Thursday, August 19

In praise of LEDs

Okay, I don’t hate all LEDs. Last week I saw a very nice LED desk lamp at Costco. Twenty bucks. Cheap enough, why not give it a try. Guess what? It’s terrific! Plenty bright, and the color of the light is like daylight. Only six watts! It gets cozy warm; you can put your hand right on top of the lamp and it’s comfortable.

The light comes from a dime-size 3 by 4 array of flat yellow dots. When it’s on, you can’t look at them without getting a big hurt on your retinas and an afterimage that lingers for quite awhile. It is similar to the LED used in the Mag-Lite 3-cell flashlight, except the Mag-Lite has only a single element that’s dome-shaped, probably to improve its focus. It, too, is something you don’t want to look at even by accident. When I first got the flashlight I called it scary bright. Outside at night it illuminated objects an awfully long distance away, which I never thought could be seen at night with a hand-held light. It cost $30 at Costco, which included an LED Mini Mag-Lite and all the batteries.

The Mag-Lite’s single LED is just a tiny yellow dot

Costco has an interesting way of marketing. Shoppers call it the treasure hunt. Here’s how it works: You’re cruising the aisles and run across some really neat thing that you’d like to buy, but maybe not today. The following week it’s gone and may never be back. The theory is buy it now or forever regret it.

A case in point—When Costco opened its third Fresno-area store several years ago, Karla and I stopped by the first week it was open. In the jewelry case they displayed a platinum solitaire diamond ring that was going for $104,499, less than half normal retail price. It was gorgeous. Sure enough, the following week it was gone! We’ve been kicking ourselves ever since.


Pete S. said...

An interesting fact about the yellow dot you see in a white LED is that it is a fluorescent material. An ultraviolet or blue LED behind it excites the fluorescent material which in turn emits the white light.

Tom Hurley said...

Nice comment, Pete S. I am wondering why all the LED makers are making the light cool in color instead of warm. Simply changing the phosphor would change the whiteness of the light. Compared to incandescent and even many compact fluorescent bulbs, white LEDs tend towards blueness.

Pete S. said...

I too have wondered about the blue-ness of white LEDs. Maybe the extra blue is leakage from the blue excitation LED, and they can't be bothered to correct for it.

Here is an LED desk lamp that intentionally produces warm-colored light to simulate an incandescent bulb (also available with daylight color balance):

Can be purchased at, but not a cheap as the one you found at Costo!