why is there no warm light small LED? - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 02, 2020, 11:15:15 am
content: I never found a small (0603 - 0402) warm white (let's say 2700k) led.Is there any reason? If I am not wrong, white LEDs are a blue led with a mixture of phosphors, so that should be possible independently of the size

author: Zero999
author_rank: Super Contributor
timestamp: October 02, 2020, 12:01:21 pm
content: They're not very common, but TME sell them.https://www.tme.eu/gb/katalog/smd-white-leds_113362/?visible_params=2%2C1088%2C10%2C1594%2C1101%2C1096%2C754%2C120%2C35%2C2922%2C1110%2C1095%2C2456%2C2612%2C2586%2C36%2C1257%2C2390%2C1113%2C1600%2C2664%2C909%2C2385%2C564%2C522%2C2585&mapped_params=35%3A1436803%2C1436749%3B754%3A1463454%3B

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 02, 2020, 12:24:26 pm
content: plenty on Aliexpress if you don't need a brand-name part

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 03, 2020, 08:45:24 am
content: Thank you, that's cooldigikeyhttps://www.digikey.jp/products/en/optoelectronics/led-indication-discrete/105?k=white+led&k=&pkeyword=white+led&sv=0&pv37=421198&sf=1&FV=-8%7C105&quantity=&ColumnSort=0&page=1&pageSize=500has none, that's why I thought it was the norm.

author: tooki
author_rank: Super Contributor
timestamp: October 03, 2020, 12:47:05 pm
content: Quote from: fabiodl on October 02, 2020, 11:15:15 amWhy? Because small LEDs like that are for indicators, not illumination, while warm white LEDs are primarily used for illumination, not indication.But they do exist. You can find almost any LED on Aliexpress.

author: EntropyWizard
author_rank: Contributor
timestamp: October 03, 2020, 02:39:38 pm
content: Digikey also has a separate category for lighting LEDs and there are some small ones there:https://www.digikey.jp/short/zw9r5r

author: Zero999
author_rank: Super Contributor
timestamp: October 03, 2020, 03:45:49 pm
content: Quote from: tooki on October 03, 2020, 12:47:05 pmYes that's true, but what about small displays on smart watches? Nowadays people want a low colour temperature mode to use at night time. This could be achieved by altering the RGB signal to the TFT LCD, but it would be more efficient and easier to incorporate some warm white LEDs into the backlight. It will be interesting to see whether small, warm white LEDs will become more popular, or not.Quote from: fabiodl on October 03, 2020, 08:45:24 amAnother thing you could search for is the metric case sizes, or just use dimensions.https://www.topline.tv/SizeChart.html

author: SilverSolder
author_rank: Super Contributor
timestamp: October 03, 2020, 05:33:30 pm
content: I like the idea of warm LED indicators / display illumination. Just like I like incandescent bulbs as indicators!

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 04, 2020, 07:16:50 am
content: Quote from: EntropyWizard on October 03, 2020, 02:39:38 pmIndeed, however if you look at the packages there's no "standard" 0603 or 0402Quote from: SilverSolder on October 03, 2020, 05:33:30 pmThat's exactly what I want to achieve! I am tired of the usual "look I can do blue" or "here's your "stylish" cold white"

author: tooki
author_rank: Super Contributor
timestamp: October 04, 2020, 12:33:43 pm
content: Quote from: Zero999 on October 03, 2020, 03:45:49 pmFor sure. IMHO backlight LEDs are a subset of illumination LEDs. But being so specialized, they’re not really sold via distributors. If you’re an LCD panel manufacturer, you’re by default big enough that you’ll be buying the LEDs directly from the LED manufacturer, perhaps as custom devices, assuming you’re not just making the LEDs yourself.(As for using WW LEDs in a device to provide adjustable color temp: more efficient? Perhaps. Easier? Certainly not. Adjusting the color temp via the LCD panel can be done in software, adjusting it via the backlight means crating two separate backlight control channels in hardware.)Quote from: fabiodl on October 04, 2020, 07:16:50 amYou think backlight LEDs are cool white (actually usually more like a neutral white) to be “stylish”?!?Think about this for a moment: why is photo paper white, and not, say, cream color? What color is sunlight? (What about at different times of day?) Why are photo flashes cool white? Why do non-backlit color displays (like OLED, plasma, and CRTs) have phosphors designed to produce a cool white?

author: SilverSolder
author_rank: Super Contributor
timestamp: October 04, 2020, 02:53:30 pm
content: It depends on the type of display! As long as it is a display that doesn't have to reproduce accurate colours, the choice of background light is a design/styling decision, right?And there are a lot of really bad styling decisons made on many products. Routers that send out blinding blue blinking light into the darkness of your bedroom, for example...

author: Siwastaja
author_rank: Super Contributor
timestamp: October 04, 2020, 03:04:03 pm
content: Blue indicator LEDs aresooo2005 that I actually have started using blue LEDs for indication, it's almost retro now.This being said, I agree that a warm white indicator LED would be a nice touch. If you want to indicate blue and white, using warm white creates a larger color contrast between them.

author: Rick Law
author_rank: Super Contributor
timestamp: October 04, 2020, 09:46:14 pm
content: Quote from: SilverSolder on October 04, 2020, 02:53:30 pm"Warm White" in my opinion is not suitable for lighting where good color representation is important. I used to have a warm-white LED desk lamp until I tried to read resister color codes under that warm-white light: purple and brown looks indistinguishable, blue and green looks indistinguishable...I have best vision round 5000K lighting. I think that is how evolution designed our eyes (sun light ~ 4500K to 5500K), but then of course evolution also make sure there will be individual/regional differences.

author: SilverSolder
author_rank: Super Contributor
timestamp: October 04, 2020, 10:42:10 pm
content: Quote from: Rick Law on October 04, 2020, 09:46:14 pmAgree - I have a 5000K twin tube Dazor over my work area. My computer monitor is colour calibrated for photo use. I do care about colour and light accuracy! But the whole room doesn't (in my case) need to be lit for accurate colour... sometimes, I like sitting in subdued light with green CRTs, red LED displays, and the like making the room cozy!

author: Siwastaja
author_rank: Super Contributor
timestamp: October 05, 2020, 06:26:49 am
content: Quote from: Rick Law on October 04, 2020, 09:46:14 pmNote that color rendition and color temperature are separate issues. Some LEDsreallysuck in color rendition (regardless of color temperature!), meaning there are large gaps in important parts of spectrum. If the resistor marking ink used falls within such spectral gap, you see it as murky dark color instead of the intended color.Color temperature itself isn't that important, as long as the amount of light, and CRI, is high enough. Of course, goingtoofar on color temperature reduces the available level of blue or red just too much; human brain has auto white balance feature, but its usable range is approximately from 3000K to 10000K, give or take. For example, at around 2500K, it's becoming very difficult to see colors properly, there is just not enough blue light. There is a huge difference between 2800K and 3200K while both are considered "warm white". The color rendition and look&feel of a classical halogen studio/photo light (a.k.a. projector bulb), calibrated to be 3200K - 3400K, is absolutely fantastic and once your eyes calibrate to that color temperature (instead of sunlight), it doesn't look "warm" at all. Incandescent bulbs have perfect 100% CRI, and the biggest problem of especially the 3400K bulbs is the very short service life of the bulb, running close to the melting point of tungsten.

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 06, 2020, 10:21:43 am
content: You think backlight LEDs are cool white (actually usually more like a neutral white) to be “stylish”?!?Think about this for a moment: why is photo paper white, and not, say, cream color? What color is sunlight? (What about at different times of day?) Why are photo flashes cool white? Why do non-backlit color displays (like OLED, plasma, and CRTs) have phosphors designed to produce a cool white?I completely agree neutral white is better for reading, etc. I was referring to power leds, (think of notebooks, mobile batteries, routers, and what not) which have nothing to do with reading and to be honest they seem to be cold white (in the best cases neutral) just to be pretend to be stylish

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 06, 2020, 10:23:15 am
content: Quote from: tooki on October 04, 2020, 12:33:43 pmI completely agree neutral white is better for reading, etc. I was referring to power/status indicator leds, (think of notebooks, mobile batteries, routers, and what not) which have nothing to do with reading and to be honest they seem to be cold white (in the best cases neutral) just to be pretend to be stylish

author: tooki
author_rank: Super Contributor
timestamp: October 06, 2020, 08:32:13 pm
content: Quote from: fabiodl on October 06, 2020, 10:23:15 amI think that has more to do with cool white being the cheapest and most readily available of the white LEDs more than anything else. I think you’re reading more into the designers’ intentions than is actually there...

author: Rick Law
author_rank: Super Contributor
timestamp: October 06, 2020, 09:16:55 pm
content: Quote from: tooki on October 06, 2020, 08:32:13 pmI think that has more to do with cool white being the cheapest and most readily available of the white LEDs more than anything else. I think you’re reading more into the designers’ intentions than is actually there...Interesting... For general lighting here in the USA, warm-white LED lights and CFL are both more expensive than daylight (5000K), and cool white (6000K+) are even more expensive than the 5000K daylight.Age is a factor too. A street-light study I read (some years ago) found that older people can see better with 5000K. I can't find the article on that anymore, but that does correspond to what I am experiencing.

author: tooki
author_rank: Super Contributor
timestamp: October 08, 2020, 03:27:22 pm
content: Again, we are talking about indicator LEDs, not lighting LEDs. Indicator LEDs are seldom even grouped into warm, natural, and cool — you most often just get “white”, which is typically a coolish white. If they offer a warm white, it may be anywhere from warmish to nearly yellow, and they may (or may not) refer to the other one as “cool” to differentiate it.With that said, it’s odd that you have found cool white LED lighting to be more expensive. Historically, it was cheaper, but nowadays seems to have no impact. A cursory look on the Home Depot website shows no price difference whatsoever between, for example, the 3000K, 4000K, 5000K, and 6500K versions of Philips’s 4-ft LED replacements.FYIW, I really dislike Philips’s color temp verbiage, calling 3000K “bright white”, 4000K “cool white”, and 5000K “daylight”, and 6500K “daylight deluxe”. The usage I prefer would call up to 3000K “warm white”, 4000K “natural white”, 5000K-6500K “daylight”*, and perhaps 7000K+ “cool white”. It makes NO sense for “cool white” to bewarmerthan “daylight”!!!I guess they carried over the definitions from their tungsten products, where “cool” tungsten was still nowhere distantly as cool as actual daylight.*In the publishing world, “D65” (spectrally accurate 6500K) lamps, mostly fluorescent historically, are used for color-accurate proofing of prints. Because they have high spectral accuracy, they don’t appear as cool to the eye as “cool white” regular fluorescent tubes or actual sunlight.

author: Zero999
author_rank: Super Contributor
timestamp: October 08, 2020, 08:16:47 pm
content: The colour temperature should depend on the time of day and application. For working, higher colour temperatures are generally better, but when lounging around at home, especially during the evening, use warm white, as too much blue interferes with sleep. I do this with my computer screen, using a program called redshift. During the day the colour temperature is 6500k, but at night it drops to 2800k and the brightness is reduced to 60%.Regarding price: lower colour temperature LEDs should be more expensive, than higher ones, as more phosphor is needed to convert the blue to longer wavelengths. In reality other factors such as production volumes play a role.

author: tooki
author_rank: Super Contributor
timestamp: October 09, 2020, 10:07:39 am
content: Yeah, iOS and macOS both have a similar feature, called night shift, built in.White LEDs used to be far too cool, and had really terrible color rendering. These aspects have improved in leaps and bounds over the last 10 years or so, mercifully. (Fluorescent tubes were generally also not great — high CRI fluorescent has existed for ages, but due to cost, almost all fluorescent lighting used fairly bad phosphors with poor color rendering and colored flicker. LED not only caught up with those but has now easily exceeded them.)