiles around my bare feet in tiny shards of glass. Many thoughts went through my mind as I stood there in pitch blackness, but I tell you now: Byron the Bulb was amongst them. Somewhat, I must admit, drowned out by the "Oh festering buggeration"-type thoughts, but still: where's an immortal sentient lightbulb when you need one?
posted by sobarel at 1:21 PM on September 26, 2014 [3 favorites]


The CFL lightbulbs in my house have burned out at an astounding rate. Not terribly different from most of the incandescents. I've only just started with LEDs so I haven't seen one of those go yet.

However, there is an incandescent bulb in the hallway which is still here. It was here when I moved in 18+ plus years ago, and it is still burning brightly. (Not 24 hours a day, though. ) I have no idea how old it is. While all the CFLs around it burn out all the freaking time, the hallway light just keeps going... and going... I refuse to replace it. I'll let it live as long as it can.

The print on the bulb is hard to read but it appears to say "More-Lite" across the top.
posted by litlnemo at 1:46 PM on September 26, 2014 [4 favorites]


(While trying to track down the "More-Lite" bulb I found this listing in the Seattle Times, September 21, 1965: "Buy More-Lite Light Bulbs from the Handicapped. They carry a no-time limit free replacement guarantee against burn-out." Damn, they weren't kidding!)
posted by litlnemo at 1:52 PM on September 26, 2014 [10 favorites]


I've been really pleased with the CFL lights I have in terms of quality of light and longevity -- the light quality isn't quite as good as incandescents, but close enough for me. The CFL bulbs do burn out, but definitely slower than the old bulbs did. I still pull from my dwindling stock of incandescents for reading lamps, but hopefully by the time they are all burnt out there will be a super nice LED or CFL reading bulb available with just the right light tones to make printed words on paper look good.
posted by Dip Flash at 2:01 PM on September 26, 2014


The CFL lightbulbs in my house have burned out at an astounding rate.

Not all CFLs are made the same - the dirt cheap ones, and older specimens of the breed, will burn out quickly if used in places where the lights are always going on and off. Without special protection circuitry, the balast only has a certain number of on/off cycles in it. Fan bulbs almost all won't be able to handle, say, bathroo

The Phillips LED bulbs I spent a fortune on two years ago ($30/bulb!) are claiming 20+ years operational life, not certain about the newer off-brand ones that are only a couple bucks each.
posted by Slap*Happy at 2:03 PM on September 26, 2014 [1 favorite]


A few brand name CFL's will keep their expectations, but most CFL factories are just cranking out as long as they can for pure profit before being bulldozed for another LED plant.

It's been a few thousand years since humanity depended on a single source of artificial light, but LED's have so many advantages that soon everything else will be a museum piece.
posted by nickggully at 2:08 PM on September 26, 2014


Let's say you design a light bulb that lasts 100 years for only a modest increment in the cost of current light bulbs. Everyone loves it, and buys it.

Now you have a world that will never buy anything else from you. Your company is dead.

Why, exactly, would you do that?
posted by Devonian at 2:09 PM on September 26, 2014 [1 favorite]


I don't know the "we" who use Edison screw lightbulbs referred to in the article, but We use bayonet cap. I mean, a light fitting that slowly eases its way out of contact as it heats and cools; screw that, Mr Edison.

While we're almost all CFL/LED at home, there's one incandescent fitting (that uses GU10 halogen spots) I promised ms scruss when we moved in that I'd change it when the bulbs blew. We've been in the house 12 years, and the damn things are still producing heat + a trickle of visible light ...

(I love the idea of obsolete cartels. Who's up for reviving the British Valve Association?)
posted by scruss at 2:11 PM on September 26, 2014 [1 favorite]


TedW: Also, I wonder what all the wingnuts who were up in arms a couple of years ago about having to switch to CFLs and LEDs would say if they knew their beloved incandescent bulbs were the real product of a shadowy conspiracy.
That's precisely what I thought. It's like they didn't know that lightbulbs are designed to burn out faster than they have to on purpose.

I've had an LED light in continuous operation since... June of last year I guess. I wrote out a tag with the date on it and put it on the harp of the lamp. I check the date and the make of the bulb when I go upstairs next.
posted by ob1quixote at 2:11 PM on September 26, 2014


Why, exactly, would you do that?

Because you think there's something more important than personal financial profit?
posted by escape from the potato planet at 2:25 PM on September 26, 2014 [6 favorites]


I assume you include the cost of retooling your factories to produce superior versions of the next consumer good plagued by planned obsolescence.

The real problem is the time scale here. For that scheme to work you have to have people believe your product will do what it says, even if that's not going to be possible to test for twenty years, second you have to know your product works for an extremely long time and not succumb to a slight, non-obvious defect, which takes a very long time, and third, once people do trust your company, there's a very good incentive for someone to come in and skimp, ruining the promise of a long lifetime to gain short term profits.

Capitalist democracies have very poor incentives for dealing with problems more than a couple of years out.
posted by Zalzidrax at 2:32 PM on September 26, 2014 [3 favorites]


When Bell Labs invented the transistor, we the-people-of-the-world had the good fortune that as the government-controlled monopoly incumbent of the US wired telecoms market, they had to license their inventions on very liberal terms. As a result, lots of people around the world could make and sell transistors... and because there was no intrinsic life-limiting factor (like thermal cycling or cathode depletion) nobody could even start to make a '1000-hour' transistor. And once you knew the magic formula for transistors, even modest outfits could have a pop.

So, there was never any chance of a cartel. Thus, no chance of a BVA-style 'one device per package' rule, which would have thoroughly shafted the integrated circuit and Moore's Law. Which, I would humbly suggest, has had something of an impact.

See also: the Internet and pre-software patents software.

I don't know what the answer is to the question "if there is no protection allowed for who can use an invention, is it worse or better than if inventors are allowed strong protection?", except that I do not think that industry incumbents should win by default in that argument. (Personally, I'm with drastic reductions in allowable protection. People will invent and companies will produce stuff, even without the "massive win through protectionism" goal.)
posted by Devonian at 2:34 PM on September 26, 2014 [7 favorites]


Let's say you design a light bulb that lasts 100 years [...] Now you have a world that will never buy anything else from you. Your company is dead.
Why, exactly, would you do that?

If you can make a substantial, short-term profit in product line A, you can then invest that into product line B, which will bring future revenue.

Or you can grow the market for your product line A, so you sell more, even if the product lasts forever. For example, how many luxury watches wear out during the owner's lifetime? Yet the watch companies keep selling new ones.
posted by Triplanetary at 2:51 PM on September 26, 2014 [5 favorites]


The BVA really doesn't sound that different from the MPEG LA, really.

Different technology package, same great cartel flavor!
posted by Kadin2048 at 3:07 PM on September 26, 2014 [2 favorites]


The CFL lightbulbs in my house have burned out at an astounding rate.

Same. And it's not just cheapos either. I've also had several that will only work in one position(say, in a lamp that mounts them downward facing) after a few weeks. The electronics boards in them just seem to be made like crap.

It seems completely hit or miss. Some of the cheapest ones have been in my apartment since before i moved in, possibly even for years. The plastic bits are yellowed from heat/UV and filthy and yet they still work great. And then sometimes the brand name ones die after 6 months or less. And these are all in fixtures that are switched on and off about as often.

I think they just have terrible quality control at the factory. If it turns on and runs for a few seconds it was obviously soldered and assembled right, NEXT! I swear i've had one last like, a month before.

I still remember those TV commercials where they show the guy moving in, putting the bulb in, going to college, meeting his wife and dating her and getting married and moving out or whatever and it going "it lasts 7 years!". Whenever i think of that commercial, i'm just like "heh, fuck you guys".

The funny thing is i don't actually care, the co-op near my house sells them for 50 cents/bulb which is even cheaper than incandescent. I'll just keep buying them because eh, whatever.
posted by emptythought at 3:17 PM on September 26, 2014 [1 favorite]


Triplanetary - yes, both those answers are good. But they're also both wrong.

In the first case, you've taken over and monopolised a market which you've then closed down, creating a huge pulse of cash - but that doesn't mean you can do the same again. In fact, you probably can't. There isn't another everlasting light bulb to invent. Perhaps you'll get lucky and find something different, but perhaps someone else will - large amounts of money don't create innovative markets. (Instead, you'll spend the money on closing down competition and creating artificial markets - nobody will have any problem thinking of examples here - but this doesn't advance the lot of the average consumer).

In the second case, you are creating luxury goods. That's a completely different dynamic to the mass market, and it doesn't advance the lot of the average consumer. The innovations you come up with are logically aimed at differentiating you from your other luxury-good competitors; you're not going to even start to look for something that takes your brand down-market.

There's a good case to be made that Apple has achieved a really smart synthesis of those two cases, and as both lead to a non-innovatory business model I could easily be persuaded!
posted by Devonian at 3:28 PM on September 26, 2014


“People of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices.” -- Adam Smith, The Wealth of Nations, 1776.
posted by JackFlash at 4:29 PM on September 26, 2014 [6 favorites]


The CFL lightbulbs in my house have burned out at an astounding rate. Not terribly different from most of the incandescents. I've only just started with LEDs so I haven't seen one of those go yet.

CFL bulbs seem to be pretty sensitive to crappy (or old) wiring.
They don't do very well in my 60s house where multiple rooms are on the same circuit.
They do much better in my neighbor's more modern house, which has a separate breaker for every room.

My LED bulbs have a different problem.
On my circuits, they buzz quietly, but perceptibly. The same (literally) bulbs in my neighbor's house are silent.

I've got about a 33/33/33 mix of the different bulb types.
The CFLs didn't do well at all and are replaced as they die with LED.
The lifespan of the LEDs is as yet to be determined, but it's not as if we were replacing incandescents at an astounding rate, so I can't see how they will ever pay off at $10/bulb.
posted by madajb at 4:37 PM on September 26, 2014


The lifespan of the LEDs is as yet to be determined, but it's not as if we were replacing incandescents at an astounding rate, so I can't see how they will ever pay off at $10/bulb.

If you're comparing them to incandescents, they'll pay off through electricity savings. $10 will run a 100 watt bulb for 1000 hours (<3 hours a day for a year), if your rates are 10c/kWh (adjust figures for your situation). After that, you've made up the cost, and it's all savings.
posted by alexei at 4:54 PM on September 26, 2014


Huh. My house is 103 years old, and the main floor wiring is kind of old, so I'm sure it doesn't help.
posted by litlnemo at 5:17 PM on September 26, 2014


I think it's wiring. We tend to assume that "electricity is the same everywhere in the house", but each building is a bunch of metal parts, attached more or less correctly, feeding a bunch of wildly different appliances. In my mom's house, for example, one of the bulbs in the laundry room used to burn out every month. Is that because I'm a crappy electrician? MAYBE. Is it because the washer and dryer are both causes of low voltage and power surges? Makes sense to me. Our current house is ~30 years old (modern wiring code, I hope) and hasn't burned down yet, but certainly has some wiring peculiarities. So I'm not surprised that the light in the front hall burns out every few months, both incandescent and CFL. In the bathroom we have a strip of six 40W globes on the ceiling, and the fifth one burns out regularly. None of the others have burned out since we got the thing 2+ years ago. Explain THAT, science!
posted by sneebler at 5:37 PM on September 26, 2014 [2 favorites]


The idea of the everlasting light bulb as economic disruptor was also a plot point in Clifford Simak's Ring Around the Sun in 1953.
posted by sneebler at 5:47 PM on September 26, 2014


Let's say you design a light bulb that lasts 100 years for only a modest increment in the cost of current light bulbs. Everyone loves it, and buys it. Now you have a world that will never buy anything else from you. Your company is dead. Why, exactly, would you do that?

For the Scrooge McDuck-style money bin you'll have when you're done. That you can broadly invest and make craptons of money for doing fuck-all, or just get naked and roll around in.
posted by ROU_Xenophobe at 6:11 PM on September 26, 2014 [1 favorite]


Yeah, if I could have $30 times the number of houses in the world times the number of lighting fixtures in the house, I'd take it. Word would get out that your bulbs are worth the extra money.

Somehow people still buy and sell can openers, even though one's pretty much as good as another and they last indefinitely.
posted by ctmf at 6:17 PM on September 26, 2014 [3 favorites]


When I moved in to my house, I replaced most of the bulbs, except the ceiling fan lights, with CFLs. That was 7 years ago, and I rarely have the need to change a bulb. I bought LED bulbs 9 or 10 years ago - the quality was horrid. Will try new ones when some CFLs die, which has to happen eventually. Home Depot recycles CFLs, if that's news to you.
posted by theora55 at 7:19 PM on September 26, 2014 [1 favorite]


If you're comparing them to incandescents, they'll pay off through electricity savings.

Yeah, we get "energy assessments" from the power company (the state makes them do it) - we're more energy efficient than 97% of the households in our community, and our house electric bill is significantly lower than our old apartment bill, despite people being home more often. This is because I put in LEDs everywhere as incandescents and CFLs burn out. Even the early LED bulbs I got for $30 and $15 have paid themselves off already - moreso now that the security lights are all 9w LED instead of 80w halogens. (Goddamn deer set them off nightly.)
posted by Slap*Happy at 7:23 PM on September 26, 2014


Just to be fair, the idea of standardization of bulb lifetime is not totally crazy. There are some basic physical principles involved in a standard incandescent lamp with a tungsten filament that result in unavoidable tradeoffs. If you make a longer life bulb, you decrease its luminous efficiency so that while you spend less on bulbs, you spend more on electricity. There is no free lunch. In fact, the standard today for a 100-watt bulb is a lifetime of 750 hours which is less than the 1000 hours back in 1925, because the increased efficiency reduces power consumption and saves more money than replacing the bulb.

The way you make a longer life bulb of the same wattage is you make the filament thicker to increase life. But this has the effect of lowering resistance, so you have to make the filament longer to achieve the same resistance and power consumption. So far so good, but the tradeoff is that a longer filament is less efficient because the same heat is spread out over more mass and area. It puts out less light for the same watts consumed. So you need more bulbs to achieve the same total amount of light and that consumes more electricity.

This reduction in efficiency is how they produce "long life" bulbs that last as long as 6000 hours. These are actually bulbs designed for 100 watts at 130V, but since househould voltage in the U.S. is only 120V, these bulbs operate at lower temperature and lower efficiency. A long life bulb will consume about 90% of the power of a standard bulb but only put out about 75% of the light. You would need 1.33 of these less efficient bulbs for the same light which would consume 1.2 times the power. So your electricity costs would go up by 20%. By using the shorter life, more efficient bulb, you save 20% in electricity over its life, which is worth much more than the 75 cents to replace the bulb.

There is an infinite range of possibilities trading off lifetime vs. efficiency. Think about all the confusion if consumers would have to read packages to determine lumens vs life for just a 100-watt bulb with every manufacturer differing. Even today (well last year, before the banning), a consumer could choose between a regular 750-hour bulb or a 6000-hour bulb, but almost 100% choose the 750-hour bulb because it is the cheapest considering electricity costs. The industry simply standardized on a 100-watt, 1700 lumen, 750-hour bulb and competed on cost rather than confusing variable specifications.

Again, physics says there is no free lunch. You don't get longer life without reducing efficiency. When the manufacturers picked a lower life standard, they were also choosing a higher efficiency that lowered consumer costs. One could argue that as long as manufacturers were competing on bulb price, they were not harming customers by standardizing on lifetime and efficiency.
posted by JackFlash at 8:04 PM on September 26, 2014 [15 favorites]


I moved into my current home eleven years ago. I replaced all the incandescent bulbs with CFLs. That was eighteen bulbs total. I have replaced three. One in the first year and two in the last year. The last one to go was replaced with a LED bulb. The fluorescent lights in the kitchen are still the ones that the place came with. Before I went CFL I had never had an incandescent bulb last more than five years.
posted by Ignorantsavage at 8:09 PM on September 26, 2014


This post is hilarious! One of my series of horrible jobs was selling incandescent light bulbs guaranteed to last 5 years. In actual fact I owned some that lasted much longer than 5 years.
Materials make a huge difference.
The filament (light emitting part) was tungsten. There were 7 supports. The glass was thicker. The screw - in base was brass, not aluminum.
There was the story of a congressional hearing about common light bulbs on the bulletin board.
The company turned awful at a certain point.
I could maintain pride in my work because the actual product was very good.
I was able to say, whatever my horrid bosses were, at least, the customer got a square deal.
They were cheaper than CFLs too!
posted by Katjusa Roquette at 11:08 PM on September 26, 2014


CFLs are horseshit, in my humble opinion. I replaced all the bulbs in my house with CFLs 4 years ago when I bought it, and have continued to replace them over and over since then. I did leave the half-dozen incandescent bulbs in my bathroom, and only one just burned out this week. Haven't tried LEDs yet.

Let's say you design a light bulb that lasts 100 years for only a modest increment in the cost of current light bulbs. Everyone loves it, and buys it. Now you have a world that will never buy anything else from you. Your company is dead. Why, exactly, would you do that?


And yet there exist tools, furniture, toys, appliances, buildings, etc. that are as good today as they were when made 20, 30, 40 or more years ago. Once on a vacation I purchased an iron in an antique shop that might've been manufactured during WWII and it still worked just fine. Planned obsolescence was not always a thing, though it sounds like irrefutable common sense to modern ears. And of course, there are still people today who as a point of pride, make things to last. But it is increasingly rare.
posted by mrbigmuscles at 6:34 AM on September 27, 2014 [3 favorites]


I thought I read that the reason incandescent lightbulbs die is the seal between the base and bulb eventually gives out with repeated heat cycling and allows air to get in, allowing the filament to burn. There are light bulbs out there that have been on for 100 years, but the reason for that is mostly to do with almost never being turned off.

The LEDs I replaced around the house after the first big price drop to around $14/ea have just about paid for themselves. Now they sell for around $6.

As for whether the cheap ones are designed to burn out ahead of schedule, bear in mind that they typically have a clear statement of a 20 year lifespan or so on the outside of the package. Nobody's going to invite a class action suit of that magnitude by knowingly building them to get nowhere near that. The ones you want to watch out for are the ones that don't say that, or that you got from some obscure source like an ebay shop and might be knockoffs. And even those might well be okay, since a fly-by-night outfit doesn't really benefit from planned obsolecence; only major brands that are in it for the long run do.
posted by George_Spiggott at 10:18 AM on September 27, 2014


>I thought I read that the reason incandescent lightbulbs die is the seal between the base and bulb eventually gives out with repeated heat cycling and allows air to get in, allowing the filament to burn.

No, the reason bulbs burn out is because the high heat causes tungsten to evaporate from the filament causing the filament to become thinner and thinner until it fails. It generally has nothing to do with failure of a "seal" as there is no seal between the bulb and base. If you pry off a base you will find that the bulb really is a totally enclosed piece of glass and the base is simply attached to the wires on the outside of the bulb.

>There are light bulbs out there that have been on for 100 years, but the reason for that is mostly to do with almost never being turned off.

You may be referring to the famous Centennial Light which has been burning since at least 1901. But the reason it lasted so long is because it is very inefficient and puts out very little light which means the filament operates at a very low temperature. You can see a picture of it in the link above. It is nominally a 60-watt bulb but compared to a modern 60-watt bulb it barely puts out an orange glow.

Turning an incandescent light on and off doesn't decrease its lifespan. While it is true that bulbs frequently burn out at the moment you turn them on, it is only because they were about at the end of their life anyway. The resistance of a tungsten filament varies with temperature. When cold it might be as low as 15 ohms which increases to 150 ohms when hot within a few milliseconds of turning on. So there is a brief inrush current that is about 10 times normal during operation. However, this inrush current does not harm the filament unless there is already a thin spot that is about to fail anyway at the end of its life. So turning standard incandescent lights on and off does not significantly decrease their life. (Halogen lights are different).
posted by JackFlash at 11:16 AM on September 27, 2014 [5 favorites]


I'd be fine with planned obsolescence if there was a law that forced mfrs to disclose the overt steps they took to control product life.
But undisclosed planned obsolescence is just evil design.
posted by Fupped Duck at 4:33 PM on September 27, 2014 [1 favorite]


That's right. If we had some idea of the overall design cycle, we might say, "yes we want Sears to stay in business because we value their efforts to reduce waste and build/distribute efficiently." I'm still severely disappointed because my only new washing machine purchase was such a great buy, only to be ruined by a planned flaw eight years later. I'd pay extra to avoid the waste of materials.
posted by sneebler at 11:58 AM on September 28, 2014


JackFlash: Again, physics says there is no free lunch. You don't get longer life without reducing efficiency.
While JackFlash' explanation is certainly true for the incandescents (blatantly, obviously true to those who understand the physics at all, in fact), it is untrue for LED bulbs (which he doesn't address - so he isn't wrong). LEDs are far more efficient at power-to-light-output conversion in the middle portion of their curves than at the fast-burnout ends.

There is additional cost from operating LEDs below "full" output, however: if it takes 100 LEDs in an array to make "60W-equivalent light" at the high burn rate, it might take 110 or 125 LEDs at 90% of that burn rate to get the same light levels. Thus, the bulb production cost is going to go up by (approximately) that amount.

However, the gains aren't linear: 25% more diodes = 23% more cost at the store = 5x the lifetime = WIN FOR CUSTOMER! (lose for manufacturer/seller). (Numbers are WAGs, but possible.)
posted by IAmBroom at 8:48 AM on September 29, 2014


LEDs are far more efficient at power-to-light-output conversion in the middle portion of their curves than at the fast-burnout ends.

That's not exactly the case. The current vs luminosity curve is close to linear. The harder you drive the LED, the brighter it becomes right up to its maximum current limit. There is no significant peak or flattening in the middle of the curve.

What is the case is that luminosity is highly dependent on junction temperature. A white LED is only 80% as efficient at 100 degrees C junction temperature as it is at room temperature.

What this means is that for the fewest LEDs, you want to run the LED with as much current as you can if you can remove the heat effectively. Since large heat sinks are a mechanical constraint, you may want to operate the LED somewhat below its peak current, but that is a heat removal and size issue, not because LEDs become less efficient at higher current.
posted by JackFlash at 11:22 AM on September 30, 2014


“People of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices.” -- Adam Smith, The Wealth of Nations, 1776.

Wow, I can't not read that in Leonard Nimoy's voice.
posted by You Can't Tip a Buick at 3:18 PM on September 30, 2014


Turning an incandescent light on and off doesn't decrease its lifespan.

My experience doesn't support that.

I spent 5 years or so babying a number of electron spectrometers. The electron source we used was a tungsten wire spot welded to two high voltage posts, very similar to an incandescent lightbulb, even to the composition and gauge of the wire we used.

Aside from spot-weld failures by new grad students, the major failure mode for filaments was knob-twisters, people who would change the applied voltage to the filament too often. Training people to be less grabby with the filament knob during instrument shimming was key to getting the greatest lifetime out of the source, important when that meant having to break vacuum and being down for a few days.

The problem with changing voltage, power-cycling being the most extreme version of that, is that it mechanically flexes the filament. As it warms up with more power, it expands, when off it contracts. Like any metal, that builds up work-hardening in the filament leading to breakage. Embrittlement of the the burnt out filaments was obvious every time we changed a filament pair.

Power cycling leads to thermal expansion which causes work hardening and ultimately filament failure. The most common break point was when power was first applied and the filament began to stretch. Anyone who has turned on a light only to have the bulb pop has experienced this.

I don't have an actual paper to point to or anything, but in my experience, flipping the power on and off greatly reduces the lifetime of an incandescent filament.
posted by bonehead at 7:24 AM on October 1, 2014


I don't doubt your experience, but all filaments are not the same. Electron spectrometer filaments are generally made of some material other than tungsten because tungsten can form undesirable oxides -- most often rhenium or a rhenium tungsten alloy. These filaments have different properties than pure tungsten.

Electron spectrometer filaments are typically five times the diameter of incandescent lamps which significantly increases their stiffness and the geometry is different. The incandescent filament is wound in a double coil of coils with thousands of turns that allows considerable flexing. The much stiffer spectrometer filament may be a straight wire or have only three or four turns and is subject to deformation during heating.

Most importantly, the spectrometer filament, by the nature of the instrument must operate in a vacuum, which greatly increases the rate of evaporation of the filament. The incandescent lamp is filled with argon to reduce filament evaporation.

Lots of studies have shown that typical incandescent lamps do not have significantly reduced life due to power cycling. As a good example, think about the red flashing traffic light at a four-way stop. That bulb turns on and off once a second, over 80,000 times a day, with no failure for many months.
posted by JackFlash at 9:00 AM on October 1, 2014


« Older Not as simple as dumping a can of dog food, it...   |   Christopher Hogwood CBE, September 10, 1941 –... Newer »


This thread has been archived and is closed to new comments