SST-20 L2 6500K is available on kaidomain for $3.19.
prophotonix never answered.
I found 2 more companies which may be willing to make a batch of custom LEDs:
At least the latter has the necessary expertise:
I haven’t mailed them, if one wants to do it - just do it.
What is the die size of old XP-G2?
Here I see 2.16 mm².
In the CRX thread 1.66 mm² for old and 2.18 mm² for new…
200 cd/mm² seems semi-consistent with the smaller number.
1.66mm^2 for the first version from 2012-2014
Then koef3 got about 216 cd/mm²
One thing to note here is that the way of measuring the die size is not perfectly accurate. It is usually done by carefully taking a picture and then counting pixels.
What about this LED (don’t know if this LED is already discussed)?
http://www.nichia.co.jp/en/product/led_product_data.html?type='NJ2W270A-Y7'
I noticed it a few months ago, but didn’t see any big benefits. The rectangular shape of the die is definitely a downside.
They do state the luminance!
Die size: 0.93mm^2
Real thermal resistance: typ 4.1cd/mm^2
Luminance at 700mA: avg 110cd/mm^2
Edit:
The Black Flat is 20% larger, but only does 66cd/mm^2 at 700mA. So the Nichia might actually be really good if one can live with the die shape! Thanks Schoki!
Edit2:
The weird thing is that it’s a 6V LED! This makes it easier to drive the LED to its max in single cell lights, there are good boost drivers available.
I wonder how far apart the two dies are. This could ruin the beam with smo reflectors.
OK, so let’s consider the dies separately, so we can compare with Blackie a bit better.
Half-Nichia:
.465 mm² die. 110 cd / mm² at 1.5 A/mm² and 5 W/mm².
Blackie:
1.122 mm² die. 110 cd / mm² at 1.25 A/mm² and 3.85 W/mm².
Nichia has a bit better thermal resistance, but it doesn’t seem to be enough.
Also, its LES is significantly higher than die size in case of Nichia.
So probably not too good….
I think we really just need to wait for the new Osrams.
I need some clarification here: candela is Lumens/Steradian, so the value changes with the amount of dies I place next to each other?
Yeah, I’m keeping tabs on octopart, hopefully soon they will be available in individual units.
Luminance is candela per square millimeter of die area. This means it’s independent of the angle from which you are looking at the LED. The luminance determines the throw when the LED is combined with a given reflector or optic. The area of the lit up reflector as seen from the position of the hotspot in some distance mutiplied by the luminance determines the Candela (which leads to throw). This means that two LEDs with two reflectors will double the Candela (which leads to throw). A larger LED with the same luminance as a smaller one will not increase throw with a reflector, only the hotspot gets larger.
+1 Well done, thanks.
That means no matter how large the emitting area is, the LED (with a given luminance and reflector) will throw the same distance. Then the only thing that changes is the hotspot size?
But increasing the reflector/lens area “seen when looking into it” gives better candela —> more throw.
Right?
And pushing more power through the LED increases the luminance?
Yes.
Here is the formula:
Luminus_intensity [cd] = luminance [cd/mm^2] * area_of_reflector_or_optic [mm^2] * losses [%]
Losses being the reflectivity of the reflector (or the transmission rate of the optic) and the transmission rate of the lens.
Generelly small LEDs which tolerate very high power densities reach the absolute highest luminance values. The Luminus CFT-90 is an outlier.
wait, so luminus intensity doesn’t depend on reflector shape?, so what if i have a very deep reflector( like 2cm diameter OTF) and 20cm OTF but narrow, both have same area, they will throw the same, right ?
No, it doesn’t. That’s a very common misconception.
If you have two reflectors with the same outer diameter but one is deeper, the deeper one will have a slightly smaller led opening. This increases the total reflective area slightly. The larger the reflector, the less important this becomes.
Deeper reflector = smaller hotspot and more corona.
Shallower reflector = bigger hotspot and less corona.
At constant diameter? Deeper reflector = larger hotspot……
Same intensity * more lm collected by the reflector = larger spot
Saying same thing in other terms…
All parabolas are the same except for the scale. All parabolic reflectors are (geometrically) the same except for the scale and 2 cut points.
Scale is usually expressed in terms of focal length (FL).
For a given emitter beam angle depends on FL and on nothing else. Larger FL = narrower beam.
For constant diameter, larger FL = smaller depth. So less deep = smaller spot.