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John Fields

On Tue, 29 Dec 2009 00:16:00 -0600, (Pete)
wrote:

I'm curious about the "Important" warning message I found on a wind-up
LED torch (flashlight) I just got for Christmas. It says:

"IMPORTANT: To extend the life of the LEDs allow 20 seconds between
turning ON & OFF. Do not turn ON & OFF repeatedly."

Hunh...? I can't imagine what effect that would have on LEDs. There's
no turn-on surge like an incandescent would have. How could the life
be shortened?

---
Since they want you to wait 20 seconds between turn-on and turn-off,
there will, ostensibly, be no turn-on surge from the supply and, since
LED's don't exhibit the same VI characteristics as incandescents, no
turn-on current spike through the LED.

What they're talking about is a _turn-off_ surge, so I suspect that 20
second wait will allow the thing to do whatever it needs to in order to
do a soft turn-off.
---

I searched the web for that message, and find a number of apparently
quite different and independent products with the same warning -- all,
interestingly from UK suppliers! (Though my unit is made in China.)
Could this be some kind of weirdly spreading myth?

---
I doubt it.

More than likely it's that the same (cheap) design has found its way
into many related products.

JF