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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? -- *When I'm not in my right mind, my left mind gets pretty crowded * Dave Plowman London SW To e-mail, change noise into sound. |
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. |
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. |
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. |
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 |
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 |
Dimming an LED
"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. |
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 -- Please don't feed the trolls |
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. -- Cheers, Rob |
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... |
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. 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". -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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 -- Please don't feed the trolls |
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. |
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 -- Cheers Clive |
Lonely Obnoxious Cantankerous Auto-contradicting Senile Ozzie Troll Alert!
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Speed, the auto-contradicting senile sociopath, blabbered, again: FLUSH the trolling senile asshole's latest troll**** unread |
More Improvised Bullshit by the Resident Senile Troll
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Lonely Obnoxious Cantankerous Auto-contradicting Senile Ozzie Troll Alert!
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Speed, the auto-contradicting senile sociopath, blabbered, again: FLUSH more of the trolling senile asshole's latest troll**** unread -- Website (from 2007) dedicated to the 86-year-old senile Australian cretin's pathological trolling: https://www.pcreview.co.uk/threads/r...d-faq.2973853/ |
Dimming an LED
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. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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. -- *When a clock is hungry it goes back four seconds* Dave Plowman London SW To e-mail, change noise into sound. |
Dimming an LED
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. |
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 |
Dimming an LED
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. -- Max Demian |
Dimming an LED
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 -- Please don't feed the trolls |
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? 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 -- Max Demian |
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 -- Please don't feed the trolls |
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. |
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. |
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. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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 |
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" |
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. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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. -- Max Demian |
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 |
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 |
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 -- Please don't feed the trolls |
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 -- Please don't feed the trolls |
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. |
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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