Life of a LED

[induction]

If my LED lamps in the house are less than 5 years old, would I be considered an asshole if I replaced them with cheaper lamps and took them with me when I sell the house?

In case this is a serious question, the general rule is, if it's nailed down it stays. If the lamps are freestanding and moveable, take them with you. If they are 'permanently' installed, they stay. If you swap them after you sell, without prior negotiation, yes, you're an asshole (and liable to civil suit).

If it's not a serious question, the answer is 11.

[armdnrdy]

If my LED lamps in the house are less than 5 years old, would I be considered an asshole if I replaced them with cheaper lamps and took them with me when I sell the house?

In case this is a serious question, the general rule is, if it's nailed down it stays. If the lamps are freestanding and moveable, take them with you. If they are 'permanently' installed, they stay. If you swap them after you sell, without prior negotiation, yes, you're an asshole (and liable to civil suit).

If it's not a serious question, the answer is 11.

I'm not sure what John does for a living but...he used the term "lamps" describing light bulbs not light fixtures.
I'm an industrial, electrical contractor. Lamp is the proper industry term.
Light bulb is the name that home owners use. 

[induction]

I see. That's a much more difficult question then. I'm going with 11.

I recently sold my house, so now I don't know what to call them.

[armdnrdy]

I started out doing residential (custom homes) about 25 years ago.
My first boss used to confuse the hell out of me by asking me to talk to the client to find out what type of "lamps" they wanted to use.
Huh? 

[Jdansti]

I'm not sure what John does for a living but...

11

[PRR]

> Is there a minimal current for the LED to start emitting light

A long long time ago, many LEDs "leaked". If you put in 1mA, it all went to leakage, nothing left for the LED crystal to light-up.

I have not seen a leaky LED in several decades. There is probably a lower limit, but it would be much dimmer than any useful current.

> does the light intensity varies along the current range that it can handle?

Over the "normal" range (say 0.1mA to 20mA for a standard LED), light is proportional to current very-nearly.

If you go much past the "normal" range, a Red LED starts to glow "orange", and light output does not increase as much as current. It is over-heating, and starting to work like an incandescent lamp.

> test conditions says a 20mA current. We presume a 4k5 limiting resistor, for a 9v supply, right?

9V supply, minus a few volts for the LED, leaves maybe 7 Volts in the resistor. 7V in 4.7K is 1.5mA. This is much less than the rated maximum steady current of 20mA. It is like a small keg of beer in a 2-ton truck. The truck is working easy and should live a long time.

The LED does not care if it gets this 1.5mA from a switch, a MOSFET, coins stuck in a row of lemons, or the properly cut-down output of a million-Watt electrical generator. All it "feels" is the current, not where it comes from.

Our little "indicator light" LEDs usually run very-very cool. Only a few degrees above room temperature.

As R.G. hints: The time factor for many electro-chemical reactions is twice as fast for every 10 degrees C increase of temperature.

The household-size "60 Watt equiv" "bulbs" do run HOT. Not hot like incandescent, but hot for a Silicon semiconductor. Even then, 50,000 hours is promised and apparently nearly-true. If you leave the LED on 4 hours a night 4 nights a week (gig-schedule), these "hot" LEDs may last 60 years. Our cooler "small indicator" LEDs should last many-many times longer. Your great-great grandchildren could still be enjoying it.

It should be noted that LEDs "usually" don't burn-up, they just get dimmer. The 70% light may be 50,000 hours, but the "NO light" life may be 500,000 hours.


Finally, if a 10-cent LED actually does fail in your lifetime, you replace it for 7 cents (prices always drop). It isn't a house roof, you don't have to sell your guitars to pay for it.

[Gargaman]

Nice!
Out of words to thank, Paul.
Best regards