Philip Greenspun’s Weblog

I got hold of LED Lighting: A Primer to Lighting the Future and learned a bunch of stuff that I didn’t know about LED light bulbs.

Many of the bulbs sold are not lighting the room via LED. The LED blasts a phosphor with a harsh narrow spectrum of (fairly blue) radiation and then the phosphor re-radiates a broader spectrum. Partly this is because the phosphor radiates more broadly than an LED and partly this is because it enables all of the electricity-to-light conversion to be done by a blue LED. A blue LED is about 30 percent more efficient than an LED of a redder color. The warmer the bulb desired, the less efficient it will be, due to the fact that more red phosphor must be used and the photons coming out of the red phosphor don’t have as much energy as those from yellow phosphor.

LED bulbs are not especially energy-efficient. They produce approximately 50 lumens/watt, which is the same as compact fluorescent bulbs.

The traditional color rendering index (CRI) to measure the extent to which a bulb puts out a broad spectrum of color is being replaced by Color Quality Scale (CQS). To some extent, this new standard is intended to make LED bulbs measure better.

Haitz’s Law says that every 10 years we are supposed to have a 10x drop in cost-per-lumen and a 20x increase in light from an LED. It is unclear how much more efficiency can be wrung from LED bulbs. This article says that someone the laws of physics have been bent by an LED in a lab at MIT, with more light output than energy in. Other sources say that LEDs are already about 80-percent efficient.

LED bulbs depend critically upon heat sink design. The bulbs don’t radiate waste energy in the form of infrared light so any inefficiency needs to be dealt with by a heat sink especially due to the fact that if the LED gets hot it will produce less light. On the other side of the spectrum, LEDs don’t put out ultraviolet light either and therefore supposedly don’t attract insects.

Household wiring is incompatible with LED bulbs in two ways: the voltage is way too high; the voltage potential rises and falls 60 times per second. LEDs operate at lower voltages and have almost no persistence, i.e., when you take the voltage away the light goes off instantaneously. In order to bring the voltage down and turn the alternating current (AC) into direct current (DC), an LED light bulb is crammed with electronics. Therefore it might not be that much more expensive to add IP-addressability and have all of a house’s light bulbs on the WiFi network.

[I’m not sure if I recommend this O’Reilly book, by the way. The author makes no attempt to explain what an LED is. I’ve found this with most books on technology written for an American audience. The lay person is assumed to be too stupid to understand anything. In this case it might be the author also who has not reached the Britney Spears level of understanding of semiconductors. He says “LEDs and SSL [solid state logic?] can be just as complex as you want to make them, especially if you have a thing for semiconductors [like Britney!] or photmetry. It’s one thing to understand the lighting in terms of heat sinks and LEDs, but it’s entirely another to get deeply involved in the electrical engineering, physics, and material sciences… Many of these elements are outside of our scope and are fully explained in white papers, journals, and textbooks, if you’d like to dig more.”]

My personal experiments with LED bulbs so far have been reasonably encouraging. I spent $38 on a Philips L-Prize Award Winning Bulb in October. It is now down to $30. I installed it in an outdoor fixture that requires a ladder to service. The other bulb is a Mitsubishi Verbatim BR30 at the top of a stairwell. This is a truly challenging destination to reach. The bulb produces a beautiful uniform light. It is rated at 85W equivalent but seems brighter. It impossible to tell whether there are really multiple small LEDs inside and the spectrum seems pretty broad. It was a little more than $30 and I got it from a specialist retailer, http://www.lights-go.com, founded by Rick Regan.

The Philips Web site distributes a calculator that shows the payback period for Massachusetts (average electricity cost 14 cents/kwh) is 3.8 years (26.7 percent ROI) when replacing $1 bulbs with $30 LED bulbs that are used 1000 hours per year. As noted above, given that LED bulbs are not substantially more efficient than CFL, it does not seem as though replacing CFL bulbs makes economic sense, though personally my experience with CFL is that the bulbs fail after a year or two, the light is slow to warm up, and disposal of the mercury-laden product is a distressing operation for a parent. A calculation that I have not seen done is of when it makes sense to buy an LED bulb given how quickly the prices are coming down. Even if one is using incandescents it might make the most sense to continue using them for one more year and then switch to a Philips bulb that is selling for $20 rather than $30 today. Philips says that a standard bulb will consume about $7 per year in electricity if operated for 1000 hours. The LED bulb that I bought has already fallen in price by more than $7 in the past month.

Based on my experience as a shopper it is a good thing that both Mitt Romney and Barack Obama constantly reassured me that America is the world’s most innovative economy. Otherwise it would be disturbing to realize that all of the innovative products that I have encountered were designed by people outside the U.S. The leaders in this market seem to be Dutch, Japanese, South Korean, Taiwanese. Does anyone know of a U.S.-based company that will be competitive in this market? General Electric has a 60-watt replacement LED bulb that consumes 30 percent more power than the Philips bulb and costs nearly twice as much.

Finally the advent of these bulbs makes me realize how poorly adapted to the modern world is the wiring in the orgy of new residential and commercial construction that the U.S. indulged in during the last two decades. We spent trillions of dollars building new structures that are wired with the wrong voltage and that have the dumbest possible controls. One would think that every new outlet would have USB power (example) and that every lighting fixture would have a 3.3V or 5V output as well (see this IEEE Spectrum article that explains more of the engineering behind a bulb).

[Separately, I have been shopping for retrofit power strips that contain USB power outlets. Despite the supercharged price and size of some of these devices (up to $50), they often put out a feeble 0.5 amps of power rather than the 2.1 amps required by popular tablets such as the iPad. Monoprice.com has some that are spec’d at 2.1 amps but the typical name brand surge protector is down at 0.5 to 1 amp shared between two USB outlets. Monoprice retails a four-port charger with a total drive capability of 2.1 amps for $7.80. Why can’t a $50 surge protector include the same capability?]

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… guarding rocks. Here’s a photo of one of the security guards hired by the Los Angeles County Museum of Art to stand outside and guard a big rock (Michael Heizer’s Levitated Mass). She has a graduate degree in philosophy and says that her main task is to discourage people from climbing on the rock.

Separately, photographers will appreciate the Stanley Kubrick exhibit, which includes a gorgeous array of lenses (see these photos from the Sony NEX-6 camera that I am testing). The exhibit will remind you that before computer 3D modeling people were forced to be creative.

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I received one of the first Google Nexus 10 tablets this week and have set it up and upgraded to Android 4.2. With both Android 4.1 and 4.2, the touch screen seems to ignore a lot of touches, especially when inside Google Chrome. One can be stabbing the screen repeatedly with a finger and the screen will actually go to “idle dim”. It is tough to follow links when on a standard Web page. The device seems to respond better to light touches, but is annoying finicky. I had a similar issue with the first generation Amazon Kindle Fire.

Anyone else have usability issues with the Nexus 10? I wonder if my hardware could be defective. I haven’t heard of unresponsive touch screens being due to a subtle hardware defect.

[Separately, the high-res screen is just beautiful (2560×1600 pixels, same as my 30″ desktop LCD; the iPad 3 and iPad 4 are 2048×1536 pixels). Text looks sharper, clearer, and more print-like than on an iPad 3. But due to the touch screen issue, I greatly prefer the iPad, Nexus 7, or almost any mobile phone. Imagine using a desktop computer with a mouse button that worked approximately 40 percent of the time and the rest of the time did nothing (with a random chance of success on every click).]

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A friend recently took over development of a business-to-business site (i.e., one where the number of users will be limited) and faces the challenge of re-architecting the software to run from a standard relational database management system rather than Mongo, a “NoSQL” database. It turns out that the business requirements are most easily met with the flexibility of programming in SQL. He shared with me this anecdote: “a friend of mine, who works at [big company with infinite money], told me about a colleague who decided to use Mongo for something there, only later to change his mind and use Postgres. When asked, the friend said, “well, it sounded really cool at first, until I realized that NoSQL is just another name for what people did before there were relational databases”.

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My trusty Lenovo 13″ laptop has finally taken one knock too many and the screen is very unhealthy. As it has served more than two years for about $600 I won’t complain. I think it is time for an SSD-based machine with at least 320 Gb of disk, 8 GB of RAM, and ideally an SD card reader for grabbing digital photos. Anyone have a favorite machine for travel? I suppose it should run windows 8 but I am not sure about the idea of convertible tablet. I am still recovering from the Tablet PC that I bought 10 years ago. I want it to be cheap enough that I won’t cry if it is dropped.

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Here’s a story that will bring cheer to Yale and Princeton alums…

I donated blood yesterday at Children’s Hospital and then went over to Harvard Medical School to visit a friend. Just outside his office was the following poster:

Underneath a headline of “Learn English at Harvard” the first sentence asks “Ready for a truly unique learning experience?”

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As a recovering audiophile myself, I was heartened to see the spirit alive at Amazon. I’m getting a 6′ optical digital cable to connect a desktop PC with an outboard digital audio converter. This is mostly because the speakers are making some funny noises and I’m too lazy to debug whether the extraneous sounds are coming from the sound card or the old M-Audio powered speakers.

Note that the function of this cable is to transmit 1s and 0s, with an error correcting code (essentially some redundant data) included so that the digital data can be completely recovered by the receiver even if there are some errors in transmission. Asking “is the sound different?” is equivalent to asking if you would get a different version of nytimes.com in a Web browser by connecting via wireless or a CAT5 cable. Yet there are 541 reviews and we learn from one review “Sound quality: The quality of the sound was on par with some of the more expensive cables I’ve had previously. I didn’t notice any interference and it sounded fairly clear.” and that “If you bought this $450 cable [competitive product], I cry for you.” Numerous other reviews refer to the sound quality of the cable.

Speaking of sound quality… what do people like for desktop digital audio converters? I don’t need a headphone amplifier (and probably wouldn’t want one powered by USB if I did), but Audioengine D1 looks pretty good.

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I’m wondering if anyone else has noticed this… whenever I wake up an iPad that has been asleep and unused for, say, a week, it still has substantial battery life remaining and is immediately ready to use. Anecdotally, however, the Android tablets either have dead batteries or have shut down so completely that they need to reboot and aren’t available for about 30 seconds (Google Nexus 7).

Is iOS much better about this than Android?

[Separately, I have two wireless access points in one apartment, separated by a brick wall. They broadcast the same SSID and use the same password. As one walks back and forth in the house, Android devices (Galaxy S3, Nexus 7) are very good about connecting to whatever happens to be the stronger base station (as evidenced by the signal strength bars at the top of the display). An iPhone 4S running iOS 6, however, is much more sluggish and often is struggling to get a handful of bits through an access point on the other side of the house, even if placed almost next to the other access point.]

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(Spoiler Alert!) Four of us went to see Flight, starring Denzel Washington, last night at the Boston Common theater. The aviation-related parts of the movie are moderately unrealistic. A plane suffers a pitch trim control failure similar to that which caused the crash of an Alaska Airlines MD-83 in 2000 (Wikipedia). One of the pilots figures out how to make a reasonably good off-airport landing nonetheless. After the crash, it is discovered that he is an alcoholic and cocaine user. (Some of the alcohol stuff seems to have been drawn from America West 556.)

Here are the parts that, based on my brief career as an airline pilot, struck me as unrealistic:

• the captain does the walk-around inspection, rather than the first officer, despite the fact that it is first flight of the day and annoying TSA security checks must be done and despite the fact that it is raining heavily; generally the first officer does the walk-around
• the captain engages in a lot of extra chat during the takeoff roll and initial climb
• despite heavy turbulence, the captain elects to speed up rather than slow down. In fact, the captain accelerates to the smooth air redline for no apparent reason. Nobody points out afterwards that this would have been likely to stress/bend the airframe.
• the captain tells the first officer to dump the fuel at one point, but smaller/newer airliners such as the one in the movie don’t offer this feature (Wikipedia); in any case, the engines continue to produce power after the fuel has supposedly been dumped
• no attempt is made to use any checklist during any phase of flight
• the captain consumes three bottles of alcohol apparently with the assumption that the airline’s accounting system won’t notice whereas in fact the alcohol stock on an airliner and the revenue from that alcohol are as carefully matched up as anything else in the American retail world
• the captain talks about a trip that he made in a Cessna 172 (slow four-seat airplane) from Georgia straight to Jamaica. This would involve a flight over Cuba, which requires a huge amount of paperwork in advance, or driving all the way around via Turks and Caicos and Haiti. The Bahamas would have been a much more likely destination for a carefree Cessna pilot.

The non-certificated member of our group asked us if we thought that the basic idea could have worked, i.e., rolling an airliner with a jammed nose-down pitch in order to produce level flight. The consensus among the pilots was that it could be possible.

We pilots were disappointed that the movie is not actually about aviation. It is yet another Hollywood celebration of addiction and recovery. If you’re not interested in alcoholism and AA you probably won’t love the movie, though it is well acted. It is unclear what one can learn from the movie other than “Being an alcoholic is a bad idea.”

[Separately, a friend in recurrent simulator training for the business jet that he owned was invited by the instructor to fly a few approaches, drink one glass of wine, and then fly an additional approach in the sim. It turned out that his performance was substantially impaired. So it is hard to understand how the main character of Flight could have done his job with so much alcohol in his system for so many years. The captain’s blood alcohol level was supposedly 0.24 percent. Compare to a Delta pilot arrested in Amsterdam for having a blood alcohol level of 0.023 percent (story). The FAA limit for private pilots is 0.04 percent, though with an additional limitation that there must have been 8 hours between the last drink and the flight. Most airline employees are subject to a 12-hour rule and a 0-percent limit.]

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A friend from Manhattan visited Cambridge last week. He was thrilled that President Obama won reelection, but told me that the main economic and social problem facing the U.S. currently is wealth disparity. It is not hard to see how rubbing elbows with the billionaires of Wall Street would make one envious (I remember walking down Madison Avenue a few years with with a millionaire friend; neither of us could afford anything that we saw in any of the shop windows (e.g., $20+ million apartments, $400,000+ Maybach automobiles, women’s shoes, etc.)). And indeed my visiting friend mentioned the absurd wealth accumulation on Wall Street as Prime Example #1 of our problem with wealth disparity.

On the other hand, from a functional on-the-ground point of view I can’t see how chipping away at wealth disparity would help grow the economy. Consider the most obvious way of reducing disparity: halting immigration. The U.S. has approximately 1 million legal immigrants each year. Many of these folks show up without any wealth and without the ability to speak English. Plainly they are not going to be wealthy any time soon. On the other hand, since many of these immigrants work hard, turning them away would shrink the overall GDP.

The second most obvious way of reducing disparity would be a tax on wealth. Indeed we have such a tax already: property tax. It does serve a wealth redistribution function as the owners of valuable property fund schools, police, fire departments, and government worker health care and pensions. However, the money from property taxes is kept within city or a state and not sent from a wealthy region of the U.S. to a poorer region. My friend was apparently against this idea, however, because he said that it was the federal government’s responsibility to shower New York City with tens of billions of dollars to help pay for cleaning up after Hurricane Sandy. Essentially after complaining that people in New York, New Jersey, and Connecticut (i.e., Wall Street) had misappropriated hundreds of billions if not trillions of dollars in wealth from comparatively poor residents of Arkansas, my friend was advocating that folks in Arkansas pay additional federal taxes (or that their children and grandchildren be saddled with additional federal debt) to help out the owners of $100 million beach houses in the Hamptons and $2 billion office buildings in Manhattan. So the idea of transferring wealth from property tax revenues in a rich-to-poor direction is apparently politically unpalatable, even to a person for whom wealth disparity is America’s #1 problem. In any case, it is difficult to see how such a property tax transfer would help the overall economy. California has a system in place where local taxes are sent to Sacramento and then sent back down to local schools before being used to fund classroom instruction (i.e., it is illegal for a wealthy town to tax its residents and spend the money directly on schools). Despite this pioneering effort at wealth redistribution, the state has an unemployment rate that is substantially higher than the national average. An argument could be made that taxing away Wall Street wealth to fund schools in poorer states could improve educational quality nationwide and that would benefit the economy in the long run, but at least with public schools there is no known correlation between funding levels and educational outcomes.

On a “what happens when you wake up and make a decision about what to do today” level, it is difficult to see why the presence of absence of billionaires on Wall Street affects the willingness for those who aren’t currently working to start working. The easiest way to grow the economy is to give people who don’t currently work sufficient incentive that they start or resume working. I’m writing this post in Cambridge, Massachusetts, where roughly 8 percent of the housing is city-owned and much of the rest is dedicated for occupancy by low-income families. A friend pays $3000 per month for a two-bedroom apartment in a newly constructed luxury full-service building. This is her reward from studying assiduously during roughly 20 years of schooling, culminating at an Ivy League university, and working a demanding job. One of her neighbors is a family of five. The father is observed to spend his days drinking and chatting with friends in Central Square. The mother stays home to care for the three children. The family receives a $4000 per month three-bedroom apartment at no cost. The family receives free health care via Medicaid and a City of Cambridge program that supplements Medicaid. The family receives food stamps from the USDA. They get a free cell phone with 250 minutes per month of service paid for by the U.S. government (details). Each child will receive a free K-12 education from the City of Cambridge (funded with over $26,000 of taxpayer money per student (source; the true spending is probably well over $40,000 per year because the official budget does not include the capital expenses of the buildings, the value of the land, or the likely pension and retiree health care costs)). This family’s basic needs are met, but if they want luxury items, however, one of the adults will have to earn some cash. That would result in GDP growth and the government collecting some payroll tax (if done via a W2 job) or at least some sales tax. How would their decision to participate in the labor market be affected by whether or not someone in New York City is rich? How would that decision be influenced by the degree of richness enjoyed by the New York City fatcat?

Economists have published papers showing some correlation between wealth disparity and economic growth but I haven’t seen an explanation for causation. People have been observed to work more hours when tax rates are reduced. At least in the absence of the Welfare State, people have been observed to work harder when they need to support children. People have been observed to work fewer hours when their financial needs have been met, e.g., due to a trust fund, pension, welfare checks, child support payments that exceed the cost of rearing a child, or alimony. But is there any evidence that anyone looks at East Hampton beach house values on zillow.com in the morning before deciding whether or not go out and look for a job? If not, what is it about wealth disparity that causes an economy to shrink or stagnate?

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