Nice LED assortment for 3$

do you prefer the diffused type for some reason?

I did some I/V curve testing of random LEDs I'd gotten from eBay sellers a few years back, the 3mm yellow diffused type seemed to have a much better "regulated" forward voltage across a reasonable range of currents, say few hundred uA to 30mA, as compared to all the others.

Like you would want to use that type to constant-voltage bias a vacuum tube's cathode or something, maybe.

Also of note is that when I tested say 30 or 40 devices from the same pack it was difficult to find even a couple with well-matched currents at around 3 volts...ALMOST LIKE they had been pulled already

You see, I only needed ONE LED. For the project I had an old LED holder, and the 3 mm LED was missing. I looked at the local 'tronics shop website and a new holder with LED was 1 Euro 75 or something plus at least 3 Euro shipping, singe LED 3 $ shipping at least. Looked at the hundreds of high end LEDs I have, RGB, any color, super bright, and had no 3 mm LED. So ebay. Took the green 3 mm LED I wanted from the box and mounted it last night. Knowing some LEDs at the quoted 10 mA change night to day and can cause blindness, I decided to derate to 1 mA.

At 3.3V and 1.8 V for the green LED, 1k5 seemed a good value. Now it is only blinding if I look right into it. As to diffused, maybe clear LEDs give less problems reading when the sun is on it (off versus on). I have some 5 mm diffuse with concave lens, that is even better, no blinding.

But hey. so much for 3 $, not even 3 Euro. As regulator, I checked all colors and sizes on the multimeter, should work. But I have 50 TL431 precision regulators for 1$84 with free shipping for that:

:-)

I did notice some 5 mm are much brighter than the 3 mm, the yellow ones are orange when on.