WyBlog

Why I won't be buying LED Christmas lights, ever

They flicker. It gives me a headache to look at them.

My wife didn't believe me when I said that they flicker. "No, they don't!", followed by "I can't tell!"

"Look closely," I said. Move your hand back and forth.

"Wow, you're right."

Of course they flicker. They're diodes. Diodes only pass current in one direction. Our electricity is 60 hz AC — alternating current. So at a minimum the LED lights would only be "on" 30 times a second. But, it's actually less:

For an imaginary cycle of 360 degrees of the AC line, about 26.5deg (1.2msec) pass before the line gets to 75V and the LEDs start to emit light. Then the LEDs are on for 127deg (5.9msec), and off for the remaining 206.5deg (9.6msec). That means we get a 5.9msec hump or pulse of light every 16.7msec: The LEDs are actually ON only about 35 percent of the time (the current and light ramp up then down during the pulse). The pulsing effect is similar to what we see in fluorescent lights, but worse because it is slower: only one side of the AC wave is used.

Ergo, flicker.

And for this we get to pay 10x the cost of good old fashioned incandescent Christmas lights, just to appease the eco-nuts.

No thanks.

Posted at 15:06 by Chris Wysocki   [/odds_n_ends]   Comments | Archived | Perm Link |
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