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Default Dimming an LED

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?

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Default Dimming an LED

On Wed, 28 Apr 2021 00:14:26 +0100, "Dave Plowman (News)"
wrote:

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


In the early days of pocket calculators, the red LEDs they used were
pulsed in order to extend the battery life, so I can guess from that
much alone what the answer is.
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Default Dimming an LED



"Dave Plowman (News)" wrote in message
...
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.


So how about LEDs? Since they generate far less
heat are they still as efficient when dimmed?


Yes, better actually.

And does dimming make a difference to their life?


With the brightest most heavily driven ones, yep.

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Default Dimming an LED



"Cursitor Doom" wrote in message
...
On Wed, 28 Apr 2021 00:14:26 +0100, "Dave Plowman (News)"
wrote:

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


In the early days of pocket calculators, the red LEDs they
used were pulsed in order to extend the battery life,


Nope, to make them brighter.

so I can guess from that much alone what the answer is.


Fraid not.

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Default Dimming an LED

On 28/04/2021 00:51, Cursitor Doom wrote:
On Wed, 28 Apr 2021 00:14:26 +0100, "Dave Plowman (News)"
wrote:

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


In the early days of pocket calculators, the red LEDs they used were
pulsed in order to extend the battery life, so I can guess from that
much alone what the answer is.


That was generally a consequence to reducing the Chip IO to drive the
LEDs in a matrix scheme with column and row multiplexing.
https://docs.broadcom.com/doc/AV02-3697EN

I was under the impression that pulsing an LED would increase heat and
lower efficiency, as the voltage across the LED would be higher during
the pulse, leading to greater heat.

Many LEDs lose efficiency at high currents. This is one discussion on
the effects:

https://electronics.stackexchange.co...ent-brightness


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Default Dimming an LED

Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


"The Inconsistency of Dimmers with LED Lamps"
Doug Lindsey, Electric Power Research Institute
Frank Sharp, Electric Power Research Institute
Teren Abear, Southern California Edison

https://www.aceee.org/files/proceedi...pers/1_154.pdf

Page9 Figure 4. Efficacy curves for all lamps with Dimmer 1

*******

It stands to reason, there's a reduction in bulb temperature
at low settings, which would have some impact on SMPS life.

For the LEDs, the model is less clear. The paper itself isn't worth
much, except it throws shade on using plain Arrhenius modeling
and accelerated life testing. We could probably say that Arrhenius
isn't dead, and a cooler LED last longer. But real life is
apparently not as nice as theory.

https://www.prognostics.umd.edu/calc...ity_review.pdf

The Arrhenius model... is not adequate to represent the failures of LEDs.
Light output degradation is the major failure mode of LEDs, and it
results from hygro-mechanical and electrical stresses in addition
to thermal stresses. A more realistic method of LED lifetime estimation
is required that reflects total consideration of temperature,
the level of forward current, relative humidity, mechanical
stress, and materials.

With PWM control, the current is delivered in constant amplitude pulses
(this prevents colour shift), but the temperature will drop due to the
reduction in average power.

It doesn't do much to explain how the first generation of
bulbs promised 25000 hours and now there are some 10000 hour bulbs.
Shades of past cartels ? :-) Well, everything is engineered
within an inch of death, so why should a lowly LED lightbulb
be spared such treatments ? If my car real axle only has 10%
margin, when 70 years ago there was 300% load margin, who
is the wiser ? No one will ever know. Some old timers will
look under a car and marvel at the spindly axle used. A car
executive had a larger steak dinner tonight because of that,
making the choice well worth it.

https://spectrum.ieee.org/tech-histo...ulb-conspiracy

Paul
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"Paul" wrote in message
...
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


"The Inconsistency of Dimmers with LED Lamps"
Doug Lindsey, Electric Power Research Institute
Frank Sharp, Electric Power Research Institute
Teren Abear, Southern California Edison

https://www.aceee.org/files/proceedi...pers/1_154.pdf

Page9 Figure 4. Efficacy curves for all lamps with Dimmer 1

*******

It stands to reason, there's a reduction in bulb temperature
at low settings, which would have some impact on SMPS life.

For the LEDs, the model is less clear. The paper itself isn't worth
much, except it throws shade on using plain Arrhenius modeling
and accelerated life testing. We could probably say that Arrhenius
isn't dead, and a cooler LED last longer. But real life is
apparently not as nice as theory.

https://www.prognostics.umd.edu/calc...ity_review.pdf

The Arrhenius model... is not adequate to represent the failures of
LEDs.
Light output degradation is the major failure mode of LEDs, and it
results from hygro-mechanical and electrical stresses in addition
to thermal stresses. A more realistic method of LED lifetime estimation
is required that reflects total consideration of temperature,
the level of forward current, relative humidity, mechanical
stress, and materials.

With PWM control, the current is delivered in constant amplitude pulses
(this prevents colour shift), but the temperature will drop due to the
reduction in average power.

It doesn't do much to explain how the first generation of
bulbs promised 25000 hours and now there are some 10000 hour bulbs.
Shades of past cartels ? :-)


Well, everything is engineered within an inch of death,


Plenty isnt, most obviously with drinking
glasses, stainless steel cutlery etc etc etc.

so why should a lowly LED lightbulb be spared such treatments ?


Because there isnt necessarily anything to gain for
the manufacturer doing that with a led light bulb.

If my car real axle only has 10% margin, when 70 years ago there was 300%
load margin, who is the wiser ?


In fact modern cars last a lot longer than they did 70 years ago.

No one will ever know. Some old timers will look under a car and marvel at
the spindly axle used. A car executive had a larger steak dinner tonight
because of that, making the choice well worth it.


https://spectrum.ieee.org/tech-histo...ulb-conspiracy


Doesn't apply to leds.

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Default Dimming an LED

Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.

Tim

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Default Dimming an LED

On 28 Apr 2021 at 00:14:26 BST, ""Dave Plowman" News)"
wrote:

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed?


At a guess, if they stay as warm, pretty much, although light as a proportion
of heat is less. If the fitting gets cooler as you dim, then I'd say yes, the
efficiency is fairly linear.

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Default Dimming an LED

Tim+ wrote:

Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Plenty of lamps now use both cold and warm LEDs, and can smoothly change
colour temperature (e.g the ikea ones between 2200 and 4000K)

Controlling those from a "hub" I can have a wake-up routine that fades
up the brightness and colour temperature together.

I'd be surprised if someone doesn't make a lamp that does the same by
itself...


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On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Some do IME. I used some of these:

https://cpc.farnell.com/philips-ligh...b38/dp/LP10204

I found that they dim in a very "tungsten" way - i.e. the colour temp
falls smoothly as they dim, and the dimming range is very wide - going
down to close to "barely glowing".


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John.

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Default Dimming an LED

On 28/04/2021 00:14, Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


The life of the dropper circuitry in the lamp will be extended by lower
temperatures, and possibly the life of the LEDs themselves by being run
less "hard". However its often the former that kills the lamp rather
than the latter.


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John.

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Default Dimming an LED

John Rumm wrote:
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Some do IME. I used some of these:

https://cpc.farnell.com/philips-ligh...b38/dp/LP10204

I found that they dim in a very "tungsten" way - i.e. the colour temp
falls smoothly as they dim, and the dimming range is very wide - going
down to close to "barely glowing".



Thanks. Whats the key search term to make sure I get the right ones? I
could do with some candle bulbs with standard bayonet fittings.

Tim

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Default Dimming an LED

Tim+ explained on 28/04/2021 :
Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


I only have two on dimmers, all the way from full on to out. The colour
remains the same irrespective of brightness setting, but I don't have
any issue with that at all. Contrast that with tungsten, which becomes
more yellow/red as it is dimmed.
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Default Dimming an LED

On 28/04/2021 00:14, Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Any effect is small compared to incandescent where it's huge, and it
depends how hard you're driving the LEDs in the first place.

Philips has produced some mains LEDs which are claimed to be more
efficient and longer lasting mostly by increasing the number of LED chip
and running them at a lower power per chip. Obviously this costs more.

https://www.mea.lighting.philips.com...mer/dubai-lamp

and Big Clive...
https://www.youtube.com/watch?v=AM2DMuryw_A

'philips dubai led' for Googling

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Cheers
Clive


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On 28/04/2021 08:18, Tim+ wrote:
John Rumm wrote:
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Some do IME. I used some of these:

https://cpc.farnell.com/philips-ligh...b38/dp/LP10204

I found that they dim in a very "tungsten" way - i.e. the colour temp
falls smoothly as they dim, and the dimming range is very wide - going
down to close to "barely glowing".



Thanks. Whats the key search term to make sure I get the right ones? I
could do with some candle bulbs with standard bayonet fittings.


Not sure if there is a key search term, I just know that that particular
one I linked to behaves in that way. There is a reasonable chance that
other lamps in the same range may behave like that.


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John.

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Default Dimming an LED

In article
,
Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, I‘ve
decided I‘m going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


I was forced into going LED in the kitchen. The design of tungsten lamp
being NLA. Basically a 100mm globe lamp in a shade above the table, which
I liked the look of. Did find an expensive LED which looks much the same,
but that also required a new dimmer (one of 3) so decided to replace the
other two tungsten circuits which light the worktops via downlighters with
LED too. And they were PAR 25, and difficult to find LEDS for them too,
but eventually did. Total cost about Ł150. I've now got used to the
colour temperature staying the same when dimmed and don't mind it. As I
already had dimming florries as under cupboard lighting, and they keep the
same colour temp when dimmed.

--
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Dave Plowman London SW
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Dave Plowman wrote:

I already had dimming florries as under cupboard lighting, and they
keep the same colour temp when dimmed.

I had a rather odd-ball CFL with internal dimmer, it went a pinkish
colour when dimmed very low.
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Default Dimming an LED

John Rumm wrote:
On 28/04/2021 08:18, Tim+ wrote:
John Rumm wrote:
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half
brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their
life?


Until they can make the colour temperature of LEDs drop as they dim,
Ive
decided Im going to just avoid using dimmers with LEDs as the just
look
ghastly as the dim IMO.

Some do IME. I used some of these:

https://cpc.farnell.com/philips-ligh...b38/dp/LP10204


I found that they dim in a very "tungsten" way - i.e. the colour temp
falls smoothly as they dim, and the dimming range is very wide - going
down to close to "barely glowing".



Thanks. Whats the key search term to make sure I get the right ones? I
could do with some candle bulbs with standard bayonet fittings.


Not sure if there is a key search term, I just know that that particular
one I linked to behaves in that way. There is a reasonable chance that
other lamps in the same range may behave like that.


Enter the fitting name plus "2200-2700K" to
catch the adjusted mixing. Throw in a
"dimming" or "dimmable".

The "2200-2700K" is what stood out in the available data.
A regular bulb won't be stated that way.

Paul

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On 28/04/2021 05:39, Paul wrote:

https://spectrum.ieee.org/tech-histo...ulb-conspiracy


Yes, I think originally incandescent lamps (tungsten I assume) had a
lifespan of about 2500 hours, but (in 1925) they reduced it to 1000.

In the 1970s they started selling "double life" lamps that lasted 2000
hours (at a slight reduction in efficiency as they operated at a lower
temperature), but they never caught on as the standard ones were heavily
discounted, presumably due to volume production.

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Harry Bloomfield, Esq. wrote:
Tim+ explained on 28/04/2021 :
Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


I only have two on dimmers, all the way from full on to out. The colour
remains the same irrespective of brightness setting, but I don't have
any issue with that at all. Contrast that with tungsten, which becomes
more yellow/red as it is dimmed.


Which is exactly the effect I want when I dim a light. It creates a
€śwarmer€ť or €ścosier€ť atmosphere. Straight dimming of an ordinary LED just
make a room look cold and dingy.

Tim

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On 28/04/2021 00:14, Dave Plowman (News) wrote:

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Increase it a bit I would have thought. Of course you've got to dim it
using PWM (from DC) or trailing edge (AC).

(I've seen idiot YouTube videos describing circuits that control LEDs
with potentiometers, either directly or via a power transistor; it's
inefficient and liable to overheat the pot and/or the transistor as some
of the comments say; also I think that controlling white LEDs in this
way is liable to change the colour of the light.)

Idiot YouTubes:
https://www.youtube.com/watch?v=wns8xrxTYhU
https://www.youtube.com/watch?v=OnjNXhxxc9w

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Default Dimming an LED

John Rumm wrote:
On 28/04/2021 08:18, Tim+ wrote:
John Rumm wrote:
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.

Some do IME. I used some of these:

https://cpc.farnell.com/philips-ligh...b38/dp/LP10204

I found that they dim in a very "tungsten" way - i.e. the colour temp
falls smoothly as they dim, and the dimming range is very wide - going
down to close to "barely glowing".



Thanks. Whats the key search term to make sure I get the right ones? I
could do with some candle bulbs with standard bayonet fittings.


Not sure if there is a key search term, I just know that that particular
one I linked to behaves in that way. There is a reasonable chance that
other lamps in the same range may behave like that.



Thanks again. I found the bayonet version that I wanted and was about to
order 5 for a ceiling light in our sitting room but then remembered that we
only ever turn the light on when we first enter the room. After that we
use a desk & standard lamp (both LED) with another standard lamp if we
need more light.

I reckoned in terms of ROI Id probably have to live to 150 to make
swapping all the bulbs worthwhile. ;-)

Still, nice to know such bulbs exist and who makes them for future
reference as Ive got some G9 fittings that need replacing in our dining
room and I would like a dimmable overhead light here.

Tim

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Default Dimming an LED

"Tim+" wrote in message
...
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Why would you want the colour temperature of an LED to drop as it is dimmed?
I know it is an unavoidable side-effect of dimming a tungsten bulb, but I
don't see why you would want it to happen unless you couldn't avoid it. I
like the fact that LEDs keep the same colour as they dim. I just wish LED
bulbs could be dimmed further: most bulbs (eg Philips Hue) have a minimum
brightness below which they go out altogether. It makes them less useful as
a very dim night light.

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Default Dimming an LED

Paul wrote:

The "2200-2700K" is what stood out in the available data.
A regular bulb won't be stated that way.


But that might just get you a bulb that can be toggled between cool and
warm white.

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Default Dimming an LED

On 28/04/2021 12:06, Andy Burns wrote:
Paul wrote:

The "2200-2700K" is what stood out in the available data.
A regular bulb won't be stated that way.


But that might just get you a bulb that can be toggled between cool and
warm white.


except cool would normally be in excess of 3500K. 2200K is a very warm
white.


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John.

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Default Dimming an LED

Max Demian wrote:
On 28/04/2021 00:14, Dave Plowman (News) wrote:

Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Increase it a bit I would have thought. Of course you've got to dim it
using PWM (from DC) or trailing edge (AC).

(I've seen idiot YouTube videos describing circuits that control LEDs
with potentiometers, either directly or via a power transistor; it's
inefficient and liable to overheat the pot and/or the transistor as some
of the comments say; also I think that controlling white LEDs in this
way is liable to change the colour of the light.)

Idiot YouTubes:
https://www.youtube.com/watch?v=wns8xrxTYhU
https://www.youtube.com/watch?v=OnjNXhxxc9w


This depends on the situation.

The beauty of design, is keeping an open mind.

Paul


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Default Dimming an LED

John Rumm wrote:

Andy Burns wrote:

Paul wrote:

The "2200-2700K" is what stood out in the available data.
A regular bulb won't be stated that way.


But that might just get you a bulb that can be toggled between cool
and warm white.


except cool would normally be in excess of 3500K. 2200K is a very warm
white.


yes, well, the ikea ones are fairly limited too, 4400K I think is
"moonlight" I'd prefer they went higher, and 2200K is "candlelight"
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Default Dimming an LED

On 28/04/2021 11:49, Tim+ wrote:
John Rumm wrote:
On 28/04/2021 08:18, Tim+ wrote:
John Rumm wrote:
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.

Some do IME. I used some of these:

https://cpc.farnell.com/philips-ligh...b38/dp/LP10204

I found that they dim in a very "tungsten" way - i.e. the colour temp
falls smoothly as they dim, and the dimming range is very wide - going
down to close to "barely glowing".



Thanks. Whats the key search term to make sure I get the right ones? I
could do with some candle bulbs with standard bayonet fittings.


Not sure if there is a key search term, I just know that that particular
one I linked to behaves in that way. There is a reasonable chance that
other lamps in the same range may behave like that.



Thanks again. I found the bayonet version that I wanted and was about to
order 5 for a ceiling light in our sitting room but then remembered that we
only ever turn the light on when we first enter the room. After that we
use a desk & standard lamp (both LED) with another standard lamp if we
need more light.

I reckoned in terms of ROI Id probably have to live to 150 to make
swapping all the bulbs worthwhile. ;-)


Well you could buy one, swap it one when a bulb goes, then rinse and
repeat. Hopefully there comes a time where you don't need to swap them
again for a very long time. So you get a convenience payback as well as
energy reduction :-)

Still, nice to know such bulbs exist and who makes them for future
reference as Ive got some G9 fittings that need replacing in our dining
room and I would like a dimmable overhead light here.


I have found the only real way to find decent lamps where there is a
very specific use case, is to just buy the odd one on spec now and then
and see how it performs.

That Philips one I go particularly because I wanted a dimmable that
could project a bit of light upwards when installed in a cap down
fitting - to get a bit more diffuse bounce back off the white ceiling.
So the dimming range and colour temp shift came as a pleasant surprise.
I replaced the other 7 to match in the end.


--
Cheers,

John.

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Default Dimming an LED

On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:


Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


So you want an LED that behaves like an incandescent? Bit like wanting
CDs to have scratches recorded on them!

The only time I miss the change in colour of incandescents is LED
torches which get dimmer and dimmer without it being obvious that the
batteries are depleted.

--
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Default Dimming an LED

On 28/04/2021 11:58, NY wrote:
"Tim+" wrote in message
...


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Why would you want the colour temperature of an LED to drop as it is
dimmed? I know it is an unavoidable side-effect of dimming a tungsten
bulb, but I don't see why you would want it to happen unless you
couldn't avoid it. I like the fact that LEDs keep the same colour as
they dim. I just wish LED bulbs could be dimmed further: most bulbs (eg
Philips Hue) have a minimum brightness below which they go out
altogether. It makes them less useful as a very dim night light.


It's hard to tell if an LED torch battery is getting flat as they just
get dimmer without the tell tale yellow effect.

--
Max Demian
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Default Dimming an LED

On 28/04/2021 13:13, Paul wrote:
Max Demian wrote:


(I've seen idiot YouTube videos describing circuits that control LEDs
with potentiometers, either directly or via a power transistor; it's
inefficient and liable to overheat the pot and/or the transistor as
some of the comments say; also I think that controlling white LEDs in
this way is liable to change the colour of the light.)

Idiot YouTubes:
https://www.youtube.com/watch?v=wns8xrxTYhU
https://www.youtube.com/watch?v=OnjNXhxxc9w


This depends on the situation.

The beauty of design, is keeping an open mind.


It's a matter of whether you like economy and dislike smoke arising from
the circuit.

--
Max Demian


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Default Dimming an LED

NY wrote:
"Tim+" wrote in message
...
Dave Plowman (News) wrote:
Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Why would you want the colour temperature of an LED to drop as it is dimmed?


Which bit of €śthey look ghastly€ť did you fail to understand, or does your
opinion someway trump my opinion?

If you like cold dim light fine, I dont.

Tim

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Default Dimming an LED

Max Demian wrote:
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:


Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


So you want an LED that behaves like an incandescent?


Yes. Why is that so hard to understand?

Bit like wanting
CDs to have scratches recorded on them!


Not in the slightest. LED bulbs are replacing incandescent bulbs which
have always got €śwarmer€ť as they are dimmed. I like this, I dont regard
it as a €śfault€ť but a feature that Im used to and like. Its often why I
use a dimmer, to create a lower but warmer level of light for the ambience.

Tim

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Default Dimming an LED



"Max Demian" wrote in message
...
On 28/04/2021 07:35, Tim+ wrote:
Dave Plowman (News) wrote:


Think it's generally known that dimming a tungsten bulb reduced its
efficiency dramatically. In other words, a 100w dimmed to half
brightness
used a lot more electricity than a 50w on full. Although dimming did
extend the life of the bulb.

So how about LEDs? Since they generate far less heat are they still as
efficient when dimmed? And does dimming make a difference to their life?


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


So you want an LED that behaves like an incandescent? Bit like wanting CDs
to have scratches recorded on them!

The only time I miss the change in colour of incandescents is LED torches
which get dimmer and dimmer without it being obvious that the batteries
are depleted.


My led torches from Aldi still behave like that.

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Default Dimming an LED



"Max Demian" wrote in message
o.uk...
On 28/04/2021 11:58, NY wrote:
"Tim+" wrote in message
...


Until they can make the colour temperature of LEDs drop as they dim, Ive
decided Im going to just avoid using dimmers with LEDs as the just look
ghastly as the dim IMO.


Why would you want the colour temperature of an LED to drop as it is
dimmed? I know it is an unavoidable side-effect of dimming a tungsten
bulb, but I don't see why you would want it to happen unless you couldn't
avoid it. I like the fact that LEDs keep the same colour as they dim. I
just wish LED bulbs could be dimmed further: most bulbs (eg Philips Hue)
have a minimum brightness below which they go out altogether. It makes
them less useful as a very dim night light.


It's hard to tell if an LED torch battery is getting flat as they just get
dimmer without the tell tale yellow effect.


I dont have any trouble seeing that it gets dimmer.

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