LED bulbs with selectable color temp

[Poppy]

My daughter picked up this package at the Home Depot.
I'd never seen it before, and thought that it is ingenious.
Color temp matching is important in multiple bulb fixtures.

 

[louie]

I also saw a similar bulb at Costco from Feit. My Costco no longer sells separate cool/warm regular LED bulbs from Feit, just these adjustable ones. They even claim high CRI. I don't need any at the moment, but will probably have to try some in the future.

 

[Dave_H]

I have very similar if not exact bulbs. Interesting though in my case switching tint OTF is not required, not sure how useful this is to others. If you need a fixed standard tint, a regular bulb is cheaper and may have better specs.

I believe this one uses two (or three?) sets of LEDs of different CCT e.g. 2700K and 5000K and adjusts the brightness of each, which creates a sort of "average", which is different from a single CCT bulb of that tint. However, your eyes may not notice.

I have some ceiling LED fixtures (clearance from HD!) I have opened up, which use two CCT sets.

There is a different product with three CCTs, plus a switch position to cycle through them by toggling the power switch with correct timing; similar to step-dimming bulbs.

My beef is the extra cost and complexity gets tossed when the bulb expires. If you select say 2700K and stick with it, the other LED set(s) get no usage, and essentially wasted.

An advantage is you can select a "neutral" tint e.g. 4000K which is not as commonly
available for regular bulbs. If both sets of LEDs are driven, that divides the power and should make them overall last longer (in theory...).


Dave

 

[Kestrel]

I'm thinking to have a timing circuit in its microcontroller, so its color temp could change throughout the day; before & after sunset would be defaulted to 'warm'. The simplest way to set it would be its first turn-on after installation to be 6pm perhaps.

 

[Dave_H]

I'm thinking to have a timing circuit in its microcontroller, so its color temp could change throughout the day; before & after sunset would be defaulted to 'warm'. The simplest way to set it would be its first turn-on after installation to be 6pm perhaps.

Sounds like something easy to do with a smart bulb and the right application. I think most if not all smart bulbs including white-only have two CCT sets. A defective Philips Hue bulb I opened up was like this.

Dave

 

[JoakimFlorence]

Those Ecosmart adjustable color temperature bulbs appear to have to have flicker.
It's only very slight at 5000K, almost totally unnoticeable at 2700K, but gets much more noticeable at intermediate temperatures like 3500K and 4000K.
At 3000K the flicker is not really too bad but is a little noticeable.

I'd be very curious what the exact circuitry is inside these bulbs. I think we can assume it only contains 2700K and 5000K white LED emitters, but exactly how the design combines those two, I do not know exactly.
One theory is that it might have a computer chip to rapidly switch between the two colors, which could account for the flicker.

Pulse width modulation (PWM) often seems to be the preferred circuitry design for dimming LEDs, to avoid wavelength shift from the blue emitter at the lower end of the voltage range which cause some color shift and throw off the overall color tint of light.
Unfortunately the trade-off seems to be that some people can perceive the flicker resulting from PWM.

Being able to selectively turn off certain emitters inside the bulb seems like it could theoretically make more sense, but I think perhaps that might add more complexity to the circuitry and I don't think there are any color temperature adjustable LED bulbs that do that. (With the exception of adjustable brightness 3-way LED bulbs)

I don't notice any flicker from the other Ecosmart dimmable bulbs that do not have adjustable color temperature. (Those are only available in 2700K, 3000K, and 5000K)

The side of the box claims "Highest quality of light. Brings out your home's true colors in the most natural way possible", which suggests that the CRI is probably a little higher than on standard LED bulbs.
Nevertheless, judging from the quality of light, I doubt the CRI is above 90 or 91. (For comparison, some of the other "high CRI" bulbs are more like 93 CRI)

(I presume all the Ecosmart dimmable bulbs are using the same CRI level LEDs inside as the color temperature adjustable bulb. They have the same "light quality" picture shown on the left side of the box. Though it's possible this could be a slightly mistaken assumption. The color temperature adjustable bulb does not advertise that it has "vivid, real color lighting" on the front side of the box)

Something else possibly worth noticing, I think they might have designed the tint on the 2700K and 5000K to be just a tiny bit more green shifted on the Planckian locus to help compensate a little bit when the two are combined together to make color temperatures in the middle. It's barely noticeable though. I'm surprised the 3500K doesn't have a slight magenta tint. It might barely have the tiniest magenta tint but it doesn't seem to be noticeable at all, and I'm not even sure that it does. Not compared to normal LED bulbs that have regular CRI.
I'm not saying the 2700K and 5000K have an obvious tint. It's not noticeable unless one is really paying close attention, scrutinising it and carefully comparing it to the light from other bulbs. The 5000K seems to be just a little bit greener and the 2700K seems to be just a little bit more yellowish. (Probably unlike most people, I actually personally prefer this. In my opinion that is actually closer to the tint of natural sunlight as seen from earth filtered through the atmosphere, even though it might be considered tinted by the standards of a theoretical perfect blackbody Planckian locus. But I know the majority of others seem to prefer white light with a more pink tint)

I can't really discern much visible difference in the tint of Ecosmart's dimmable 3000K bulb (permanently at 3000K) compared to the adjustable color temperature 3000K setting. Maybe the non-color-adjustable one is a tiny bit more pleasantly yellowish but it's very difficult to tell. And I'd say the light tint of the adjustable color temperature 3000K setting might even be somewhere between that of the permanent 3000K and a 3000K LED bulb that has ordinary CRI. It could also be possible that the frosted glass shell of the Ecosmart's dimmable permanent 3000K bulb (which is constructed more like a filament bulb) might be filtering away more of the blue light than plastic diffusion covers do, and that could be responsible for altering the tint.
But I'd say the slight magenta tint, if it does exist, starts becoming more noticeable at 3500K, for the color adjustable bulb, then for any of the other color temperature settings.

 

[sween1911]

These smart bulbs blow my mind. Not only changing the color temp but all the multi-color options through the phone app.

I can neither confirm nor deny that I bought one and swapped it for the bulb in the lamp in our living room, and then waited until my wife was engrossed in a TV show before using the app to flip it to red to freak her out.

 

[JoakimFlorence]

These smart bulbs blow my mind. Not only changing the color temp but all the multi-color options through the phone app.

Those options to be able to change color temperature and color come with some subtle disadvantages, and even some limitations, which most people do not realise, and probably do not care about.

There are some trade-offs. As I pointed out, these bulbs seem to have flicker, and then there is very slight and minor of issue of precise color tint, which doesn't totally line up from the ends of the color temperature range to the middle. (This is due to the Planck curve being curved on the color coordinate diagram)

They're not really using the most advanced technology to achieve this, they're using some design shortcuts to keep costs down.

 

[JoakimFlorence]

Color temp matching is important in multiple bulb fixtures.

I presume by that that you mean it is much more preferable to have all the bulbs be 3000K, 3500K, or 4000K, rather than using a combination of 2700K and 5000K bulbs together because you find the light color of one too orange and the light color of the other too bluish.

Another problem, which many may not realise, is that if you simply combine 2700K and 5000K, the resulting mix of light is going to end up having a slight magenta tint color cast.
The thing is, as you start increasing color temperature from 2700K, the ratio of green light (in the combined white spectrum) at first starts increasing at a more rapid rate than blue light, but eventually rate of increase in blue light starts catching up by the time you get to 5000K.

But apparently this doesn't seem to be too much of a problem in these color adjustable bulbs for some reason.

 

[sween1911]

When you go to the circus and see a bear ride a bicycle, we marvel not at the bear's attire, not at how well the bear rides the bicycle, but DUDE IT'S A BEAR RIDING A BICYCLE!

Maybe I'm old and all this stuff is still cool to me, but I can change the colors and dim the bulb with my phone!

 

[N8N]

Feit has these as well, just saw them at Costco last night. Listed as 90+ CRI.

8.8W (60W Replacement) Selectable Color A19 E26 Base LED Bulb (6-Pack)

Enjoy all the benefits of advanced LED energy-saving technology with Feit Electric A19 60-watt equivalent selectable color LED light bulbs. LED bulbs feature high color rendering index light with superior light quality and rich vivid color. These selectable color temperature bulbs feature 5...

www.feit.com

about $10 for a 6-pack. I have been pretty impressed with Feit's "enhance" bulbs to the point that probably 80% of my A19s are Feit, albeit all "warm white". They dim smoothly and quietly and I have had few failures (I can't actually remember any, but I won't say "none" as I may be forgetting some) I almost bought a pack of these until I realized that I don't have any actual use for them...

I'd be interested to see a drive report because this certainly is interesting.

 

[Dave_H]

I presume by that that you mean it is much more preferable to have all the bulbs be 3000K, 3500K, or 4000K, rather than using a combination of 2700K and 5000K bulbs together because you find the light color of one too orange and the light color of the other too bluish.

Another problem, which many may not realise, is that if you simply combine 2700K and 5000K, the resulting mix of light is going to end up having a slight magenta tint color cast.
The thing is, as you start increasing color temperature from 2700K, the ratio of green light (in the combined white spectrum) at first starts increasing at a more rapid rate than blue light, but eventually rate of increase in blue light starts catching up by the time you get to 5000K.

But apparently this doesn't seem to be too much of a problem in these color adjustable bulbs for some reason.

Check out this thread on my opening up low-cost LED bulbs (those which have plastic tops, so far)"

Inside low-cost LED ac bulbs

I thought to start a thread about what's inside ordinary low-cost LED ac bulbs, as I have taking the plastic tops off a number of them. This is usually not a complete teardown, and does not include glass bulbs, such as filament bulbs. Majority of these use high-voltage linear regulation...

www.candlepowerforums.com

I have not opened the EcoSmart A19 bulb yet. However, Sylvania Smart+ RGBW Wi-Fi bulb (which are available OTC here for 2/$5) contains two sets of white LEDs with different CCT. Similar with Commercial Electric LED ceiling fixture with CCT change feature (switch).

I was wondering about the result of mixing two CCTs instead of a single CCT at desired value; good info in this thread.


Dave

 

[PhotonWrangler]

Check out this thread on my opening up low-cost LED bulbs (those which have plastic tops, so far)"

Inside low-cost LED ac bulbs

I thought to start a thread about what's inside ordinary low-cost LED ac bulbs, as I have taking the plastic tops off a number of them. This is usually not a complete teardown, and does not include glass bulbs, such as filament bulbs. Majority of these use high-voltage linear regulation...

www.candlepowerforums.com

I have not opened the EcoSmart A19 bulb yet. However, Sylvania Smart+ RGBW Wi-Fi bulb (which are available OTC here for 2/$5) contains two sets of white LEDs with different CCT. Similar with Commercial Electric LED ceiling fixture with CCT change feature (switch).

I was wondering about the result of mixing two CCTs instead of a single CCT at desired value; good info in this thread.


Dave

I have a G-E bulb with adjustable color temp - only three levels though, and it requires an app to change the setting. It's kind of annoying.

 

[JoakimFlorence]

I had an idea how this 5-way color temperature light might work.
I'm sure this is not how it actually works but I thought I'd share the idea I came up with.
There would be 3 different types of emitters; 2700K, 3500K, and 5000K.
Each of the levels would be divided, in a 5/8 to 3/8 ratio, or perhaps 2/3 and 1/3.
When you start with the 2700K setting, both sections of the 2700K would be powered.
When you switch to 3000K, the 5/8 section of 2700K emitters and the 3/8 section of the 3500K emitters would turn on. (This might be 5 warmer white and 3 brighter white LEDs) This would result in a combined light close to 3000K in color temperature.

When you switch to 4000K, the bigger section of the 3500K would turn on, combined with the smaller section of the 5000K.
(While it's true that to get exactly 4000K the sections would need to be divided 2/3 and 1/3, 5/8ths is still close to 2/3. So the resulting light might just be a little bit higher than 4000K, but I doubt anyone would notice. I calculate 4062.5K)

It would not be too difficult to build this directly into a 5-way switch, since each position on the switch would connect to two sections. (The switch would have to be specially designed) But I think it might be more convenient to connect the switch to a specially designed computer chip and then have that used to activate a set of six transistors to be able to turn on the different sections.

 

[Dave_H]

Of the selectable-CCT bulbs I've looked inside so far, all use only two sets of LEDs. Three or more would be too much overhead especially in small (A19) bulbs, unless some sort of exceptional resolution is desired. Anything is possible, it is a matter of keeping complexity and cost low generally; for premium products, who knows.

I don't know about Wi-Fi bulb applications, can they provide infinite CCT resolution, or just steps similar to manual switch? RGBW bulbs might possibly use some of the colours combined with white LEDs to get the "right" CCT, but only speculation.

Dave