Aluminum PCB strip enough to cool 3x 1W led?

shiftline

Newly Enlightened
Joined
Aug 22, 2014
Messages
39
I want to build some waterproof underwater lighting.

I'm thinking of putting 3x1W leds on an aluminum PCB and sealing it in an acrilic tube to user underwater in an aquarium.

Would the aluminum PCB be enough for cooling in my situation??

Second question, If i want 2 of these light tubes would i use two 3x1w led driver or could i used a 3x2w driver and run them in parallel off the driver?

LED Specs

Specifications:


1W :35mil
Forward Current: 350mA
Forward Voltage: 3.2V~ 3.6V
Viewing Angle: 120 deg
Luminous Flux: 90 lm~ 100 lm
Output power: 1w
Light color:
Warm White 3000-3500K;
Cool White 6000-6500K
Natural White 4000-4500k
$_57.JPG



0PCS x 14CMx1.6CM Aluminium PCB Circuit Board for 3 x 1w,3w,5w LED in Series
$(KGrHqIOKpMFHkYlOtd0BR6mYOLfc!~~60_57.JPG




 

DIWdiver

Flashlight Enthusiast
Joined
Jan 27, 2010
Messages
2,725
Location
Connecticut, USA
The board isn't the problem. The problem is the acrylic tube.

The board's job is to transfer the heat from the LEDs to the air. But where does the heat go from there? It has to go through the acrylic tube and into the water.

Acrylic is not a good conductor of heat. In fact, it's approximately 1000 times worse than aluminum. I ran a quick calculation assuming the tube would be 3/4" ID, 1" OD, 6" long, and 2W of heat flux. It looks like the temperature at the inside surface of the tube will be warmer than the water by a whopping 3 degrees C. That's over 5 degrees F!;)

Actually, it looks like the tube isn't a problem.

There will be some temperature differential at the air/acrylic interface. You could minimize this by painting the inside of the tube black.

There will also be some temperature differential at the PCB/air interface. You could minimize this by painting the board and LEDs black.

Heck, if you're going to paint everything black, just leave the power turned off. You can't tell the difference anyway, and then you have no heat issues!

Okay, all kidding aside, if this was my project, I'd just run the board in the air, and see how hot it gets. I'd expect the temperature rise to at least double when you put it in the tube and into the water. Gut feeling is that at 0.3W/in^2, the board would be fine in free air, but questionable inside a plastic tube. Probably fine for intermittent use, but for continuous duty, you may not get the life you'd like.
 

shiftline

Newly Enlightened
Joined
Aug 22, 2014
Messages
39
I could use a glass tube (test tube) as it would transfer heat better. Other option may be to buy a 6w one and run it at 3w? Or would that even make a difference..?


Sent from my iPhone using Candlepowerforums
 

Nick Paizis

Newly Enlightened
Joined
Mar 5, 2015
Messages
1
Hi,
eventhough I am new in leds, I have done some testings that might be useful for your prodject.
Firstly, to my experience, if you run 1w led at 3v, you get good light and low heat. If you need more light, use 4 leds instead of 3.
Secondly, for your prodjest I yould use COB, seal the top part and leave the aluminium back in the water for cooling. I tested an 8W cob rated 24-27V, running at 24V, geting no more than 50 C with no aditional cooling. Same temperatures I get from 1W leds on a star 20mm heatsink.This means that in water you are relay good anyway.

Here is the data I collected:

SetupBeam AngleLuxAmpVoltPowerlux/wDistancecalculated lumenslum/w
8w cob1803360,11242,64127,270,60380144
8x1w led1202900,14243,3686,310,6032898


Note that lumens is an indication only, Lux is the real measure I can do.

I hope that helps
 
Top