LED Bulb Efficiency vs. Operating Life...

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[none]

In article <nnd$4d9a769b$61464ae6@e846562bf142425e>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

On 26.12.22 18:16, Ricky wrote:
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.

This can be offset by operating the leds vastly below capacity.
E.g. I have a flash light costing 3.5 euro with 37 leds.
I estimate that the leds have an effectively infinite life span.
Unlike light bulbs you can diminish the current and have approximately
proportional light.

Groetjes Albert
--
Don\'t praise the day before the evening. One swallow doesn\'t make spring.
You must not say \"hey\" before you have crossed the bridge. Don\'t sell the
hide of the bear until you shot it. Better one bird in the hand than ten in
the air. First gain is a cat spinning. - the Wise from Antrim -

 

[Martin Brown]

On 19/01/2023 15:11, albert wrote:

In article <nnd$4d9a769b$61464ae6@e846562bf142425e>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
On 26.12.22 18:16, Ricky wrote:
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.

This can be offset by operating the leds vastly below capacity.
E.g. I have a flash light costing 3.5 euro with 37 leds.
I estimate that the leds have an effectively infinite life span.
Unlike light bulbs you can diminish the current and have approximately
proportional light.

The catch is that if they are all in series with a current source or
worse rectified mains then the first one to fail takes the entire chain
out so MTBF is about 1/N th of the N components in the chain. I have
seen some where there were ~60 white leds in series.

Traffic lights seem to have about 4 chains that are independent so you
don\'t get nice even illumination if one fails but they don\'t just stop
completely one day like the old filament bulbs did.

--
Regards,
Martin Brown

 

[bitrex]

On 1/19/2023 10:37 AM, Martin Brown wrote:

On 19/01/2023 15:11, albert wrote:
In article <nnd$4d9a769b$61464ae6@e846562bf142425e>,
Sjouke Burry  <burrynulnulfour@ppllaanneett.nnll> wrote:
On 26.12.22 18:16, Ricky wrote:
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.

This can be offset by operating the leds vastly below capacity.
E.g. I have a flash light costing 3.5 euro with 37 leds.
I estimate that the leds have an effectively infinite life span.
Unlike light bulbs you can diminish the current and have approximately
proportional light.

The catch is that if they are all in series with a current source or
worse rectified mains then the first one to fail takes the entire chain
out so MTBF is about 1/N th of the N components in the chain. I have
seen some where there were ~60 white leds in series.

Traffic lights seem to have about 4 chains that are independent so you
don\'t get nice even illumination if one fails but they don\'t just stop
completely one day like the old filament bulbs did.

I guess one way to build a highly-reliable LED bulb might be to use LEDs
manufactured with intrinsically high forward voltages, and then boost
instead of buck the AC -> DC to maybe 400 volts, so you could eliminate
the electrolytic cap also.

Another thing I\'ve seen is an IC with a switch matrix that monitors the
line voltage and cuts series/parallel strings in and out in proportion
to the instantaneous line voltage to keep illumination mostly constant

 

[Phil Hobbs]

albert wrote:

In article <nnd$4d9a769b$61464ae6@e846562bf142425e>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
On 26.12.22 18:16, Ricky wrote:
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.

This can be offset by operating the leds vastly below capacity.
E.g. I have a flash light costing 3.5 euro with 37 leds.
I estimate that the leds have an effectively infinite life span.
Unlike light bulbs you can diminish the current and have approximately
proportional light.

Groetjes Albert

Depending on the construction of the lamp, there are a few things that
cause LED output to degrade:

1. Darkening of the package material with time, heat, and optical dose.
This is what\'s usually responsible for old optocouplers gradually failing.

2. Loss of fluorescent efficiency. This is slow for white LEDs, since
the fluor is mostly inorganic Ce:YAG.

3. Propagation of dislocations into the active region, leading to lots
of nonradiative recombination.

1 and 3 are thermally activated, and 3 is also caused by
electromigration at very high current densities.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Thu, 19 Jan 2023 15:37:17 +0000, Martin Brown
<\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 19/01/2023 15:11, albert wrote:
In article <nnd$4d9a769b$61464ae6@e846562bf142425e>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
On 26.12.22 18:16, Ricky wrote:
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.

This can be offset by operating the leds vastly below capacity.
E.g. I have a flash light costing 3.5 euro with 37 leds.
I estimate that the leds have an effectively infinite life span.
Unlike light bulbs you can diminish the current and have approximately
proportional light.

The catch is that if they are all in series with a current source or
worse rectified mains then the first one to fail takes the entire chain
out so MTBF is about 1/N th of the N components in the chain. I have
seen some where there were ~60 white leds in series.

Traffic lights seem to have about 4 chains that are independent so you
don\'t get nice even illumination if one fails but they don\'t just stop
completely one day like the old filament bulbs did.

Old traffic lights had special hi-rel, often dual-filament bulbs.

 

[bitrex]

On 12/27/2022 11:39 AM, John Larkin wrote:

On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

 

[bitrex]

On 12/28/2022 11:00 AM, John Larkin wrote:

On Wed, 28 Dec 2022 12:02:10 +0000, Clive Arthur
clive@nowaytoday.co.uk> wrote:

On 28/12/2022 05:27, Jan Panteltje wrote:
On a sunny day (Tue, 27 Dec 2022 15:47:22 +0000) it happened Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote in <tof42a$11vb$1@gioia.aioe.org>:

On 26/12/2022 17:16, Ricky wrote:
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.

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 out tape over many LEDs on equipment I have, can still see those
through the tape.
It avoids blinding.

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.

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.

A regular-size red or amber common cathode 7 segment display, in series
with a TL431 configured as a zener, and the segments driven from 5 volts
looks just about perfect brightness to me! Seems stable with
temperature, too.

 

[Ricky]

On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex wrote:

On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars. Everytime I move my line of view, they create a dozen spots of light. When there are more than one it gets insane looking. Seems like most people don\'t even see this.. The first time it happened to me I was trying to merge where there was no merge lane and the ramp was coming from an angle, rather than merging while driving parallel, so the rear view mirror didn\'t show anything useful. A quick look over my shoulder showed one car passing me, just as I needed to either go or stop. As I turned my head back, the tail lights (those tall Cadillac tail lights) suddenly blossomed into a dozen pairs of lights and I thought it was a bunch of cars! I had to hit my brakes to avoid an accident, only to find there was only the one car. Insane that they would create this sort of hazard, even if everyone doesn\'t see it. It\'s the sort of thing that would be changed on an airliner, after the first accident it causes.

I\'ve never found out how rapid the blinking is.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[bitrex]

On 1/19/2023 5:20 PM, Ricky wrote:

On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex wrote:
On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars. Everytime I move my line of view, they create a dozen spots of light. When there are more than one it gets insane looking. Seems like most people don\'t even see this. The first time it happened to me I was trying to merge where there was no merge lane and the ramp was coming from an angle, rather than merging while driving parallel, so the rear view mirror didn\'t show anything useful. A quick look over my shoulder showed one car passing me, just as I needed to either go or stop. As I turned my head back, the tail lights (those tall Cadillac tail lights) suddenly blossomed into a dozen pairs of lights and I thought it was a bunch of cars! I had to hit my brakes to avoid an accident, only to find there was only the one car. Insane that they would create this sort of hazard, even if everyone doesn\'t see it. It\'s the sort of thing that would be changed on an airliner, after the first accident it causes.

I\'ve never found out how rapid the blinking is.

I usually see those flashing brake light mods on street racer-type cars
around Providence RI, kids put them on their old Eclipse etc. to make
them look cool. I don\'t know that they\'re much improvement over a
regular high-level lamp at avoiding being rear-ended, though.

There\'s some failure mode of LED street lamps and outdoor floodlights,
etc. where the whole unit blinks at about 2 Hz.

 

[John Larkin]

On Thu, 19 Jan 2023 16:51:10 -0500, bitrex <user@example.net> wrote:

On 12/28/2022 11:00 AM, John Larkin wrote:
On Wed, 28 Dec 2022 12:02:10 +0000, Clive Arthur
clive@nowaytoday.co.uk> wrote:

On 28/12/2022 05:27, Jan Panteltje wrote:
On a sunny day (Tue, 27 Dec 2022 15:47:22 +0000) it happened Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote in <tof42a$11vb$1@gioia.aioe.org>:

On 26/12/2022 17:16, Ricky wrote:
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.

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 out tape over many LEDs on equipment I have, can still see those
through the tape.
It avoids blinding.

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.

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.


A regular-size red or amber common cathode 7 segment display, in series
with a TL431 configured as a zener, and the segments driven from 5 volts
looks just about perfect brightness to me! Seems stable with
temperature, too.

We haven\'t used a 7-seg in ages. This is the last one, displaying a
unit number from 0 to 7.

LCDs are much better.

 

[Ricky]

On Thursday, January 19, 2023 at 5:31:57 PM UTC-5, bitrex wrote:

On 1/19/2023 5:20 PM, Ricky wrote:
On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex wrote:
On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars. Everytime I move my line of view, they create a dozen spots of light. When there are more than one it gets insane looking. Seems like most people don\'t even see this. The first time it happened to me I was trying to merge where there was no merge lane and the ramp was coming from an angle, rather than merging while driving parallel, so the rear view mirror didn\'t show anything useful. A quick look over my shoulder showed one car passing me, just as I needed to either go or stop. As I turned my head back, the tail lights (those tall Cadillac tail lights) suddenly blossomed into a dozen pairs of lights and I thought it was a bunch of cars! I had to hit my brakes to avoid an accident, only to find there was only the one car. Insane that they would create this sort of hazard, even if everyone doesn\'t see it. It\'s the sort of thing that would be changed on an airliner, after the first accident it causes.

I\'ve never found out how rapid the blinking is.

I usually see those flashing brake light mods on street racer-type cars
around Providence RI, kids put them on their old Eclipse etc. to make
them look cool. I don\'t know that they\'re much improvement over a
regular high-level lamp at avoiding being rear-ended, though.

We aren\'t talking about the same thing. I\'m talking about tail/brake lights where the brightness is adjusted by PWM. It saves a few cents by leaving off the inductor too smooth the waveform into a level.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Martin Brown]

On 20/01/2023 00:58, Ricky wrote:

On Thursday, January 19, 2023 at 5:31:57 PM UTC-5, bitrex wrote:
On 1/19/2023 5:20 PM, Ricky wrote:
On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex wrote:
On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars.
Everytime I move my line of view, they create a dozen spots of
light. When there are more than one it gets insane looking. Seems
like most people don\'t even see this. The first time it happened
to me I was trying to merge where there was no merge lane and the
ramp was coming from an angle, rather than merging while driving
parallel, so the rear view mirror didn\'t show anything useful. A
quick look over my shoulder showed one car passing me, just as I
needed to either go or stop. As I turned my head back, the tail
lights (those tall Cadillac tail lights) suddenly blossomed into
a dozen pairs of lights and I thought it was a bunch of cars! I
had to hit my brakes to avoid an accident, only to find there was
only the one car. Insane that they would create this sort of
hazard, even if everyone doesn\'t see it. It\'s the sort of thing
that would be changed on an airliner, after the first accident it
causes.

I\'ve never found out how rapid the blinking is.

I usually see those flashing brake light mods on street racer-type
cars around Providence RI, kids put them on their old Eclipse etc.
to make them look cool. I don\'t know that they\'re much improvement
over a regular high-level lamp at avoiding being rear-ended,
though.

We aren\'t talking about the same thing. I\'m talking about tail/brake
lights where the brightness is adjusted by PWM. It saves a few cents
by leaving off the inductor too smooth the waveform into a level.

The problem is that they PWM pulse them at a frequency that some people
can see in their peripheral vision (which is much more flicker
sensitive). I guess the engineers who designed it didn\'t think about
their choice of frequency too hard. Anything above about 300HZ frequency
would look pretty much continuous but there seem to be several car
makers (and street furniture makers that use ~100Hz at a guess).

People who see this as a problem are the same ones who don\'t get on with
walls full of TVs or large screen monitors at 60Hz refresh rates.

--
Regards,
Martin Brown

 

[Ricky]

On Friday, January 20, 2023 at 4:03:46 AM UTC-5, Martin Brown wrote:

On 20/01/2023 00:58, Ricky wrote:
On Thursday, January 19, 2023 at 5:31:57 PM UTC-5, bitrex wrote:
On 1/19/2023 5:20 PM, Ricky wrote:
On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex wrote:
On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars.
Everytime I move my line of view, they create a dozen spots of
light. When there are more than one it gets insane looking. Seems
like most people don\'t even see this. The first time it happened
to me I was trying to merge where there was no merge lane and the
ramp was coming from an angle, rather than merging while driving
parallel, so the rear view mirror didn\'t show anything useful. A
quick look over my shoulder showed one car passing me, just as I
needed to either go or stop. As I turned my head back, the tail
lights (those tall Cadillac tail lights) suddenly blossomed into
a dozen pairs of lights and I thought it was a bunch of cars! I
had to hit my brakes to avoid an accident, only to find there was
only the one car. Insane that they would create this sort of
hazard, even if everyone doesn\'t see it. It\'s the sort of thing
that would be changed on an airliner, after the first accident it
causes.

I\'ve never found out how rapid the blinking is.

I usually see those flashing brake light mods on street racer-type
cars around Providence RI, kids put them on their old Eclipse etc.
to make them look cool. I don\'t know that they\'re much improvement
over a regular high-level lamp at avoiding being rear-ended,
though.

We aren\'t talking about the same thing. I\'m talking about tail/brake
lights where the brightness is adjusted by PWM. It saves a few cents
by leaving off the inductor too smooth the waveform into a level.
The problem is that they PWM pulse them at a frequency that some people
can see in their peripheral vision (which is much more flicker
sensitive). I guess the engineers who designed it didn\'t think about
their choice of frequency too hard. Anything above about 300HZ frequency
would look pretty much continuous but there seem to be several car
makers (and street furniture makers that use ~100Hz at a guess).

People who see this as a problem are the same ones who don\'t get on with
walls full of TVs or large screen monitors at 60Hz refresh rates.

I think we are talking about different things. I don\'t \"see\" the flickering. I see the resulting pattern of images when my view changes, like the sign sticks you wave in the air to display text. I find it disturbing because when I\'m driving, my spidey sense is always watching the lights of other cars. When I move my eyes and the field of tail lights explodes from two or three cars, to a dozen, it is very disturbing. This has nothing to do with peripheral vision \"seeing\" the flicker.

They need to speed up the rate of flashing, so that this is not visible. It\'s interesting that not all cars do this. I first saw the flashing in a Cadillac some 20 years ago, or more. So, even today, either not all cars have LED taillights, or some car makers design them to not blink, or blink very fast so it is not observable. The difference in circuitry is very slight. Essentially it requires an inductor and capacitor and maybe a diode, to smooth the current rather than just blinking the LEDs. Or with two strings of LED, it requires two control circuits to set the brightness of each string.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[Martin Brown]

On 20/01/2023 09:18, Ricky wrote:

On Friday, January 20, 2023 at 4:03:46 AM UTC-5, Martin Brown wrote:
On 20/01/2023 00:58, Ricky wrote:
On Thursday, January 19, 2023 at 5:31:57 PM UTC-5, bitrex wrote:
On 1/19/2023 5:20 PM, Ricky wrote:
On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex
wrote:
On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars.
Everytime I move my line of view, they create a dozen spots
of light. When there are more than one it gets insane
looking. Seems like most people don\'t even see this. The
first time it happened to me I was trying to merge where
there was no merge lane and the ramp was coming from an
angle, rather than merging while driving parallel, so the
rear view mirror didn\'t show anything useful. A quick look
over my shoulder showed one car passing me, just as I needed
to either go or stop. As I turned my head back, the tail
lights (those tall Cadillac tail lights) suddenly blossomed
into a dozen pairs of lights and I thought it was a bunch of
cars! I had to hit my brakes to avoid an accident, only to
find there was only the one car. Insane that they would
create this sort of hazard, even if everyone doesn\'t see it.
It\'s the sort of thing that would be changed on an airliner,
after the first accident it causes.

I\'ve never found out how rapid the blinking is.

I usually see those flashing brake light mods on street
racer-type cars around Providence RI, kids put them on their
old Eclipse etc. to make them look cool. I don\'t know that
they\'re much improvement over a regular high-level lamp at
avoiding being rear-ended, though.

We aren\'t talking about the same thing. I\'m talking about
tail/brake lights where the brightness is adjusted by PWM. It
saves a few cents by leaving off the inductor too smooth the
waveform into a level.
The problem is that they PWM pulse them at a frequency that some
people can see in their peripheral vision (which is much more
flicker sensitive). I guess the engineers who designed it didn\'t
think about their choice of frequency too hard. Anything above
about 300HZ frequency would look pretty much continuous but there
seem to be several car makers (and street furniture makers that use
~100Hz at a guess).

People who see this as a problem are the same ones who don\'t get on
with walls full of TVs or large screen monitors at 60Hz refresh
rates.

I think we are talking about different things. I don\'t \"see\" the
flickering. I see the resulting pattern of images when my view
changes, like the sign sticks you wave in the air to display text. I
find it disturbing because when I\'m driving, my spidey sense is
always watching the lights of other cars. When I move my eyes and
the field of tail lights explodes from two or three cars, to a dozen,
it is very disturbing. This has nothing to do with peripheral vision
\"seeing\" the flicker.

It has everything to do with peripheral vision seeing the flicker. That
is why the LED light motif breaks up into several strobe flash images.

If the frequency was about 3 or 4x higher then they would overlap. FWIW
I do see some of them flicker in my peripheral vision and with those
slower ones the flash images are further apart. It is the eye cadence
movements that make them so prominent after dark.

They need to speed up the rate of flashing, so that this is not
visible. It\'s interesting that not all cars do this. I first saw
the flashing in a Cadillac some 20 years ago, or more. So, even
today, either not all cars have LED taillights, or some car makers
design them to not blink, or blink very fast so it is not observable.

I agree - increase the frequency and it would smear them out and look
much more like a continuous light source. They can be very distracting.

It seems unlikely to me that they had leds bright enough for automotive
indicators 20 years ago. The breakthrough in high efficiency LEDs was
later than that. The first ones I can recall seeing used in anger were
on motorway service vehicles for the \"please don\'t hit me\" yellow
warning lights. They had sophisticated optics in front of the emitter
which made them very strongly collimated beams that were bright from a
great distance but never dazzling when you got close to them.

The difference in circuitry is very slight. Essentially it requires
an inductor and capacitor and maybe a diode, to smooth the current
rather than just blinking the LEDs. Or with two strings of LED, it
requires two control circuits to set the brightness of each string.

It would be good enough to just up the frequency by a factor of 5x - it
isn\'t like they are even close to losing efficiency by switching losses
at what are essentially audio frequencies. I guess they don\'t see it as
a problem since plenty of automakers have exactly the same fault.

--
Regards,
Martin Brown

 

[Clive Arthur]

On 20/01/2023 09:51, Martin Brown wrote:

<snip>

It has everything to do with peripheral vision seeing the flicker. That
is why the LED light motif breaks up into several strobe flash images.

What Ricky\'s talking about is when you sweep your eyes eg left to right
and see a line of red dots, rather than a smudged single line as you
would with an incandescent lamp. Particularly noticeable in the dark of
course.

Many years ago I diagnosed a faulty instrument without looking inside
because I noticed the power-on LED was showing this effect and it was
supposed to run from a DC rail supplied from the mains via transformer,
rectifier and reservoir capacitor. The capacitor had become
disconnected. The service engineer was mightily impressed - \"Clive can
see 100Hz!\"

--
Cheers
Clive

 

[panteltje]

On a sunny day (Fri, 20 Jan 2023 10:25:32 +0000) it happened Clive Arthur
<clive@nowaytoday.co.uk> wrote in <tqdq6s$20t98$1@dont-email.me>:

On 20/01/2023 09:51, Martin Brown wrote:

snip

It has everything to do with peripheral vision seeing the flicker. That
is why the LED light motif breaks up into several strobe flash images.

What Ricky\'s talking about is when you sweep your eyes eg left to right
and see a line of red dots, rather than a smudged single line as you
would with an incandescent lamp. Particularly noticeable in the dark of
course.

Many years ago I diagnosed a faulty instrument without looking inside
because I noticed the power-on LED was showing this effect and it was
supposed to run from a DC rail supplied from the mains via transformer,
rectifier and reservoir capacitor. The capacitor had become
disconnected. The service engineer was mightily impressed - \"Clive can
see 100Hz!\"

I have used the effect many times to its advantage:
http://panteltje.com/panteltje/pic/sign_pic/

and here:
http://panteltje.com/panteltje/quadcopter/hsign.html

The eye and both a camera with sufficient long exposure seem to be able to see the dots.
my Sony superhad video smeared it out though (second link)
They should really run the lights with DC.

My cheap satellite receiver 7 segment channel indicator has the same problem if I move my view fast.

Indeed one day something will go wrong and you get legislation to fix this..
Long time ago I proposed here something like the first link on the side of your car for advertising...

 

[Ricky]

On Friday, January 20, 2023 at 4:52:14 AM UTC-5, Martin Brown wrote:

On 20/01/2023 09:18, Ricky wrote:
On Friday, January 20, 2023 at 4:03:46 AM UTC-5, Martin Brown wrote:
On 20/01/2023 00:58, Ricky wrote:
On Thursday, January 19, 2023 at 5:31:57 PM UTC-5, bitrex wrote:
On 1/19/2023 5:20 PM, Ricky wrote:
On Thursday, January 19, 2023 at 4:45:52 PM UTC-5, bitrex
wrote:
On 12/27/2022 11:39 AM, John Larkin wrote:
On Tue, 27 Dec 2022 15:47:22 +0000, Martin Brown
\'\'\'newspam\'\'\'@nonad.co.uk> wrote:

On 26/12/2022 17:16, Ricky wrote:
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.

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.

Especially when they start blinking

I can\'t stand the fast blinking LED tail lights on cars.
Everytime I move my line of view, they create a dozen spots
of light. When there are more than one it gets insane
looking. Seems like most people don\'t even see this. The
first time it happened to me I was trying to merge where
there was no merge lane and the ramp was coming from an
angle, rather than merging while driving parallel, so the
rear view mirror didn\'t show anything useful. A quick look
over my shoulder showed one car passing me, just as I needed
to either go or stop. As I turned my head back, the tail
lights (those tall Cadillac tail lights) suddenly blossomed
into a dozen pairs of lights and I thought it was a bunch of
cars! I had to hit my brakes to avoid an accident, only to
find there was only the one car. Insane that they would
create this sort of hazard, even if everyone doesn\'t see it.
It\'s the sort of thing that would be changed on an airliner,
after the first accident it causes.

I\'ve never found out how rapid the blinking is.

I usually see those flashing brake light mods on street
racer-type cars around Providence RI, kids put them on their
old Eclipse etc. to make them look cool. I don\'t know that
they\'re much improvement over a regular high-level lamp at
avoiding being rear-ended, though.

We aren\'t talking about the same thing. I\'m talking about
tail/brake lights where the brightness is adjusted by PWM. It
saves a few cents by leaving off the inductor too smooth the
waveform into a level.
The problem is that they PWM pulse them at a frequency that some
people can see in their peripheral vision (which is much more
flicker sensitive). I guess the engineers who designed it didn\'t
think about their choice of frequency too hard. Anything above
about 300HZ frequency would look pretty much continuous but there
seem to be several car makers (and street furniture makers that use
~100Hz at a guess).

People who see this as a problem are the same ones who don\'t get on
with walls full of TVs or large screen monitors at 60Hz refresh
rates.

I think we are talking about different things. I don\'t \"see\" the
flickering. I see the resulting pattern of images when my view
changes, like the sign sticks you wave in the air to display text. I
find it disturbing because when I\'m driving, my spidey sense is
always watching the lights of other cars. When I move my eyes and
the field of tail lights explodes from two or three cars, to a dozen,
it is very disturbing. This has nothing to do with peripheral vision
\"seeing\" the flicker.
It has everything to do with peripheral vision seeing the flicker. That
is why the LED light motif breaks up into several strobe flash images.

Sometimes I think you literally can\'t understand the written word. I am the guy experiencing the issue, yet you are telling me what I saw. It was looking straight at the object and moving my eyes a small amount. Any amount of movement creates the separate images of the flickering light. This is not a matter of peripheral vision.

If the frequency was about 3 or 4x higher then they would overlap. FWIW
I do see some of them flicker in my peripheral vision and with those
slower ones the flash images are further apart. It is the eye cadence
movements that make them so prominent after dark.

They need to speed up the rate of flashing, so that this is not
visible. It\'s interesting that not all cars do this. I first saw
the flashing in a Cadillac some 20 years ago, or more. So, even
today, either not all cars have LED taillights, or some car makers
design them to not blink, or blink very fast so it is not observable.
I agree - increase the frequency and it would smear them out and look
much more like a continuous light source. They can be very distracting.

It seems unlikely to me that they had leds bright enough for automotive
indicators 20 years ago.

Talk to Cadillac. You are aware that a tail light is only red, and you can use a large number of LEDs, no?

The breakthrough in high efficiency LEDs was
later than that. The first ones I can recall seeing used in anger were
on motorway service vehicles for the \"please don\'t hit me\" yellow
warning lights. They had sophisticated optics in front of the emitter
which made them very strongly collimated beams that were bright from a
great distance but never dazzling when you got close to them.
The difference in circuitry is very slight. Essentially it requires
an inductor and capacitor and maybe a diode, to smooth the current
rather than just blinking the LEDs. Or with two strings of LED, it
requires two control circuits to set the brightness of each string.
It would be good enough to just up the frequency by a factor of 5x - it
isn\'t like they are even close to losing efficiency by switching losses
at what are essentially audio frequencies. I guess they don\'t see it as
a problem since plenty of automakers have exactly the same fault.

If you say so.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Clive Arthur]

On 20/01/2023 10:49, panteltje wrote:

<snip>

I have used the effect many times to its advantage:
http://panteltje.com/panteltje/pic/sign_pic/

and here:
http://panteltje.com/panteltje/quadcopter/hsign.html

The eye and both a camera with sufficient long exposure seem to be able to see the dots.
my Sony superhad video smeared it out though (second link)
They should really run the lights with DC.

I made one of those, also on Veroboard, though mine had 16 red LEDs. I
had the idea of mounting it on a rear windscreen wiper to send polite
and friendly messages to the car behind. Then I got a proper job.

--
Cheers
Clive

 

[Carlos E.R.]

On 2022-12-26 19:49, Sjouke Burry wrote:

On 26.12.22 18:16, Ricky wrote:
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.

I assume that high efficiency means more light for less watts.

--
Cheers, Carlos.