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Author Topic: LED Heatsink 10W?  (Read 19596 times)

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Offline BigBrother

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LED Heatsink 10W?
« on: July 26, 2012, 09:27:06 AM »
I want to use these 10W LED lamps but I'm not sure how big of a heatsink I'll need or if I can find one that'd be best for use as/in a lighting fixture.

budget: 10$/ea (I need 4, maybe 5)
 

Offline Short Circuit

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Re: LED Heatsink 10W?
« Reply #1 on: July 26, 2012, 10:25:59 AM »
Crazy idea perhaps, but did you happen to try to enter the topic title in the ebay search box...

Not clear what will be most suitable for this particular led, probably best to wait until you have it in your hands.
Usually, that gives much better impression on mounting requirements than the typical eBay images.
 

Offline Psi

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Re: LED Heatsink 10W?
« Reply #2 on: July 26, 2012, 11:19:28 AM »


That's one of the four sections of my room lighting.
Heatsink is 10.5cm x 5.5cm with thick fins on the back.

It has 3 white leds (3.2W each) and most of the time these are all i use.
The others there are 1W in RGB but only used to tint the color a little.

So i estimate it's dissipating at least 10W

It gets hot enough that you don't want to hold it for more than 5 seconds or so, probably around 50degC.
Which is within the specs of the leds.

The entire lighting rig has been my room lighting for 4 years now and no leds have died.

« Last Edit: July 26, 2012, 11:29:29 AM by Psi »
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Offline BigBrother

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Re: LED Heatsink 10W?
« Reply #3 on: July 26, 2012, 12:09:59 PM »


That's one of the four sections of my room lighting.
Heatsink is 10.5cm x 5.5cm with thick fins on the back.

It has 3 white leds (3.2W each) and most of the time these are all i use.
The others there are 1W in RGB but only used to tint the color a little.

So i estimate it's dissipating at least 10W

It gets hot enough that you don't want to hold it for more than 5 seconds or so, probably around 50degC.
Which is within the specs of the leds.

The entire lighting rig has been my room lighting for 4 years now and no leds have died.


nice! and wow, 4 years... long time. what kind of power supply are you using?
 

Offline Psi

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Re: LED Heatsink 10W?
« Reply #4 on: July 26, 2012, 01:26:34 PM »
When i made it i couldn't find a power supply in my junkbox that could handle 8A so i mod'ed the led PWM driver so the white and RGB led sections were powered separately. Then i used a ATX powersupply plus an old 5A 12V supply.

The driver isn't anything special, it's a bit of a mess really :P
LEDs are arrange in series to get multiple sections of around 11V and 4 mosfets drive the White/Red/Green/Blue sections from 12V through resistors for current limit.

mosfets are driven from a ATMega at around 1kHz PWM, the mcu also does IR remote control.

Eventually i'll make a new one using 1-2 of the deal extreme 30W RGB single leds. Probably with a 230V switchmode built onto it and UPB control through the house wiring.

This is it...




« Last Edit: July 26, 2012, 01:33:11 PM by Psi »
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Offline BigBrother

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Re: LED Heatsink 10W?
« Reply #5 on: July 26, 2012, 01:39:05 PM »
damn... maybe if I had the ceiling fan from the next room which is a 2 bulb socket with a glass globe around it, I could do something similar to what you have. But, alas, what I have is 3 separate glass cones for one bulb each... so I'll have to figure something out in order to stuff a power supply, the heatsink, the LED and a reflective cone.
 

Offline slateraptor

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Re: LED Heatsink 10W?
« Reply #6 on: July 26, 2012, 02:36:21 PM »
This is it...

In the words of Borat: "Sexy time...yeah."
 

Offline Psi

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Re: LED Heatsink 10W?
« Reply #7 on: July 26, 2012, 03:03:39 PM »
There's actually an issue with RGB lighting, girls keep setting it to pink.
hehe
« Last Edit: July 26, 2012, 03:14:25 PM by Psi »
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Offline T4P

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Re: LED Heatsink 10W?
« Reply #8 on: July 26, 2012, 06:37:03 PM »
Me thinks that heatsink is a bit tiny for 10W  ::)
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Offline Psi

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Re: LED Heatsink 10W?
« Reply #9 on: July 26, 2012, 06:41:00 PM »
Well it works fine for me. And we're talking about 3x 3.2W leds plus a few other leds on around 10%.
And then there is a few large resistors thermal epoxyied to the other side.

I can't see it being under than 10W

The metal is pretty thick, about 4mm.
The picture maybe distorting the size a bit, its 10.5cm x 5.5cm
« Last Edit: July 26, 2012, 06:43:58 PM by Psi »
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Offline T4P

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Re: LED Heatsink 10W?
« Reply #10 on: July 26, 2012, 06:47:27 PM »
Well it works fine for me. And we're talking about 3x 3.2W leds plus a few other leds on around 10%.
And then there is a few large resistors thermal epoxyied to the other side.

I can't see it being under than 10W

The metal is pretty thick, about 4mm.
The picture maybe distorting the size a bit, its 10.5cm x 5.5cm

Well ... mistake then.
So what's the temperatures it's giving out?
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Offline Psi

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Re: LED Heatsink 10W?
« Reply #11 on: July 26, 2012, 06:49:39 PM »
Well it works fine for me. And we're talking about 3x 3.2W leds plus a few other leds on around 10%.
And then there is a few large resistors thermal epoxyied to the other side.

I can't see it being under than 10W

The metal is pretty thick, about 4mm.
The picture maybe distorting the size a bit, its 10.5cm x 5.5cm

Well ... mistake then.
So what's the temperatures it's giving out?

I don't have an IR probe to check but as i said above, you can hang onto it but it starts to hurt after above 5 seconds, I estimate around 50degC. The leds i'm using are rated to max 80C operating temp
« Last Edit: July 26, 2012, 06:51:42 PM by Psi »
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Offline mianchen

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Re: LED Heatsink 10W?
« Reply #12 on: July 27, 2012, 03:55:25 AM »
Very NICE !!!



Is this plastic or glass?
 

Offline T4P

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Re: LED Heatsink 10W?
« Reply #13 on: July 27, 2012, 04:55:21 AM »
me thinks acrylic
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Offline Psi

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Re: LED Heatsink 10W?
« Reply #14 on: July 27, 2012, 07:51:29 AM »
It's a cut up recipe-book holder :)
Either perspex, acrylic or polycarbonate, not sure which.
The top side has been sanded to make it less transparent (looking at the light hurt your eyes when it was 100% transparent)
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Offline poorchava

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Re: LED Heatsink 10W?
« Reply #15 on: July 27, 2012, 09:03:48 AM »
Yeah, those definitely need some semi-transparent screen. I remember experimenting with 10W green, while and blue leds. Once I've flashed the led in front of my eyes, for a few minutes i would see shapes of the actual semiconcudtor dies in the array when i closed my eyes. I guess such strong pulse of light into retina affects it's sensitivity for some period of time.

Be aware that flashing strong light sources in front of an eye can cause retinal detachment which can be fixed only by surgery.
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Offline DmitryL

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Re: LED Heatsink 10W?
« Reply #16 on: July 28, 2012, 01:49:53 AM »
I want to use these 10W LED lamps but I'm not sure how big of a heatsink I'll need or if I can find one that'd be best for use as/in a lighting fixture.

When I was making my LED table lamp, here:
https://www.dropbox.com/sh/l15vcdx76q2xp17/03UPDBDFGM#/

I was selecting the heatsink by thermal resistance :) There was a Dave's video about this.
E.g. I knew that I was going to dissipate ~15Wt, then I went to ebay and looked for "LED heatsink", selected appropriate one one with thermal resistance ~2degrees/Wt, that gave me acceptable LED temperature not exceeding 70 degrees.
Note that my heatsink has vertical fins, this greatly improves its efficiency because the airflow.

 

Offline BigBrother

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Re: LED Heatsink 10W?
« Reply #17 on: July 28, 2012, 03:08:19 PM »
I've looked a few places and people seem to think this will work as a 10W heatsink. not sure if it'd work in warmer conditions of my room (around 80-85F)... or at all. comments?
 

Offline DmitryL

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Re: LED Heatsink 10W?
« Reply #18 on: July 28, 2012, 07:29:53 PM »
I've looked a few places and people seem to think this will work as a 10W heatsink. not sure if it'd work in warmer conditions of my room (around 80-85F)... or at all. comments?

I probably will :) I made experiments myself, attached 20Wt resistor and measured temperature across heatsink.

BTW, I'm not a specialist in thermal design, but something tells me that for the best performance fins shold be positioned the way allowing the best airflow through them (convection). For this type of heatsing, I'm afraid,  it is when your LED beam will be horisontal :)

IMHO, if this heatsink is positioned flat  top facing up or down, there will be not much airflow through fins and from thermal resistance point of view it won't differ much from a simple flat bar :)
Don't know if it s acceptable or not..


 

Offline BigBrother

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Re: LED Heatsink 10W?
« Reply #19 on: July 29, 2012, 04:23:25 PM »
so... the general consensus on an LED heatsink is that lower thermal resistance per watt is better? I found this one on mouser. (if that link doesn't work, it's Mouser Part #:  567-882-300AB )
 

Offline Psi

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Re: LED Heatsink 10W?
« Reply #20 on: July 29, 2012, 04:39:42 PM »
The thermal resistance of that heatsink (1.55 C / W) means if you put 10W on it the temp will rise 10*1.55 = 15.5degrees above ambient.

Note, if your LED takes 10W then some of that is light energy and doesn't become heat.
ie, you don't get 10W of heat out of a 10W led. Check it's efficiency to calculate the actual heat output.

Just in case you didn't notice, the pic on that headsink is generic.  It's actually 76.2mm tall.
« Last Edit: July 29, 2012, 04:44:47 PM by Psi »
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Offline BigBrother

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Re: LED Heatsink 10W?
« Reply #21 on: July 29, 2012, 06:12:57 PM »
The thermal resistance of that heatsink (1.55 C / W) means if you put 10W on it the temp will rise 10*1.55 = 15.5degrees above ambient.

Note, if your LED takes 10W then some of that is light energy and doesn't become heat.
ie, you don't get 10W of heat out of a 10W led. Check it's efficiency to calculate the actual heat output.

Just in case you didn't notice, the pic on that headsink is generic.  It's actually 76.2mm tall.
meh, that's only 3" tall...oh. eh... I'll restart my search again then.
 

Offline Psi

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Re: LED Heatsink 10W?
« Reply #22 on: July 29, 2012, 06:30:32 PM »
Only 3" tall?  76mm is pretty large and 15degC rise isn't bad.

25 ambient would result in 40deg C (actually less because that's the full 10W and not just the heat output)
« Last Edit: July 29, 2012, 06:32:07 PM by Psi »
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Offline BigBrother

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Re: LED Heatsink 10W?
« Reply #23 on: July 30, 2012, 01:05:13 PM »
ok, the glass cup for the socket is 3 3/4" (95mm) on the wide end and 1 3/4" (44.45mm) at the base and it's 5" (127mm) tall. for reference, an i5 2500k stock cooler sits in about 2". this is a bit more re-assuring to me as now I have actual numbers to go by for a heatsink and to stuff a power supply inside or out. anyone know of a power supply that I could wrap around the outside of the cup? would be scores better than figuring out how to stuff it all inside the cup.

« Last Edit: July 30, 2012, 01:09:18 PM by BigBrother »
 

Offline T4P

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Re: LED Heatsink 10W?
« Reply #24 on: July 30, 2012, 06:10:55 PM »
Looks like it is the same heatsink as the E5700 at least.
In any case you shouldn't just stuff a heatsink in there without any form of airflow, it needs to have open airflow not just depending on the stationary air inside the glass or else the LED's a quick goner
The stock heatsink is 0.23C/W with the fan on, without the fan who knows!

Wait, this one on the left?

OR this one
« Last Edit: July 30, 2012, 06:20:53 PM by T4P »
http://the4thpin.comeze.com <-- Rants and Reviews! sorry my english  :palm:
 


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