Heatsinks for DIY LED lamps

K

kliend

Active Member
Are you running at 50w or 24w? If 50w you'll want more spread between COBs most likely...?? That's something you want to think about.

I'm doing 50w, 4 x COBs on a 40in x 5.88 from heatsink USA with good results. I'd still have an oscillating fan blowing across the heatsink every rotation. Cheers!
 
J

Jerry Liebler

Member
rollyouron said:
I just ordered my leds and drivers from Kingbright. I need help on heatsink to choose from heatsink usa. I want to run this passive. The only thing I know for sure is how long I want it to be. 32 inches I'm mounting 4 3590 and mw 185. If it's going to be 32 inches long what width do I need to buy. Thanks and sorry I'm not good at math.
Click to expand...
The 4.6" or the 5.375" profile will do just fine! Assuming you get cd bin leds 200W x .44= 88 heat watts, 110 cm2/w for passive means you need an area greater than 9860 cm2. 9860/32" means the profile needs more than 302.5 cm2/". The 4.6" serated profile @342.88 cm2/" works but the base plate is on the thin side (.23") while the 5.375" profile @345.08cm2/" with a generous base plate (.38") is a bit better.
I agree with Kilend, putting all 4 cobs on a 32" heat sink while technically possible results in very concentrated light. IMHO It would be much better to spread them out, on 2 smaller heat sinks. What is the area you are trying to light?
 
Last edited:
R

rollyouron

Well-Known Member
Jerry Liebler said:
The 4.6" or the 5.375" profile will do just fine! Assuming you get cd bin leds 200W x .44= 88 heat watts, 110 cm2/w for passive means you need an area greater than 9860 cm2. 9860/32" means the profile needs more than 302.5 cm2/". The 4.6" serated profile @342.88 cm2/" works but the base plate is on the thin side (.23") while the 5.375" profile @345.08cm2/" with a generous base plate (.38") is a bit better.
I agree with Kilend, putting all 4 cobs on a 32" heat sink while technically possible results in very concentrated light. IMHO It would be much better to spread them out, on 2 smaller heat sinks. What is the area you are trying to light?
Click to expand...
Thanks very much Jerry! Yes I'm running 3590 3500k cd 72v
 
J

Jerry Liebler

Member
rollyouron said:
Jerry, It's 2 plants in a scrog. The screen is 32 x 20 inches
Click to expand...
IMHO, it would be better to use 2 pieces, each, 30" long of the 4.23" profile (9892 cm2) with the cobs at the corners of a 16" x 24" rectangle. A couple of pieces of angle aluminum could tie the two heat sinks together and provide a mounting spot for the driver in the center of the "fixture".
 
klx

klx

Well-Known Member
Not yet. Still sourcing the heatsinks, Im in Oz. Ullrich didnt have what I want either but they have loads more on the NZ site.

I am looking to build a 9 COB light and passively cool 3 CXB3590s per heatsink. What are you after and what did Conrad quote you? They only seem to have up to 151mm lengths. I am looking for 900mm lengths.
 
Last edited:
threetwobravo

threetwobravo

Member
klx said:
Not yet. Still sourcing the heatsinks. Ullrich didnt have what I want either but they have loads more on the NZ site.

I am looking to build a 9 COB light and passively cool 3 CXB3590s per heatsink. What are you after and what did Conrad quote you?
Click to expand...
Yea I'm just going for 6 COB at moment, Ullrich in NZ has nothing in stock that will passively cool and you need to buy 250kg worth for them to make any of the out of stock profiles.

I was wanting to do a passive cooled system as well but as I can't get anything at a cost effective price (shipping costs kill it) I'm going for a active cooled modular set up. The guy at Conrad was a good cunt and quoted 6 x MF18-151.5 (120mm x 150mm) heat sinks cheaper than buying 6 arctic 11 cpu coolers from either buying here in NZ or shipping them from amazon. I'm confident the workmanship will far outreach the arctic 11 or anything from china. The MF18-151.5has a good 8mm base on it and I'll pair it up with some good quality 120mm fans.

I can't see why Conrad wouldn't sell you any of their profiles by the meter even tho the longest length they list is 151mm, check the links below bro

http://www.conradheatsinks.com/products/flat100_350.html

http://www.conradheatsinks.com/prices.html

Heres what Ullrich NZ has in stock UA1632, UA1633, UA1634, UA1635 & UA2238

The UA2238 is the closest that I thought would be any good but it only has a 4 mm base which is far to thin.
 
Last edited:
  • Like
Reactions: klx
klx

klx

Well-Known Member
Yeah I was thinking 6mm base as a minimum so the MF15 should be cool. Will need to work out the perimeter and double check the numbers and make sure 900mm will be enough for 3 @ 50W.

Cheers bro for the links, I will ask em what they can do for metre lengths, it does add up going passive but if i can get the price to anywhere near decent I will take the hit up front. Just gotta keep telling myself it will pay for itself in the end lol
 
threetwobravo

threetwobravo

Member
klx said:
Yeah I was thinking 6mm base as a minimum so the MF15 should be cool. Will need to work out the perimeter and double check the numbers and make sure 900mm will be enough for 3 @ 50W.

Cheers bro for the links, I will ask em what they can do for metre lengths, it does add up going passive but if i can get the price to anywhere near decent I will take the hit up front. Just gotta keep telling myself it will pay for itself in the end lol
Click to expand...
Safe as man, yea hopefully they can do meter lengths for you, the postage on those for me would prob be to much, the MF35 might be the go 350mm wide and has 8 mm base.

haha know what ya mean I just dropped $700 on COB's and drivers alone but this will pay for its self the end and thats a fact,power is stupid expensive here and I actually value the learning experience of building the thing. Having a funny feeling knowing how to build these will also pay for it self if you get my drift.
 
klx

klx

Well-Known Member
MF35 would be sick but I cant justify the cost. I will take a closer look on the weekend at all the profiles and see what i can come up with.

Hell yeah man. Just saying the word LED here is like blasphemy, I cant wait til they see the numbers these lights can pull they will be demanding to know haha.

Laters...
 
ttystikk

ttystikk

Well-Known Member
threetwobravo said:
Safe as man, yea hopefully they can do meter lengths for you, the postage on those for me would prob be to much, the MF35 might be the go 350mm wide and has 8 mm base.

haha know what ya mean I just dropped $700 on COB's and drivers alone but this will pay for its self the end and thats a fact,power is stupid expensive here and I actually value the learning experience of building the thing. Having a funny feeling knowing how to build these will also pay for it self if you get my drift.
Click to expand...
That's not merely a funny feeling; that's the feeling you get when you smell an opportunity!

I'm with you in that I strongly believe COB LED lighting is the stuff that will put everything that's come before on the shelf. It's more efficient, better spectrum, directional lighting pattern is MUCH easier to deal with indoors, lenses and light intensity options allow for fine tuning the lighting to the space... and mates, I think I have an answer for the cooling problem.

I need to test it thoroughly, but if it works for me it will work for anyone.

I'm the wild eyed weed growing revolutionary your Hydrofarm rep warned you about; I'm the one who will turn the entire indoor cultivation industry right on its ear... and it will never look the same again.
 
klx

klx

Well-Known Member
threetwobravo said:
Yea I'm just going for 6 COB at moment, Ullrich in NZ has nothing in stock that will passively cool and you need to buy 250kg worth for them to make any of the out of stock profiles.

I was wanting to do a passive cooled system as well but as I can't get anything at a cost effective price (shipping costs kill it) I'm going for a active cooled modular set up. The guy at Conrad was a good cunt and quoted 6 x MF18-151.5 (120mm x 150mm) heat sinks cheaper than buying 6 arctic 11 cpu coolers from either buying here in NZ or shipping them from amazon. I'm confident the workmanship will far outreach the arctic 11 or anything from china. The MF18-151.5has a good 8mm base on it and I'll pair it up with some good quality 120mm fans.
Click to expand...
I have been having a closer look at the Conrad heatsinks and unless I have my maths wrong the MF18-151.5 can passively cool ~39 watts of heat.

How hard do you plan on running your COBs?
 
threetwobravo

threetwobravo

Member
klx said:
I have been having a closer look at the Conrad heatsinks and unless I have my maths wrong the MF18-151.5 can passively cool ~39 watts of heat.

How hard do you plan on running your COBs?
Click to expand...
True? I haven't fully got my head round the formula for working that out. What formula are you using?
I'll be running them at 50W
 
klx

klx

Well-Known Member
Credit to SupraSPL:

First you calculate the perimeter:

(profile width X 2) + (fin height X 2 X # of fins) + (base height * 2) = Perimeter

MF18 - (125 x 2) + (74 x 2 x 1) + (8 x 2) = 2930mm

Then, Perimeter * fin length = Surface Area.

Switching to cm - 293 X 15 = 4395 cm^

Then for passive cooling its 110cm^ per watt:

4395 / 110 = 39.9 watts.

Someone can chime in if I have misinterpreted any of that
 
Last edited:
SupraSPL

SupraSPL

Well-Known Member
You have the formula right, I think it was the fin height that was off. Here is what I get for MF18.151

Perimeter = (125X2) + (56*2*18 ) + (8X2) = 2282mm
Perimeter = 228.2 cm
228.2 * 15.15 fin length = 3457 cm²

Assuming 120cm²/heat W, that heatsink would be good for 29 heat W.

BUT, the distance between the fins is very small and the fin height is relatively tall, so that heatsink might not be considered passive cooling friendly, because of that I would recommend testing the heatsink temp before committing to a large build using that heatsink passively.
 
klx

klx

Well-Known Member
Thanks, yes fin height is 62 not 82 doh!!!

At 29 watts they could still be ok to cool one CXB3590 36V at 1.4A.

I am liking the look of the MF15 Series but the base it thinner at 6mm. Do you think is thick enough?
 
threetwobravo

threetwobravo

Member
I'm getting 37.7 W passive for the MF30 and 43.95W passive for the MF35, still a bit short for my liking. I'm going to stick with putting some fans on the MF18.151.

If they made them a bit longer I'd say we'd be in business
 
Last edited:
  • Like
Reactions: klx
You must log in or register to reply here.
Top