EBay seller selling fake LED's (non functional). - Page 1
Forum section: electronics / general

author: AhhhChoo
author_rank: Newbie
timestamp: April 01, 2014, 07:01:39 pm
content: HiJust so as no one else goes buying off this seller, the LED's they are selling are 100% fake. The 10W LED's (the ones we thought we'd try) don't actually contain any LED elements, just empty LED heatsink casings.Sellers name isitshotsale77www.ebay.co.uk/itm/400651599999We haven't lost much our selves, but someone might go buying a whole load of them thinking they are working parts when they are not. Becareful people.

author: sleemanj
author_rank: Super Contributor
timestamp: April 01, 2014, 08:47:25 pm
content: What did the seller say when you contacted them about it and gave them a chance to put it right before you placed your negative feedback?Edit to add: fake leds, while anything is possible, I'd be surprised. Especially since they have good feedbacks for this product from othershttp://www.feedbackselector.com/feedsearch.php?seller=itshotsale77&itemName=900-9000LM&pageNum=2click the next link at bottom of page, it searches 2000 feedbacks at a time, the only negative in the first few pages is yours on the first page and somebody who posted a positive but noted that 2 of 5 were doa.

author: jancumps
author_rank: Unknown
timestamp: April 01, 2014, 08:53:31 pm
content: Get it right with the seller first please. He's got 150.000+ positive reviews.Something can go wrong and then you first work it out before naming and shaming.

author: jancumps
author_rank: Unknown
timestamp: April 01, 2014, 09:01:09 pm
content: I've pinged the seller to point him to this post so that he's aware of a sale gone bad. I bet this is solvable.

author: mazurov
author_rank: Frequent Contributor
timestamp: April 01, 2014, 09:34:22 pm
content: Quote from: jancumps on April 01, 2014, 08:53:31 pmDon't pay much attention to this number. The ebay accounts are bought and sold all the time. 100K+ is typically grown sequentially by several owners; you will be obviously dealing with the last one only.I found places with 1K-10K feedback to be most adequate. Couple of 150K+ shops didn't even pay attention to my negative fb and ppal disputes when I had issues with their wares.

author: AhhhChoo
author_rank: Newbie
timestamp: April 02, 2014, 08:24:35 am
content: I've been asked to keep quiet about it (by the seller). They want to be allowed to continue to sell the fake LED's to the unsuspecting public. Should I keep quiet or should I let the world know about this chinese dealer selling fake goods?Excuses don't cut it with me I'm affraid, knowingly selling fake/faulty goods is wrong no matter what. They had their one and only chance as soon as they took my money and supplied the fake/faulty goods, I really dislike dealers who try it on and continue to do so given the chance (which is what they are asking me to allow).

author: amyk
author_rank: Super Contributor
timestamp: April 02, 2014, 09:41:23 am
content: Quote from: AhhhChoo on April 02, 2014, 08:24:35 amIs that just your assumption or did they really tell you that it's fake and they want to keep selling them...?My bet is on a bad production run, i.e. accident.Any pictures of these?

author: M4trix
author_rank: Frequent Contributor
timestamp: April 02, 2014, 10:45:22 am
content: Quote from: AhhhChoo on April 02, 2014, 08:24:35 amDon't stop and if needed escalate the case to a higher level. The whole market is flooded with fake, counterfeit parts. Most fakes are manufactured in China and this really should stop. Yea, it's a hard task but at least it should be brought down to a lowest degree as possible. That's why this thread and others are important to show people and educate them about all dangers lurking out there when using fake parts. Even the US army and their equipment is plagued with Chinese counterfeits! I also was a victim once when a chinese ebay seller sold me fake MJL3281/MJL1302. I got strange readings from these transistors and strange behaviour in one of my amps so I got one out and smashed it with a hammer. I must say I was surprised when I saw two small dies wired in parallel and glued to the case with white silicon glue! Of course the seller told me he didn't know nothing about this and he put the blame on his 'source' So, I gave the seller two options, to stop selling fakes or I'll report him to the ebay customer service. He chose, not to sell them anymore. Therefore, guys, don't keep it to yourself or cover such cases. Frauds should be behind bars!

author: Kjelt
author_rank: Super Contributor
timestamp: April 02, 2014, 11:32:25 am
content: Quote from: M4trix on April 02, 2014, 10:45:22 amThis "bought crap components in good faith from a reliable source" also happens with a good reputation firm like Farnell.When alerted they stop selling that batch (if lucky) but for the unfortunate people that already bought them they get a reply "there are no guarantees on any semiconductors". Its not that they test their merchandise before selling. So not much difference there.

author: M4trix
author_rank: Frequent Contributor
timestamp: April 02, 2014, 12:11:57 pm
content: Quote from: Kjelt on April 02, 2014, 11:32:25 amI can't believe that a respectable dealer like Farnell gave a such poor excuse for selling fake/counterfeit parts. It's like a slap in your face. Ok, I can accept something like, some parts are dodgy because of the manufacturing process so don't worry, our parts are 100% genuine. Anyways, it would be nice to have a sticky thread about fake parts and to have a place where people could share their experiences with fake parts.

author: PeterG
author_rank: Frequent Contributor
timestamp: April 02, 2014, 01:00:03 pm
content: Quote from: M4trix on April 02, 2014, 12:11:57 pmSeconded.

author: mrflibble
author_rank: Super Contributor
timestamp: April 02, 2014, 01:19:33 pm
content: Quote from: M4trix on April 02, 2014, 12:11:57 pmYou mean like this sticky thread?The Bad Experience Thread

author: M4trix
author_rank: Frequent Contributor
timestamp: April 02, 2014, 03:40:48 pm
content: Quote from: mrflibble on April 02, 2014, 01:19:33 pmOh, my bad.

author: jancumps
author_rank: Unknown
timestamp: April 02, 2014, 05:48:21 pm
content: Quote from: AhhhChoo on April 02, 2014, 08:24:35 amWell, if what you write in the first paragraph is exactly what he asked you, you should post that in here, because at that point it's not a one-sided story anymore. Can you post what he asked you?

author: Corporate666
author_rank: Unknown
timestamp: April 02, 2014, 09:29:14 pm
content: Quote from: mazurov on April 01, 2014, 09:34:22 pmeBay is very strict that accounts can't be sold without their consent, and from what I've heard from other sellers, they enforce it pretty rigorously. Even in cases where someone sells their business (even an online eBaying business) to someone else, eBay generally refuses to allow the user account to be transferred because the account reflects the person operating it, not the business abstractly.That's not to say someone can't just give their login to someone else, but from what I have seen, eBay watches for this and terminates accounts when they find it.

author: Corporate666
author_rank: Unknown
timestamp: April 02, 2014, 11:50:22 pm
content: Not necessarily related to the OP, but I looked at this eBay seller and just had to laugh at the feedback.People buying $1 headphones and complaining that they don't sound good, or a $5 dress and complaining the material is not of good quality. It astounds me the depths of cheapness that people have sunk to, while still expecting some form of quality.In regards to the 10W LED's... of course, it's dishonest to sell something that isn't what it's sold as... but a 10-watt LED being sold for 50p with free shipping? What exactly do people think they are buying? It's basically whatever was leftover on the floor of some clearing house for second hand Chinese stock. Someone somewhere looked inside a box and said "those look like LED's" when they were really leftover demonstration units from one of the million junk LED makers that went bust. Someone probably bought it in huge bulk and is just listing it at 20% over their cost to get rid of it all.Why on earth would anyone buy a Chinese 10W LED, let alone one from a seller who also sells lingerie, piggy banks, childrens clothing and plastic jewelry beads? Is it just the wattage that people can't resist? That 10W LED probably isn't anywhere close to being able to take 10W in the first place (even if it had dies in it), and whatever wattage it does take will be using the cheapest shittiest leftovers from the cheapest LED junk fab shop, so that it's probably achieving 30 lumens per watt. I bet a single half-decent 3W LED from someone like Cree will put out infinitely more light than this Chinese slice of shit, and will do so for ages longer and much more efficiently.I just can't understand why anyone would buy this? To me, it's like buying a $1 insulin pump from Alibaba.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: April 03, 2014, 12:30:35 am
content: To the original poster,How did you test the LED to determine that it is an empty case?The schematic shown on the eBay listing shows a 3x3 array of LEDs, so the forward voltage will be around 10V.Did you break the thing apart?Regards,Jay_Diddy_B

author: Unknown
author_rank: Unknown
timestamp: April 03, 2014, 12:41:58 am
content: Quote from: Corporate666 on April 02, 2014, 11:50:22 pmDon't knock them until you try one. Mine works just fine.Must go now, feeling sleepy ...

author: TerraHertz
author_rank: Super Contributor
timestamp: April 04, 2014, 10:33:54 am
content: Quote from: Jay_Diddy_B on April 03, 2014, 12:30:35 amThis.And the other thing I wondered: what prevents the OP from posting a picture of the broken-open 'empty' LED?Or the full text of the claimed 'request to keep quiet'?In short, why should we believe OP, any more than he believed the seller?

author: GeoffS
author_rank: Unknown
timestamp: April 04, 2014, 01:00:16 pm
content: If you have evidence, then why not post it and let people make up their own mind as to it's accuracy?

author: SpectrHz
author_rank: Contributor
timestamp: April 04, 2014, 01:02:52 pm
content: Quote from: AhhhChoo on April 04, 2014, 12:45:36 pmThis is a strange defensive measure you have taken... You come to the forums posting a controversial topic, (sole reason I clicked on it) about being scammed, and the seller has hardly any negative feedback? I smell an ebay purchase gone wrong, and you should have posted pictures from the get-go. So now, you are complaining about conjecture and that we are too critical and want more info... Well, it IS an engineering forum... Did you expect everyone to side with you from the limited info you provided?

author: mrflibble
author_rank: Super Contributor
timestamp: April 04, 2014, 01:05:53 pm
content: Quote from: AhhhChoo on April 04, 2014, 12:45:36 pmVested interest? Wut?Are we reading the same forum? All I see is some legitimate points being raised, that would apply to any ebay transaction gone wrong.QuoteGetting a warning about ebay sellers can be handy, but it does help to have a more complete picture. Especially, well, especially given some points that have already been raised. But now I might have a vested interest in that whathisname ebay seller as well.Anyways, if you have extra info that would help other people decide to avoid or not to avoid that buyer, please provide it.

author: sleemanj
author_rank: Super Contributor
timestamp: April 04, 2014, 01:35:17 pm
content: Quote from: AhhhChoo on April 04, 2014, 12:45:36 pmA lot of us sell stuff online, and we know only too well that some buyers start bad mouthing before even contacting the seller first, when if they did the seller will gladly sort out the problem. Mistakes happen, things do arrive DOA, or get lost in the post, or damaged or...Your initial post sounded like you had not contacted the seller before posting.Additionally, I have never heard of anybody else ever having reported that they got any of these high power multiple die leds that didn't have any actual die in them as you indicate is the case with yours. Not having any die in there is far more interesting than just a DOA.A google search doesn't reveal any obvious indication that this is something that is happening at all. If yours really doesn't have any die in it (as opposed to just being DOA - of course one assumes that you did actually properly current limit when you tested it) then it seems you're the only person who has actually stated this anywhere on the internet, and yet you're not going to post any evidence because people are skeptical - of course people are skeptical, because you are not posting any evidence of your claim.I went to buy a couple of these 1 pound 10w leds from the seller to confirm for myself the total lack of any active component in them, out of curiosity, but unfortunately they don't ship to NZ for some reason.

author: AhhhChoo
author_rank: Newbie
timestamp: April 04, 2014, 01:37:16 pm
content: Okey doke.The yellow filling is just colored silicone rubber, so is fairly easy to seperate out. Another set of LED's we have from else where are filled with a solid compound rather than a rubber compound.But anyway, pictures aren't going to help for some of you I know, but c'est la vie. We think youreallyneed to investigate for yourselves from this point on.

author: jancumps
author_rank: Unknown
timestamp: April 04, 2014, 01:53:36 pm
content: I asked you to fix with the seller first because:- I'd like to hear both sides of the story- you are here anonymously, but you name the seller explicitly, both in name and in link to his shop.- that's how you resolve sales disputes on ebay.

author: sleemanj
author_rank: Super Contributor
timestamp: April 04, 2014, 02:05:12 pm
content: Quote from: AhhhChoo on April 04, 2014, 01:37:16 pmWell, I'll be. It certainly looks like in that image that they are completely empty.I found a seller which looks like they are selling the same ones (same images, same selections, same text) on the au ebay site and ship to NZ, for a buck each (10W). Have bought a couple to satisfy my curiosity.

author: jancumps
author_rank: Unknown
timestamp: April 04, 2014, 02:11:39 pm
content: cool

author: M4trix
author_rank: Frequent Contributor
timestamp: April 04, 2014, 02:29:11 pm
content: Quote from: sleemanj on April 04, 2014, 02:05:12 pmIn case you receive same fake LED's, what will you do? Report the seller?

author: SpectrHz
author_rank: Contributor
timestamp: April 04, 2014, 02:29:43 pm
content: What a strange attitude you have... Regardless, it is interesting that they are totally empty... I wonder, would it even be worth leaving the elements out, at the risk of being called out for it? Or maybe just a manufacturing fluke?seems like a lot of effort to go to for a blatant scam.

author: JoeN
author_rank: Frequent Contributor
timestamp: April 04, 2014, 07:22:50 pm
content: Quote from: mazurov on April 01, 2014, 09:34:22 pmThe last time a seller ignored my ppal dispute I had my money back in 3 days after the escalation to a claim, the least amount of time it takes. It's good when they do that, PayPal will side with you. They have to respond.

author: amyk
author_rank: Super Contributor
timestamp: April 05, 2014, 03:34:08 pm
content: QuoteIt's silicone with the yellow phosphor, which is what a real working white LED (with die inside) of that construction would use too:http://www.digikey.com/en-US/articles/techzone/2011/feb/phosphor-film-conversion-for-white-ledsQuote from: SpectrHz on April 04, 2014, 02:29:43 pmThat's what I'm thinking as well - maybe they ran out of die somehow (and didn't notice), or the die dispenser malfunctioned, and the rest of the production line just continued filling in the blank leadframes with encapsulant.

author: London Lad
author_rank: Regular Contributor
timestamp: April 05, 2014, 04:33:25 pm
content: Bound to be a mistake if there really is no die but they are 99 pence including shipping to the UK !!!!Hardly worth starting a war over

author: TerraHertz
author_rank: Super Contributor
timestamp: April 06, 2014, 09:56:15 am
content: Quote from: AhhhChoo on April 04, 2014, 01:37:16 pmCool, thanks for showing. You know if you'd posted that in the first place, it would have saved some time."pictures aren't going to help for some of you I know" - That's unreasonably defensive. I think most people who asked you about it just wondered why you didn't post the pics originally.Anyway, the next question is, is it the real phosphor blue to yellow re-emitter compound, or just a batch of silicone someone mixed up? That would differentiate between 'production line goof', and outright intentional fraud.If you get a blue LED, and shine it through a fragment of the filler you cut out, is there any evidence of yellow fluorescence?

author: all_repair
author_rank: Frequent Contributor
timestamp: April 06, 2014, 10:46:54 am
content: You guys are getting it wrong as you are assuming the sellers are just like you who have engineering background and likely honest in nature. You can find these direct Chinese sellers not on ebay, but on Taobao. They give good value and good service. Those who sell China stuff on ebay are just reselles and traders, pure bussinessmen, slightly better than bankers and 2nd hand car salemen. They work to get their ratings up and have learned the ebay and able to game the ebay system. Ebay is not much better when tings do not work out well. These resellers when things do not turn out well shall manage the system. If they can get replacement from original seller in China, they shall assist. If they could not, and if the value is small, they shall absorb to buy the rating as you can see from some of buyer who sing and dance when he got his. When the amount is bigger, they shall walk away with no hesistation at all, but they shall manage the situation. They are not well like by original sellers in China as they pressed down price, drag payment and give a bad impression of the China product. The original sellers shall tell up front the problem, fake, broken, 2nd hand, option for cheap cnc controller, option for expensive controller, etc but all these declarations are intentionally left out.

author: miguelvp
author_rank: Super Contributor
timestamp: April 06, 2014, 10:52:34 am
content: So I was out of a job for a while and with a mortgage, what did I do, I start doing the ebay thing and even if I had a couple of close calls I remedy the situation immediately and kept my 100% rating.Haven't done it since 5 years when I got another job (an awesome job at that) but I call BS when you claim ignorance as a seller.

author: mrflibble
author_rank: Super Contributor
timestamp: April 06, 2014, 12:26:38 pm
content: Quote from: TerraHertz on April 06, 2014, 09:56:15 amGood question, and indeed a reasonable experiment to try to differentiate between "outright fraud" and "could be an honest mistake".

author: sleemanj
author_rank: Super Contributor
timestamp: April 15, 2014, 04:51:15 am
content: Quote from: sleemanj on April 04, 2014, 02:05:12 pmMy two leds arrived today, and somewhat disappointingly, they work perfectly.They were shipped in anti static bags inside a bubble envelope.The filling appears to be silicone (I haven't pulled it out but it feels a bit squishy) the same as the original poster's.You can't see any dies through the coating, nor bond wires, and I was thinking they were fake. But nope, I hooked em up with a 1k resistor and brought the voltage up slowly, all 9 dies in each were well lit up with 5 mA. Since it's not heatsunk I didn't bother pushing a proper amount of current into it, 5mA was enough to cause the old retina burn in.So, on the basis of that, I can at least say that not all these "10W" for a Buck led's are fakes, the two I got aren't, and they look identical to the ones that the original poster got.For sake of completeness, here's the listing I bought:http://www.ebay.com.au/itm/141172937767?var=440244682801&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649but looks like they've gone out of stock of the 10W ones.Photos attached.

author: miguelvp
author_rank: Super Contributor
timestamp: April 15, 2014, 05:15:51 am
content: Cool, maybe I'll revive my 1920x1200 lcd panel projector project after all.But for what is worth, your seller is a different one than his seller, looks like he still has a lot of them left from the picture that he posted earlier, maybe hook a 9V power supply and make sure it's the right polarity?

author: London Lad
author_rank: Regular Contributor
timestamp: April 15, 2014, 10:40:33 am
content: The dome being soft is quite common in high power leds these days

author: amyk
author_rank: Super Contributor
timestamp: April 15, 2014, 12:59:26 pm
content: If you're willing to sacrifice one of those working ones, it would be great to see what the die inside looks like. They're tiny, and the bond wires are also equally thin, so they can be pretty difficult to spot if encased in a mass of silicone. I'm not surprised that the die isn't visible - it's surrounded by the yellow phosphor, otherwise you'd see blue light.Quote from: London Lad on April 15, 2014, 10:40:33 amDefinitely, it's a cheaper process than epoxy encapsulation.

author: sleemanj
author_rank: Super Contributor
timestamp: April 15, 2014, 02:13:33 pm
content: Quote from: amyk on April 15, 2014, 12:59:26 pmDone.Careful picking away revealed one row, I couldn't see any bond wires, either they are too small to see with the naked eye, or perhaps embedded in the silicone I removed (I did look, but couldn't see anything), or perhaps there is some other means of connecting them, possibly using the substrate.Two rows were killed in the process, not sure if it was that I killed one of the dies or the electrical connection.I was able to light a couple of the dies in the exposed row just using my multimeter diode test and probing pretty much on top of the die either side. At least a couple of times, then I guess the coating was scratched off. Anyway, yeah, they are indeed blue.The die measure 0.59mm according to my calipers.So there you go, that's what's inside these leds.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 01, 2014, 10:10:02 pm
content: While we're on the topic on leds (I bought some after reading this thread) how hot should they be kept to? what's the maximum temperature this type of led should be run at?

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2014, 01:53:34 am
content: Quote from: AhhhChoo on April 02, 2014, 08:24:35 amThey actually asked you that, or you think they asked you that?A screenshot of the conversation / communications would be helpful.If indeed they asked you to be quiet, you should probably approach ebay to alert them of a fraud.If they didn't ask you to do what you think they asked you to do, you should probably approach ebay to alert them of a fraud too.

author: sleemanj
author_rank: Super Contributor
timestamp: May 02, 2014, 03:05:17 am
content: Quote from: AmmoJammo on May 01, 2014, 10:10:02 pmCooler the better. You probably want to keep the heatsink temperature down to about 70'C to 80'C. Don't even think about lighting one up full power without a heatsink for more than a fraction of a second flash to check it's working.About a year ago I did a quick google search for somebody and came up with the maximum silicon junction for the typical 1W type of led to be about 120'C, I'd guess that most of these power leds would be about the same. I don't think I found out the thermal resistance junction to tab/case/pad though.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 02, 2014, 05:41:41 am
content: I bought some of the 50watt leds, rated upto 34volts input. At 34volts they draw about 550ma. Hmm. Under 20watts...

author: Kjelt
author_rank: Super Contributor
timestamp: May 02, 2014, 10:42:16 am
content: Quote from: 3roomlab on May 02, 2014, 03:43:29 amand 99,99% of them probably are, but things happen and they don't always buy directly from the semi fabs companies esp. with ONS, rare components that are no longer made or in small quantities. Hey it happens to the best of firms, if the DOD gets caught with their pants down it can happen to any firm.

author: Towger
author_rank: Super Contributor
timestamp: May 02, 2014, 11:16:46 am
content: Quote from: AmmoJammo on May 02, 2014, 05:41:41 amTheir rating is in Chinese watts... I have a few 30W, 50W, and 100W white and RGB, from memory the 50w should draw around 1400ma at 34V. Are you sure they did not sent you a 30W module... The 30W, 50W and 100W are in the same physical package. Can you count the dies through the silicon?

author: David_AVD
author_rank: Super Contributor
timestamp: May 02, 2014, 11:48:57 am
content: Did you test them at all ?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 02, 2014, 12:00:06 pm
content: Quote from: Towger on May 02, 2014, 11:16:46 amI have this many!It was running off 25volts so I could take the photo50 dies in total.

author: M. András
author_rank: Super Contributor
timestamp: May 02, 2014, 12:00:36 pm
content: Quote from: pereczes on May 02, 2014, 11:45:17 amand where are the pictures of it showing what you recieved?

author: sleemanj
author_rank: Super Contributor
timestamp: May 02, 2014, 01:09:33 pm
content: Out of interest, what voltage and current limit did you test with, and what, if any, was the actual current drawn?(I'm trying to be careful not to teach a grandmother to suck eggs here - but well aware that sometimes people forget that LEDs really need a current limit :-)).Quote from: pereczes on May 02, 2014, 11:45:17 amLooks like on one of those photos you were scraping pretty hard. Note that the die are very small, half a millimeter or so across and can easily be pushed off the substrate and "vanish" (I just tried it myself with the one I pulled apart) looking like just a spec of dirt or something if you can find it.When I disassembled mine I was very careful and used the tip of a knife to cut and peel away the silicone to reveal the die.

author: sotos
author_rank: Frequent Contributor
timestamp: May 02, 2014, 01:15:06 pm
content: Except led’s he sells perfumes, Christmas lights, woman’s wrist watch, woman’s shorts, dresses, cats dog sleep warm bed house. What did you expect?

author: Towger
author_rank: Super Contributor
timestamp: May 02, 2014, 01:55:21 pm
content: Quote from: AmmoJammo on May 02, 2014, 12:00:06 pmYep. Thats a 50W module. I'll try one of mine and see how much power it draws, unfortunately they are at work and I am off until Tuesday.

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2014, 02:08:10 pm
content: QuoteThat's why the story (or more precisely this kind of stories) never made sense to me: in the end, they seller would have spent the postage and potentially some on the goods (if as others alleged he is just a middleman).What did he get in return? Nothing.Why would anyone do that?

author: mamalala
author_rank: Unknown
timestamp: May 02, 2014, 02:13:10 pm
content: Quote from: pereczes on May 02, 2014, 11:45:17 amAt least the product photo seems to be right. There are no die's to bee seen there. Normally one can just see the separate LED die's under the silicone. But not in those images. Sure, doesn't help with the seller selling fakes, but still... He could go all-out and claim "product as shown in the image" and be fine, since in the image these modules are empty.Greetings,Chris

author: London Lad
author_rank: Regular Contributor
timestamp: May 02, 2014, 02:14:13 pm
content: Quote from: dannyf on May 02, 2014, 02:08:10 pmExactly, the LEDs aren't 'fake' and there is no intention to defraud people out of 99p, either the two cases we know of here are the buyers not finding the dies or the seller has a faulty batch that were improperly manufactured.

author: mamalala
author_rank: Unknown
timestamp: May 02, 2014, 02:21:17 pm
content: Quote from: dannyf on May 02, 2014, 02:08:10 pmThose sellers are usually nothing more than box-pushers. They get boxes of stuff, if needed repackage them into smaller qty's, and then sell them. Most of the time they have no clue about what they sell. Just compare the eBay descriptions of the articles, from different sellers. Quite often these descriptions are 1:1 copied from elsewhere, including typos and stuff (yes, i know that often a single seller also appears under many eBay names, but i mean really different sellers).So if they get fakes they will likely be totally unaware of that. Luckily so far i never had a problem with stuff from Chinese sellers. On the contrary, i always got quick service from them, items re-sent if lost or broken, or the money reimbursed. And if something would really go wrong, i could always open a case with eBay and PayPal and get the money back that way. This is where PayPal is really the only thing to use: buying from Chinese sellers? Use PayPal only, to have at least a good chance to get the money back if the seller wants to play stupid.Greetings,Chris

author: sleemanj
author_rank: Super Contributor
timestamp: May 02, 2014, 02:50:56 pm
content: Quote from: pereczes on May 02, 2014, 01:37:24 pmEven in the working led i took apart i could not find the conductor, exact same construction soft silicon.Again, the die are VERY small, it is easy to scrape them off without finding them if you are not careful. The conductors, I never located any discete bond wires in my (previously) working unit which i disassembled and documented already above, but again it was working before i tore it apart so there was definately a conductive path somewhere but even with magnification i failed to find one, again, this was a (previously) working unit.l'm not saying you are wrong, just that it would be easy to accidentally lose the dies (if present) if you are roughly scraping out the silicone, and never find them. And never see any bond wires even when you find the dies (if present).

author: London Lad
author_rank: Regular Contributor
timestamp: May 02, 2014, 03:21:50 pm
content: The bond wire are much smaller than 1/10 mm

author: London Lad
author_rank: Regular Contributor
timestamp: May 02, 2014, 04:06:11 pm
content: I'm not trying to convince you (or anyone else) that the dies are not missing, just that if they are missing its most likely a manufacturing fault and not deliberate.I don't know what size the bond wires are but the ones I've seen look considerably smaller than 1/10 mmI ordered some of the same LEDs that the OP bought so I'll be interested to see when they arrive.

author: SeanB
author_rank: Super Contributor
timestamp: May 02, 2014, 04:07:12 pm
content: Send the reply to Ebay complaints dept, as the doing of business outside the Fleabay purview is frowned on.

author: London Lad
author_rank: Regular Contributor
timestamp: May 02, 2014, 04:16:09 pm
content: Quote from: SeanB on May 02, 2014, 04:07:12 pmI think the seller means contact them directly via the ebay message system rather than opening a case.

author: neslekkim
author_rank: Super Contributor
timestamp: May 02, 2014, 04:24:47 pm
content: Quote from: London Lad on May 02, 2014, 04:16:09 pmI find it more and more difficult to contact an seller without opening an case these days, on ebay.com it opens case, on ebay.co.uk it still allows you to contact seller without opening case.Have one going now, were I bought an stepup converterhttp://www.ebay.com/itm/141015393957and I got some led bulbs instead.. damn..

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2014, 04:48:33 pm
content: QuoteIt is hard to make a business out of buying parts, paying postage (however inexpensive it is), shipping a part over and getting nothing for that.QuoteAs long as you have to pay for postage, no matter how much cheaper it is, that business model makes zero sense to me.

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2014, 05:25:09 pm
content: QuoteWell, out of the two cases of "fake" leds we have here, both complained, and 1 is getting a full refund and you can tell us where you stand on that.So if your experience is representative, 100% of the customers will make noise;If your experience isn't representative, ...

author: Kjelt
author_rank: Super Contributor
timestamp: May 02, 2014, 05:51:46 pm
content: I think a lot of people might not even check the leds until it is too late or don't bother raising a case and take the loss.Let's say it in another way if you had a business selling a product X and you had a couple of complaints that product X was garbage, would you still be selling them or would you start an investigation and till that time take the product offline. Think there you have a big difference between a good seller and a i don't give any s*it seller.

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2014, 06:21:12 pm
content: QuoteIn that case, using a 10% probability of claiming refund to refute a substantial probability of claiming refund isn't too strong.

author: sleemanj
author_rank: Super Contributor
timestamp: May 03, 2014, 12:35:05 am
content: Quote from: pereczes on May 02, 2014, 03:07:47 pmin the working one i disassembled ALREADY DOCUMENTED IN THIS THREAD the die are NOT VISIBLE unlit through the silicone and as Ihave already posted they measure, o.59mm WITH MY CALIPERS directly measuring them after excavation, and that is probably slightly overread. about half of a millimeter each side.Comparing to "very small leds on circuits like arduino" is silly, they are bare die, not a discrete led with a casing and such soldered onto a heatsink, it is just a tiny grain of appropriately doped silicon bonded by some means to an aluminium substrate.As I have already posted the conductive path is not visibly apparent even with silicone removed, perhaps if i used a microcope i might have found them, obviously there was one because the led was working before i destroyed it. It's possible that the substrate itself has a part to play there.

author: dannyf
author_rank: Super Contributor
timestamp: May 03, 2014, 12:59:39 am
content: QuoteIt is helpful in a discussion to have an open mind. The fact that others have observations contradicting to yours doesn't by itself mean they are wrong. However strongly you believe in your observations and your ability to interpret them correctly, your experience is just as anecdote as the next person's.Hope it helps.

author: amyk
author_rank: Super Contributor
timestamp: May 03, 2014, 01:44:09 am
content: Just to clear up a few misunderstandings..."Die" can be both plural and singular.The visibility of the die through the phosphor depends on the concentration of phosphor in the silicone. Warm white LEDs will have a higher concentration and therefore look more opaque than cool white. Here's a good comparison from a seller of these:http://image.dhgate.com/albu_297105739_00-1.0x0/high-power-10w-warm-white-white-led-lamp.jpgWhen the light is to be made warm enough, the phosphor will look completely opaque.Regarding ampacity of bond wires, look at these documents:https://www.idt.com/document/atc/power-systems-design-estimating-bond-wire-current-carrying-capacityhttp://ece.wpi.edu/analog/resources/wire_current_handling.pdfhttp://www.palomartechnologies.com/blog/bid/53773/Gold-Ball-Bonding-for-LEDs-and-High-Power-ApplicationsThat 1A is spread across 3 parallel strings, so there's ~333mA in each one. The first linked document suggests that a 1 mil copper wire 3mm long would already be capable of carrying 560mA. 1 mil is 25.4um - and pretty much invisible to a human eye. If you've ever seen the bond wires of a MOSFET rated at >10A continuous you'd be surprised the first time how thin they are.Here's a 15A 2N3055 with the dimensions marked. Note the diameter of the bond wires relative to the die.

author: sleemanj
author_rank: Super Contributor
timestamp: May 03, 2014, 01:45:46 am
content: Quote from: pereczes on May 03, 2014, 12:47:51 amThis thread you are posting in. It includes all the details and photos of the previously working unit I disassembled, it also includes photos proving the unit was working.https://www.eevblog.com/forum/reviews/ebay-seller-selling-fake-led's-(non-functional)/msg425931/#msg425931https://www.eevblog.com/forum/reviews/ebay-seller-selling-fake-led's-(non-functional)/msg426172/#msg426172It is a 10W unit. 3 columns of 3 die.Die are not visible through the silicone.Die are squares of 0.59 mm diameter, measured with my digital calipers (but possibly overread slightly if there was any silicone still sticking to the edges of the die).Here are some more photoshttp://imgur.com/a/gePGSThe middle die from the exposed column is missing because I pushed it off yesterday to see how hard it was, it was easy.

author: Corporate666
author_rank: Unknown
timestamp: May 03, 2014, 02:29:30 am
content: Quote from: pereczes on May 02, 2014, 05:53:44 pmThere is no way anyone is selling fake non-working items on eBay as a calculated ruse to make money. eBay watches closely the feedback and number of cases, and even if a seller is selling thousands of items per day, if they are getting a lot of cases, they get banned from eBay.This eBay seller is getting more than 400 feedbacks per day - which means they are probably selling 1,000 to 1,500 items per day. They are not trying to be a big name in the LED business. Their business is buying wholesale lots of stuff at various Chinese outlets and listing it all on eBay. Somewhere, somehow a batch of junk LED's was made. Maybe they were photo samples. Maybe someone screwed up at the factory and the machine that puts the dies on didn't run, who knows. Point is, those were ultimately sold (probably numerous times) and this seller got them at some auction or as part of a huge lot of parts - and listed them all on eBay.The idea that they are selling dozens of legit items and then using that as a front to unload fake LED's just doesn't make sense.And Chinese customer service is nothing like Western service. "refund" is a foreign word to them... that's why they want to offer partial refunds. They don't know what dies are, they don't know what LED's are, they don't know what fake LED's are - it's just a box of stuff they bought as part of a container load of parts.The thing to do is just ask for a refund. It would be polite to do it through a message rather than opening up a dispute first. But if they don't reply, open a dispute and get your $$ back.

author: London Lad
author_rank: Regular Contributor
timestamp: May 03, 2014, 10:14:55 am
content: Quote from: Corporate666 on May 03, 2014, 02:29:30 amSpot on.I import thousands of Chinese components and assemblies every month and despite the distance, culture and language differences we have many positive business relationships spanning more than seven years.

author: mamalala
author_rank: Unknown
timestamp: May 03, 2014, 10:45:09 pm
content: Quote from: pereczes on May 03, 2014, 10:11:08 pmI have about 20 of these 10-watts floodlights here. Half of them cold-white, the other half warm-white. In every one of them the 9 dies are visible, and all of them are in 3 rows with 3 dies each. They are all effectively in series, since they all run roughly at around 30 volts @ 300 mili-amps. There are 10 watt chips available that have a 3s3p configuration, that is, three parallel strings of 3 dies in series.However, i had a 20 watt and a 50 watt quality LED here as well, and in those it was nearly impossible to see the single LED dies. Only under a bright light i was able to "see" the spots. But then, the 20 watt one was around 30 dollars, and the 50 watt one was around 70 dollars. That is, they really were quality chips, with well-specced characteristics.Those cheap Chinese LED's are far from that, of course.Greetings,Chris

author: David_AVD
author_rank: Super Contributor
timestamp: May 03, 2014, 11:02:29 pm
content: Quote from: pereczes on May 03, 2014, 10:11:08 pmSome of the high power LEDs (like the 20W white ones I use) need 18-20V to work. I don't recall what voltage they start illuminating, but 12V may not be enough.The easiest way to determine the Vf of the LED is to feed it from a much higher voltage (maybe 24V or higher) via a fairly high value resistor (say 10K). It may not be very bright, but it will be visible.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 04, 2014, 09:10:52 am
content: Quote from: Towger on May 02, 2014, 01:55:21 pmWe shall continue our own little conversation!34volts, 550ma, 19watts...35volts, 725ma, 25watts...Should I just keep turning it up till it breaks? lmao..

author: amyk
author_rank: Super Contributor
timestamp: May 04, 2014, 10:48:11 am
content: Give it some good heatsinking and then see if you can push it to 50W.Are those meters and the room being illuminated by it? That's pretty damn bright.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 04, 2014, 10:51:43 am
content: Quote from: amyk on May 04, 2014, 10:48:11 amI think they'll catch on fire before they get to 50watts...and, ah, no, the room is being illuminated by two 36watt fluro lights

author: GEuser
author_rank: Frequent Contributor
timestamp: May 04, 2014, 01:26:16 pm
content: @AmmoJammo (just quick as off topic)How is the auto range speed of that QM1549 , fast enough? , please ...

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 04, 2014, 09:01:41 pm
content: Quote from: GEuser on May 04, 2014, 01:26:16 pmThe QM1549 is reasonable... I bought it because the QM1543 is so stupidly slow!I'm sure if you go into your local Jaycar, they'll be happy for you to have a play

author: Towger
author_rank: Super Contributor
timestamp: May 06, 2014, 12:54:15 pm
content: Quote from: AmmoJammo on May 02, 2014, 12:00:06 pmI said I would do some testing. Here are the results:A warm white 50W Led module at:34V drawing 1.24A = 42Wand35.2V drawing 1.5A = 52.8W

author: Towger
author_rank: Super Contributor
timestamp: May 06, 2014, 01:03:07 pm
content: Here are two more photos of the setup, which made the above post too large.In the above two photos there was a paper card over the LED module to reduce the light.The dies were photo graphed at just over 22V, they were two bright at 24v.

author: amyk
author_rank: Super Contributor
timestamp: May 06, 2014, 01:16:22 pm
content: Judging by the lead connections and the pencilled markings, the original polarity was marked wrong?Maybe that could also lead many buyers to think they're broken, and also why they're so cheap...

author: Towger
author_rank: Super Contributor
timestamp: May 06, 2014, 01:33:43 pm
content: Quote from: amyk on May 06, 2014, 01:16:22 pmI added the pencil markings. All the ones I have see have the + and - like that. There is a 'slot' in the white plastic near the  + and - marks which is the correct polarity. It looks like they are 'press fit' against connectors in the LED floods. In the RGB versions the connections between the 'tabs' and this 'slot' is cut and the tabs are also cut to separate out the RGB die strings.

author: neslekkim
author_rank: Super Contributor
timestamp: May 06, 2014, 02:34:10 pm
content: Does it exists RGB versions of these also?, I have ordered the various sizes of these to test a little, maybe make better ligtning in the office.But RGB would have been awesome

author: Towger
author_rank: Super Contributor
timestamp: May 06, 2014, 04:54:23 pm
content: Just search for 100w RGB led on eBay. In reality they are closer to 90w unless you push it, but you need good heatsink and fan with to cool one. An old P4 CPU with heatsink compound is fine, the hard part is drilling holes to attach the LED.The Cree RGB led modules are more efficient, but they cost much more.

author: neslekkim
author_rank: Super Contributor
timestamp: May 06, 2014, 05:27:46 pm
content: Are all RGB version like this?http://www.ebay.com/itm/380599436493looks like the lamp is divided in three, for each color?

author: mamalala
author_rank: Unknown
timestamp: May 06, 2014, 06:54:15 pm
content: Quote from: neslekkim on May 06, 2014, 05:27:46 pmFrom what i know, yes. At least those cheap ones (never checked for better ones). This makes it rather awkward to use them at times, since you need some distance to the target you light up, so the RGB can "mix". Otherwise you end up with RGB stripes in varying intensities...Greetings,Chris

author: Towger
author_rank: Super Contributor
timestamp: May 06, 2014, 07:11:00 pm
content: Yep thats the one. That seller specialises is LEDs and his own led drivers etc etc. The total opposite of those who sell everything and anything and don't know that they do!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 06, 2014, 08:56:41 pm
content: Quote from: Towger on May 06, 2014, 12:54:15 pmSo, why does the one I've tested appear to measure low?Is it actually low, or is it an issue with my setup/power supply?I'm using an ebay boost regulator, originally designed to go to 33volts, modified to be adjusted up to 34voltsAs I don't have a suitable power supply...Is it possible that ripple is throwing my measurements off?

author: amyk
author_rank: Super Contributor
timestamp: May 06, 2014, 09:17:43 pm
content: Quote from: AmmoJammo on May 06, 2014, 08:56:41 pmI guess an exponential I-V curve combined with some small variability in the LEDs themselves could be the cause, along with temperature; although the specs say 33-35V @ 1.5A these really need a constant-current driver, not a regular voltage source. It's possible that the 33-35V spec is when it's reached steady-state operating temperature.Beware thermal runaway.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 06, 2014, 09:47:10 pm
content: Specs say 32-34voltsand I'm measuring half the power that someone else has!I don't see that as being caused by small variables in the leds.... Maybe I am doing something wrong

author: dannyf
author_rank: Super Contributor
timestamp: May 06, 2014, 09:52:17 pm
content: Because of the shape of V-I curve, a tiny error in V measurement can mean big errors.

author: David_AVD
author_rank: Super Contributor
timestamp: May 06, 2014, 11:24:58 pm
content: Are people really trying to use (or test) these LEDs with a constant voltage source? Sounds like a recipe for disaster.

author: dannyf
author_rank: Super Contributor
timestamp: May 07, 2014, 01:05:33 am
content: QuoteNot that bad: those power leds look substantially like resistors at high current levels.

author: Corporate666
author_rank: Unknown
timestamp: May 08, 2014, 04:36:01 am
content: Quote from: dannyf on May 07, 2014, 01:05:33 amExcept the forward voltage of the LED will drop as the temperature goes up - which it will with a 10W/50W/100W LED. A lot. And with a constant voltage driver, that means current goes up a lot.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 08, 2014, 07:49:09 am
content: Quote from: Corporate666 on May 08, 2014, 04:36:01 amexcept that the current Im measuring is 1/3rd what its meant to be in the first place... Would be nice if it went up!

author: David_AVD
author_rank: Super Contributor
timestamp: May 08, 2014, 09:34:35 am
content: The voltage specs on those cheap high power LEDs are not always correct.What I do is set the PSU current limit to the LED rated current and wind the voltage up to see if it reaches it.A few volts difference can make a huge difference to the current drawn. YMMV and all that.

author: Towger
author_rank: Super Contributor
timestamp: May 08, 2014, 10:17:47 am
content: Quote from: AmmoJammo on May 08, 2014, 07:49:09 amI would say it is your boost regulator. The (cough) 'quality' PSU I was using can supply up to 60V at 5A when run in parallel, as per the photo. Amongst other 'features' it sends out a large 'pulse' when the output is off and the mains power is then switched off in this mode. I need to measure the pulse, I have a feeling it is the full 60V+, as the flash from the LED is blindingFor those who were worried about the faith of my $2 ebay LED been run at a CV, the current rises around 200ma over 30 seconds as the LED and heatsink warms up before settling down. No LEDs were hurt during the couple of minutes it took to take the photos.

author: amyk
author_rank: Super Contributor
timestamp: May 08, 2014, 10:20:21 am
content: Quote from: AmmoJammo on May 08, 2014, 07:49:09 amNote Towger's values above -QuoteThat's a ~3.5% increase in voltage giving a 21% increase in current. Also as it warms up the forward voltage will drop.

author: dannyf
author_rank: Super Contributor
timestamp: May 08, 2014, 12:42:19 pm
content: QuoteDatasheets publish such data.As to tempco, I would imagine it is not far from -2mv/c * number of real diodes in serial.

author: Towger
author_rank: Super Contributor
timestamp: May 08, 2014, 01:13:19 pm
content: RGB '100W' LED module driven by an Adriano Uno clone with CC drivers set to 900ma per channel, cooled by a large AMD heat sink and fan:

author: neslekkim
author_rank: Super Contributor
timestamp: May 08, 2014, 06:42:16 pm
content: Quote from: pereczes on May 08, 2014, 12:29:18 pmWhich board are you driving them with on the pictures here?

author: Corporate666
author_rank: Unknown
timestamp: May 08, 2014, 09:50:53 pm
content: Quote from: AmmoJammo on May 08, 2014, 07:49:09 amSorry, I wasn't trying to comment on your particular case, just in general about driving LED's with constant voltage sources. At best, the temperature will change Vf which will change the current, so even the highest current achieved is less than max, it will still cause brightness (and color temperature) fluctuations. May not matter for some applications, but for any sort of commercial or usable lighting it would.As for your LED's - I went back through the thread... it's clear there are 50 dies in your 50W LED... so I can only guess that the listed Vf is wrong. That seems odd though, since 34V (if I remember correctly you stated this was the stated forward voltage of your array) seems about right for 10 dies in series. Are you sure your power supply is capable of delivering the current at that voltage - i.e. you're not running into a V/I limit?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 08, 2014, 10:07:15 pm
content: Quote from: Corporate666 on May 08, 2014, 09:50:53 pmCould be onto something thereBut I'd have to assume that if the current increased when I increased the voltage, that the psu must be able to deliver more than 550ma at the lower voltageI tested one of the same psu modules in another application... set to 28volts output, with 12.4volts input. A 12ohm resistor across the output, putting a 2.3amp load on it, and it ran fine for 40 minutes, till I decided to shut it down, as one heatsink was up to 95 degrees Celsius...I will however try to find a power supply that can give more current, and see what happens.

author: Corporate666
author_rank: Unknown
timestamp: May 09, 2014, 02:15:09 am
content: Quote from: AmmoJammo on May 08, 2014, 10:07:15 pmNot sure what you mean with the above sentence... but the current would be proportional to the voltage with an LED, so I wouldn't expect the same current at a lower voltage. I am not sure what your meter setup was but you should be able to easily test current through the LED and voltage across it. Those Chinese LED's have terrible spec sheets... if it says 34V, is that at 25C and 50W or is that the "test voltage" of the LED at something less than it's max? If you use your meters and confirm that 34V = 550mA, I'd crank the volts up... I can't think what manufacturing flaw could lead to an LED with a whacky V/I relationship.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 09, 2014, 01:21:08 pm
content: Quote from: pereczes on May 09, 2014, 07:59:27 amMine isn't the same, it doesn't have any current limiting or adjustment (only voltage adjustment)And, with 2.3amps output, at 28volts, (about 65watts) one heatsink got to 95 degrees Celsius... so, no, I don't think it'll do 100watts..

author: amyk
author_rank: Super Contributor
timestamp: May 10, 2014, 12:56:10 am
content: Quote from: Corporate666 on May 09, 2014, 02:15:09 amA LED is a non-ohmic device, current is proportional to exponential of the voltage.

author: Corporate666
author_rank: Unknown
timestamp: May 10, 2014, 01:05:08 am
content: Quote from: amyk on May 10, 2014, 12:56:10 amI understand that - I didn't mean it was a 1:1 ratio (perhaps proportional is the wrong word). I thought Ammo was saying that if his PSU couldn't deliver more than 550mA at 34V, that it should have been able to deliver more than 550mA at a lower voltage... maybe I understood him wrong, but I was just saying that while the PSU may be able to deliver a higher current level at a lower voltage, that lower voltage may not be sufficient to push that current through the LED.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 10, 2014, 01:26:25 am
content: Quote from: Corporate666 on May 10, 2014, 01:05:08 amKinda what I was saying, but not quiteIf the LED needs 1500ma at 34volts, but my PSU was limiting the current, then the PSU wouldn't have been able to do more current at the higher voltage that I tested, as the PSU would still be limiting the current.

author: David_AVD
author_rank: Super Contributor
timestamp: May 10, 2014, 02:52:54 am
content: Quote from: AmmoJammo on May 10, 2014, 01:26:25 amRemember that the power supply current limiting will likely result in the actual output voltage dropping (or stabilising).

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 10, 2014, 03:06:45 am
content: Quote from: David_AVD on May 10, 2014, 02:52:54 amThat's what I thought... It wasn't me that said:"Are you sure your power supply is capable of delivering the current at that voltage - i.e. you're not running into a V/I limit?"

author: London Lad
author_rank: Regular Contributor
timestamp: May 12, 2014, 12:07:23 pm
content: For what its worth I ordered the same 10 watt LEDs from the same vendor as the OP and they arrived last week.Stuck to a heat sink and powered from a constant current power supply at the specified current shown in the ebay listing they happily sit at the specified voltage give or take a tenth of a volt.Light output seems more or less to spec when measured with a light meter and compared to a known output light source. I cant be sure as I have no access to a proper integrating sphere.The bond wires are not visible to the naked eye but the die locations are.

author: dannyf
author_rank: Super Contributor
timestamp: May 13, 2014, 10:27:38 am
content: QuoteThank you for the public service.QuoteI think your experiment is fairly conclusive as to where the problem was.

author: neslekkim
author_rank: Super Contributor
timestamp: May 21, 2014, 05:02:46 pm
content: I bought some of these leds that was linked to, 5x 10watts, and one of each of 20, 30, 50 and 100watts.Almost impossible to see the die, only when hold in an angle I can see them.All work, but I have to turn up quite a lot on the psu to get them on, around 22-24volts before some of the die's start ligthing up. Does it mean that this is not best quality since some light up before of others, or is it natural?My psu (Tenma), did not display any amp usage, so Idon't know yet how many amps they where using, will check with an multimeter later, but need to get some heatsinks first.Do anyone know of any projects that use such leds?, I guess one should have an decent driver for these so they don't burn out, or use too much power?

author: amyk
author_rank: Super Contributor
timestamp: May 21, 2014, 08:24:37 pm
content: Quote from: neslekkim on May 21, 2014, 05:02:46 pmNatural variations in Vf will cause that, and the higher voltage is just because there are several die in series.Yes, you should really be using a CC driver on these LEDs.

author: neslekkim
author_rank: Super Contributor
timestamp: May 21, 2014, 11:32:05 pm
content: Quote from: amyk on May 21, 2014, 08:24:37 pmI asked, but there is of course no datasheets on these, so I have to find out what they can take.. I guess PWM can be used also?

author: miguelvp
author_rank: Super Contributor
timestamp: May 22, 2014, 01:39:03 am
content: Quote from: neslekkim on May 21, 2014, 11:32:05 pmWill this work?http://www.wayengineer.com/led-driver-module-upgrade-version-p-1040.htmlI know cheap parts so probably not too reliable, also some typosInput voltage range: 5-30VOutput voltage: 1.25V-26V (output is always lower 2V than input in the buck mode)Output current: 0.15A-2A (adjustable)Limit parameters: maximumoutput currentinput voltageis 32V, maximum input current is 2.6AGuessing that is the range of the current, they forgot to put a dash in the middle

author: dannyf
author_rank: Super Contributor
timestamp: May 22, 2014, 01:48:48 am
content: any smps can be made into a led driver. i would get an ebay module and modify it.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 22, 2014, 09:06:15 am
content: Umm... I bought some of the 10watt leds.... (I had bought 50watt from the same seller... and never measured 50watts into them...)http://www.ebay.com.au/itm/141172937767They are meant to be 12volt max, and draw 900ma... (12volts x 0.9amps = 10.8watts)Ah... at 12volt, they don't turn on.... they show no signs of life till 14volts....by 30volts, they are only drawing 110ma.... 3.3watts?

author: sleemanj
author_rank: Super Contributor
timestamp: May 22, 2014, 09:16:36 am
content: Quote from: AmmoJammo on May 22, 2014, 09:06:15 amHow many die can you count?The 10W ones should have 3 parallel columns of 3 leds. Each led will be around 3v forward (so around 9v forward voltage over the module)Do you have any current limiting device? Measuring the voltage directly across the LED module?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 22, 2014, 09:19:32 am
content: Quote from: sleemanj on May 22, 2014, 09:16:36 am9.... in series....Power supply has a current limit set to 500ma... PSU only goes to 30volts...

author: sleemanj
author_rank: Super Contributor
timestamp: May 22, 2014, 10:22:02 am
content: Quote from: AmmoJammo on May 22, 2014, 09:40:07 amHah, wow, that's an interesting one, weird.Get a bigger power supply and crank the juice up more :-)

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 22, 2014, 10:43:31 am
content: I was going to run them straight off a 12 volt battery with no real circuitry in between :p

author: David_AVD
author_rank: Super Contributor
timestamp: May 22, 2014, 11:01:01 am
content: The 20W LEDs I used for strobes required about 18-20V from memory. I ran them from 24V with a CC regulator and they worked a treat. Damn bright!Playing with any high power LED without a CC circuit in place is not the way to go.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 22, 2014, 11:11:49 am
content: Quote from: David_AVD on May 22, 2014, 11:01:01 amShe'll be right! I ordered 10, so I had sparesI was going to chuck a 0.5ohm resistor in series just for a lil bit of current limiting...Not much point now that I have 34volt leds!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 23, 2014, 01:12:02 am
content: Does anyone have a link to a seller who they got 10watt, 12volt leds from?I still need some to run off 12volts...

author: sleemanj
author_rank: Super Contributor
timestamp: May 23, 2014, 05:34:42 am
content: Quote from: AmmoJammo on May 23, 2014, 01:12:02 amBack on page 3 where I bought mine :-)http://www.ebay.com.au/itm/141172937767?var=440244682801&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649I bought warm white 10W, and they are 3x3 not the weird 1x9 like yours.(edit: actually, looks like you bought from the same seller, so perhaps it's luck of the draw, or the cool-white ones you have are different)

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 23, 2014, 05:50:17 am
content: I bought cool and warm white. Both appear to be 1x9.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 23, 2014, 11:34:19 am
content: Quote from: AmmoJammo on May 23, 2014, 05:50:17 amSeller responded:QuoteAnyway! As mentioned, I bought five cool white, and five warm white...I photographed one of the cool white, and they all look the same, however, the testing I did was with one of the warm white, and it needs 34voltsI haven't tested the other four warm white, and you can't see the dies through the silicone stuff...

author: sleemanj
author_rank: Super Contributor
timestamp: May 23, 2014, 11:44:22 am
content: Take the three bucks, add another 3, and buy a 60v boost converter on eBay :-)http://www.ebay.com.au/itm/DC-DC-Boost-Converter-4-34V-Step-up-to-4-60V-Adjustable-Module-15W-LM2587-/171127940202?pt=AU_B_I_Electrical_Test_Equipment&hash=item27d805246a&_uhb=1(disclaimer, have not bought one, no idea if seller is any good, just the cheapest I found)

author: sleemanj
author_rank: Super Contributor
timestamp: May 23, 2014, 12:06:54 pm
content: Quote from: AcHmed99 on May 23, 2014, 11:21:36 amCPU heatsinks can dissipate quite a lot of power and can be bought for a few bucks second hand.

author: sleemanj
author_rank: Super Contributor
timestamp: May 23, 2014, 01:29:38 pm
content: Quote from: AcHmed99 on May 23, 2014, 12:54:57 pmI don't have 20w available.But I just did a test with a "10w" led on an old intel heatsink, I think from a Pentium 4. I got about 45 (C) above ambient measured (with thermocouple) on one of the led's tabs.After about 1/2 an hour and seemed fairly stable, I didn't measure the actual power through the led just set the current to about 900mA (it's a 3x3 led).This is without fan running.The heatsink is approx 69x85mm and 38mm high, finned aluminium. The led was attached with double sided glass fibre thermal transfer tape. Led was pointing up, so heatsink was upside down which probably reduces it's effectiveness by some amount.Looks like this:

author: neslekkim
author_rank: Super Contributor
timestamp: May 23, 2014, 08:51:05 pm
content: Quote from: sleemanj on May 23, 2014, 05:34:42 amsame seller I used also, bought only cool white, and I think mine looked the same as the other cool white ones.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: May 23, 2014, 10:39:46 pm
content: Quote from: sleemanj on May 23, 2014, 11:44:22 amI have three of these:http://www.ebay.com.au/itm/351023576452But now, based on your temperature tests, I'm not sure I'd be able to fit a large enough heatsink into the torch I'd wanted to use anyway...It was a Milwaukee 12volt torch, that originally had a 10watt, 14.4volt globe, which draws 8.5watts at 12volts, and 5.5watts at 9volts...I was simply going to run the led directly off the battery, and see how it wentQuote from: neslekkim on May 23, 2014, 08:51:05 pmYou mean yours are 12volt too?Why does nothing ever work out for me?!

author: RobFromEarth
author_rank: Regular Contributor
timestamp: May 29, 2014, 08:47:18 pm
content: I have three of these:http://www.ebay.com.au/itm/351023576452I just bought one of these too, i have a 50W rgb led like this:http://www.ebay.com/itm/221270078822?_trksid=p2059210.m2749.l2649&var=520164494273&ssPageName=STRK%3AMEBIDX%3AITI also have a three channel controller that's rated at 600mA (each channel) and works at 12-24v (constant current). I think the 50W led is rated at 350mA per channel? I see that and much higher. I've never found any official specs or even a manufacturer name.How are folks powering LEDs like these when each color requires sometimes different volts/amps? The controller sends 24V to all three channels, but the red requires 20V max. On my old setup i was using constant voltage just to learn (just resistors to limit C, i had it working well enough aside from the massive waste of energy, so i decided to finally use a constant current controller.All of the controllers that i can find that let you vary volts and/or amps on each channel cost a *lot* more, and virtually every RGB LED i find (not just the cheap chinese based ones) require a lower voltage for red. I think putting a resistor on just the red channel will bring the current down as well as the volts, so that wouldn't work.Edit- i know the 600mA would be overdriving the LEDs, but interested to see how far i can push it with a good heatsink (with a fan)

author: onlooker
author_rank: Frequent Contributor
timestamp: May 31, 2014, 01:31:00 pm
content: I have never really played with power LEDs, but, to the basic understanding, the term "constant current source" literally implies voltage of the power source should be "irrelevant" . Then, in reality, the voltage is speced as a range, instaed of, a fixed voltage that is to be applied to your LED. As long as the working voltage of your LED is in the range, you are fine.As to the current value, from the few datasheets I read, at the minimum, all can set the current per channel by resisters. Which driver were you referring to?

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 01, 2014, 02:00:32 am
content: Yes, by putting a resistor on the output of the channel before the LED right? I guess my point was i thought that was one of the main points, to not waste lots of energy in the for of heat on the resistors. Otherwise, i might just as well be using constant voltage. My old system uses a constant voltage controller, it works well enough, except that the resistors get so warm that the room warms up, and that's using the smallest voltage drop i could.The controller i'm using now inputs a range, just like you say, 12-28 volts, the voltage on each channel (r, g and b) is the same as the input voltage, but the current stays at 600mA on each. The red channel on most all rgb emitters i've seen require a lower max voltage than the minimum voltage on the other channels, so there is no voltage range that works for all three LED diodes. So i'm guessing that the way folks normally power these is to put a resistor on the red output channel of the controller (before the LED) to drop the voltage down to the RED channels spec, but that would also lower the current, making the red channel dimmer than the other channels. I was hoping to find how other people are normally doing it.I should add, this is off topic, but the topic is dead, and this is one of the very few threads that i've found anywhere that talks about the specific LEDs i'm using, the inexpensive 50 and 100 watt RGB leds that are all over ebay. Eventually i'll use a better LED, but the main idea i think is to get something working, sowheni melt or fry something, i've only lost about 1/4 or 1/2 what a decent LED would cost. I succeded in blowing the red LEDs in a 50w led..Thanks

author: Corporate666
author_rank: Unknown
timestamp: June 01, 2014, 03:44:41 am
content: Quote from: RobFromEarth on June 01, 2014, 02:00:32 amI wouldn't go to the trouble of using a CC LED supply and then putting a resistor inline with one of the channels... what are the forward voltages of the three colors in your LED? Is the red really that much less that there are no drivers that support appropriate voltage ranges to drive it?I would just use separate drivers for each channel in that case.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 01, 2014, 06:36:58 am
content: I went to copy/paste the specs off the ebay channel, but they seemed to have changed. Most say 32-34VDC for all colors, i've seen that before, but before most of them said this: (this is a copy from when i bought the LED):1. Forward Voltage: RED 16-18v GREEN 24-28v BLUE 24-28v2. DC Forward Currect (IF) : 1500mA mA3. Output power: 48W4. Light Color: RGB5. View angle: 120Maybe they have new LEDs now with new specs, but the pictures and prices are the same.Seeing the new specs, i wanted to see if they were true, it would solve a few problems with this project if they were. I hooked up a variable power supply to red, started at 15V, red came on dim and blinks on and off. Increased until i think (forgot to write) it was 16V and was on solid and bright, up to 18, all good and a bit brighter, up to 21, blew the red out. Changed power supplies to make sure it wasn't a problem with the PS, no, red is blown. These are cheaply made LEDs, maybe the red channel was faulty, but from that, it seems the old specs were more correct than the new.Anyway, point is, according to the original specs (and experience now), red max volts is 18v, the min volts on the other colors are 24V. I'll look for another controller that has several versions for each channel's I and V. I was thinking i could keep the wiring to a minimum (fewer controllers) to make opportunity for failure later less likely (at some point there will be quite a few more), but you're probably right, that's probably the way to go. It's been impossible to get specs for these LEDs, everyone has different specs, and apparently the only way to verify anything is to hook it up to see if it blows up.One person did give me this link as a manufacturer of these panel style LEDshttp://www.epileds.com.twI didn't see any mention on that site of these models of LED, maybe these cheap LEDs are what become of the diodes that don't quite make the cut for the higher quality emitters.

author: David_AVD
author_rank: Super Contributor
timestamp: June 01, 2014, 07:24:02 am
content: Quote from: RobFromEarth on June 01, 2014, 06:36:58 amWell, using a constant voltage supply with no limiting (either a resistor or active device) will do that.

author: Towger
author_rank: Super Contributor
timestamp: June 01, 2014, 07:48:47 am
content: You need a CC driver per channel. Set all the drivers to your required current eg 600ma. Set the psu, to a voltage below the drivers max, but a few volts above the highest LEDs max.Switch it all on... Then measure the voltage on each channel. By the magic that is ohms law the LEDs will (should :-) ) all be in at their proper voltage, with the red lower than green and blue.

author: onlooker
author_rank: Frequent Contributor
timestamp: June 01, 2014, 01:33:19 pm
content: Well, the resister I was referring to is just simply a shunt/current feedback/current sensing resistor. The voltage drop on it is in 10s mV. It is NOT what one would use as in a constant voltage setup as suggested in the replies to my earlier post. Thinking just serial a resister alone and hoping the voltage drop would play magic is obviously a misunderstanding of a CC setup. One needs to feed the signal to the driver IC.The below is from WS2801 datasheetQuote

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 01, 2014, 11:39:20 pm
content: QuoteQuoteSo the LED will just keep drawing more power until it blows, i knew that, but it should be ok for a second or two just to verify? The idea was to keep increasing power to find out where it blows, these are cheap enough, and there are no "official" specs, so i figured it was worth it, but maybe it wasn't after all.QuoteDid you mean, "but a few volts below the highest LEDs max"? The drivers that i have don't have a way to set the current per channel that i can see. Here is the specs for the driver:Supply voltage: DC9-32VOutput: 3 channelsOutput current: <600mA(each channel)With 12VDC, ea channel can drive 1-3 3W LEDs (series)With 24VDC, ea channel can drive 1-6 3W LEDs (series)These are also very cheap drivers found on ebay, and like the LEDs i'll replace them with higher quality once i get everything working. Like the LEDs, there is no official specs or data sheet. I do have one of them now, i don't see any adjustments (pots, dip switches, etc) where i would adjust for current.Thanks again, I'm so close to having this working it seems, everything is working except the red channel, it sounds like i need to start using single channel drivers so i can control the volts on each. But there are so many 3 channel controllers made, and almost every RGB LED i've seen has the same condition, the red max volts is lower than the min on the other colors, you'd think they would have this designed into the drivers to adjust them, i'm just hoping it's possible that i'm still missing something. Maybe people are just running the red channel overspec and the LEDs they are using are able to cope for awhile..

author: David_AVD
author_rank: Super Contributor
timestamp: June 02, 2014, 12:14:52 am
content: The LED needs to be driven from a constant current (CC) source. The maximum voltage that the CC source can supply needs to be at least a little more than the LED forward voltage so the CC part of it has some working overhead.The CC source will limit the LED current to some predetermined amount. But... if the CC source can't supply enough voltage to the LED to satisfy the forward voltage, the desired current will never be achieved.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 02, 2014, 10:21:10 pm
content: I wasn't sure about that david, thanks for pointing that out. And thanks for all of the useful info, i'll most likely have to look for single channel drivers then since the only ones that let you control volts/amps on each channel to avoid sending red too much are too expensive for the project (i want to have several dozen of these at some point).Thank you,Rob

author: David_AVD
author_rank: Super Contributor
timestamp: June 02, 2014, 10:29:33 pm
content: The CC driver can't "send too much voltage" to the LED if you set the current limit correctly. That's the whole idea. If all 3 LED colours require the same current, then using a triple channel CC driver will be fine generally.The reason you see the resistor added to the red channel is to keep the voltage drop over the (linear) CC element within spec. What that spec is will depend on the CC driver chosen. Too much voltage dropped across the CC element may see its power dissipation exceeded.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 05, 2014, 07:43:31 am
content: I didn't know that, but not sure i understand totally.. If the driver is made to send 600mA, it'll adjust the voltage to change the current as it needs to keep it constant, i see that part, but why would itnotsend too much voltage? On the 50w RGB led i mentioned, the specs are RED 16-18v GREEN 24-28v BLUE 24-28v, so according to that, thereisno voltage that i can power the driver with that will work on all of the channels of the led, unless the driver lets you adjust the voltage output for each channel, or i put a resistor on the output for a channel, or am i missing something again?i.e., powering the led driver i mentioned with 24 volts, the minimum required for green and blue, the volts is higher than what the red channel is spec'd for, wouldn't it blow or decrease life, since all channels are sending 600mA at 24 volts?

author: David_AVD
author_rank: Super Contributor
timestamp: June 05, 2014, 11:40:45 am
content: The CC driver will try to maintain the set current by varying the voltage applied to the LED. If the driver runs out of voltage before the desired current is reached, the current will max out to some lower level.The LED forward voltage is relatively stable and acts somewhat like a zener diode. If you try to force too voltage into it, the current drawn will sharply rise (if the supply can deliver it) and the LED will go POOF!

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 05, 2014, 12:25:41 pm
content: So if i am going to use constant current with this LED, i need to either find one that will let me adjust voltage on each channel, or go with single channel drivers so each channel can have one that supplies the right voltage, that's what i was afraid of, but at least it's still workable. Not sure why the market is so saturated with 3 channel drivers that don't let you adjust voltage on red, while most every high power rgb led requires lower volts on the red than on green and blue, otherwise, as you say, poof..

author: theatrus
author_rank: Frequent Contributor
timestamp: June 05, 2014, 03:36:10 pm
content: You do not adjust voltage on a CC driver. Get that part out of your headA CC driver it's self adjusts voltage, from 0-Voutmax, in order to drive a set current through a sense resistor. If you have fewer LEDs in series or LEDs with lower Vf, there wouldn't be an issue.However, you should never mix different Vf LEDs in *parallel* on one driver channel. In fact parallel should be avoided all together. Also, linear CC drivers are very inefficient if their input voltage is not closely matched to the Vf of the string - use a switch mode driver.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 05, 2014, 06:49:43 pm
content: Ah, now that makes sense. Of course you wouldn't want to adjust volts, that would kill the point of having a CC driver! Why didn't i think of that!But i don't see any right now that i went through in my notes that have a different voltage for each channel, they all have the same voltage on each channel. But that means none of them are made to work with any LEDs, yet people still commonly use them Ok i ramble a bit, you guys are awesome to help me with my lack of understanding, i think i almost get it..I'm just using a single high power (50watt) RGB LED, it's not an led strip or string.The specs for the LED i'm using:1. Forward Voltage: RED 16-18v GREEN 24-28v BLUE 24-28v2. DC Forward Currect (IF) : 1500mA mAThe specs for the led driver that i'm using:constant current decoderDC9-32V input,3* 600ma channel outputVolts max on red on the LED is 18v, volts min on other colors is 24v. Volts out on CC driver is the same on each channel, i know it varies up and down a bit when adjusting to maintain current, but if i power the driver with 24v, the minimum for both green and blue, how to get the red to power on safely when volts is way above the max volts for it (by 6 volts)?

author: mariush
author_rank: Super Contributor
timestamp: June 05, 2014, 08:28:45 pm
content: if i power the driver with 24v, the minimum for both green and blue, how to get the red to power on safely when volts is way above the max volts for it (by 6 volts)?Worst case scenario, you could put a resistor in series with the red leds, which would drop 6-8v. You have ohm's law .. V = i x R ... if you want 500mA to go through, R = V / i = 8v / 0.5 = 16 ohm. Pick a 15 ohm or a 18ohm and you're good.The power dissipated in the resistor will be P = I x I x R = 0.25 x R ... so 3.75w for the 15ohm or 4.5w for the 18ohm resistor, meaning you'd have to use a 7-10w rated resistor or better.---Pay attention to the specs of your LED. It's a 50w led, and it says 1.5 A forward current, but that's for all three channels (colors) combined. You may not have exactly 500mA on each color, you probably have something like 10w red, 20w green, 20w blue ..red is much brighter than the other colors so the wattage could be different.Some drivers need more than the output voltage they have to reach, so if you power the driver with 24v and the driver can only output up to 23.5v or something like that, the driver may never reach the current limit you set.

author: David_AVD
author_rank: Super Contributor
timestamp: June 05, 2014, 09:31:47 pm
content: Quote from: RobFromEarth on June 05, 2014, 06:49:43 pmThe CC driver will adjust the drive current to the LED by varying the voltage. Because the LED is not linear (like a resistor), small changes in the applied voltage can make a huge difference to the current drawn.At voltages under some minimum level, the LED won't light up at all and the current drawn will be near zero. As you wind up the voltage the LED will start emitting light.Increasing the voltage will increase the light output, but after only a fairly small increase you'll be at the LED's limit. Push it any harder than that and it will draw exponentially more current and damage will occur.So, the LED has a very narrow voltage range it can be operated over. The CC driver adjusts the applied voltage to cause the desired current draw. The rest of the voltage (Vsupply - Vled) is dropped and dissipated as heat in the LED driver.I've assumed a linear CC source for this discussion. Other types operate a little differently, but the end result is the same for the LED.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 05, 2014, 10:06:42 pm
content: Thanks mariush,Yes, that's the same way i calculated resistors when i did the constant voltage version of the fixture. It worked really well, but also wasted a ton of current as heat in resistors. Also, the resistor for this case... Tt seems like it negates the advantage of using a CC driver. But, if i did that, would it still be CC on the red channel?David, yeah i found that out by hooking up to a variable power supply, at some number of volts below, the led would be super dim, a bit higher the led would be dim, but would actually blink. A bit higher it was perfect, then about 2 volts higher, the red channel went out permanently. Do you know if it's the current that kills it or the voltage? i.e. if i decide try it with just one led to see, if i use a lower current driver, do you think it may be ok? I know overspec is overspec, but for purposes of the project, if i can get a thousand or so hours of life from the emitter instead of the rated 40k hours (or whatever) it would be worth doing that way.

author: David_AVD
author_rank: Super Contributor
timestamp: June 05, 2014, 10:38:50 pm
content: It's the current (not voltage) that kills the LED. The excessive current is caused by applying too high a voltage to the LED without current limiting. The LED wanted to clamp the voltage at (say) 18V, but you forced it higher and the LED drew way more current than it was designed for.When you put a resistor in series with an LED you are providing current limiting that is dependent on the resistor value, the LED forward voltage and the power supply voltage. If the resistor is low enough in value and the power supply is high enough, you'll still get too much current through the LED.A linear CC source is like a variable resistor in series with a voltage. It automatically adjusts in value to maintain the desired current. The heat dissipated in a linear CC element is the same as it would have been in a simple series resistor. It's simply the current times the voltage dropped (P = I * V).Some RGB CC drivers use a resistor in the red supply to share some of that wasted power. The CC source still regulates the resistor + LED combination, but the CC driver doesn't heat up as much.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 05, 2014, 10:53:37 pm
content: Thanks for explaining this all for me, it makes a ton more sense now. I'll look closer at the parts i that thought i needed and see if i can come up with something that will work better. It's a lot more work that i expected to get it working, but will be worth it in the end. From all of this info, it seems the best way will be to get single channel drivers, each tailored to the channels on the led. Much more work to wire it in, more work to fit it all into the fixture, but now i know what i need to be doing. Thanks for helping me!Rob

author: onlooker
author_rank: Frequent Contributor
timestamp: June 06, 2014, 02:13:22 am
content: Let me try once more:1). If you were thinking serial a resistor alone (not the feedback type setup) to reduce the current, you are as well to just directly power you LED without using any CC driver since when the resistor value makes the current reaching the reducing point, the whole power source voltage will be passed to your LED+your resistor (100% PWM). In other words, the CC driver is redundant or a waste.2). It is hard to imagine a 50W LED driver/controller/decoder can not adjust current per channel. A cheapy WS2801 can do it and a ebay $3 3 channel controller can do it even better.http://www.ebay.com/itm/DC-12V-24V-12A-3-Channels-Dimmer-Controller-for-RGB-LED-Light-Strip-/301016573243?pt=US_Lighting_Parts_and_Accessories&hash=item4615fc653b(Disclaimer: no association and do not know if it will perform to the spec)For example, it mentioned "gradually color changing and color spring". Without the ability to adjust current per channel, these can't be done.3). You still need to understand what a CC is about and what the voltage spec of a driver module is about. And you seemed to have confused the voltage that is needed to power you driver module with the actual voltage applied to your 3 LEDs by the driver module. They are all different in general.If it is a proper decoder,The "DC9-32V input" is the voltage to power the driver module/decoder, it is not the voltage applied to each channel. The key function of the LED driver is to "calculate" and apply a proper voltage to each channel INDEPENDENTLY such that each channel will pass the set current (e.g. 600mA).Let's say you have your RBG LED connected to the 3 channels and powered the driver with a 32V power supply. Now you measure the voltages on the 3 channels. The red channel will show about 17V, the GREEN 26V and the BLUE 26V (or what ever voltages required to pass the set current) all at the same time.You call your driver decoder. Is it using a DMX decoder? In that case, you may set per channel current digitally. If with MCU, you can even program dynamic color patterns.Hope these help.

author: dannyf
author_rank: Super Contributor
timestamp: June 06, 2014, 10:48:29 am
content: Quotevia PWM?

author: onlooker
author_rank: Frequent Contributor
timestamp: June 06, 2014, 11:56:33 am
content: Ok, the two examples I gave are wrong. It looks like one is not a CC driver,it just applies the input voltage to the LED stripes plus PWM and the other uses internal MOSFET and external load resistor to do CC. A proper driver should have high efficiency DC/DC converter. It looks like some multi-channel IC for of this type may require LEDs to have matching LED strings. But some (e.g. ISL97900 says "is LED driver incorporates an independent current controlled driving mechanism for each of the LED's" ) can do true independent channels. The best bet may be just use 3 single channel drivers. If using a single power supply is desired, you need to have the high efficiency driver type.Maybe the OP can provide more details about his decoder.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 07, 2014, 08:47:30 am
content: I did get it that if i have to use a resistor on the red channel, the point of using a cc driver is moot. The drivers i was looking at specify an input voltage range that they work with, and i was assuming they deliver whatever voltage you power the driver with on the input to each output channel, but raise and lower it as required to maintain whatever current they're set for.QuoteI didn't see anywhere in the specs that it specified output voltages for each channel, that's why i assumed that it used whatever the input voltage value is, that's wrong?

author: David_AVD
author_rank: Super Contributor
timestamp: June 07, 2014, 09:28:58 am
content: Using a resistor on the red channel doesn't render the CC driver moot. It simple means that the CC driver doesn't have to drop as much voltage to get the current down to the right level. This is assuming the resistor value is chosen correctly.The output voltage of the CC driver will be less than the input voltage - whatever it needs to be to achieve the correct current. The drive current will often be set with a resistor in each CC drive element. Unless it's marked, you'd have to reverse engineer the circuit to work out what value corresponds to what current level.

author: onlooker
author_rank: Frequent Contributor
timestamp: June 07, 2014, 02:40:24 pm
content: Edit: To be clear, by OP I meant the new "OP"(=RFE) of this particular diversion of the thread.Ok, I am learning more along the way. My previous posts were assuming we were talking about CC drivers since the OP's RGB LED reqiures CC driver. Now, I realized that the DMX decoder the OP looked at is not a CC, but a CV type.These controllers/decoders may come in two types: the CC type and the CV type. A CC type should have mentioned it in its description since it is a strong salling point.A CV type will likely just apply the power supply directly on the output with PWM. It can only be used on LED modules speced to a fix voltage. Such LED modules can be just some regular LEDs serialed with a resister. If efficiency is not the concern, the OP can make his LED a fix voltage module in this way too. Once the fix voltage LED is selected, the input voltage to the decoder should be set to this fixed voltage and it can't be in a range anymore. For a 3 channel CV decoder (OP looked at) the LEDs must be modules with the same fixed voltage spec.Regardless a CC type or a CV type, the OP may still want to use a PWM decoder/controller to make the project a little more interesting. Otherwise, just using a simple CC or CV driver, the OP would be looking at a boring steady light.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 07, 2014, 04:34:48 pm
content: Ok, david that makes sense too. It's just that why buy a CC driver AND resistors. The main hope is to make it work as simply and cheaply as possible. If i use the CC driver, the voltage i need to drop on red is much higher than if i just scrap the whole cc driver idea and use three resistors, it's also cheaper and takes less room, given how big a 10 watt resistor is.

author: snp654
author_rank: Newbie
timestamp: June 11, 2014, 05:07:20 pm
content: I just attempted to take apart one of these 10W leds and let me tell you, its merely IMPOSSIBLE to remove the rubber compound without destroying the die and wire bonds. As soon as you peel the rubber up, the die comes right up with it (leaving a "empty" look). Check the yellow rubber pieces, I bet your die is stuck to it. Keep in mind that the die is EXTREMELY small. I performed this tear down under a microscope with precision tools. On a properly populated LED, you should be able to see the 9 dies through the yellow compound. I have bought over 50 of these from China with 100% success thus far.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 16, 2014, 01:41:12 pm
content: Yes onlooker, i am using CC drivers, my old setup used CV, and it works great, but it's so inefficient, i have almost two dozen of them running this way, and functionally, it works the way i was hoping, but kills the point with all of the power it wastes. So all of my questions were regarding CC drivers.With everyone's help, i think i have that resolved, the main thing right now is figuring out the best way to power everything. I have a 10A 24V (240watt) power supply, i was thinking that i should do fine by running several wires from the positive and negative post to the drivers, in other words, power them parallel, and the only thing i should need to be careful of is to stay roughly at 80% of the max load of the supply. So, 240 watts should be ok for (4) 50 watt LEDs right?I was actually hoping to power it using cat5, but cat 5 is usually 22 or 24 gauge, so i was going to double up on the wires, i.e. two wires for + and two for - (for each driver), this should be safe?

author: David_AVD
author_rank: Super Contributor
timestamp: June 16, 2014, 09:24:58 pm
content: It's not the CV vs CC that is the cause of the inefficiency.Any process where you use a linear element (diode, resistor, linear regulator, etc) will see the difference between the supply and LED voltage dissipated as heat. The wasted power is simply (Vsupply - Vled) * Iled.To maximise the efficiency you need to use a switch-mode regulator so the overall power loss is low. You "trade" voltage for current. You'll see inductors on the switch-mode CC drivers.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 17, 2014, 02:45:54 am
content: Ok, i think i understood that sort of, but that help explain that part, thanks, and i wondered why they always have those copper windings, now it makes sense.Does anyone have a suggestion on how best to wire the power? I was thinking before about using cat 5 with two wires each for + and - to handle the current (1.5A or so max), but probably will just use 18 gauge- it's simpler. But wire type aside, is it better to make several runs parallel from a power source for multiple light fixtures? The other option was to have each fixture have it's own separate power source, but i didn't like that because it would mean more AC cables running everywhere instead of low voltage. This way, it's one. larger power supply powering multiple fixtures, i'm just not sure if finding the max fixtures i can run on one power supply is as simple as what i was saying. The distance from power source to emitter would be a few feet usually, a dozen at most, so voltage drop with 18 gauge shouldn't be a problem.

author: David_AVD
author_rank: Super Contributor
timestamp: June 17, 2014, 08:07:18 am
content: I use CAT5 (1 pair for 0V and 1 pair for V+) for 12V 10W RGB floods with no issues over moderate distances.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 18, 2014, 11:40:57 pm
content: I'll use cat5 for sure for 10w, and i'm going to give it a shot for the 50w, only with three wires for each - and +, no harm in testing. These lights won't be on 24/7, more like a few hours per week..I just came across some info about constant current controllers. It was an old post, so rather than getting yet another account at yet another forum, i thought i'd ask here. Here is part of the post:A Buck Puck is an active device because it changes it's internal resistance constantly to give a perfect 1000ma current flow. This makes it voltage agnostic. You can feed it from 5-32 volts, and it will run whatever LED you have at 1000ma (which as a side effect adjusts it's voltage to fit whatever the forward voltage of the LED(s) are). The six wire Buck Puck has one additional feature: it will allow a small device to turn it on and off. It is like the PEX but with active current limiting.I've seen the same behavior implied with constant current controllers in general, is this specific to buck pucks, or constant controllers in general? I've never found a direct answer about how i can use a RGB led on any 3 channel controller when the red channel always has a lower volts max than the other channels' minimum voltages. In other words, from specs, all of the RGB LEDs i've found require at a maximum, X volts for red, while needing a larger voltage as aminimumfor the other colors.I guess it boils down to, i don't understand the idea that's implied that voltage doesn't matter, and the led just somehow takes whatever voltage is needed and magically avoids getting too high a voltage. And if that's the case, there should be nothing wrong with using a 24 volt constant current driver on 2-3volt LEDs, as long as the current doesn't go above the max amount (750mA in this case)

author: dannyf
author_rank: Super Contributor
timestamp: June 19, 2014, 12:03:13 am
content: It is basically a variable output voltage power supply to deliver (always) 1000ma into the load.Nothing more complicated than that.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 19, 2014, 06:29:23 am
content: Does that mean that if i have an RGB driver that takes in 24 volts and supplies 750mA on each channel, i can hook it to an RGB 10W LED that expects only 2-3 volts max and a current of 750mA on each channel? The current is right, but the fact that the voltage is twelve times the max rating, that won't blow the lid off of the led?

author: David_AVD
author_rank: Super Contributor
timestamp: June 19, 2014, 06:42:05 am
content: It won't blow the LED, but a linear CC driver may not be rated to drop that much voltage and deal with the resultant power dissipation. A switching type CC driver should be ok though.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 19, 2014, 11:34:18 am
content: Ok, is there any way to tell from specs whether it's safe, or do most people just try it and see what happens? It seems like it would be hard to judge whether you're affecting how long the LED will work. And by the way, thanks for helping me with this, i don't feel like a slow person in general. Except with electricity because it can do some funky damage.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 19, 2014, 11:42:56 am
content: I just reread that, what is a switching type cc driver, does that refer to pwm? I know the ones i'm using are pwm..

author: dannyf
author_rank: Super Contributor
timestamp: June 19, 2014, 12:12:59 pm
content: QuoteThe module will adjust its output voltage (to the LED) so that only 750ma current will flow through the led.How much input voltage the module can take is (largely) irrelevant.

author: David_AVD
author_rank: Super Contributor
timestamp: June 19, 2014, 12:14:37 pm
content: You can have a linear CC driver with PWM dimming or a switch-mode CC driver with dimming. The switch-mode is already doing PWM in a manner and the dimming control modifies that.The CC driver should have specs to say what the allowable supply and LED voltage ranges are.

author: onlooker
author_rank: Frequent Contributor
timestamp: June 20, 2014, 11:37:15 am
content: RFE, if you are still in doubt, you may test the setup with dummy resistive loads such as power resistors from several ohms to a few tens of ohms in value, or bulb for, say, car lamps.1st, pick 3 of them with different resistor values or voltage specs. 12V bulbs for car lamps are good here. Serial two 12V ones give you a 24V speced load. For power resistors 10R10W, or 20R15W should be more than workable.Then connect them to the CC in place of what your RGB LED would.Now measure the voltages crossing your dummy loads. You will see a different voltage on ecah channel. But all channels have the same current 0.6A. Though, the input is from the same shared voltage source.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 22, 2014, 07:02:26 pm
content: Ok, thanks again. After re reading all of the messages from people that took time to help, it seems i'm making a big deal out of something that isn't much of anything. But the specs for this particular LED (that costs $41) say specifically what the max voltages are, using a CC driver apparently makes that info n/a. So still being unsure, i hooked it up anyway. Oddly enough, it works, all leds look equally bright (so red doesn't seem overdriven). Well, i still don't understand why something that has an absolute max voltage rating of 8 volts (in this vase, for the red) works fine at 12 volts. I get it that the 12 volts is being adjusted up/down to make sure there is 600mA available (in the case of this particular driver), but anything over 9 volts blew the red when running it using just a current limiting resistor. Well, you guys all say this is how it works, and i tried it with my new $41 led, and it worked exactly like you all said it would, so i'll shut up now and be happy it didn't blow. Thanks for all of the help and info, i just wish i would have stayed with electronics engineering in college instead of switching over to soft eng now!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: June 22, 2014, 08:18:43 pm
content: A guy I used to work with had run LEDs directly off the rectified mains voltage, with a suitable resistorWorked fine, except when he wired an LED backwards and it promptly failed...

author: dannyf
author_rank: Super Contributor
timestamp: June 23, 2014, 09:39:47 am
content: QuoteIt didn't work at 12v - it works at something less than 8v.That's like saying that your phone, designed to work with 5vdc, cannot be charged from the 110vac/220vac mains: that's why you have a charger to step down the mains voltage to 5vdc.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 25, 2014, 07:23:44 am
content: The input to this driver can be anything from 9-24V, and my assumption was that the output voltage would equal the input voltage, otherwise what's the point of having a range of input voltages. The led i have hooked up to it right now has these specs:RED 16-18v GREEN 24-28v BLUE 24-28vI have 24V on the input. I measured volts on the red channel and it reads around 24v. Yeah, i feel a little slow i guess here, but i still don't see why hooking 24v into an led that's rated at 18v max is going to be safe, even if the current is maintained in spec. If it's fine, then who cares what i think right? But how can i know how many volts is safe if the max rating stated by the mfg. isn't really the max rating? If i have a driver that will take 120vdc on the input, and supply 600mA on the output channels, that will be safe as well?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: June 25, 2014, 07:50:22 am
content: Did you have the led connected when measuring the voltage?

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 25, 2014, 04:08:28 pm
content: I disconnected the common and red from the driver and measured between those leads, it read around 24v, i'm just not sure if it's safe to run for very long since it's 6v higher than what the red is supposed to get according to the mfg. specs, even though the driver maintains 600mA, which is 150mA lower than max. I guess what i am getting from the forum is don't worry about it, it's safe. But 24v is a lot higher than the mfg. stated maximum voltage of 18v, and i've blown other LEDs by trying to push the max volts.

author: mamalala
author_rank: Unknown
timestamp: June 25, 2014, 08:13:32 pm
content: Quote from: RobFromEarth on June 25, 2014, 04:08:28 pm

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: June 25, 2014, 08:21:49 pm
content: connect the led.it will be getting 600ma at somewhere around 17volts.you can't limit the current if there's nothing to limit the current into...

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 26, 2014, 03:46:23 am
content: Ok, so for whatever black box reason, something somewhere keeps the voltage at whatever the LED's rated max is, but at least i know it works, or should anyway, for this particular led/driver combo. I still don't know how it works, so once the specs/voltages/led/driver changes, i'm right back where i started. The driver takes a range of voltages, 9-24 in this case, and outputs the input voltage, supplying 600mA on four outputs, one each for red, green, blue and white. the G and B and W have similar mins and maxes, but the red's max voltage is always quite a bit lower. Noone is saying it straight out, but from what i'm getting, just hook the darn thing up and it will work, even though1. the input voltage to the driver = the output voltage, whatever volts you feed it is what it has on the outputs2. but the current stays at 600mA, it converts volts to current as needed to keep it at 600mA (so the volts varies a bit)3. the volts is the same on every output, so 24v in means 24v on each output, and it does vary a bit to keep the current on each at 600mA4. Each channel, green, blue and white is fine with this particular LED, but red's max volts is 18.So what i gather, somehow, maybe it's magic, the 24v on the output doesn't blow the LED. So i'm guessing that the 24V is what it's getting, and it *is* overspec, but since the current is being maintained, it's not showing obvious signs of damage, but since it's being run at quite a bit higher than the 18v max spec, lifetime will be decreased. This is all speculation and guesses, i haven't seen any direct answers yet, but it's what seems to be said. Well ammo said 17v is what it will get. Ok for the cheap LED and it worked, but the driver output measured around 24v (when disconnected), not 17v, and don't want to try with the other led until i get this part since they're $40 each

author: David_AVD
author_rank: Super Contributor
timestamp: June 26, 2014, 07:22:05 am
content: Rob, a couple of pages back I explained that an LED works somewhat like a zener diode. It conducts very little below a certain threshold.As soon as you get to that threshold it starts to keep the voltage across it constant. If you try to force a higher voltage (via a low impedance supply) the LED will blow up. You've seen that first hand.The CC regulator tries to maintain a set current flow in the LED. It does this by cranking up the voltage while keeping an eye on the current.As soon as the set current is achieved it stops increasing the voltage. If the actual current starts to drop (LED cools down or whatever) it will increase the voltage again to get back to the set current.Conversely, if the actual current starts to increase (LED warms up for example) it will decrease the voltage again to get back to the set current.All of this happens automatically and at such a rapid rate that you don't see the regulation happen visibly. Has it "clicked" yet?

author: RobFromEarth
author_rank: Regular Contributor
timestamp: June 27, 2014, 02:13:26 pm
content: QuoteI do remember you mentioning that, i've heard of zener diodes, but i'm not familiar with them, so it was mostly greek to me, but thanks for explaining more now it makes more sense (to me anyway). It apparently must be common sense, something i lack when it comes to subatomic particles like electrons and neutrons.The thing that's not "clicking" is that if i put 24 volts in, why i'm not getting 24 volts out, it must be going somewhere. In the case of using a current limiting resistor, it's lost as heat, but there is no heat, or very little, with the cc drivers. Well it's a black box to me, but it works, that's the important thing, i was hoping to understand it better so i can know what i'm doing with different drivers/power supplies, leds etc, but i'll just have to accept that my mind is probably too small to contain it all at one time. Thanks everyone for all of the help, i do understand much better than i did.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: July 03, 2014, 09:00:44 am
content: I bought 10 more 10watt leds from a different seller...guess what...THEY'RE ALL STILL BLOODY WELL 32 VOLTS LEDS, NOT 12 VOLT?!?!So, now I have TWENTY leds, that I can't use!

author: David_AVD
author_rank: Super Contributor
timestamp: July 03, 2014, 12:24:29 pm
content: Quote from: AmmoJammo on July 03, 2014, 09:00:44 amLink please?

author: amyk
author_rank: Super Contributor
timestamp: July 03, 2014, 12:53:44 pm
content: Buy or build a constant-current boost converter...

author: dannyf
author_rank: Super Contributor
timestamp: July 03, 2014, 01:50:59 pm
content: QuoteBecause you paid dearly for that driver.Otherwise, you could simply use a wire in place of that driver: 24 volt in, 24 volt out.

author: Corporate666
author_rank: Unknown
timestamp: July 03, 2014, 04:56:14 pm
content: Quote from: RobFromEarth on June 27, 2014, 02:13:26 pmVolts and amps are related - you can't have one without the other (V=IR)... so for amps to rise, volts have to go up also. That's what the LED driver does... it will adjust the voltage until the specified current is reached.When you measure the output of your driver, you see the maximum voltage of 24V. That is because you put your multimeter probes over those two wires... the meter is high resistance, let's say 1 megaohm... and to push 600mA through 1 megaohm would require a TON of voltage (V=IR). The supply can't produce that voltage so it quickly hits it's upper limit and stays there. You could only realistically test the output with an LED (or dummy load) connected... then the power supply will actually be regulating the output and you could measure what that voltage level is that is bring produced to achieve the specified current.As for what happens to the voltage... there are two kinds of power supply. Linear and switching. A linear supply has to burn off that extra energy, usually in the form of heat. A switching supply quickly turns on and off the output... the ratio of on/off determines the output power. So if you had 100V/1A input (100W) and turned on and off the output very quickly...on for 1/1000th of a second, then off for 1/1000th of a second... the output would be on half the time and off half the time. That would be about 50W of output power (if it was 100% efficient, which it's not - but close). Of course, electronics don't like to be turned on and off quickly and still keep working, so you need something to smooth out those on/off transitions and provide a constant output. That something is either an inductor or a capacitor or both. The inductor or capacitor is sized such that it stores enough energy to power the circuit during the off phase without having too much loss or power consumption during the on phase.Make sense?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: July 03, 2014, 10:20:38 pm
content: Quote from: David_AVD on July 03, 2014, 12:24:29 pmSecond lot came from here:http://www.ebay.com.au/itm/231113487725

author: David_AVD
author_rank: Super Contributor
timestamp: July 03, 2014, 10:54:23 pm
content: Do the physical dimensions agree with the 10W specs? Wondering if they sent you 20W LEDs ?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: July 03, 2014, 11:34:51 pm
content: Quote from: David_AVD on July 03, 2014, 10:54:23 pm20mm wide, 29mm long (including the terminals for connecting power)They're the same as the first 10watt I bought, all 9 dies in series, rather than a 3x3 grid.

author: David_AVD
author_rank: Super Contributor
timestamp: July 04, 2014, 12:50:39 am
content: Seems a clear case of "item not as described" to me and cause for a claim.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: July 04, 2014, 09:14:23 pm
content: Quote from: David_AVD on July 04, 2014, 12:50:39 amThat's what I'm doing... The first lot, I got half my money back, but I still need 12volt leds!One is for an oil lamp, I want to put an LED in, with a simple constant current regulator being run from a 15volt plug pack that I got for free... I also want to use one or two in torches, one directly off an 11.1volt lithium-ion battery... I believe the LEDs will shut off completely at 9volts, which is the safe discharge point of the battery...

author: David_AVD
author_rank: Super Contributor
timestamp: July 04, 2014, 11:02:56 pm
content: I'd probably use a boost converter and the 20-something Volt LEDs.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: July 04, 2014, 11:23:30 pm
content: Quote from: David_AVD on July 04, 2014, 11:02:56 pm30+ volt...

author: David_AVD
author_rank: Super Contributor
timestamp: July 05, 2014, 12:16:28 am
content: Quote from: AmmoJammo on July 04, 2014, 11:23:30 pmLOL - ok 30+ Volt then. I'm sure there's a heap of simple IC + inductor solutions out there these days.

author: sleemanj
author_rank: Super Contributor
timestamp: July 05, 2014, 01:27:56 am
content: Quote from: AmmoJammo on July 03, 2014, 11:34:51 pmYou might be better looking on Aliexpress (or Taobao) tend to get more places who specialise in electronics and can easily check the feedback for those specific items, here's a couple of AliExpress seller who has good feedback for the 10W 9-12V ones.http://www.aliexpress.com/item/10PCS-LOT-10W-900-1000LM-LED-Bulb-IC-SMD-Lamp-Light-Daylight-white-High-Power-LED/892676886.htmlhttp://www.aliexpress.com/item/Free-shipping-10W-LED-Integrated-High-power-LED-Lamp-Beads-white-900mA-9-0-12-0V/1675873447.html#feedback

author: RobFromEarth
author_rank: Regular Contributor
timestamp: July 05, 2014, 05:37:34 am
content: Thanks for that explanation, i was aware of the switching, this is the same thing as PWM? The fact that i wasn't getting the right measurement because there is no load, that was mentioned by someone else too, and i still managed to overlook it. Clumsy, even for a newb.. Is PWM just one specific type of SMPS then?Quote from: Corporate666 on July 03, 2014, 04:56:14 pmVolts and amps are related - you can't have one without the other (V=IR)... so for amps to rise, volts have to go up also. That's what the LED driver does... it will adjust the voltage until the specified current is reached.When you measure the output of your driver, you see the maximum voltage of 24V. That is because you put your multimeter probes over those two wires... the meter is high resistance, let's say 1 megaohm... and to push 600mA through 1 megaohm would require a TON of voltage (V=IR). The supply can't produce that voltage so it quickly hits it's upper limit and stays there. You could only realistically test the output with an LED (or dummy load) connected... then the power supply will actually be regulating the output and you could measure what that voltage level is that is bring produced to achieve the specified current.As for what happens to the voltage... there are two kinds of power supply. Linear and switching. A linear supply has to burn off that extra energy, usually in the form of heat. A switching supply quickly turns on and off the output... the ratio of on/off determines the output power. So if you had 100V/1A input (100W) and turned on and off the output very quickly...on for 1/1000th of a second, then off for 1/1000th of a second... the output would be on half the time and off half the time. That would be about 50W of output power (if it was 100% efficient, which it's not - but close). Of course, electronics don't like to be turned on and off quickly and still keep working, so you need something to smooth out those on/off transitions and provide a constant output. That something is either an inductor or a capacitor or both. The inductor or capacitor is sized such that it stores enough energy to power the circuit during the off phase without having too much loss or power consumption during the on phase.Make sense?

author: Corporate666
author_rank: Unknown
timestamp: July 05, 2014, 06:34:46 am
content: Quote from: RobFromEarth on July 05, 2014, 05:37:34 amIt's similar to PWM in that the ratio of on/off decides the output level. In an SMPS there is usually a feedback mechanism to the switching control so that the switching on/off time can be adjusted to stick to the specified output level. Great Wiki article on SMPS's.http://en.wikipedia.org/wiki/Switched-mode_power_supply

author: RobFromEarth
author_rank: Regular Contributor
timestamp: July 06, 2014, 04:24:13 am
content: I had read most of that before but reading it again.. Fantastic, thanks!

author: idpromnut
author_rank: Unknown
timestamp: July 10, 2014, 12:16:27 pm
content: @AmmoJammo: the auction you linked,http://www.ebay.com.au/itm/231113487725;near the bottom there is a chart showing the different options you can buy, and all options are listed as between 30-34V...

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: July 10, 2014, 12:25:59 pm
content: Quote from: idpromnut on July 10, 2014, 12:16:27 pmThat would be because they've changed the listing after they had to give me a refundlol

author: idpromnut
author_rank: Unknown
timestamp: July 11, 2014, 11:31:49 am
content: Quote from: AmmoJammo on July 10, 2014, 12:25:59 pmRight on!

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 13, 2014, 11:00:44 pm
content: Technically off topic i think because the original OP had a different subject, but i wanted to post here since this seems to be the most relevant thread on the planet.Thanks in part to people's help here i got some lights working. Optics is an entirely different challenge but at least i have the lights working.People had to more or less pound it through my thick head that my driver can safely power the leds, even though the LED voltage max was quite a bit below what the input voltage to the driver was.But i'm having a similar problem. I needed to use some lower power LEDs, and i never was able to get any info that would help me figure out exactly how i can know if an LED with a given max voltage spec will work with a given driver, since the voltage max ratings for LEDs are i guess more or less irrelevant when using constant current drivers.The leds are all RGBW, and the original ones required around 12v to operate, except the red channel has a max volts of around 8 volts if i remember. These new leds are also rgbw, but volts mix/max are very different:Channel min maxred 2.1 3.2green 3.2 4.2blue 3.2 4.0white 3.2 4.0Remembering that people said voltage was more or less not important, i hooked one up. It seemed to work fantastic. At first! After a few minutes a saw what looked like a little tiny miniature explosion on the driver board, and green went out. Looking closer, one of the wires in one of the relays looks like it broke in two.I checked my wiring and everything seemed to be good, but then this particular LED has 8 solder pads, and the + and - are all jumbled around, so it's pretty much impossible to solder all the +'s together (not in a straight line). In other words, every pad needed to be individually soldered, so possibly i missed something in the 3 hour solder session, but i don't think so.Is there a way to know how much play there is? I mean, i'm pretty sure i can't use this driver to power LEDs that require 120v, and apparently i can't use it for less than 5v, is there some way to know a voltage range that will work?I probably should clarify.. these are the drivers we have, they bought a ton of them so it's what i need to use, so no options to buy other drivers with different specs, and these have some functions that we need anyway. They can be powered with anything from 12v to i think 24v, they don't function with less than 12.Thanks again

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 13, 2014, 11:14:50 pm
content: I should add, the driver supplies 650mA on each channel The max current for the original both the original and these new LEDs are both 750mA.

author: David_AVD
author_rank: Super Contributor
timestamp: August 13, 2014, 11:47:22 pm
content: Assuming a linear constant current driver, there will be a maximum voltage it can drop across the CC element for the stated current rating.So, imagine your CC driver is regulating at 650mA (0.65A), the input voltage (to the driver board) is 24V and the LED's Vf is around 4V.The CC element in the driver is dissipating 0.65A x (24V - 4V) = 13 Watts of heat!With a 14V LED, the dissipation would only be around 4 Watts.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 14, 2014, 12:50:55 am
content: Wow thank you now i get what should have been obvious i guess.. I kept saying before that it doesn't make sense what was being said, the voltage must be going somewhere, but i kept hearing that LED max voltage specs are more or less irrelevant for constant current drivers. Now everything makes sense suddenly. So i need to be looking at the specs for the CC driver. Too bad they're super inexpensive drivers made in china, i think even documentation in chinese doesn't exist, but at least this makes sense now thanks! I think the only options, forget using this driver (can't happen) or find an inexpensive way to bring the voltage down before it does into the driver, another challenge for the electrically challenged..Thanks!

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 14, 2014, 04:17:03 am
content: I want to make sure i have this right once and for all... The driver is 4 channels, it sends 650mA to each channel, and the input voltage can be anything from 12 to 24 volts. I'm using 12volts on the input. So, this particular led (the one that blew the driver) has these voltage specs:Channel min maxred 2.1 3.2green 3.2 4.2blue 3.2 4.0white 3.2 4.0So for the red channel, 12volts (input voltage) minus X (the voltage that the channel requires) gives me how much power the driver has to burn off by using ohms law P=I*E gives the power that the driver has to dissipate. What should i use for X, when the voltage is given as a range (min and max)?I know most leds have a forward voltage, but for the ones i'm using i only see a min and a max. Anyway, once i get that wattage, what is the driver spec called that i can use to be sure it can handle what i calculate? In your example, you used 24v input voltage, and that gives 13 watts of dissipated power, what am i looking for in the driver's data sheet to be sure it can handle dissipating 13w ? Feels like i'm still missing something basic here..

author: David_AVD
author_rank: Super Contributor
timestamp: August 14, 2014, 05:41:42 am
content: For dissipation calculations, use the minimum voltage stated as that's the worst case (highest voltage drop) for the CC driver.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 16, 2014, 02:41:06 pm
content: That makes sense, thanks, but how do i know how much power the driver can safely drop?

author: David_AVD
author_rank: Super Contributor
timestamp: August 16, 2014, 11:36:27 pm
content: Quote from: RobFromEarth on August 16, 2014, 02:41:06 pmThat's the million dollar question. You could try asking the supplier.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 19, 2014, 03:22:30 am
content: Ok, it's an unknown without mfg specs. The mfg doesn't respond, and they have no documentation, but at least i know that it's unknowable, thank you!

author: SteveyG
author_rank: Unknown
timestamp: August 27, 2014, 09:07:07 pm
content: Quote from: RobFromEarth on August 16, 2014, 02:41:06 pmAre you sure it is a linear driver? Even the cheapest Chinese ones on ebay are switchers. If it's a switcher, there'll possibly be a minimum LED forward voltage due to the resolution available on the PWM generator, but from a 12V source, it wouldn't typically be a problem to drive a LED with the specs you mention.Perhaps a link to the driver you have purchased as everyone is speculating at the moment and giving you different answers which may be confusing you.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 31, 2014, 12:39:29 am
content: Thanks, no it's not linear, it's using pwm, or a form of it anyway. There are no specs to see, only a model number. I'm sure there are thousands of other drivers, but having gone through dozens, these are the best ones for our project, at least for the larger lights. The smaller ones we're having a problem with because there isn't a version that can work with the lower volts.So far, we have 8 of the larger lights working, just not sure how safely. I think i don't understand how to pick wire gauge for the power cable going into the driver. The drivers for the larger lights, each of them are 4 channel (rgbw), and each channel has 650ma (it's constant current). If i add up the currents, 650mA times 4 channels equals 2.6 amps, so the power cable that i use needs to handle 2.6 amps, i bumped it up to 3 amps for safety.Sorry to make another long story below, but i'm missing something here, and i thought if i spelled out how i am getting from A to B, someone with more experience than me (most of you!) might be able to point out where i'm messing up. I'm pretty sure that a led isn't going to require a big thick beefy 16 gauge cable to power it.The page at:http://www.powerstream.com/Wire_Size.htmshows how much current a given gauge can carry. There are two columns for it, one is called "max amps for chassis wiring", the other is called "max amps for power transmission". I think that chassis wiring means wiring that's inside the unit, wiring that typically won't carry the full load all of the time, and is short length, and power transmission would be for power cables, longer lengths. I am using a 12v 500watt power supply that plugs into ac on one side, and the 12 volts out needs to go to the driver using a cable of gauge X, the gauge being the question.Since the driver is sending 3 amps to the lights (2.6 amps for the channels + extra for safety), the power cable between the 12v power supply and the driver needs to handle 3 amps right? According to the info at that page, i need 16 gauge wire for power? That can't be right, that's an awfully beefy cable for a basic LED!I do have several of these lights up and working, the wire gauge i'm using is 22, it was an un-educated guess i made before i looked it up. They're working fine now, but on the one hand, i'd hate to walk away and come back later to find the house is burned down, on the other, i was hoping to lower cost and weight by using the smallest gauge that will safely work.Thanks!

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 31, 2014, 10:08:35 am
content: Wow, no help, not even to save people from a painful fiery death? Well i'm pretty sure this is a basic electronics question, and some people are thinking "what a fool" to have so little experience and play with electronics. But i started with 1/4 watt single color LEDs and battery power. A few months later, i have 40 watt rgbw leds working via dmx and programming them via dmx software, so i've learned a ton in a short period of time. It boggles my mind how much can be accomplished without really having grasped some of the basics. I was hoping to be able to get some help here, rather than hit the text books, it will take weeks to crawl through that material to learn the little bits and pieces that i'm missing, the rest i have a working grasp of.The system is actually working just fine as it is, but it would be better if i know it's also running safely.

author: dannyf
author_rank: Super Contributor
timestamp: August 31, 2014, 11:22:30 am
content: QuoteIt is nice for others to help you but no one is obligated to help you. Demanding that others help you will do nothing but the opposite.As to your lack of knowledge, it is far better for you if you start in a more systemic way. Get a basic book on electronics (if college level books are too hard, start with a highschool level book, etc.) and go from there. It is far better than asking in a piecemeal fashion.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: August 31, 2014, 11:56:47 am
content: Sorry if that came off like a demand to you, it wasn't, sorry if i offended you, not sure what in that post could sound like a demand though. If you don't want to help, feel free to not, you're under no obligations, just like you say. I've been learning in a very systematic way for several months, and have learned a ton of things by doing. Though it may work well for you, reading books isn't necessarily the most effective way for some people to learn new material. Sure it works, but it sure is slow, and i've learned tons from forums from people who were really interested and knowledgeable about things that i'm not, forums are still about that hopefully.

author: sleemanj
author_rank: Super Contributor
timestamp: August 31, 2014, 01:01:53 pm
content: Quote from: RobFromEarth on August 31, 2014, 12:39:29 amYou can pretty much ignore the power transmission number, that's when you are generally talking about a wiring bundle (eg, the flex inside your walls, 2/3 wires inside a common insulation) and as such the heat dissipation is significantly reduced. It's also very conservative.3A over 22AWG should be fine.It's all about the power dissipation. If the wire is not getting noticeably hot running at full load, and it's not dropping too many volts for you, then no worries.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: September 01, 2014, 04:52:13 am
content: Ok, thanks, i wasn't sure if it meant just for wire over a given length or something else. But doesn't voltage play a part also? i.e. a cable may be able to safely pass I amps at E volts, but if volts goes too much higher, don't you need a thicker cable, or it it strictly the current that dictates the gauge needed?

author: sleemanj
author_rank: Super Contributor
timestamp: September 01, 2014, 06:24:20 am
content: Quote from: RobFromEarth on September 01, 2014, 04:52:13 amThe wire only "knows" about itself, and what it "knows" is exactly what you know, that it has a resistance, and that it's passing a current.The voltage that the wire drops is defined therefore by Ohm's Law.V=IRYou know I - the current you are passing (3A),You know R the resistance of your wire (whatever it is, measure if you like),Thus you calculate V, that being the voltage difference between one end of the wire and the other.Voltage is a consideration in wire only in so far as insulation - high voltages can pierce insulation and establish a spark to lower potential things.

author: RobFromEarth
author_rank: Regular Contributor
timestamp: September 01, 2014, 08:10:19 am
content: That's pretty clear, just think of the wire as a resistor and use basic ohms law, that makes sense now, thank you. Really basic stuff, i don't blame some people for being irritated, thanks for the explanation.