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Cultivated Reef

Another DIY LED fixture


M@rine_lover

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M@rine_lover

After running for 20 hours... it's time to take the temperature :o !

 

I have pointed the digital thermomter directly to the black portion of the star PCB near to the soldering point of the emitter and the reading is 38~39 degree within acceptable range.

 

I have make another 2 tests; one is pointed directly to the aluminum plate...reading is 35~36 degree and the other pointed to the aluminum plate with splash glass and the reading is as low as 32~33 degree.

 

This test will be carry on for 3 days to further confirm the average reading then follows by another test without fan but this one, I need to take leave to monitor closely :angry: !

 

38degree.jpg

 

Close shot

Closeshot.jpg

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M@rine_lover
Ok. Just wanted to make sure you weren't holding it far away and taking an average reading of a larger area ;)

 

Tried pointing very near this time and the degree increased 0.5 :D .

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Evil, at what temperature would you start to get concerned? Are we talking shortened bulb life at higher temperatures or intensity or both? Maybe failure altogether if the temperature is high enough - any idea how high?

 

Just curious.

 

Thanks,

Mark

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If you can keep temperatures near the LED below 60C, you are usually good. Lower is better of course. I have been getting temps of about 40C average temps along the heatsink with the HeatsinkUSA units. I'm quite surprised that M@rine_lover is getting such good temps. Is that with fans running, or no?

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He mentioned those first numbers are with the fans running. He said he'd be doing another test later with no fans.

 

Is your 40degC number with or w/o fans?

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M@rine_lover
If you can keep temperatures near the LED below 60C, you are usually good. Lower is better of course. I have been getting temps of about 40C average temps along the heatsink with the HeatsinkUSA units. I'm quite surprised that M@rine_lover is getting such good temps. Is that with fans running, or no?

 

Yes. 2 fans are running at the same time:happy:. I will testing without fan a few days later :D .

 

IMHO, temperature taking on the LED w/o fan is depend on individual room temperature and also the casing ventlilation design. So for me, I'm expecting 60 and below after running for 12 hrs.

 

What do you think?

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If you can keep it there, great. With the setup in an enclosure though, your temps may climb higher seeing as you have no air movement, a relatively small air volume, and an insulator encasing it (acrylic).

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M@rine_lover
If you can keep it there, great. With the setup in an enclosure though, your temps may climb higher seeing as you have no air movement, a relatively small air volume, and an insulator encasing it (acrylic).

 

yap...possible to climb higher :rolleyes:!

 

I may change my plan to switch on 1 fan instead of off both as real life It's very little possible for 2 fans to break down together at the same as both fans are using different PS :happy: .

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yap...possible to climb higher :rolleyes:!

 

I may change my plan to switch on 1 fan instead of off both as real life It's very little possible for 2 fans to break down together at the same as both fans are using different PS :happy: .

 

There is more of a chance of the fan failing before the power supply, so running two will give you redundancy.

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M@rine_lover
How are you mounting these above your tank?

 

Currently just sit on top of the tank...however, I still think of creating an acrylic holder to let the fixture to sit on but in designing stage lol :D !

 

There is more of a chance of the fan failing before the power supply, so running two will give you redundancy.

 

PS of the fan or PS of the LEDs :huh: ?

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Now, seriously you are taking a big risk to shorten the life span on your LEDs. 3mm plate will get very hot in no time without any fans being ON.... Your LEDs would work great for the time being but on longterm they will losse their life by a great margin. Its all good and well to test and see what your results shows but on serious node, be careful not to run your LEDs for longer period without any fans and such a thin heatsink plate.

Wishing you all the best and watching it with great interest.

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M@rine_lover

Thanks to a senior LED guru :bowdown: , who told me that LED maximum temperature is rated at the LED junction which cannot be measured directly and It not as simple as just taking the measurement of the star or aluminum plate :wacko: . And first of all, need to consider the thermal resistance of the LED :ninja: .

 

The formula for calculating junction temperature is as below;

 

Junction Temp = Thermal Resistance X Wattage + Temperature of star

 

SSC P4 specification;

 

Thermal Resistance for RθJ-B is 8.5 ºC/watt

RθJ-B is measured with a SSC metal core pcb.(25 ºC≤TJ≤110 ºC)

 

Thermal Resistance for RθJ-C is 6.9 ºC/watt

RθJ-C is measured with only emitter. (25 ºC≤TJ≤110 ºC)

 

Temperature Junction, TJ is 145 ºC (@ IF≤700mA)

 

Ok..now back to my actual reading on star was 39 ºC taken yesterday, so my Junction Temperature will be 8.5*4+39 = 73 ºC

 

Reference to SSC spec, as long the TJ is within this range (25 ºC≤TJ≤110 ºC) is considered in good range and my is only 73 ºC :lockdown: however, I would like to add extra 5% of my reading may be due to the accurancy of the digital thermometer used which will be somewhere around 78 ºC

 

SSCP4.jpg

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M@rine_lover
Now, seriously you are taking a big risk to shorten the life span on your LEDs. 3mm plate will get very hot in no time without any fans being ON.... Your LEDs would work great for the time being but on longterm they will losse their life by a great margin. Its all good and well to test and see what your results shows but on serious node, be careful not to run your LEDs for longer period without any fans and such a thin heatsink plate.

Wishing you all the best and watching it with great interest.

 

Have tested w/o fan for 2 hours this afternoon and the reading shoot up >55ºC :wacko: as such I have stop the test and immediately switch off the lighting omgomgomg!

 

According to the Junction temperature formula the actual reading will be 90ºC and if I keep on testing...I'm sure that it will definitey burnt off my LED in no time :scarry: !

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