Can 2.5V to light up a typical 3mm LED?

[Jasen Betts]

I acknowledge the safety measure, but is the threat real?

Not with ordinary resin encapsulated thru-hole LEDs. the die bonding
tends to fail before thermal runaway can transform the die into a
bulk resistor

rectifier diodes have stronger bonding and do often fail shorted.

 

[Mr. Man-wai Chang]

Not with ordinary resin encapsulated thru-hole LEDs. the die bonding
tends to fail before thermal runaway can transform the die into a
bulk resistor

So I should not expect a diode to behave like a fuse or a resistor? OK....

rectifier diodes have stronger bonding and do often fail shorted.

Let's just talk about average LED. I don't need rectifier for the
meantime...

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[Mr. Man-wai Chang]

In professional applications, you'll also need to consider the power
dissipation, but that's another few pages of discussion ;-)

Talking about the wattage over the current-limiting resistor?

http://www.elmassian.com/trains/dcc-battery-rc-electronics/misc-electronics/led-lighting-basics

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