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Sourcing 5mm RGB LEDs for LED Cube

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Oleenick:
Hello EEVblog forum!

I'm working on an 8 x 8 x 8 LED Cube. I'm at the stage where I need to order ~600 5mm RGB LEDs. Specifically, 5mm RGB common anode diffused lens LEDs.
My main question for today is: How should I source these? Here are my thoughts so far...

I was considering buying from somewhere like LCSC:
TOGIALED https://lcsc.com/product-detail/Others_TOGIALED-TJ-L5FYTXHMCYLCRGB-A5_C331057.html AUD$57.35 for 600 <--- This one is my current best pick
MEIHUA https://lcsc.com/product-detail/Light-Emitting-Diodes-LED_MEIHUA-MHLA5319URGBDWT_C417349.html AUD$123.85 for 600

I can get some for great prices on ebay here: https://www.ebay.com.au/itm/1000pcs-5mm-RGB-LED-Common-anode-Tri-Color-Emitting-Diodes-Diffused/291498458196
1000 for AUD$46.52

Trouble is, I don't know whether to trust the brightness of any of the afformentioned LEDs.
The specs of the TOGIALED one from LCSC state that the avg. brightness is R: 400, G: 1500, B: 300 mcd. (@20mA)
While the MEIHUA also from LCSC has an avg. brightness of R: 600, G: 1500, B: 300 mcd. (@20mA)
The ebay one doesn't give a brightness, only a part number (F51BW9RGB-C) for which I can't find a brightness elesewhere online.

Just the brightness is throwing me off. The high variation in mcd for each colour is strange. Is it because they're using percieved brightness values, where green is more predominant due to the human eye?
Even larger brands like Kingbright have LEDs with high variations between colour brightness: https://www.kingbrightusa.com/category.asp?catalog_name=LED&category_name=KCRound+Tri%2DColor&Page=1

So... Should I be worried about these brightness differences or is there something else I don't know?
What are your experiences with ordering LEDs in bulk from eBay or other places like element14?

Thanks in advance, I really appreciate any help.

ataradov:
Why not order a few samples, test them and then decide if they will work for your application?

It is really hard to order LEDs just based on their parameters.

DaJMasta:
5mm is pretty big for an LED, maybe it's the size you want for your design, but 3mm will probably offer much better prices and pretty comparable brightness.

The output difference is the inherent difference in output efficiency, and one way or another, your driver circuit will have to compensate for it.  This is going to be true for basically every LED or set of LEDs unless you have wildly different packages or current limits for each, so the approach is probably just to do your RGB value to actual PWM value as a mapping table or function in software to get things closer to what you'd expect from something rendering true color.  That also means the difference between your lowest output to your highest output divided by your pwm step size is the effective resolution of the output - so wider variation in intensity of the diodes means fewer of your pwm step distinctions are usable because the lowest intensity LED will need several steps to match the brightness of a single step of a brighter one.

Then you've got the issue of human eye color sensing, and honestly I'm not sure how mcd or candela in general is specified for that, since it's supposedly a reference to a green monochromatic source, the datasheet values may actually need to be scaled somewhat to figure out what it would "look like" rather than what it measures on a test apparatus, but I don't know the standard test setup well enough to say how.

tooki:
3mm (T1) and 5mm (T1¾) are the most common THT LED sizes, making them both exceedingly cheap. No idea why you think 5mm is “pretty big”, nor why it’d be “much” cheaper. It’s also hands-down the standard LED size used for LED cube builds.

Jan Audio:
Ebay 8 dollar per 100.
Mouser 80 dollar per 100.

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