"Arfa Daily" wrote in message
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"Trevor Wilson" wrote in message
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"(PeteCresswell)" wrote in message
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Do LED lights fail completely or gradually?

i.e are they all-or-nothing?

I've got a nice little LED flashlight that, one day, started
getting dim.

Noticed that some of the contacts were corroded and wire-brushed
the ones on the back of the emitter module. The plate that
connects the two stacks of AA batteries in the back recess of the
light's body is inaccessible so, after scratching it a little
with a long knife to no avail, I folded up some alu foil and
stuffed it down there... but still no luck.

Fooled around with it today, and couldn't even get a dim light by
applying 6v from a known good source to the feet of the emitter
module.

My first thought was that I'd hosed the LED completely by
accidentally applying reverse polarity somewhere along the line.
Possible?

If not, what about the gradual dimming? Does that fit with LED
failure, or does it narrow the cause down to some sort of
electrical contact issue?

**White LEDs wear out pretty quickly. They are a blue LED with a
fluorescent coating. The coating fails. Regular coloured LEDs can last
for many decades, whilst I've found white LEDs will dim to around 30% of
their original output after about 1 - 2 years of continuous duty (at
rated current). Higher currents will accelerate that wear.

Trevor Wilson

I believe that some of these LED flashlights use drive electronics built
into the head, to pulse the LEDs rather than DC drive them. It apparently
produces a greater light density per amp, and helps to prolongue the life
of the LEDs. It's possible that the one that has failed may have such
electronics, and that's where the problem lies ??

**Certainly possible. However, it depends on the electronics driving the
LED. Manufacturers have a tendency to drive the LED as hard as possible, in
order to obtain maximum brightness. They don't care if the thing fails in
six months. The money is already in the bank.

Trevor Wilson