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I haven't found an LED yet that works in my dimmable ceiling fixture, where I can dim it to the lowest possible level and get a pleasing light. The incandescent

I haven't found an LED yet that works in my dimmable ceiling fixture, where I can dim it to the lowest possible level and get a pleasing light. The incandescent gives a very dim, warm orange glow which is great for movie watching or other mood-setting purposes. The LED still emits a rather harsh and not-as-dim light even if it's rated in the warm spectrum. Have you seen a solution for that?

gowld 9y ago
LEDs are terrible with dimmers. They flicker, and they have bad response curves to the dim-level. Yes, there exist properly dimmable LEDs, but buying 5 different bulbs to find one that works negates the savings.
- amluto 9y ago
  This isn't the LED's fault. It's the fault of the fact that dimmers are awful designs. They feed a nasty chopped-up waveform to the fixture that has RMS voltage proportional to the desired power output. Aside from the fact that it has a bad power factor, it's more or less okay for plain old line voltage incandescent lights. For LEDs, several things go wrong. First, LEDs want DC or high frequency PWM. The driver is given a nasty waveform at 60 Hz. So the driver needs to rectify that waveform to DC, filter it, and then decode the waveform to dim the LED as the user requested. This is a big hack and doesn't work all that well. Second, modern power supplies aren't resistors. Supplying them with input power with rapid voltage swings is not so great. Third, the dimmers themselves are usually wired in series with the bulb without access to a neutral wire, and incandescent dimmers expect to draw their own power using current through the bulb. Given that LED drivers are highly nonlinear, this makes it very awkward for the dimmer to power itself. "Dimmable" LEDs will intentionally leak some current to power their dimmers. High-end dimmers in newer homes will have a neutral connection. If you can find a "ELV" or "reverse phase" dimmer and you have the wiring for it, you can at least avoid the inrush current problem. An anecdote: I have a fancy computer power supply that buzzes rather loudly when the lights are on. This is presumably because the lights are drawing a big inrush current spike 120 times per seconds due to dimming. To top it off, LEDs have much higher frequency response than incandescent bulbs. This means that, unless you drive them with clean DC or with a very high-frequency PWM input, they'll flicker. (Not the kind of flicker you're talking about -- the kind you're seeing is the system malfunctioning. I'm talking about the kind where it flickers as designed and someone waved their fingers and decided it was hard to notice.) There's a new standard called IEEE 1789 that describes what levels of flicker are likely to be harmful (causing low productivity, headaches, general crappy feelings, etc.) and what levels are very likely to be safe. Very few LED drivers meet this standard so far. At least California has imposed a less stringent but still helpful for Title 24 compliance [1] for the last couple of years. (This is extra nasty given that incandescent bulbs don't actually produce light proportional to the power with which they're driven.) [1] It's Title 24 JA8.
  - gowld 9y ago
    Ok, but the dimmers worked fine with the incandescents. Your post gives a lot of reasons why the high-efficiency of LEDs comes at a cost of lower flexibility to adapt to important use cases.
burntwater 9y ago
I believe some fixtures solve this by having two sets of LEDs; as you dim down the standard LEDs, the low-level LEDs kick in. I've seen that in a few theatrical/architectural lights, no idea if it's available in the consumer market yet.
kalleboo 9y ago
For our hallway, rather than buying an LED lamp that's compatible with a dimmer, we bought one with built-in dimming. You flip the wall switch twice and it goes into a dim warm orange "nightlight" mode. Flip it twice again and it goes into full brightness daytime mode.

gowld 9y ago

LEDs are terrible with dimmers. They flicker, and they have bad response curves to the dim-level. Yes, there exist properly dimmable LEDs, but buying 5 different bulbs to find one that works negates the savings.

amluto 9y ago
This isn't the LED's fault. It's the fault of the fact that dimmers are awful designs. They feed a nasty chopped-up waveform to the fixture that has RMS voltage proportional to the desired power output. Aside from the fact that it has a bad power factor, it's more or less okay for plain old line voltage incandescent lights. For LEDs, several things go wrong. First, LEDs want DC or high frequency PWM. The driver is given a nasty waveform at 60 Hz. So the driver needs to rectify that waveform to DC, filter it, and then decode the waveform to dim the LED as the user requested. This is a big hack and doesn't work all that well. Second, modern power supplies aren't resistors. Supplying them with input power with rapid voltage swings is not so great. Third, the dimmers themselves are usually wired in series with the bulb without access to a neutral wire, and incandescent dimmers expect to draw their own power using current through the bulb. Given that LED drivers are highly nonlinear, this makes it very awkward for the dimmer to power itself. "Dimmable" LEDs will intentionally leak some current to power their dimmers. High-end dimmers in newer homes will have a neutral connection. If you can find a "ELV" or "reverse phase" dimmer and you have the wiring for it, you can at least avoid the inrush current problem. An anecdote: I have a fancy computer power supply that buzzes rather loudly when the lights are on. This is presumably because the lights are drawing a big inrush current spike 120 times per seconds due to dimming. To top it off, LEDs have much higher frequency response than incandescent bulbs. This means that, unless you drive them with clean DC or with a very high-frequency PWM input, they'll flicker. (Not the kind of flicker you're talking about -- the kind you're seeing is the system malfunctioning. I'm talking about the kind where it flickers as designed and someone waved their fingers and decided it was hard to notice.) There's a new standard called IEEE 1789 that describes what levels of flicker are likely to be harmful (causing low productivity, headaches, general crappy feelings, etc.) and what levels are very likely to be safe. Very few LED drivers meet this standard so far. At least California has imposed a less stringent but still helpful for Title 24 compliance [1] for the last couple of years. (This is extra nasty given that incandescent bulbs don't actually produce light proportional to the power with which they're driven.) [1] It's Title 24 JA8.
- gowld 9y ago
  Ok, but the dimmers worked fine with the incandescents. Your post gives a lot of reasons why the high-efficiency of LEDs comes at a cost of lower flexibility to adapt to important use cases.

burntwater 9y ago

I believe some fixtures solve this by having two sets of LEDs; as you dim down the standard LEDs, the low-level LEDs kick in. I've seen that in a few theatrical/architectural lights, no idea if it's available in the consumer market yet.

kalleboo 9y ago

For our hallway, rather than buying an LED lamp that's compatible with a dimmer, we bought one with built-in dimming. You flip the wall switch twice and it goes into a dim warm orange "nightlight" mode. Flip it twice again and it goes into full brightness daytime mode.