Question about LED temperature(not color) and LUX

[donkeegrow]

Hi there,

I've just built my next light which consist of the following:
5x BXEB-L0340U-35E0750-C-C3
5x BXEB-L0340U-40E0750-C-C3
1x HLG-185H-C1400B
1x 100kOhm dimmer

I'm using an aluminium plate of 480x260x3mm as a "heatsink" with a CPU fan aimed downwards cooling towards it. Right now I'm running it around 1060mA. Meassuring the temperature with a IR thermometer it looks like the heatsink becomes about 40*C and isn't uncomfortable to touch. Aiming with the thermometer under at the LEDs it looks like the warmest spot is about 46*C.
I believe I've understood correctly that the EB series 2 seemed to decrease a little extra in efficiency when going over 1050mA which is ok.

Questions about heat
What is considered a good temperature of the LEDs?
How hot do I dare to get the LEDs(setting aside a bit lower efficiency because of heat)?

Intensity calculations
I just want to get a hunch of how many hours that would be enough for a specific plant using this site:
https://www.ledtonic.com/blogs/guides/d ... quirements

I meassured the LUX output of the light at a specific distance(app: Lux Light Meter, recommended by Shane at Migro). I followed his "hack" video and I get this calculation: (25000lux/1.4/100=179) + (25000/1.25/90=222) = 401par
Video reference:

Now I also checked a site which gives an approximation depending on the type of light you got: https://www.waveformlighting.com/hortic ... calculator
Now this one gives (50000Lux with Low CRI LED 3500K(lowest score)) 802 µmol/s/m2

Question about the calculations
Is the latter just an over optimistic value or is there a difference between the calculations I haven't understood yet?

Thanks in advance!

[PeteR_1]

My Bridgelux EB Vesta build uses an Aluminum Sheet (Bun) Pan and has similar temperatures at the "typical" currents which is the recommended "Maximum" for running "Soft" or without heat sinks.
Vesta build... viewtopic.php?f=32&t=5761

BTW, The Maximum Case Temperature for the LED Strip is noted as 85 deg C On Page 7 in the Gen 3 data sheet... https://www.bridgelux.com/sites/default ... ev%20A.PDF

Generic Conversion Factors for White PC (Phosphor Converted) LEDS - Lumens to PPF (PPF/Lm) Factor (Cf):
0.014 = 5000K 80 CRI Cool
0.015 = 4000K 80 CRI Neutral
0.016 = 3000K 80 CRI Warm

Lux * Cfactor = PPFD
e.g., [20000 Lux * 0.015 (4000K) = PPFD 300 umol/m2/s]

This topic may provide some clarification... viewtopic.php?f=15&t=5756

An inexpensive Digital Lux Meter (Silicon Diode, 0- 200K Lux Range) is recommended instead of using phones. Phones do not usually have cosine correction so are not always accurate or repeatable...
I have several (more expensive) Lux Meters but always use my Benetech GM1010, purchased for under $10.00 (US).

Benetech GM1010 lux meter... https://www.aliexpress.com/item/3225651 ... hweb201603_

Target DLI (mol/m2/day) for Plants

Simple DLI formula for Single (Sole) Source Light;
PPFD * Hours * 0.0036 = DLI
e.g., [300 umol/m2/s * 16 Hrs (Photo-period) * 0.0036 (umol/mol) = 17.28 (mol/m2/day)]
e.g., [DLI 30 / 0.0036 ] / 600 umol/m2/s (PPFD) = 13.8 Hours (Photo-period).

Target DLI... https://gpnmag.com/wp-content/uploads/2 ... N_0519.pdf

[donkeegrow]

Thanks for your reply PeteR_1!

I actually borrowed a Flir E6 to check the temperatures more accurately.
@ 0.7A without fan the LED strips have a max of 55C
@ 0.7A with fan the LED strips have a max of 42C

@1A without fan the LED strips have a max of 65C(didn't dare to let it continue to go higher since it started to smell a little)
@1A with fan the LED strips have a max of 54C

Yes I saw the value of 85 deg C, but I still wonder what is considered as a normal temperature for others to run them at. This, also with respect to degradation. Though I will probably go with 0.7A.


I will consider buying the lux meter you recommended, but it all depends on from where. Last time I got from China I had to pay 20$ extra for administrative fees and customs. Maybe I can find it cheap somewhere else

Thanks again for your input!

[PeteR_1]

@donkeegrow ,
You're welcome.

Thanks for sharing your measurements. I plan to run the LED strips as "Cool" as possible, with passive cooling.

Have some (inexpensive) Samsung F-Series Gen3 LT-F564B (560 mm) en route for test builds with the 26 x 18 Bun Pans, will be running them at less than 50% of "Maximum" current (~ 0.750 Amp each max.) on the Mean Well XLG-240-H-AB Driver. Attached is a snapshot of the Samsung Engine Calculator tool for the eight (8) F564B LED Strips, Calculates out to; 49000 Lm , ~ 704 PPF (umol/s), ~ 2.54 PPE (umol/J, System Efficacy) @ 750 mA (0.750 A) per strip ...

Samsung Engine Calculator F564B @ 600 - 700 mA. (less than 1/2 nominal test amps)

Samsung F-Series Gen3 LT564B, 9000Lm, 4000K (each strip ~ $4.00 with Tariff, Tax and Shipping)... https://www.arrow.com/en/products/si-b8 ... lectronics
Samsung Gen3 F-Series datasheets... https://static6.arrow.com/aropdfconvers ... -01-05.pdf
Samsung Engine Calculator tool... https://www.samsung.com/led/support/too ... alculator/

[wuwuorganics]

Dang, that price dropped real low on those f series strips. I got excited when I saw them at like 7.50 per strip so just had to impulse buy some (grabbed 8). Would love to see the results of tests/build with these strips though.

[wuwuorganics]

Dang, that price dropped real low on those f series strips. I got excited when I saw them at like 7.50 per strip so just had to impulse buy some (grabbed 8). Would love to see the results of tests/build with these strips though.

[PeteR_1]

Dang, that price dropped real low on those f series strips. I got excited when I saw them at like 7.50 per strip so just had to impulse buy some (grabbed 8). Would love to see the results of tests/build with these strips though.

Ordered a batch of F524Bs as soon as I found them and cancelled my Bridgelux Gen3 "backorder" with Future Electronics (due to the 6 wk lead time). Will start a new topic later this week with the Samsung F564B build and tests. Attached is a comparison of eight (8) 560 mm strips; Gen3 F564B and inFlux_L09 (Gen2 ?) on a 240 Watt driver at 0.700 A. per strip. The inFlux_L09 are also available from Arrow.
Samsung inFlux_09, 3500K ($5.22 each including Tariff and Taxes)... https://www.arrow.com/en/products/sl-b8 ... lectronics

Samsung Gen3 F564B and inFlux_L09 (Gen2 ?) comparison at 0.700 A. (700 mA) with 240 Watt LED Driver

Eight (8) Samsung F564B @ 240 Watts (0.700 A per strip) = ~ PPF 660 (umol/s) which is more than adequate for ~ PPFD 825 (umol/s) over a 2 x 4 ft area (~ 0.8 sq m)

[Welight]

Typically FR4 boards ie Bridgelux, Samsung are poorer at heat dissipation than Alum, FR4 or fibreglass is after all an insulator. The net effect of high temp is a reduction in efficiency and in general dependent on the importance there is a generic rule that suggests that when the Tj goes from 25C to 85C the colour point alters, the DUV shifts .002. Nothing that is really a deal breaker dependent on how particular you are

[donkeegrow]

@donkeegrow ,
You're welcome.

Thanks for sharing your measurements. I plan to run the LED strips as "Cool" as possible, with passive cooling.

Have some (inexpensive) Samsung F-Series Gen3 LT-F564B (560 mm) en route for test builds with the 26 x 18 Bun Pans, will be running them at less than 50% of "Maximum" current (~ 0.750 Amp each max.) on the Mean Well XLG-240-H-AB Driver. Attached is a snapshot of the Samsung Engine Calculator tool for the eight (8) F564B LED Strips, Calculates out to; 49000 Lm , ~ 704 PPF (umol/s), ~ 2.54 PPE (umol/J, System Efficacy) @ 750 mA (0.750 A) per strip ...
Samsung_F564B - mA Comparisons.PNG

Samsung F-Series Gen3 LT564B, 9000Lm, 4000K (each strip ~ $4.00 with Tariff, Tax and Shipping)... https://www.arrow.com/en/products/si-b8 ... lectronics
Samsung Gen3 F-Series datasheets... https://static6.arrow.com/aropdfconvers ... -01-05.pdf
Samsung Engine Calculator tool... https://www.samsung.com/led/support/too ... alculator/

Thank you for this information. So when you have calculated the Flux, what guide or tool did you use to convert to the PPF value and which height(needed if I understand it right)? I just wonder if I could do something like it since the lux meter in the phones isn't accurate enough. Would be nice to be able to understand how you did the estimation/calculation so I could try doing something like it also. If it's just an annoying question it's fine to disregard it I could just wait and see the results also

[PeteR_1]

Thank you for this information. So when you have calculated the Flux, what guide or tool did you use to convert to the PPF value and which height(needed if I understand it right)? I just wonder if I could do something like it since the lux meter in the phones isn't accurate enough. Would be nice to be able to understand how you did the estimation/calculation so I could try doing something like it also. If it's just an annoying question it's fine to disregard it I could just wait and see the results also

You’re welcome.

The formula to convert Lumens (or Lux) is;
PPF (umol/s) = Lm * PPF/Lm factor

PPFD (umol/m2/s) = Lux * PPF/Lm factor

The Conversion factor for 4000K Samsung (Lm301B / H) is 0.0144 PPF/Lm


You just have to calculate the total Lumens output from the single strip or fixture, can also be based on Lumens per Watts, then multiply by the conversion factor.
From the Samsung Engine Calculator...

5748 Lm (@ 30 Watts) * 0.0144 = 82.77 PPF

45985 Lm (@ 240 Watts) * 0.0144 = 662.18 PPF

178.1 Lm/W * 0.0144 = 2.564 PPE [PPF/W (J)] System Efficacy

200 Watts * 2.564 PPE (PPF/W) = 512.8 PPF


The actual height above the canopy has to be measured and can be configured by;
1. Spreading out the strips to create a uniform canopy over the actual grow area or
2. Creating concentrated “Bars” of light for greater intensity, similar to Linear LED High Bay fixtures.
Note that the output from LEDs without Lenses can be calculated at 100% towards the canopy although there will be some losses due to the 115 - 120 degree (wide) Beam angle.


The F-Series light fixture was built / assembled, just have to get some free time to take the measurements.

Photo of newly assembled Samsung F564B 18x26 Fixture, illuminated by Bridgelux Vesta 2750 18x26 fixture (@ 35 watts input)...