Posts Tagged ‘LED’

An inspiring story of incompetence

September 13, 2011
A liquid filled light bulb

A liquid-filled light LED bulb. Designed with delightful incompetence.


Schadenfreude is the german word that describes the pleasure derived  from another person’s misfortune. Reading this WIRED story about the design of LED light bulbs, I will confess to feeling great pleasure at reading about the utter incompetence with which these were designed. On reflection, it was not exactly pleasure at their misfortune, but relief. My feeling was that “If they can bring their product to market after ignoring really obvious problems with their product, then maybe I should should not be so hard on myself about the mistakes I have made in my work. Either way, I felt inspired to follow my ideas with renewed vigor.

The story relates how in 1997 Ron Lenk had the idea of cooling LED’s inside a light bulb with a gel rather than gas – what a great idea! He patented the idea and founded a company, Switch to manufacture their Superbulb. All kinds of things happened, but things were looking tricky when they hired a physicist, David Horn, in 2009 who noticed that something was very wrong. On touching the outer envelope with his finger, he noticed that it wasn’t warm! If the bulb wasn’t getting warm, then the gel within the bulb wasn’t doing its job of cooling the LEDs. So after two years of experiments and development, it took an outsider to notice that something was very wrong. Everyone in the development team must have known that!

They seem to have things in hand now. But this willingness to notice problems that everyone would prefer to ignore is critical to the success of projects. It’s an example of negative feedback, and  it often takes an outsider to provide it. It put me in my mind of my own project in which I am trying to measure temperatures by timing pulses of sound down tubes. Even though the idea is mine, I will confess to thinking its a pretty clever idea. But making it work reliably takes all kinds of skills that I don’t have. I had been feeling really fed up about the project – there are still one or two things that I can’t figure out – but reading this story inspired me to look at things again. Because after all, tomorrow is another day.



March 25, 2011
Spectra Glasses

Looking through the diffraction grating glasses.

Understanding light, and its connections to electricity and heat is the central theme of Protons for Breakfast. And a primary tool for understanding light is the spectrometer. So at Protons‘ we give out diffraction grating glasses (above) which split light into its component frequencies, each of which we perceive as having a different colour. These are big hit.



We become more quantitative too by using hand-held plastic spectrometers (link or link) that display the spectra against a wavelength scale. And brilliantly conceived and simple though these are, they are tricky to use. And although they give a quantitative measure of the wavelength of light, they give no information about the relative intensities of the different wavelengths.

John Mountford capturing spectra at Protons for Breakfast

John Mountford capturing spectra at Protons for Breakfast. Click to enlarge.

It turns out be difficult (=expensive) to get accurate information on the relative intensities of light at different wavelengths. But my colleague John Mountford noticed that an instrument for doing this was temporarily available, and so we took it along to Protons and tried it out. The results were very impressive and below I have put three screenshots of the light from three types of lamps: conventional incandescent, compact fluorescent, and the new fangled LED lamps. Each spectrum is strikingly different and to the physics detective, tells the tale of how the light is made.  I will be looking at each of these three lighting technologies in future weeks, but for now just enjoy this beautiful data. If you would like to plot your own graphs, you can download an Excel spreadsheet containing spectroscopic data.

Spectrum of Incandescent light bulb

The spectrum of an incandescent light bulb. Notice that the bulb gives out mainly red and infra red light. The bulb appears yellow to us because we are insensitive to red light and the small amount of blue, and detect primarily the green and yellow. Click for enlarged image.

The spectrum of a compact fluorescent light bulb.

The spectrum of a compact fluorescent light bulb. Notice the very intense sharp 'emission lines' from the mercury within the bulb, and the relatively weak, smooth background from the phosphor. Click for enlarged image.

The spectrum of an LED light bulb. Notice the bright blue emission from the LED itself and the fluorescence of the phosphor in the green, yellow and red. Click for enlarged image.

The spectrum of an LED light bulb. Notice the bright blue emission from the LED itself and the fluorescence of the phosphor in the green, yellow and red. Click for enlarged image.

Consumable light

August 26, 2010

Imagine that after all the talk and hype, scientists and engineers finally came up with affordable LED lighting solutions which cost less to use even than compact fluorescent  light bulbs. This could actually happen within 5 years. But imagine it were true now! Wow! What would happen?

  • Would we simply use the same amount of light and pocket substantial savings in cash, energy and carbon?
  • Would we revel in the technology and – since it was now so cheap – find new ways to consume more light (and electricity and carbon)?
  • Would the third world – in which people spend many evening hours in near darkness – consume more light?

These questions were addressed in a recent scientific paper (which seems to be free to download for the moment!) and the analysis really moved me. Of course no one knows what technology will actually become available. Or when. Or at what cost. And no one knows how these technology developments will interact with human society worldwide. But the paper considers a wide variety of possible scenarios. Reading the paper I was struck again and again by the straightforwardness and thoroughness of their analysis, and the contrast between the sophistication of their analysis, and the naivite of my own prior thoughts on the matter. It’s a long paper and quite technical, but there are two things I would like to comment on: the concept of light consumption, and my own technological utopianism.

Light consumption

I had never thought of light itself as a product, but of course in can be thought of that way. A lumen is the unit used to measure the amount of useful emitted by a light bulb. It is a product of the amount of amount of light of all frequencies (colours) emitted, and the sensitivity of the human eye to those colours. Although we are not usually aware of it, when we are buying light bulbs we are actually seeking devices to produce (consume) a certain number of lumens of light in our homes. By quantifying this consumption, and charting historical ‘consumption’ over several centuries, the authors can make plausible estimate for how consumption might change  as new technologies become available.

Technological Utopianism

The most profound effect of the paper was to puncture my sense that improved light technology would some how ‘solve a problem’. It had seemed so obvious to me that LED lighting would reduce the carbon costing of lighting and thus reduce the carbon emissions associated with lighting. I had been aware of the problem that if I saved (say £100) on my electricity bill, I would use that £100 to consume some other resource – which would have a carbon cost associated with it. But I had not really considered the effects on the third world – which would ‘consume lumens’ voraciously if they were cheap enough – and the effects of the market to develop new ways in which we could ‘consume lumens’ – mood sensitive lights or uniformly illuminated floors and walls – or whatever our collective imagination comes up with. In short, if a perfect lighting technology – and LED lighting is very nearly that – became available it would not definitively solve any societal problems.

The growth in LED lighting still seems inevitable – and I still hope it will happen. Allowing large swathes of the third world to function in the evening will bring enormous benefits. And reducing energy (carbon) consumption in ‘lumen saturated’ societies such as our own is definitely a ‘good thing’. But the problem of carbon emissions that we face collectively is unlikely to be solved by a technological fix. I feel like I have just become a technological realist.

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