# Why did they just now invent the LED bulb? **URL:** \ **Category:** Factual Questions\ **Created:** [April 22, 2012, 9:49pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633 "2012-04-22T21:49:17Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Rigamarole](https://avatars.discourse-cdn.com/v4/letter/r/77aa72/32.png) [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)\ **Post date:** [April 22, 2012, 9:49pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/1 "2012-04-22T21:49:17Z")
So, we’ve been using LEDs for a very, very long time. Did it just not occur to anyone before to make an LED light bulb? Or do these new bulbs contain some kind of special technology that wasn’t possible before? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [April 22, 2012, 10:01pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/2 "2012-04-22T22:01:59Z")
Making LEDs that produce anything close to natural light has been a rather large challenge. I don’t think most people would want their rooms bathed in a harsh green, like living inside a gigantic “on” button. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 22, 2012, 10:15pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/3 "2012-04-22T22:15:02Z")
Also, super-brightness (like 1,000 lumen) LEDs are a relatively new development. A lot of research into thermal management, phosphors, and topcoats had to be done before they were practical. Before that, it would take an array of many hundreds of LEDs to equal the light of a 60W incandescent lamp. Now there are single LEDs (rather, modules) that are brighter than a 250W lamp. ---
**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\ **Post date:** [April 22, 2012, 10:21pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/4 "2012-04-22T22:21:20Z")
1. Blue and by extension white (which are blue LEDs with a yellow phosphor) are fairly recent. I still remember how odd it was to see a blue LED at an electronics show, and paying $10 for a bag of three for such a novelty. Also, it’s only been recently that Cree and others have been making LEDs that are efficient and powerful enough for general lighting. IRC the first white LEDs were _less_ efficient than incandescents. 2. Most consumers were and still are happy with general purpose incandescent-bulbs, it’s taking a government ban to force them to change. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [April 22, 2012, 10:25pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/5 "2012-04-22T22:25:49Z")
Actually, bright blue LEDs are almost a decade old now. It was probably a need to develop ways to produce and market them in bulk that kept them off the market until now. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [April 22, 2012, 10:46pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/6 "2012-04-22T22:46:10Z")
It’s been very hard to figure out how to dissipate the heat for bulbs powerful enough to replace the “wattage” we’re used to, too. [Here’s an article from Wired](http://www.wired.com/magazine/2011/08/ff_lightbulbs/all/1) about the race to get the bulbs perfected and on the market. ---
**Author:** ![BrotherCadfael](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)\ **Post date:** [April 22, 2012, 11:28pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/7 "2012-04-22T23:28:57Z")
Is the heat from the LEDs themselves, or from the transformer necessary to run them? If the latter, wouldn’t it make sense to have a central transformer, and run 5v DC (or whatever) to wherever the lights need to be? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 22, 2012, 11:36pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/8 "2012-04-22T23:36:01Z")
> [@BrotherCadfael](#): > > Is the heat from the LEDs themselves, or from the transformer necessary to run them? If the latter, wouldn’t it make sense to have a central transformer, and run 5v DC (or whatever) to wherever the lights need to be? Watts are Watts. If an LED “bulb” is rated at 17W, that means that the LEDs themselves are dissipating 17W. Since the LEDs themselves are pretty small, it takes clever engineering to get rid of the heat. Unlike incandescent lamps, LEDs want to operate at temperatures below 150C (and even better, below 100C). The cooler the LEDs run, the longer their lifespan. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [April 22, 2012, 11:40pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/9 "2012-04-22T23:40:31Z")
Here’s a good quote from the article: > [@](#): > > Before we get to that point, or even to viable, affordable home LED bulbs, engineers have to solve a pair of challenges: cooling the diodes, and the shape of the light. Cooling is essential because hot diodes don’t last long. Also, the cooler they are kept, the more wattage they can handle, which translates into more light per diode. Getting an LED to cast a light in a shape that will properly illuminate a room is perhaps an even more difficult challenge. LEDs are point lighting sources; they shine in only one direction. That makes them fine for floodlights or traffic signs. But for LEDs to replace the Edison bulb, the shape of light they emit has to be round. > > Once you’ve got that, you also need a driver to control the individual diodes, which means additional circuitry and firmware. So far, putting all those elements into a single, affordable package has proven to be an immense challenge. It looks like the consumers have no interest in anything except a replacement bulb that fits into standard light sockets and emits a glow similar to what an incandescent bulb emits. The answer to LED can’t involve re-wiring or new appliances. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 22, 2012, 11:48pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/10 "2012-04-22T23:48:31Z")
An interesting note: [Cree has achieved 231 lm/Watt in the lab](http://optics.org/news/2/5/8). This is well over half-way to the maximum theoretical efficiency for a white light source. It’s pretty interesting - in general _transducers_ (devices which change one form of energy into another) have very poor efficiency. LEDs are getting close to perfection. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [April 22, 2012, 11:52pm UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/11 "2012-04-22T23:52:47Z")
> [@Mdcastleman](#): > > 1. Most consumers were and still are happy with general purpose incandescent-bulbs, it’s taking a government ban to force them to change. No such government ban exists in the United States, no matter how many times people repeat this. [New York Times](http://www.nytimes.com/2011/05/26/garden/fearing-the-phase-out-of-incandescent-bulbs.html?_r=1&pagewanted=all) > [@](#): > > Late in his second term, George W. Bush signed into law the Energy Independence and Security Act of 2007, which requires light bulb makers to improve the efficiency of incandescent bulbs by 25 percent. The details of the law dictated a phase-out of the manufacture of certain bulbs in their current incarnation, starting with 100-watt bulbs next January. > > The law does not ban the use or manufacture of all incandescent bulbs, nor does it mandate the use of compact fluorescent ones. It simply requires that companies make some of their incandescent bulbs work a bit better, meeting a series of rolling deadlines between 2012 and 2014. > > Furthermore, all sorts of exemptions are written into the law, which means that all sorts of bulbs are getting a free pass and can keep their energy-guzzling ways indefinitely, including “specialty bulbs” like the Edison bulbs favored by Mr. Henault, as well as three-way bulbs, silver-bottomed bulbs, chandelier bulbs, refrigerator bulbs, plant lights and many, many others. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [April 23, 2012, 12:54am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/12 "2012-04-23T00:54:10Z")
Only a slight hijack, I hope…in the 1960’s, we thought that electroluminescence was the lighting wave of the future. We envisioned entire walls and/or ceilings glowing with an even, soft light. Although the phenomenon was discovered in 1907, it hasn’t become commercially feasible yet. (Or perhaps no one wants glowing walls or ceilings.) ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [April 23, 2012, 1:03am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/13 "2012-04-23T01:03:18Z")
> [@beowulff](#): > > Watts are Watts. > If an LED “bulb” is rated at 17W, that means that the LEDs themselves are dissipating 17W. Since the LEDs themselves are pretty small, it takes clever engineering to get rid of the heat. Unlike incandescent lamps, LEDs want to operate at temperatures below 150C (and even better, below 100C). The cooler the LEDs run, the longer their lifespan. Minor nitpick, but the efficiency is high enough so that if total input power is 17 W, heat dissipation will be less; [this LED you posted about](http://optics.org/news/2/5/8) is over 50% efficient, thus power loss is less than 8.5 W. Anyway, most of the power loss is in the LEDs themselves; the transformer (actually an electronic switchmode power supply) can be in excess of 90% efficient for modern designs (incidentally, the solution used in cheap LED bulbs, [using a capacitor for its capacitive reactance](http://talkingelectronics.com/projects/30%20LED%20Projects/30%20LED%20Projects.html#69), plus a few other parts, can be even more efficient, albeit not the ideal way to drive LEDs and prone to flicker). Also, for kicks: [Ultra-efficient LED puts out more power than is pumped in](http://www.wired.co.uk/news/archive/2012-03/09/230-percent-efficient-leds) (its only 69 picowatts though, but who knows what this means for practical LEDs; the more than 100% efficiency is because it converts heat to light, along with the actual electricity consumed) ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [April 23, 2012, 1:08am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/14 "2012-04-23T01:08:27Z")
The OP’s question is like asking why we didn’t have the iPhone a few years after the invention of the transistor or why we paid several billion dollars to sequence the first human genome when we can now do it for less then ten thousand dollars. Technology is hard and unpredictable. When it involves fundamental advances in materials and solid-state devices, it takes many thousands of people working for many years to make significant progress. The dream of solid-state illumination has been alive for decades, but the red LEDs of 1990 were just becoming bright and efficient enough to use for tail lights in cars. LEDs are a natural for colored light applications. If you want red light with an incandescent source, you make white light and filter out everything except the red, an inefficient process. I remember going to a conference in the late 1980’s in which someone proudly announced the development of a blue LED made with Silicon Carbide. After great applause, they turned out all the lights in the room and passed around a sample that you could just barely see when you were holding it in your hand in the dark. A breakthrough occurred in 1993 when Shuji Nakamura at Nichia made the first high luminousity blue LED using Gallium Nitride. Suddenly the race was on at HP (then the world’s largest manufacturer of LEDs), Nichia, Cree, and other companies to develop white LEDs and to increase their efficiency and lower their cost to the point where they could compete with white light applications. Things have proceeded about as quickly as the optimists like Roland Haitz at HP predicted. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 23, 2012, 1:10am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/15 "2012-04-23T01:10:43Z")
> [@Michael63129](#): > > Minor nitpick, but the efficiency is high enough so that if total input power is 17 W, heat dissipation will be less; [this LED you posted about](http://optics.org/news/2/5/8) is over 50% efficient, thus power loss is less than 8.5 W. > > Anyway, most of the power loss is in the LEDs themselves; the transformer (actually an electronic switchmode power supply) can be in excess of 90% efficient for modern designs (incidentally, the solution used in cheap LED bulbs, [using a capacitor for its capacitive reactance](http://talkingelectronics.com/projects/30%20LED%20Projects/30%20LED%20Projects.html#69), plus a few other parts, can be even more efficient, albeit not the ideal way to drive LEDs and prone to flicker). > > Also, for kicks: [Ultra-efficient LED puts out more power than is pumped in](http://www.wired.co.uk/news/archive/2012-03/09/230-percent-efficient-leds) (its only 69 picowatts though, but who knows what this means for practical LEDs; the more than 100% efficiency is because it converts heat to light, along with the actual electricity consumed) Sorry, but that’s not the case. The efficiency of the LED might be 30% - for turning electricity into light, but it’s still dissipating nearly 100% of the power of the lamp itself. The converter/drivers for the LEDs are somewhere in the neighborhood of 95% efficiency. So for the 17W lamp, the LEDs might actually be dissipating 16W, and the drivers 1W. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [April 23, 2012, 1:38am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/16 "2012-04-23T01:38:49Z")
> [@beowulff](#): > > Sorry, but that’s not the case. > The efficiency of the LED might be 30% - for turning electricity into light, but it’s still dissipating nearly 100% of the power of the lamp itself. The converter/drivers for the LEDs are somewhere in the neighborhood of 95% efficiency. So for the 17W lamp, the LEDs might actually be dissipating 16W, and the drivers 1W. You are saying the wattage listed on the packaging is the heat dissipated, not the total electrical power consumption? So a “17W” LED bulb that is 30% efficient actually emits about 6W of light and consumes 22W total? I did not know that. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [April 23, 2012, 1:40am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/17 "2012-04-23T01:40:16Z")
> [@beowulff](#): > > Sorry, but that’s not the case. > The efficiency of the LED might be 30% - for turning electricity into light, but it’s still dissipating nearly 100% of the power of the lamp itself. The converter/drivers for the LEDs are somewhere in the neighborhood of 95% efficiency. So for the 17W lamp, the LEDs might actually be dissipating 16W, and the drivers 1W. Every light source that I have seen is specified by the input power - a 60 W light bulb draws 60 W, producing several watts of light and the rest heat (power in = light out + heat loss). It even says that [here](http://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDs): > [@](#): > > Most of the electricity in an LED becomes heat rather than light (about 70% heat and 30% light). One would expect that if their LED bulb draws 17 W (or just the LED itself), that is the total power consumed, not how much heat is dissipated; this is always the case when a power consumption rating is used, whether it is a light bulb, TV or motor (the last may also be specified by output power, but that is like saying how much light a light bulb produces). ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 23, 2012, 1:43am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/18 "2012-04-23T01:43:18Z")
> [@Absolute](#): > > You are saying the wattage listed on the packaging is the heat dissipated, not the total electrical power consumption? So a “17W” LED bulb that is 30% efficient actually emits about 6W of light and consumes 22W total? > > I did not know that. No, it consumes 17W, of which 5W is emitted as light and 12W as heat (assuming the LEDs are 30% efficient at turning electricity into light). The 12W is divided between the LEDs and the power supply, such that the LEDs dissipate 11W or so, and the power supply 1W. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 23, 2012, 3:37am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/19 "2012-04-23T03:37:45Z")
> [@Michael63129](#): > > Also, for kicks: [Ultra-efficient LED puts out more power than is pumped in](http://www.wired.co.uk/news/archive/2012-03/09/230-percent-efficient-leds) (its only 69 picowatts though, but who knows what this means for practical LEDs; the more than 100% efficiency is because it converts heat to light, along with the actual electricity consumed) There’s something seriously wrong there. That article is quick to reassure that the bulb doesn’t violate the First Law of Thermodynamics, but neglects to mention that it does violate the Second. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 23, 2012, 3:39am UTC](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633/20 "2012-04-23T03:39:26Z")
> [@Chronos](#): > > There’s something seriously wrong there. That article is quick to reassure that the bulb doesn’t violate the First Law of Thermodynamics, but neglects to mention that it does violate the Second. Yeah, apparently it uses ambient thermal energy to increase the emission of photos that would otherwise be trapped. So, it’s kind of cheating… [Next page](https://boards.straightdope.com/t/why-did-they-just-now-invent-the-led-bulb/619633.md?page=2)