# LED measuring - lumens, efficiency and spectral characteristics



## Mike cz (Sep 5, 2012)

_Measurements were previously published in the local forum:http://forum.fotonmag.cz/index.php?showtopic=886&st=0&start=0 _
*Method of measurement and equipment*
*-Measurements are performed in the laboratory with an integration sphere and a spectrometer in the Technical University in Liberec.
-The spectrometer measures the spectral characteristics of a LED, it means that measures the entire spectrum of the LED and thus the radiant flux at each wavelength.
-This is a completely accurate measurement.
-**Luminous flux is subtracted ~3 seconds after turning on the LED*. _(This is a relatively stable value)_
* -Multimeters and laboratory resources are great devices with **multi-digit** display from Agilent.* 














*Measured*
Cree XM-L U2 (LEDTECH, 16mm CuSTAR)
Cree XM-L U2 (LCK-LED, 16mm STAR )
Cree XM-L T6 (LCK-LED, 16mm STAR )
Cree XM-L U2 (LCK-LED, 16mm STAR ) !new!
Cree XM-L T5 (Cutter, 16mm STAR )
LUMINUS SST-90 N (xxx, 20mm STAR )
Cree XPG-R5 (LEDTECH, 10mm STAR )
Cree XP-G R5 (LCK-LED, 16mm STAR )



*Cree XP-G R5, LCK-LED, 16mm STAR*
-nice measured efficiency at 124.8 lm/W at 350mA (in the datasheet is min. 129lm/W)
-maximum power is low 383lm (in the datasheet is 493lm), the reason is poor STAR, which does not account for heat from the chip
-last value in the table is peak 1sec
-2A for XP-G is much

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)






*Cree XPG-R5, LEDTECH, 10mm STAR*
-nice measured efficiency at 126.8 lm/W at 350mA (in the datasheet is min. 129lm/W)
-maximum power is weak 383lm, 493lm is in the datasheet, even lower than the XPG from LCKLED
-2A for XP-G is much

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)






*Cree XM-L T5, Cutter, 14mm STAR*
-the next disappointment is from LED (4900K neutral) XML T5 from the cutter, error is in poor STAR
-LED has a problem with a current greater than 3A!

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)






*Cree XM-L T6**, LCK-LED, 16mm_STAR*
-this XML T6 is very good, luminous flux 930lm at 3A is excellent and efficiency 149lm/W at 350 mA is perfect (in the datasheet is min. 144lm/W)
-this XM-L has the perfect STAR!

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)






*Cree XM-L U2, LCK-LED, 16mm STAR*
-STAR is the same as above=> perfect results
-unfortunately, the new series of LED XM-L U2 from LCK-LED.com on other STAR is very bad, see below :/ /

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)






*Cree XM-L U2, new series LCK-LED, 16mm STAR*
-here is a new series of XM-L U2 from LCK-LED on other STAR - STAR and LED are bad
-I did not measure more than 3A, luminous flux LED is bad

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)






*Cree XM-L U2, LED-TECH, 16mm Copper STAR**!*
-this LED has been measured in the forum, I measured the LED at the same time
-luminous flux and current of the XM-L soldered directly to the copper are extreme!
-there is no problem to use LED to 4A (with 1243lm) or more... *Luminous flux at 6A is 1504 lumen!*
-efficiency at 350mA (1W) is 159.4 lm (in the datasheet is min. 154.6 lm/W), excelent efficiency 168.5 lm/W is at 100mA (0.3 Watts)
_*This LED XM-L U2 Cu STAR is an exceptional piece, all other series were about ~2% worse_
Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)





*LUMINUS SST-90 N, EVB, 20mm STAR*
-SST90 is one of the first SST90

Graph of Spectral characteristics





Graph of Efficiency (lm/W)





Graph of Luminous flux (lumens)





*SUMMARY GRAPHS*

Graph of Luminous flux (lumens)





Graph of Efficiency (lm/W)





Graph of Efficiency at 350mA


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## Gunner12 (Sep 5, 2012)

Great data! I was thinking about making a thrower and the LED-Tech star seems like a great alternative to finding a copper heatsink.
It's amazing that the XM-L is more efficient then the SST-90 at all currents.

Do you also have data on the temperature and Vf of the LEDs at various drive currents?


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## Mike cz (Sep 6, 2012)

These data are for each LED in the table of Graph Spectral Characteristics:
*Czech...................English*
*Napětí[V]..............Voltage [V]
Proud[mA].............Current [mA]
Výkon[W]..............Power [W]
Světelný tok[lm]....Luminous flux [lm]
Účinnost[lm/W]**.....Efficacy [lm**/W]*

Ambient temperature and temperature of cooler is 20 ° C.

LEDs are measured after 3 seconds after switching - This time is sufficient to test the insulating layer of STAR under LED, because LED housing heats up in tens of seconds. Temperature of massive cooler is still constant at 20 °C.

Theoretically temperatures:
_LED housing: 2.5°C/W
__insulating layer of aluminum STAR: (2-3)°C/W- __in the case of cooper STAR is 0,0...°C_/W
_ Power of LED XM-L: 10W

=>heating the chip: (2.5+3)°C/W * 10W = 55 °C_
_+temperature of cooler__: 20°C
*=>*_*temperature of LED chip: 20+55= 75°C*


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## Gunner12 (Sep 6, 2012)

Don't know how I missed the tables, thanks for the research and work you put into providing this data! I never realized that the LED chips run that hot (AKA, I was too lazy to do the calculations).

Do you think there will be a big improvement in output at higher currents if the chips themselves were soldered onto a copper sheet?


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## IMSabbel (Sep 8, 2012)

Fantastic.

Seeing this I really want one of those copper board XMLs. 5A at 3.4V is just insane.


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## SemiMan (Sep 8, 2012)

Interesting test though I disagree with the conclusion at times.

Keep in mind the XML and XPG data sheets assume the die is at 25c. The data sheet also reflects this. Only newer parts are tested with the die at 85C.

Hence say for the XPG, even on a good star, you are likely looking at:

4 c\w for the led
0.5 c\w for soldering
3 c\w for the thermal interface material (or so)
0.5 c\w for the star
0.5 c\w between the star and the big heat sink

That is about 8.5 C\W. By your test, that puts the led temperature at about 60C. Cree PCT puts the XPG-R5 at 420 lumens at 1.5A and 60C.

It is very difficult, even in your configuration to get accuracy much beyond about 5%. So it is at least close. I am not saying the star was great, but it is indicative.

The XML tends to be more forgiving due to the large area of the heat pad. The XPG heat pad is quite small for the power level.

Keep up the great tests. I would love to see you repeat this with the thermal cooler at 60C or 70C to represent real world conditions.


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## jtr1962 (Sep 8, 2012)

Very nice work and very interesting data! :twothumbs I've done an extensive amount of lumens testing myself, although none in the past year or so. See the link in my signature


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## ledsmoke (Sep 9, 2012)

Thank you very much for this *Mike cz* 
This is a fantastic ressource for everyone to consult. TY


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