nogod_
Well-Known Member
Hard to argue with a bird in hand but there is no way in hell a 7" x 40" piece of aluminum is going to passively cool 500w.
Careful with no-brainers...theyll gitcha.
Careful with no-brainers...theyll gitcha.
Heatsinks for DIY LED lamps
- Thread starter SupraSPL
- Start date
dom-one dela nooch
Member
lol ! i run 23 watts per cob at 250 watts total at 700ma my friend ,,,,,dont know where you got 500 watts from 
dom-one dela nooch
Member
i run 250 watts total at 23 watts a cob,,,,,, dont know where you got 500 watts my friend lol
JorgeGonzales
Well-Known Member
10 50W heatsinks.
dom-one dela nooch
Member
its not hard to understand 10 cobs at 23 watts a cob is 250 watts at 700ma .....that answer your question
nogod_
Well-Known Member
Wellllll.......there is no way to calculate how many of those heatsinks youd need. because they are designed for a single [75w] cob.
In your case youd need a heatsink less than half that size....which you would have to source elsewhere, my friend.
[Edit for accuracy]
In your case youd need a heatsink less than half that size....which you would have to source elsewhere, my friend.
[Edit for accuracy]
Last edited:
dom-one dela nooch
Member
oh i see where you guys are coming from now but no i do not run 500 watts so my passive heatsink is fine thank you .
dom-one dela nooch
Member
well i need 10 heatsinks for 10 cobs so think there is lol
JorgeGonzales
Well-Known Member
Exactly. You are dissipating about 8W a cob. These heatsinks are good for 3-4x that, so wouldn't make sense at all for you.
You would need 10 heatsinks, but not 10 of these. There's more than one pair of shoes for sale in the world.
nevergoodenuf
Well-Known Member
If you don't care about the extra cost, I would call that upgradeable. I have 120 watts running thru a Luna 300 on a heat sink with a .22C/W. Nothing like Overkill.
dom-one dela nooch
Member
yes this is what i am trying to say that if on an budget and running at 50 watts then they be ideal at 4 for 200 watt driver but for me at %64 10 cob set ups they make no sense ,,,,glad thats cleared that up lol
ttystikk
Well-Known Member
I'd love to have you out for a visit sometime. Your philosophy on overkill is very similar to mine, lol
nevergoodenuf
Well-Known Member
Thanks, I guess I just broke a lot of shit as a kid.
ttystikk
Well-Known Member
I build prototypes specifically TO break them by running them hard and putting them away wet. When they quit breaking I'll know I'm into something lol
Greengenes707
Well-Known Member
Wish you would understand what you are looking at. The 140mm are 75w sinks. Actually handle 100w dissipation well under Crees specs.
HSusa give options right....one size/price doesn't fit all correct???(rhetorical)
Same goes for pin sinks. Different sizes and price for different applications.
4 140mm sinks can more than handle the 250w your using. And can actually fit 3 cobs fine if you started with a blank and want to get technical. That is the point, better cooling with less weight and cost. Using ones like 100mm for 25w application would be cheaper and more efficient at cooling than any extruded profile...physics and thermodynamics.
I suggest checking yourself before you wreck yourself. Get the facts and data straight first.
Angled aluminum has been in DIY since my drone and will remain for applications like pins and cpu coolers.
nogod_
Well-Known Member
Hello all, its heatsink appreciation month here at RIU and in the spirit of the holidays I have been crunching numbers for my latest project: attempting to incorporate round-pin heatsinks into a forced-air duct, or "cool-tube", or "vinyl fencepost" as it were.
Unfortunately the best tool for the job turns out to be elliptical fin heatsinks. These work best because they are designed with the direction of the airflow in mind. In this configuration all of the fins are arranged in a uniform direction which allows for low resistance and maximum airflow in this type of application. They look like this and I cant find any for the price I want. oh well:
Next best are round-pin sinks. I found this fun little calculator to play with....http://www.myheatsinks.com/calculate/round-pin-heat-sink-calculator/
It only calculates for square sinks but in my case thats actually preferable.
So plugging my numbers in.....100mm x 100mm x 40mm with 60mm of clearance in the tube [4" x 4" x 36" tube]. i get about .34C°/w with an airflow of 324lfm from my fan. i realize thats just the first heatsink in the line and the latter sinks will inherit a higher Ta
But at least it gives me (maybe you) a ballpark idea of what size sinks Ill need to get the job done.
Btw I converted from CFM to LFM using this calculator...
http://www.engineering.com/calculators/airflow.htm
Why is this significant?
Until now I had no idea how pin sinks work with active cooling. As far as I can tell, everyone is using them passively. Ive grown to like active cooling, maybe you like it to?
Maybe you avoid it because you like to run remote drivers like me and cable management gives you headaches.
Here's a secret:
4-pole m12 connectors.
They look like this and allow you to consolidate everything into one tidy package:
Thats the male side that i have hooked to the junction box on top of my bars. Kinda like an xlr but with as many wires[and poles] as you want and they are threaded so you dont accidentally unplug your shit.
Anyway, options!
Unfortunately the best tool for the job turns out to be elliptical fin heatsinks. These work best because they are designed with the direction of the airflow in mind. In this configuration all of the fins are arranged in a uniform direction which allows for low resistance and maximum airflow in this type of application. They look like this and I cant find any for the price I want. oh well:
Next best are round-pin sinks. I found this fun little calculator to play with....http://www.myheatsinks.com/calculate/round-pin-heat-sink-calculator/
It only calculates for square sinks but in my case thats actually preferable.
So plugging my numbers in.....100mm x 100mm x 40mm with 60mm of clearance in the tube [4" x 4" x 36" tube]. i get about .34C°/w with an airflow of 324lfm from my fan. i realize thats just the first heatsink in the line and the latter sinks will inherit a higher Ta
But at least it gives me (maybe you) a ballpark idea of what size sinks Ill need to get the job done.
Btw I converted from CFM to LFM using this calculator...
http://www.engineering.com/calculators/airflow.htm
Why is this significant?
Until now I had no idea how pin sinks work with active cooling. As far as I can tell, everyone is using them passively. Ive grown to like active cooling, maybe you like it to?
Maybe you avoid it because you like to run remote drivers like me and cable management gives you headaches.
Here's a secret:
4-pole m12 connectors.
They look like this and allow you to consolidate everything into one tidy package:
Thats the male side that i have hooked to the junction box on top of my bars. Kinda like an xlr but with as many wires[and poles] as you want and they are threaded so you dont accidentally unplug your shit.
Anyway, options!
Keesje
Well-Known Member
Guys,
SupraSPL stated that for efficient cooling you should consider about 120 cm² (19 in²) of heat sink surface pet Watt of heat.
However, today I read a document by Cree and they state: A rough estimate of approximately 5-10 in² (32-64 cm²) of heat sink surface area per watt of heat can be used for a first-order estimate of heat sink size.
That is quite a big difference.
Can anyone explain this difference?
Thanks
SupraSPL stated that for efficient cooling you should consider about 120 cm² (19 in²) of heat sink surface pet Watt of heat.
However, today I read a document by Cree and they state: A rough estimate of approximately 5-10 in² (32-64 cm²) of heat sink surface area per watt of heat can be used for a first-order estimate of heat sink size.
That is quite a big difference.
Can anyone explain this difference?
Thanks
cree nominal temp is much higher than most of us target.