"Pete" wrote in message
...

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?

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?

A well designed LED torch has a DC-DC converter driving the LED(s) so that
you can use most of the energy in the batteries without the LEDs dimming too
much.

If you just use a series resistor you either have the LED dimming a lot
before the batteries are dead or you end up wasting a lot of energy in the
resistor, or both.

So it could be a requirement of the DC-DC converter rather than the LEDs.

However it still seems rather odd.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.