You'd think that, with the sun, we'd have all the light in the world. However, our need to illuminate is a strong one, stronger even than the desire to purchase a fluoro light saber online. Thank Ra we have Daniel Rutter to show us the light side of lights, so we can get some enlightenment.
Want to light up your case? Want to light up your car? Want to light up your, um, bar fridge?
Can do. There are lots of photon pumps that run from the 12-volt rail in a PC (or in a car). You can get many of them from ordinary computer shops these days.
But exactly what kind of light you should use for a given frivolous purpose depends on what you want to do.
Do you want to illuminate a large area -- your whole motherboard, say -- brightly? Do you want to spotlight one component? Do you just want to mark out the edges of something?
Read on to find out which lighting technology is good for what.
IncandescentYou're not likely to light up your PC with a tungsten filament globe, but you probably are going to light your computer room up this way.
Incandescent bulbs are cheap, last a reasonably long time (generally one to two thousand hours of use), are usefully bright, and give okay yellow-white light with a Colour Rendering Index (CRI) of 100. That means they output all visible light frequencies. No matter what colour something is, an incandescent bulb will provide photons of the right frequency for it to reflect. So you'll see all objects in the room as they actually are, albeit tinted a bit yellow.
ABOVE: LEDs work well for lighting up fans.
Incandescent lamps are a balancing act between efficiency, toughness and longevity. The tubular bulbs in most car interior lights, for instance, last a really long time and will put up with a lot of vibration, but their efficiency is lousy and they suck a lot more power than you'd expect from their brightness.
Household incandescent bulbs, in contrast, have better efficiency and medium life, and are quite fragile. But they're certainly cheap.
Regular light bulbs are good for around 15 to 20 lumens per watt of output. The more lumens per watt, the more efficient a light is.
Halogen downlights (most of which run from 12 volts -- you can run them from a PC power supply, if you must. . .) aren't as much more efficient than regular nitrogen-filled light bulbs as they look. They manage around 20 to 25 LPW, but their integrated reflectors make them look brighter, because they're throwing all of their light in one direction.
Incandescent globes of any sort are not a good choice for coloured lighting. Sticking a high-powered yellowish light behind a filter that eats most of its photons is certainly a cheap way to get every room lit a different colour during your party, but it's very wasteful.If you must put Christmas tree lights in your PC, use LED ones.
ABOVE: 'Bubble lights' use a single LED at the end of a bubbly stick of acrylic. Magical, honestly.
LEDsIf you don't overdrive an LED, it's likely to run continuously for many tens of thousands of hours without losing much brightness. 100,000 hours, or 11.4 years, is a commonly quoted figure before an LED will drop to 80% brightness. LEDs' actual useful life-until-broken is likely to be substantially longer again.
No current high brightness LEDs have actually been tested for 11.4 years, of course. But it's safe to say that a conservatively driven LED will last a spectacularly long time.
If you're looking for a lighting technology you can pass on to your grandchildren, this is the one.
Coloured LEDs -- which are the ones you're likely to use for decorative purposes -- are quite efficient. Not incredibly so, but they manage from about 20 to more than 50 lumens per watt, depending on the colour and how hard they're driven. Efficiency drops as you drive them harder, and many high-scoring LEDs' rated current is well above the current at which their efficiency peaks.
ABOVE: LEDs are small enough that they can fit into the motor assembly of a fan!
Coloured LEDs, though, have a CRI of zero. They only emit one frequency, so everything they light up appears in shades of that one colour.
Most decorative LED products consume a trivially small amount of power, by the standards of a normal PC PSU, but they also don't output a ton of light. A few standard 5mm LEDs won't be enough to light up a whole case. They'll do great for spotlighting your CPU cooler, though!
White LEDs, on the other hand, aren't likely to be any more efficient than a halogen downlight. They'll consume a lot less power, but they'll put out a lot less light, too; the ratio of power to light will be about the same.
The reason why white LEDs are less efficient is that they're actually blue LEDs, with a phosphor coating over the 'die' that emits the blue light. The phosphor absorbs some of the blue light and emits red and green light to fill out the white spectrum. It's a long way from 100% efficient though, so white LEDs come in at around 15 to 25 lumens per watt.
ABOVE: You can get CCFLs with one, two or three colours of phosphor coating all on the one tube.
Most current white LEDs emit blue-white light with a CRI of 85 or better; that's good enough for practically any purpose, including lighting your fine art prints.
To get a lot of light out of LEDs -- like, enough to brightly light the whole of the inside of your PC's case - you either need a lot of LEDs [optional pic here - boardpers1, 2 or 3.jpg; caption: 'This is the 36-LED board from the caselight project in issue 12!'], or you need a few really big LEDs.
Luxeon Star LEDs from Lumileds (www.lumileds.com) are the most powerful LEDs on the market at the moment. With a heatsink [optional picture here -- heatsunk1 or 2.jpg] stuck to them, the top-of-range five-watt Luxeons can easily output 50 times as much light as a standard 5mm 'high intensity' LED. Two or three of the cheaper one-watt Stars make a nifty caselight, as seen in the project in issue 12 of Atomic.
Unfortunately, nobody seems to sell pre-built caselights using Luxeon LEDs, and the bare LEDs aren't easy to find in Australia. Try Prime Electronics (www.prime-electronics.com.au).
Issue: 137 | June, 2012