Changing out LEDs in solar garden lights - why does white work and green not? - Page 1
Forum section: electronics / beginners

author: stryker
author_rank: Regular Contributor
timestamp: February 15, 2020, 06:16:51 am
content: Hi EEVblog brains trust,I thought it would be a pleasant to have green solar garden lights around the edges in our back yard. So I bought a bunch of very cheap solar garden lights based around YX8050 with a 200mA AAA NiCd cell. The circuit aside from solar cell, AAA and the YX8050 IC has a single inductor so while I couldn't find a datasheet for YX8050 specifically, it seems like a drop-in replacement for TO-94 YX8018 which is commonly available from AlliExpress with lots of references around the interwebs.Without a datasheet I checked it on the scope and found the LED is fed pulses of 3.3V at max, down to -500mV or so with a mean of 800mV at a frequency 10kHz+ when the cell is fully charged. So I naively thought I would swap out the standard white LEDs for green and they'd work just fine, but both 5mm green LEDs I have on hand one clear and the other diffuse are equally pathetically dim that it's easy to think they're not running at all once back in the housing. The white in contrast is far from bright enough to read under, but runs for hours in a usefully decorative way.I've tried to find out why green doesn't work to see if there's any remedy to this pickle, or even to know the correct terms to be searching for when buying a coloured drop-in replacement that would work, but so far all I've seen is vague references to white LEDs being more efficient than green, without finding the science to back it up.Can you direct me to some relevant reading that could help me understand what's happening here, and any guidance as to if making these run green is possible (or is this IC perfectly tuned to just white making cheapie solar garden lights a poor donor as a starting point?)ThanksGeoff

author: OwO
author_rank: Super Contributor
timestamp: February 15, 2020, 08:48:40 am
content: YX8050 datasheet:

author: sleemanj
author_rank: Super Contributor
timestamp: February 15, 2020, 08:51:30 am
content: I would guess at two factorsfirst, that the green led isn't very efficient, as you have found out modern white (blue with a phosphor) leds are very very good at producing light we can see from very small amounts of, your random old green diffuse led perhaps not so muchsecond, the IC may be specifically designed around the forward voltage of the white led which is in the area of 3v, your green led will be somewhat lower than that, you could put a plain diode (or a schottky) in series with your green led to bump up the forward voltage a smidge and see if that helpsthe datasheet for the YX8050 specifically states white leds in one of it's tables

author: OwO
author_rank: Super Contributor
timestamp: February 15, 2020, 09:00:52 am
content: You can try the schottky + capacitor circuit suggested in figure 2-1 which will drive the LED smoothly. The table of inductor vs current suggests it's constant duty cycle control in discontinuous mode.

author: Zero999
author_rank: Super Contributor
timestamp: February 15, 2020, 03:28:32 pm
content: Your green LED uses a crappy old GaP chemistry, which is cheap, has a low forward voltage but very poor efficiency. It should work well with a modern InGaN green LED.

author: stryker
author_rank: Regular Contributor
timestamp: February 15, 2020, 11:24:59 pm
content: Thanks for the rapid replies, and that datasheet guys.I did have the VFmeasured for the 3 LEDs but forgot to put it in my post. It's nothing surprising, but for completeness I'll add it hereWhite diffuse that came in the garden lights measures 2.77VClear green from my parts bin measures 2.00VDiffuse green from my parts bin measures 1.97VI'll have a read of the datasheet, and try the series suggestion.Will report back - thanks!Geoff

author: floobydust
author_rank: Super Contributor
timestamp: February 16, 2020, 01:08:02 am
content: I find you can increase efficiency of these by adding a capacitor across the LED or at boost-converter input. Even 1uF but 2.2-10uF worked good. It might help this thing startup and run with low Vf LED's, although I would instead use high efficiency 3V InGaN greens which are crazy bright and efficient.

author: Jwillis
author_rank: Super Contributor
timestamp: February 16, 2020, 07:17:23 am
content: The current is adjusted with the inductor. Your green light may require more than the 11.5mA -15 mA that is set by the 29µH inductor.

author: Zero999
author_rank: Super Contributor
timestamp: February 16, 2020, 08:44:52 am
content: Quote from: stryker on February 15, 2020, 11:24:59 pmTry replacing the green LED with one with a bright InGaN die. I had a quick look through Digi-Key and found these. No doubt you can get cheapr on ebay or whatever, but it might be more difficult to ensure you get InGaN and not some cheaper chemistry. Look for something with a forward voltage of around 3.2V and a wavelength of 520nm to 530nm and it should be InGaN.https://www.digikey.com.au/product-detail/en/kingbright/WP7083ZGD-G/754-1890-ND/3084179https://www.digikey.com.au/product-detail/en/kingbright/WP7113ZGC-G/754-1487-ND/2261462https://www.digikey.com.au/product-detail/en/inolux/INL-5AG30/1830-1011-ND/7604626Another possibility is phosphor converted LEDs, which are deep blue/violet LEDs, with a phosphor to produce the main colour. They're often sold for use in decorations or grow lamps and will be specified by chromaticity, not wavelength. Quite often you'll see things such as pastel and colour names in the data sheets. The forward voltage and electrical characteristics will be identical to deep blue/violet LEDs.https://www.tme.eu/gb/details/osc64l5111a/tht-leds-5mm/optosupply/

author: tooki
author_rank: Super Contributor
timestamp: February 16, 2020, 12:34:07 pm
content: Quote from: Zero999 on February 15, 2020, 03:28:32 pm^^^ this.If you’re looking on eBay/Ali, search for “emerald” or “true green”, and make sure the forward voltage is around 3V. Those should work well.

author: Jwillis
author_rank: Super Contributor
timestamp: February 17, 2020, 12:40:53 am
content: I have those same green LEDs .At 3.3V they need 20mA to glow at full brightness. 20mA to 30mA theirs very little change to brightness. 65mA and they are obviously being over powered because they start to glow yellow.They are still pathetic at 20mA. They barely glow at 11ma to 15mA .But if you plan on using the same LED the current must be increased by changing the inductor. 18uH to 22uH.

author: tooki
author_rank: Super Contributor
timestamp: February 17, 2020, 03:46:02 am
content: A modern green LED is blindingly bright at 3.2V/20mA.

author: rdl
author_rank: Super Contributor
timestamp: February 17, 2020, 07:25:20 am
content: Here's a picture. Regular green LED on the left. Kingbright InGaN green LED (WP7083ZGD/G) on the right. The regular LED is running at 15 mA compared to only 0.32 mA for the InGaN green LED. Shop around though, because I paid almost $1 for a single.

author: Zero999
author_rank: Super Contributor
timestamp: February 17, 2020, 09:18:26 am
content: Quote from: tooki on February 16, 2020, 12:34:07 pmI'd be worried about fakes. I've never bought LEDs from eBay/Ali. Have you had any luck?Quote from: Jwillis on February 17, 2020, 12:40:53 amI have some genuine green InGaN LEDs and I can get them to glow from ambient electromagnetic noise, by connecting one leg to an earthed object such as a radiator or tap and holding the other one in my hand. Overdriving them shifts their colour towards the blue end of the spectrum.

author: Jwillis
author_rank: Super Contributor
timestamp: February 17, 2020, 09:31:56 am
content: Quote from: Zero999 on February 17, 2020, 09:18:26 amDo you have a part number for those. These I have are just the cheap bargain assorted ones you can get 1000 for a buck deal. I have other high end type but they are white ,RGB , IR and UV. Some decent bright colors would be nice.But regardless of what LED the OP ends up using , he may have to adjust that inductor .

author: tooki
author_rank: Super Contributor
timestamp: February 17, 2020, 11:58:45 am
content: Quote from: Zero999 on February 17, 2020, 09:18:26 amYes, I’ve had great luck with eBay/Ali LEDs on the whole. I got a pack of 500 InGaN green LEDs for a few dollars and they’re so damned bright that to use them as indicator lights indoors, I have to run them at just 0.5mA. Like you say, they’re easy to illuminate just with noise. (And corollary to your observation that overdriving them shifts them to blue, when run at very low currents, they shift a bit towards yellow, appearing closer to the color of old-school GaP green LEDs.)The only cheap LEDs that somewhat disappointed were a pack of diffused warm white, which were just too yellow, and a pack of “cyan” ones, which are pleasant, but have huge spread in peak wavelength amongst the samples. Some were very close to normal blue, and others getting green enough that I’d call them turquoise. But for my purposes, as individual indicators, not a problem.As an aside, one of my favorite finds among eBay/Ali LEDs are the pink ones, which are blue with a warm red phosphor. They just look great, and I’ve been using them more and more. I wish I could find bona fide purple ones made the same way, but alas, eBay/Ali vendors invariably label their UV LEDs as “purple”, too...

author: Zero999
author_rank: Super Contributor
timestamp: February 17, 2020, 10:07:06 pm
content: Jwillis,No I don't have the part number, but I did post a few links a couple of posts ago, to some parts which I know are InGaN based.https://www.eevblog.com/forum/beginners/changing-out-leds-in-solar-garden-lights-why-does-white-work-and-green-not/msg2921492/#msg2921492tooki,What sort of purple are you after? 410nm to 420nm gives a nice violet colour, but is quite close to UV and is quite harsh to look at.The only manufacturer of phosphor converted purple LEDs, I'm aware of is OptoSupply, but I've never tried them. Look at part numbers: OSCD4L5111A (Lavender) and OSK64L5111A (Sakura). They also make a range of other colours.http://www.optosupply.com/uppic/201683604722.pdfhttp://www.optosupply.com/uppic/201682360345.pdfThey are available from Rapid Electronics, TME and some eBay sellers who appear to be buying from the aforementioned and adding a profit margin.

author: floobydust
author_rank: Super Contributor
timestamp: February 18, 2020, 04:42:14 am
content: PC purple are called "pink" LED's, try search for that, they are plentiful on eBay or Ali. Some colour names do not translate at all.My dollar store solar LED light uses YX805, 27uH, one AAA cell, 180kHz. It craters when given a low Vf green GaP LED, very dim.I have crazy bright pure green SMD 1206 LED's and 5mm "traffic light" LED's that are blindingly bright at even a few mA. Very long time ago, I bought some 5mm from IC Touch but green is low brightness 2.2V @20mA, not ad 3.2-3.4V@20mA and they gave a refund. I think they updated their spec for Vf. So I look for that in ads.Some IC datasheet and solar light scope traces:https://skootsone.yolasite.com/solar-led.php

author: Zero999
author_rank: Super Contributor
timestamp: February 18, 2020, 10:59:36 am
content: Quote from: floobydust on February 18, 2020, 04:42:14 amYes, I understand colour is subjective and translating between different languages is an issue, but in my experience pink LEDs tend to be just that: hot pink. Some might be a purplish pink, others more magenta or fuchsia, but there's generally too much red and other wavelengths to be a true purple, which is mostly blue and a little red.I had another look and found the Lumex SSL-LX5093VC which, going by the chromacity coordinates, appears to be a truer purple than the OptoSupply LEDs I linked to before, but it's more expensive.https://www.lumex.com/content/files/ProductAttachment/SSL-LX5093VC.pdfhttps://www.mouser.co.uk/ProductDetail/Lumex/SSL-LX5093VC?qs=sGAEpiMZZMsl8UZd3ZuU6eQQc5BIt9T92fOOCbm3%252BCE%3Dhttps://www.digikey.co.uk/product-detail/en/lumex-opto-components-inc/SSL-LX5093VC/67-2064-ND/1842141

author: floobydust
author_rank: Super Contributor
timestamp: February 18, 2020, 07:33:49 pm
content: Kingbright offers special colourspink, purple, special blues. I wish these would be more prevalent, aren't we getting bored with LED colours.

author: Zero999
author_rank: Super Contributor
timestamp: February 18, 2020, 08:20:39 pm
content: Quote from: floobydust on February 18, 2020, 07:33:49 pmThey only do the pink ones in the common 5mm T-13/4package.The other colours aren't available in the 5mm T-13/4package, only pink. It would be good to get the other colours in 5mm and some diffused options would also be nice.I really think we're spoilt with the range of LEDs we have now. I remember when I first got into electronics, when all that was commonly available was reg, yellow and green. Orange was around, but not that easy to get hold of. I remember seeing some of the first blue LEDs in the Mapin catalogue in the early 90s and how stupidly expensive they were at around £3 each, compared to red which was just £0.20.I suppose it's just now we know what's possible and feel like there could be an even greater range, than there is.

author: stryker
author_rank: Regular Contributor
timestamp: February 22, 2020, 01:08:13 am
content: Thanks for everything guys. I've gone through the parts bin and found I have some ofthese 10mm green waterclear LEDsthat would appear to do the job at least based on VF, however in reality none I've tested show anything higher than VF2.5-3.0V, nowhere near the advertised 3.2-3.4V.Regardless, aside from the size meaning you have to assemble in-place rather than soldering the board then reassembling it, the result is a bright glow without adding other components. I've stuck it outside now to see what it's like tonight.The other downside of not being diffused is most of the light comes out the top, so I might need to add some tinlfoil in the bottom of the case as a reflector, or find something to wrap the LED in so it shines more out the sides.

author: tooki
author_rank: Super Contributor
timestamp: February 22, 2020, 11:24:44 am
content: Quote from: Zero999 on February 17, 2020, 10:07:06 pmPC purple is really what I'm after. I found a string of battery-powered christmas lights that have them, and I wish I could find those separately. As I said, even if they do exist on eBay/Ali, they're impossible to find, since the word "purple" has been hijacked by all the UV LED listings.As for OptoSupply, I think I did come across those once, I just don't know of any vendor that carries them that can ship to Switzerland with customs pre-cleared (DDP incoterms). :/Quote from: floobydust on February 18, 2020, 04:42:14 amNo, they're not. I already said I have PC pink, and I like them a lot, but they are decidedly pink, not purple.Quote from: Zero999 on February 18, 2020, 10:59:36 amExactly.Quote from: floobydust on February 18, 2020, 07:33:49 pmI need to see if I can get my hands on any of these, those look like some nice colors!Quote from: Zero999 on February 18, 2020, 08:20:39 pmHuh? Look at the link. The pink ones also come in T1 and various SMD packages, as do many other colors.I, too, am baffled at why diffused LEDs are so rare now.Quote from: Zero999 on February 18, 2020, 08:20:39 pmRight??? I got into electronics as a kid in the 80s, and red, orange, yellow, and green (and only the shade we now call yellow-green) were all you could get (well, IR, too). Blue didn't come out until the very end of the 80s, and I remember that they cost upwards of $20 a piece initially!!!It's incredible to me that the blue LED went from being the elusive color, hard to make and not very bright, to the one that not only became the brightest chemistry possible, but also became the foundation for all the phosphor-converted LEDs that we now rely on. (I have heard mention of phosphor-converted-UV white LEDs, but I don't think I've encountered one in the wild, and strongly suspect they're extinct now.)

author: rdl
author_rank: Super Contributor
timestamp: February 22, 2020, 11:55:51 am
content: It was sometime in the early 90s I think when I first noticed Digi-key had blue LEDs available. If I remember right, they were made by Cree and sold for around $5 each. I bought a few of them and I'm almost certain I still have at least one stashed away somewhere.

author: Zero999
author_rank: Super Contributor
timestamp: February 22, 2020, 05:39:47 pm
content: Quote from: stryker on February 22, 2020, 01:08:13 amWhat test current did you use? The 3.2V to 3.4V is normally specified at a relatively high current such as 20mA. If you were using the diode test on a multimeter, then you should expect a much lower voltage.QuoteYou could try roughing the lens up with some fine sandpaper.It can be difficult to find green InGaN diffused LEDs. I've seen some on eBay, but I'm suspicious about whether they're really the old yellow-green type. The Kingbright WP7083ZGD/G is the only one I know of which is widely available, but it isn't cheap.https://www.digikey.com.au/product-detail/en/kingbright/WP7083ZGD-G/754-1890-ND/3084179

author: tooki
author_rank: Super Contributor
timestamp: February 22, 2020, 06:16:39 pm
content: Quote from: Zero999 on February 22, 2020, 05:39:47 pmIt's certainly easy enough to find out: look at the wavelength. A green LED under about 540nm is a modern "true" green with InGaN or GaN chemistry, if it's 550 or above it's the old yellow-green. Both kinds are readily available on eBay and Ali as well as DK, etc. The vendors are usually much more likely to list the wavelength than the chemistry, so that's what I go by.

author: Zero999
author_rank: Super Contributor
timestamp: February 22, 2020, 09:44:22 pm
content: Quote from: tooki on February 22, 2020, 06:16:39 pmI agree and for vendors such as Digi-Key, I do trust specifications such as the wavelength, although I do check the data sheet as well, but I'm often hesitant to rely on eBay, especially from vendors who also sell unrelated items.

author: Jwillis
author_rank: Super Contributor
timestamp: February 22, 2020, 11:52:40 pm
content: Slap a reflector collimator on top and that should spread out the light better. Depends on how much room you have to work with.

author: tooki
author_rank: Super Contributor
timestamp: February 23, 2020, 04:50:03 am
content: Quote from: Zero999 on February 22, 2020, 09:44:22 pmSo buy from the electronics vendors, or from specialized vendors that just do LEDs.

author: stryker
author_rank: Regular Contributor
timestamp: February 24, 2020, 01:42:30 pm
content: Quote from: Zero999 on February 22, 2020, 05:39:47 pmI'm using one of those ATmega328 based component testers that come as a kit,similar to this one on banggoodto get a guide on the VFvalue on the LEDs.

author: stryker
author_rank: Regular Contributor
timestamp: February 24, 2020, 01:58:13 pm
content: Quote from: Jwillis on February 22, 2020, 11:52:40 pmThis looks like a workable idea however all I've found focus the beam rather than spread it more diffusely...do you have a source & product in mind that might suit here? Thanks

author: Zero999
author_rank: Super Contributor
timestamp: February 24, 2020, 09:55:33 pm
content: Quote from: tooki on February 23, 2020, 04:50:03 amI'm more cynical about eBay for buying diffused InGaN green LEDs, than the water clear type, simply because they're not many options from the usual trusted supplies such as Digi-Key, Mouser, TME, RS Components etc. I wouldn't buy anything, without asking the seller first. I know it's easy to return things, but I'd rather not have the hassle.Quote from: tooki on February 22, 2020, 11:24:44 amCan you now buy from TME, Mouser or Digi-Key? More expensive, than eBay and you need to put in a reasonable size order to get free shipping, but at least you know what you're getting.QuoteYes, that's what I meant. I misworded it.QuoteDiffused InGaN green is difficult to find, but I can't fine diffused phosphor converted yellow anywhere. The only yellow LEDs, available in a diffused package are the cappy old dim ones.I don't know why. Perhaps it's because they can make them seem brighter with a narrow beam?QuoteYes, photometrically speaking, i.e. in terms of raw power out vs power in, deep blue is the most efficient LED colour, followed by red. Pure InGaN green is more efficient, than blue and red, in terms of lumens/Watt, but that's only because the human eye is much more sensitive to green and relatively insensitive to blue. Photometrically, InGaN green is much less efficient than red and blue.I believe larger bandgap LEDs will generally be more efficient, assuming everything else is equal. I think it's due to Ohm's law. To produce red, a lower bandgap, thus voltage drop diode is required, hence relatively high Ohmic losses, compared to a larger bandgap diode, with a higher forward voltage. In theory more efficient infrared LEDs could be made if it was possible for a higher bandgap semiconductor could be made to emit two photons, per excitation.The quest is still on for more efficient green and yellow LEDs. InGaN is good enough for blue-green to pure green, but deep InGaN blue/violet and a phosphor is more efficient for greenish-yellow through to pure yellow and amber region.

author: Jwillis
author_rank: Super Contributor
timestamp: February 25, 2020, 01:07:25 am
content: Quote from: stryker on February 24, 2020, 01:58:13 pmIf this is the kind of thing that may work ,you want 120o. 180oexist but seem rare.You've probably already converted your LEDs . But why wouldn't a green cylindrical filter placed on the inside work and just use the white lights. You can get clear plastic sheets of what ever colour you like. Cut to length and roll into a cylinder and slip it inside.

author: Zero999
author_rank: Super Contributor
timestamp: February 25, 2020, 09:19:09 am
content: Quote from: stryker on February 24, 2020, 01:42:30 pmDoes it not display the test current on the screen? It's probably quite low.I Googled the M12864 and found this document, containing a schematic. The test pins are connected to some I/O ports, via 470k and 680R resistors, presumably to limit the current to different levels. Going by the forward voltages you've given, the supply voltage of the MCU is 5V and the 680R resistors, the diode test current will be under 4mA.http://www.n5dux.com/ham/files/pdf/M12864%20Transistor%20Tester%20Instructions.pdf

author: stryker
author_rank: Regular Contributor
timestamp: February 25, 2020, 12:54:01 pm
content: Quote from: Zero999 on February 25, 2020, 09:19:09 amIt doesn't. All it confirms is the battery and supply voltages at startupQuote from: Zero999 on February 25, 2020, 09:19:09 amThanks for the link. IIRC there was a similar doc for the one I built. It's been a very handy little swiss army knife of the workbench to have around.

author: tooki
author_rank: Super Contributor
timestamp: February 25, 2020, 02:42:27 pm
content: Quote from: Zero999 on February 24, 2020, 09:55:33 pmAvailability on DK, Mouser, etc. is no predictor of availability on eBay/Ali. There are tons of components the big guys carry that you never, ever see on eBay/Ali, but then there are also tons of components that are easy to find on eBay/Ali but that none of the big guys carry at all.If you see an LED being sold just as “green” without a wavelength or voltage spec, then you may or may not get a modern LED. But if they say it’s low-500s nm wavelength, then it is. I’m a bit puzzled as to why you have such extraordinary skepticism about buying LEDs on eBay/Ali: if anything, they’re one of the items that makes the most sense to get there, since the most critical specs (color, voltage, package type) are easily verified without special skill or equipment. It’s not like, say, op-amps or transistors, where fakes may work, but don’t meet specs in ways that require expertise and equipment to verify.For what it’s worth, I’ve had no trouble whatsoever with eBay/Ali LEDs, with the understanding that I may not going to get carefully binned LEDs whose color matches perfectly.

author: Zero999
author_rank: Super Contributor
timestamp: February 26, 2020, 02:10:36 pm
content: Quote from: tooki on February 25, 2020, 02:42:27 pmYou have a point about availability of items from eBay/Ali and the usual distributors.I'm not that sceptical about buying LEDs from eBay/Ali. As a general rule, I believe most sellers are honest and are not trying to rip people off. I would not hesitate in buying ordinary red, yellow, blue water clear/diffused or transparent green LEDs from eBay/Ali. The issue is, when buying from a distributor, they give the part number and data sheet, so I can be more sure about what I'm getting. Most Bay/Ali sellers don't have the part number or data sheet, so it could be anything. Quite often the specification listed will also be inconsistent, such as specifying the same intensity for all LEDs in the store, irrespective of their colour. You're right, any idiot can tell a red LED from a green one, but a layperson wouldn't necessarily know the relationship between colour and wavelength.https://www.ebay.co.uk/itm/Diffused-LEDs-1-8mm-3mm-5mm-Red-Blue-White-Green-Yellow-Orange-1st-CLASS-POST/121116641268?_trkparms=aid%3D1110002%26algo%3DSPLICE.SOI%26ao%3D1%26asc%3D20200116171858%26meid%3Df494b5f861284305985eed5123449fff%26pid%3D100008%26rk%3D3%26rkt%3D12%26sd%3D291252890071%26itm%3D121116641268%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DPromotedSellersOtherItemsV2%26brand%3DUnbranded&_trksid=p2047675.c100008.m2219Regarding searching for purple, rather than UV LEDs on eBay. Try adding -UV to the search string. I find I get more phosphor converted purple LEDs that way, although it doesn't eliminate violet or UV sold as purple, because the seller doesn't know and just puts purple in the listing, as that's the colour they see when they're powered.Quote from: stryker on February 25, 2020, 12:54:01 pmI have one of the more expensive Peak component testers I bought awhile ago, which does show the test current.https://docs.rs-online.com/36ac/0900766b803abf3e.pdfIf you have an oscilloscope you can measure it, by connecting a low value resistor, say 10R in series with the LED and pushing the test button and looking at the waveform. The current can be calculated using Ohm's law.

author: tooki
author_rank: Super Contributor
timestamp: February 27, 2020, 03:56:46 am
content: Quote from: Zero999 on February 26, 2020, 02:10:36 pmAs I’ve said at least once before: if you’re this skeptical (which you are, despite your claims to the contrary, since your explanations are just trying to justify that skepticism), then buy from the eBay/Ali vendors that specialize in LEDs. You’re not usually going to get the kind of datasheets you get from name brands that literally charge 10-20 times as much, but you will get all the key specs. (And on Ali especially, some are the actual web storefronts for manufacturers, and their websites sometimes have actual datasheets.) I don’t know why you keep trying to convince me that there are eBay vendors out there that have crappy specs; I never claimed otherwise. But that doesn’t mean that good vendors don’t exist!!!!Quote from: Zero999 on February 26, 2020, 02:10:36 pmYeah that’s kinda web basics, innit?Believe me, I’ve done extremely careful search term pruning, but never found PC purple LEDs being sold from China, other than built into Christmas lights and the like. Invariably, they were actually UV. The only discrete PC purple ones that came up were from western vendors selling them at outrageous prices. It’s been a while since I searched for them, so maybe it’s changed now, but I have extremely good google-fu (and eBay/Ali), and I could not find any.

author: Zero999
author_rank: Super Contributor
timestamp: February 27, 2020, 06:47:39 pm
content: Quote from: tooki on February 27, 2020, 03:56:46 amOf course I'm sceptical of anyone selling something very cheaply. I would be silly not to be. If I just want some generic, LEDs, not fussy about the colour or chemistry, then eBay/Ali seem ideal, but as I'm after something more specific, it's more tricky.I thought the store I linked to above looked decent, as they specialise in LEDs, until I noticed they specify the same brightness for all LED colours. Do you know of any sellers of InGaN diffuses green LEDs, who are good and will not sell me the crappy yellow-green ones?QuoteFirstly few LEDs sold as UV from eBay/Ali are actually UV. They're normally deep violet, around the 400nm to 420nm mark. This is not an issue in most applications, as it will still make most florescent materials glow brightly and the human eye isn't that sensitise to such wavelengths anyway. It's also much safer than real UV.Secondly, how do you know the Christmas lights aren't actually deep violet, rather than phosphor converted?Finally, have you actually tried messaging your favourite LED seller, asking them if it's something they can source?

author: tooki
author_rank: Super Contributor
timestamp: February 28, 2020, 04:26:46 am
content: Quote from: Zero999 on February 27, 2020, 06:47:39 pmBut InGaN green LEDs aren't anything remotely exotic these days. If anything, they've already significantly displaced traditional green LEDs. In every LED assortment I've ordered from eBay, the green have been InGaN. (But of course, they're also usually either SMD, or THT with stupid clear housing.)Quote from: Zero999 on February 27, 2020, 06:47:39 pmThat's a general component vendor who sells a few LEDs. Not an LED specialist by a long shot.With that said, if you look at their other LEDs, they are listing different brightnesses per color. It is (distantly) possible that the diffused ones, being intended as indicators, were actually selected to have the same brightness.The best LED vendor I've found so far ishttps://chelead.aliexpress.com/Everything I've gotten from them has matched the specs perfectly, packaging was good, and the selection is spectacular (nobody else carries even distantly as many white LED displays, for example, nor the 1-2mm thin LEDs). Anyhow, this store generally refers to the traditional yellow-green ones as "green", "light green", or "green 570nm", and the InGaN ones as "pure green". They have diffused InGaN green LEDs in diffused white (milky), diffused green, with and without flanges, in various sizes…Even so, they suck at listing the chemistry (they list everything as being AlGaInP, which is plainly incorrect). But the colors and voltages have all been absolutely correct in my experience. (In general, if a vendor is savvy enough to distinguish between yellow-green and other shades of green, and lists the wavelengths, you're not going to get surprised.)Another vendor that looks promising, but which I've never ordered from yet, is the one with the hands-down most bizarre name of any electronics supplier I've ever seen:https://molesmell.aliexpress.com(I wonder how much that name costs them in sales. And if they even realize what it means in English.)Quote from: Zero999 on February 27, 2020, 06:47:39 pmWell, they're usually listed as 395-400nm. Better vendors have quite granular wavelengths, from 400nm all the way down to even the mid-200nm, though the price increasesdramaticallythe farther you go.What counts as UV and what as violet seems to be a matter of opinion, as one sees various different cutoffs (heck, just within wikipedia, there's massive disagreement between pages). Without question, 395nm is right up at the longest wavelengths of what can be considered UV. But it's certainly not visible violet!Interestingly, if you search for e.g. 430nm LEDs, which are definitely in the true violet range, you find plenty — but only the high-wattage kind for illumination and glue curing. But never small indicator-style ones.Quote from: Zero999 on February 27, 2020, 06:47:39 pmBecause I own some, and they're nothing like the UV or pure violet LEDs. It's not the feeble glow of UV LEDs, it's a rich, bright purple. (And one that is easily split by a prism into its constituent blue and red.)The other clue is in pictures: the UV LED epoxy tends to glow a pale whitish blue, while pictures of the PC purple tend to show the epoxy as being more purple to pink. (Just like in real life.)Quote from: Zero999 on February 27, 2020, 06:47:39 pmNah, since I'm just a hobbyist. I wouldn't be ordering enough volume to warrant them custom ordering them. (If they had them at hand, they'd already list them.)

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: February 28, 2020, 05:26:53 am
content: Quote from: tooki on February 28, 2020, 04:26:46 amBet you an Ittinger it's actuallygoodfor sales. Most sellers have forgettable names, but if ever see Molesmell in search results even once, you'll remember them.(These sellers are too expensive for me ... usually go withSongxin Light Store, but that's mostly by virtue of them often having the best price, although they have been reliable so far.)

author: Chris56000
author_rank: Frequent Contributor
timestamp: February 28, 2020, 08:11:35 pm
content: Hi!At the risk of causing howls of derision, is it possible to make "brown" and "grey" light sources to complete the full set of Electronic Engineering colours?!Chris Williams

author: tooki
author_rank: Super Contributor
timestamp: February 28, 2020, 08:17:16 pm
content: Quote from: Chris56000 on February 28, 2020, 08:11:35 pmWell, brown is just dark orange, and gray is dark white.Technology Connections just did a video on this, in fact:

author: stryker
author_rank: Regular Contributor
timestamp: February 29, 2020, 10:29:39 am
content: Hi again brains trust,I foundthis Instructable by Becky Sternthat illustrated hot glue as one of the ideas for an LED diffuser.I'm pleased to say that combining that, with a square of aluminium foil tucked in around the base, shiny side up (Aldi Goliath brand, nothing but the best) and the 10mm green clear LEDs with the 3V VFI linked earlier, and the result is pretty much what I was looking for.The hot snot expands the beam of light to slightly past the width of the base, and the shiny foil bounces that back to fill the cylinder nicely. Without the foil, only the top half is visibly lit (with much of the light absorbed by the black plastic base that doubles as the top of the plastic garden spike). With the variability of the LEDs in that parts bin even from just one order I'll choose those with the highest measured VFfor these.Thanks to everyone for the helpful discussion and suggestions. I've learned a heap in this thread.One down, just 29 to go...cheers!Geoff

author: Zero999
author_rank: Super Contributor
timestamp: February 29, 2020, 07:49:15 pm
content: Quote from: tooki on February 28, 2020, 04:26:46 amYes, it's the InGaN green diffused, I'm sceptical about. I'll just have to order some and give them ago.QuoteThanks. Do you know of any ebay sellers? I don't have an Alie account, but will obviously get one, if needs be.QuoteYes, UV is not quite that well defined, since the sensitivity depends on the viewer. It probably also depends on the application. There are other areas of the EM spectrum which are divided depending on the origin of the radiation or application. One example is gamma, vs X-rays, of the same energy, the former being from atomic decay and the latter from the rapid deceleration of an electron.QuoteA true UV LED should light a dim pinkish/white colour, rather than purple, when vied with the naked eye, obviously cameras may differ and high quality UV LEDs use an epoxy which doesn't fluoresce.QuoteIf it's just for hobbyist purposes, then how about buying some cheap Christmas lights and dismantling them?Quote from: stryker on February 29, 2020, 10:29:39 amThat looks good. I'm not sure if the forward voltage really matters. InGaN has superior efficiency to the older yellow-green LEDs. A higher forward voltage drop might be slightly brighter, as it will have a higher power dissipation or it might just emit a slightly more bluish green. I suggest you experiment.