How come LEDs don't dim below 20 percent!
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DIWdiver
Flashlight Enthusiast
Some kinds of dimmers are hard to operate at low load (like an LED) and low settings. Your standard home-center lamp dimmer is like this. And some dimmer designers might choose not to go below a certain percentage.
PWM dimmers are not so limited. It should be easy for most PWM dimmers to go to 1% or less. I know some LED drivers claim as high as 3000:1 dimming ratios.
Most single-die or single-string LEDs can go to 1% or less on analog dimming. I've seen some go FAR below that.
However there are limits. It's well known that the spectral characteristics change as current changes. There's some debate about how significant this is with small changes in current, but there's little debate that as you get to extremes, it can be a substantial change. PWM dimming (done well) eliminates this issue.
In multi-string LEDs, e.g. a COB that has 10 strings of 10 dies, you may see the strings don't current balance well if you under-drive them substantially. This is more likely to be significant in "economy" LEDs than in name brands.
You may not care much about those, but here's a big one. Luminus specifies (or at least they used to) a minimum drive current that's more than 10% of the maximum drive current. I was informed that they could not guarantee that the LEDs would light correctly below that. I never completely bought into that, but it was pretty clear in their product literature, so pretty much a show-stopper for a professional design. This was important to me at the time because I was designing a driver for one of their LEDs that was intended to go below 10% on analog dimming. Maybe their lawyers made them say that because they saw one freaky die from a prototype batch a million years ago. Or maybe there is (was?) something more to it. I just don't know. That's the only manufacturer I've ever known to specify a minimum current for their LEDs.
With that said, there is (or at least can be) a minimum current below which an LED will suddenly stop emitting light. I have seen single strings of LEDs where some dies are emitting and others are not. In my case this occurred at EXTREMELY low currents - to the point where you had to dim the lights and get very close to tell which ones were on and which weren't. I suppose in deep darkness it would have been easy to tell, but I never tried that.
Lastly, in commercially available "LED bulbs" it's possible that they have internal drivers or similar circuitry that doesn't function well below some minimum dimming level.
PWM dimmers are not so limited. It should be easy for most PWM dimmers to go to 1% or less. I know some LED drivers claim as high as 3000:1 dimming ratios.
Most single-die or single-string LEDs can go to 1% or less on analog dimming. I've seen some go FAR below that.
However there are limits. It's well known that the spectral characteristics change as current changes. There's some debate about how significant this is with small changes in current, but there's little debate that as you get to extremes, it can be a substantial change. PWM dimming (done well) eliminates this issue.
In multi-string LEDs, e.g. a COB that has 10 strings of 10 dies, you may see the strings don't current balance well if you under-drive them substantially. This is more likely to be significant in "economy" LEDs than in name brands.
You may not care much about those, but here's a big one. Luminus specifies (or at least they used to) a minimum drive current that's more than 10% of the maximum drive current. I was informed that they could not guarantee that the LEDs would light correctly below that. I never completely bought into that, but it was pretty clear in their product literature, so pretty much a show-stopper for a professional design. This was important to me at the time because I was designing a driver for one of their LEDs that was intended to go below 10% on analog dimming. Maybe their lawyers made them say that because they saw one freaky die from a prototype batch a million years ago. Or maybe there is (was?) something more to it. I just don't know. That's the only manufacturer I've ever known to specify a minimum current for their LEDs.
With that said, there is (or at least can be) a minimum current below which an LED will suddenly stop emitting light. I have seen single strings of LEDs where some dies are emitting and others are not. In my case this occurred at EXTREMELY low currents - to the point where you had to dim the lights and get very close to tell which ones were on and which weren't. I suppose in deep darkness it would have been easy to tell, but I never tried that.
Lastly, in commercially available "LED bulbs" it's possible that they have internal drivers or similar circuitry that doesn't function well below some minimum dimming level.
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Many good answers. Can I put Soraa mr16 in this monorail and add a PWM dimmer to get good dimming? Will PWM flicker??
To the ops question, this is the only part of the answer that is really applicable.
It costs money (and time) to make a driver that dims deeply on what are traditionally high power, resistive halogen circuits and that goes doubly for low voltage MR16 with all the electronic transformers out there.
That is the reason why many plug in LED bulbs do not dim well.
Unless someone knows the circuitry inside the Soraa and/or has tested it, there is no way to know for sure whether PWM dimming will work. You can always buy one and try it and then go from there.
mr16 GU5.3 have no circuitry. 12v power comes from rail. But PWM will flicker??
If it's an LED MR16, it most certainly has circuitry in it, from simple to very complex.
No idea what PWM will do as I do not know what circuitry is in the Soraa.
DIWdiver
Flashlight Enthusiast
I took a quick look at Soraa.com, and I see they offer 34 different MR16-GU5.3 bulbs (I counted!). I looked at a few of the spec sheets, and they say "Works with trailing edge and leading edge phase cutdimmers, 12V AC magnetic and electronic transformersand 12V DC transformers (see www.soraa.com/resources)".
At soraa.com/resources/compatibility I found charts of transformer/dimmer combinations that will work with their MR16 bulbs. They also show how low the dimming goes, and even highlight those that go below 20%!
At soraa.com/resources/compatibility I found charts of transformer/dimmer combinations that will work with their MR16 bulbs. They also show how low the dimming goes, and even highlight those that go below 20%!
No, AC dimmers are old tech for retrofit fixtures. Very bad compromises. I need LED friendly DC dimmers made for LED.
They don't have this.
color shift
flicker
drop out
pop on
dead travel
ghosting
buzzing
