littlejacob
Well-Known Member
Bonjour
Thanks testicles
Merci
Thanks testicles
Merci
Heatsinks for DIY LED lamps
- Thread starter SupraSPL
- Start date
littlejacob
Well-Known Member
Bonjour
If you are satisfied of a certain size of heatsink @1400mA. If you switch to 700mA is that mean that you can split the h.s in 2 and keep the same temperature and use a smaller fan!??
Have a great day ★
If you are satisfied of a certain size of heatsink @1400mA. If you switch to 700mA is that mean that you can split the h.s in 2 and keep the same temperature and use a smaller fan!??
Have a great day ★
alesh
Well-Known Member
You'll get even better temps assuming that you move the air with the same speed.
1) At lower current the LEDs operate at a higher efficiency
2) At half the current the dissipation is less than a half
3) The heat sink cut in half is slightly more efficient too
littlejacob
Well-Known Member
Bonjour
Thanks again, again and again alesh my friend
Ok, but I will certainly decrease the fan speed a little, when I will do it...
First thing first: try my lights as they are, and then, change/adapt/add/transform a few things.
Have a great day ★
Thanks again, again and again alesh my friend
Ok, but I will certainly decrease the fan speed a little, when I will do it...
First thing first: try my lights as they are, and then, change/adapt/add/transform a few things.
Have a great day ★
CanadianONE
Well-Known Member
@SupraSPL maybe you have a minute to give me some advice. I haven't quite wrapped my head around all the heatsink equations you have posted.
12" chunk of this profile heatsink actively cooled would be able to handle how many (watts) CXB3070 AB 1.4A This is a profile available on ebay and I was just curious what it could handle. Really appreciate any advice you can give.
12" chunk of this profile heatsink actively cooled would be able to handle how many (watts) CXB3070 AB 1.4A This is a profile available on ebay and I was just curious what it could handle. Really appreciate any advice you can give.
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EfficientWatt
Well-Known Member
Didn't double check but :
Perimeter in cm (2.71+2.71+2.82+((1.41-0.185)*52))*2.54 = 182.7 cm
Total surface area : 182.7 * (12*2.54) = 5569 cm²
(Using 40cm² per W of heat) : 5569/40 = 139W max of heat (with proper ventilation)
CXB3070 36V AB's @1400mA (according to supra's numbers) dissipate 54.57% of heat,
So 139/0.5457 = 254W of CXB3070 AB 36V @1400mA.
254/49.83 = 5.1
Can't split a cob so we need top round it down to:
5 , is your answer.
(if i didn't mess up along the way)
Perimeter in cm (2.71+2.71+2.82+((1.41-0.185)*52))*2.54 = 182.7 cm
Total surface area : 182.7 * (12*2.54) = 5569 cm²
(Using 40cm² per W of heat) : 5569/40 = 139W max of heat (with proper ventilation)
CXB3070 36V AB's @1400mA (according to supra's numbers) dissipate 54.57% of heat,
So 139/0.5457 = 254W of CXB3070 AB 36V @1400mA.
254/49.83 = 5.1
Can't split a cob so we need top round it down to:
5 , is your answer.
(if i didn't mess up along the way)
CanadianONE
Well-Known Member
Thanks a bunch @EfficientWatt hopefully someone else can chime in for verification.
Getgrowingson
Well-Known Member
Just make sure you put a couple fans on that heatsink as the fins go the opposite way. Want to make sure all fins where there is heat being dissipated is getting air movement. Most heatsinks with a n single fan would be like this:
========0=======
Yours should be something like thksy:
////////////////////
0//0//0//0//0//0//
///////////////////
Not that many fans but you get the idea
========0=======
Yours should be something like thksy:
////////////////////
0//0//0//0//0//0//
///////////////////
Not that many fans but you get the idea
CanadianONE
Well-Known Member
The fins run lengthwise Not side to side
Getgrowingson
Well-Known Member
Hahahaha maybe I should open the damn picture file next time
what type of copper is best for heatsink material ?
I was thinking of making some nice fat copper base plates\shims to attach to a normal aluminum heatsink or aluminum channel, for each individual cob. Does anybody know what grade of copper and what type I should be using ?
was thinking of using copper flat bars from onlinemetals
I was thinking of making some nice fat copper base plates\shims to attach to a normal aluminum heatsink or aluminum channel, for each individual cob. Does anybody know what grade of copper and what type I should be using ?
was thinking of using copper flat bars from onlinemetals
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SupraSPL
Well-Known Member
Good math, I agree.
One thing that might be worth pointing out, the base is thinner than the heatsinks we normally use. Thick base is important if you have an uneven heat load and 50W COBs are a good example of that. Probably not a huge issue but I have not tested it to be sure.
CanadianONE
Well-Known Member
So maybe more suitable to lower wattage situations.
SupraSPL
Well-Known Member
Sure, the idea is to take an instantaneous lux reading and power consumption reading when the fixture is cool, then let it warm up to a stable temp and take another lux reading and power reading. Then check to see what percentage the lux/W has decreased. At very low currents you can have as little as .1% temp droop, a good range (IMO) for hard driven COBs is 2-5%. If it is 7% or more it is probably a good idea to address the cooling situation.
For posterity, using the watt meter is not a perfect method because the driver efficiency tends to increase a bit as it warms up. If you want more accuracy you would have to use dissipation wattage by checking the voltage and amperage on the DC side of the circuit, preferably at the same time using a pair of multimeters.
It can be tricky to get an accurate instant reading because at high currents the the lux will drop off very quickly and the driver current output can spike when first clicked on, so you might want to try the cold start test a few times to get confirming repeatability.
For posterity, using the watt meter is not a perfect method because the driver efficiency tends to increase a bit as it warms up. If you want more accuracy you would have to use dissipation wattage by checking the voltage and amperage on the DC side of the circuit, preferably at the same time using a pair of multimeters.
It can be tricky to get an accurate instant reading because at high currents the the lux will drop off very quickly and the driver current output can spike when first clicked on, so you might want to try the cold start test a few times to get confirming repeatability.
I am building a few LED strips that are I would like to hang (for the most part) from long heatsink bars. I would prefer to get passive cooling, but it may not be an option. I will be using 3 cree 3070s at 50 watts each. I would mount the cobs to the heatsink and the drivers would be mounted away from the heatsinks. The distance/spread of the cobs would be(theoretically, this is not the exact size of the heatsink, it would be longer)at the 1", 18", 36"(most likely) or 1", 24",48." What are viable options for passive cooling at these spreads on one long heatsink? Thanks.
caretak3r
Well-Known Member
verdict on this one?