Best way to get 600x RGB leds?

I am making an 8*8*8 LED cube and need around ~600 RGB Leds. (Common anode, heavily diffused, 8-10mm, true "quality") The problem I have is that I don't want to buy a ton of leds, and find that 1 out of every 5 has a problem. I would want no more than 1 out of 500 to have a problem, & all of them to have very similar brightness for each color. (to the point that you can't tell one LED from another)

So I'm posting this topic with the question that I would like to request some guidance on how I can determine if a seller is selling a good quality or bad quality bulbs if I don't trust the listed specs. (if listed at all)

digikey or mouser or any other real electronics supplier, but they aint going to be cheap

http://item.mobileweb.ebay.com/viewitem?sbk=1&nav=SEARCH&itemId=350789428943

You honestly think places like digikey and mouser simply don't buy in tons of chinese made goods?... of course they do...

yea but its from a company with bin and lot numbers, not a pile of scrap swept off the floor and dumped into an evenlope PLUS you can return them without it costing you 30$ worth of postage and customs paperwork

love the

20ma?

in those specs, rock solid

you dont know the brand, you dont know the specs, you dont know the quality, you dont know the uniformity

cheap or quality, pick one

You’re building it in layers, right? Test each layer as you build it. Replace any LEDs you don’t like the look of.

[quote author=TECH GEEK link=topic=181204.msg1343110#msg1343110 date=1375713095] So I'm posting this topic with the question that I would like to request some guidance on how I can determine if a seller is selling a good quality or bad quality bulbs if I don't trust the listed specs. (if listed at all) [/quote] The problem with LEDs direct from china via ebay is that you often get the rejects. Those that fall outside the specifications in some way. I got a bunch of RGB LEDs and the red is much fainter then the other two consistently except in the odd LED. The ones with the brighter red I had to replace to match the others. One or two tested fine at low current but immediately crackled and burnt out when fed with the correct current, again on the red. I would say that about 6 in 100 were not suitable for my use.

However, as pointed out previously you pay for the provenance and traceability. This is something that a manufacturer of mass market consumer equipment would demand and would not pay too much for due to the number of components they are taking. For small numbers like 600 then it gets pricy.

Personally I would steer clear of eBay when it comes to LEDs.

I needed 2000 RGBs for a 12x12x12 cube so opted to get them from eBay to save money. In the long run it has been a complete headache. They have no real datasheet so you have no idea about the true specifications, there is no consistency (some of mine had deformed lenses, they are different colour shades etc.), there's no way to return dodgy, and you end up replacing them constantly as they fail randomly even though they are being run well within what little specification you are told about.

I've basically had to ditch an entire layer of my cube due to failures and it took forever to debug other issues caused by random LEDs burning out and becoming dead shorts (not easy to find in a multiplexing scenario).

Save yourself the hassle and buy from a reputable source.

I actually have had great results with the LEDs I have purchased from ebay. I purchase from this supplier http://myworld.ebay.com/led.shop*2010. I have bought hundreds of 3mm and 5mm LEDs for various projects with only a couple of burnouts.

Any application needing equal brightness/coloration of a large quantity should naturally involve a burn-in and selection step to weed out the inevitable variations found in manufacturing.

I remember having to do this many many years ago with a matrix of rectangular LEDs I was using to build an audio spectrum display. Those were all 1st run parts from a reputable supplier. Even so, the varied from one to the other quite a bit. They were all perfectly fine individually but close together, the variations were quite noticeable.

JohnHoward: I remember having to do this many many years ago with a matrix of rectangular LEDs I was using to build an audio spectrum display. Those were all 1st run parts from a reputable supplier. Even so, the varied from one to the other quite a bit. They were all perfectly fine individually but close together, the variations were quite noticeable.

This is why LED driver ships have "dot correction" and some of them can even store the corrections in internal EEPROMs (TLC5940).

You can buy matched/binned LEDs but expect to pay a lot more.

I would question

You can buy matched/binned LEDs but expect to pay a lot more.

Seriously... The price for matched or matchable led's as the case may be is going to be paid one way or the other. Either your time to "Grade" parts or theirs. My personal experience with "Ebay" leds follows the mainstream closely. Devices had different brightness, placement of individual chips within the device and frequently different placement of the "lead frame" within the plastic package itself. These are DEFECTS, things that many see as being less than desirable. Good well matched parts require intervention at the testing level for specification of matching parameters. This is necessary in order to be able to produce well matched displays. Parts on Ebay are surplus and rejects. If there was any real value there in gradable and matchable parts it is an accident, not intentional because any gradable and matchable parts would then be mainstream parts... Ya think? Why sell a dollar for 50 cents?. This is something that should be considered carefully when purchasing other components... Is Cheap worth the possibility of replacing a less than less than working part?. For an experimenter the parts are accessible, for a manufacturer very expensive. Personally I consider the task and my time to be important enough to not want to fix or revisit a piece of completed work unless it is to make it better. Yes I buy a great many Ebay parts but only for experimentation... If they are not suitable they are at least cheap... On point a while back I found a little piece of code for an Uno that simply cycles two of three colors using two of three at any time and I thought it interesting to change the pins and write it to a Tiny 85 and use it on my desk with some batteries and all on a breadboard to prevent it being picked up easily and thus disappearing. I had to try 5 different ones from a bag of 100 I bought from Amazon before I found a suitable one... one with 'nearly' equal brightness and placement of light within the translucent plastic lense. I did however expect this when I purchased the devices from a 'reputable' dealer... The "Free Shipping" was the giveaway.. free shipping, counter to popular belief isn't free... It's included in the sales price. I for one am slightly insulted when presented with 'free shipping'... how is it free when I am giving them money?.

Doc

Docedison: I would question

You can buy matched/binned LEDs but expect to pay a lot more.

Seriously... The price for matched or matchable led's as the case may be is going to be paid one way or the other. Either your time to "Grade" parts or theirs. My personal experience with "Ebay" leds follows the mainstream closely. Devices had different brightness, placement of individual chips within the device and frequently different placement of the "lead frame" within the plastic package itself. These are DEFECTS, things that many see as being less than desirable. Good well matched parts require intervention at the testing level for specification of matching parameters. This is necessary in order to be able to produce well matched displays. Parts on Ebay are surplus and rejects. If there was any real value there in gradable and matchable parts it is an accident, not intentional because any gradable and matchable parts would then be mainstream parts... Ya think? Why sell a dollar for 50 cents?. This is something that should be considered carefully when purchasing other components... Is Cheap worth the possibility of replacing a less than less than working part?. For an experimenter the parts are accessible, for a manufacturer very expensive. Personally I consider the task and my time to be important enough to not want to fix or revisit a piece of completed work unless it is to make it better. Yes I buy a great many Ebay parts but only for experimentation... If they are not suitable they are at least cheap... On point a while back I found a little piece of code for an Uno that simply cycles two of three colors using two of three at any time and I thought it interesting to change the pins and write it to a Tiny 85 and use it on my desk with some batteries and all on a breadboard to prevent it being picked up easily and thus disappearing. I had to try 5 different ones from a bag of 100 I bought from Amazon before I found a suitable one... one with 'nearly' equal brightness and placement of light within the translucent plastic lense. I did however expect this when I purchased the devices from a 'reputable' dealer... The "Free Shipping" was the giveaway.. free shipping, counter to popular belief isn't free... It's included in the sales price. I for one am slightly insulted when presented with 'free shipping'... how is it free when I am giving them money?.

Doc

Items I have ordered from China recently have arrived with "0.00" on the postage meter stamp on the envelope. I get the feeling China is subsidizing it's cottage industry of selling factory 2nds. One item I briefly considered returning (they mixed up my order with someone else) was going to require $16 and change for me to mail back. They just told me to keep the stuff (a couple of Mega2560 clones and a package of photocell detectors!) as a 'gift'.