I know it costs more to make a more efficient LED bulb for room lighting. Is there also a tradeoff between efficiency and operating life? I can't think of a mechanism, but I'm not so familiar with LED light bulb design.
Lots of light, high chip temp, shorter chip life.
Don't they usually fail from the other electronics?
In the one I took apart all the LED modules were fine. The drive electronics failed.
LED efficiency drops radically at high currents and high temps, and LEDs degrade ditto. There is no tradeoff of efficiency vs reliability. The real tradeoff is light vs cost.
For fun, blast an LED with freeze spray.
mandag den 26. december 2022 kl. 22.01.16 UTC+1 skrev John Larkin:
On a sunny day (Mon, 26 Dec 2022 11:13:38 -0800 (PST)) it happened Ricky snipped-for-privacy@gmail.com wrote in snipped-for-privacy@googlegroups.com:
I have had several cheap China made LED bulbs fail
So it all depends on the circuit.
I suspect that the limit is more on die surface brightness - too much and the phosphor life is compromised and it changes colour temperature.
Efficiency should make no difference provided that you choose a surface brightness than allows the phosphor to survive fr full working life.
Does that still work well with the modern high efficiency ones?
It used to be spectacular to dunk one of the 1970's red LEDs into LN2. They became incredibly bright as the crystal lattice stiffened up and resistive losses all but ceased. They tended to fail due to this abuse.
An old and a modern LED in series makes quite a good pop science demo.
If you push the blue light flux and/or residual heating high enough it can damage/darken the phosphor used to generate the yellow light.
The surface brightness of recent LEDs is now about the same per unit area as the sun - which makes it a bad idea to look directly at them. Blue, violet or UV ones especially.
I have a 12-volt, roughly 1 cm square, array that looks like a welding torch. It's the kind used in street lamps.
Why don't they diffuse LED street lamps? They are annoying.
On a sunny day (Tue, 27 Dec 2022 15:47:22 +0000) it happened Martin Brown <'''newspam'''@nonad.co.uk> wrote in <tof42a$11vb$ snipped-for-privacy@gioia.aioe.org>:
I have out tape over many LEDs on equipment I have, can still see those through the tape. It avoids blinding.
The engineers designing them are control freaks and want the ray trace illumination pattern to go exactly where they choose to send it. I agree that a bit of diffusion would help take the edge of them.
I find their very hard full cut off somewhat annoying when combined with black poles since it is impossible to pick out the road ahead. OTOH as an astronomer I appreciate the darker skies (especially since the ones round here switch off completely midnight through 5am).
OTOH if you have ever been near a low pressure sodium street lamp on the bench - even though diffused they are hellishly bright close up!
Nothing LED annoys me quite so much as red and green traffic indicators that flash at a speed that peripheral vision can time resolve. When near a pedestrian crossing I see a line of distinct images from them as my eye cadence sweeps the scene. Some makes are particularly bad for it.
A place I worked once produced an instrument with a five digit seven-segment LED display. Because they were new and fashionable, blue LEDs were used.
Every single one I saw in the field had Kapton tape over the display, which tamed it to a nice gentle dull orange.
LED stop lights tend to have weird patterns of obviously-series LEDs that are out or flashing intermittently.
Blue LEDs are especially annoying, and people with cataracts sometimes can't see blue.
We used the Cree SiC blues when they were new. They needed 50 mA to be visible. As time went on and blues got more efficient, our customers started complaining. 1 mA is plenty now.
We run test LEDs on a pc board at 100 uA now, so they don't blind you when probing.
On a sunny day (Wed, 28 Dec 2022 07:57:31 -0800) it happened John Larkin snipped-for-privacy@highlandSNIPMEtechnology.com wrote in snipped-for-privacy@4ax.com:
Lasers are tricky too, I have some high powered ones, do not do this at home:
No it is not bended due to gravitational effects :-) its the camera optics.
The ones I hate blink rapidly on being activated. There are also headlights that flash very rapidly. Both are highly visible without flashing. Why do people think they need so much overkill?
How do you get the doves to fly into it? What about aircraft? If your beam hits an aircraft, you will hear about it. Not in friendly terms either.
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