Heatsinks for DIY LED lamps

Fastslappy

Fastslappy

Well-Known Member
no nub & too deep of thread on that fleabay
notice on my screw there's NO thread at the 1st mm of length & the threads don;t stick out very far ?
that allows U to Set the screw correctly into the pilot hole before it's threads start cutting
do you get my point here yet ?
 
Airwalker16

Airwalker16

Well-Known Member
Fastslappy said:
no nub & too deep of thread on that fleabay
notice on my screw there's NO thread at the 1st mm of length & the threads don;t stick out very far ?
that allows U to Set the screw correctly into the pilot hole before it's threads start cutting
do you get my point here yet ?
Click to expand...
Before they start cutting because you haven't tapped that hole? I can't find those kind of screws anywhere. Plus, your are more like 10mm long
 
Airwalker16

Airwalker16

Well-Known Member
I honestly feel aluminum is soft enough for me to just screw those steel M3x10mm pan head's into a wide enough hole like the 3/32".
 
Fastslappy

Fastslappy

Well-Known Member
I have all the taps I need ,
I'm just trying / testing a different approach
IF Kaptan (sp) tape will work holding a COB then why have to tap the holders ?
when a type of screw will do that work for me in soft AL with the same fine touch but quicker
PurpleBuz said:
all that just to avoid buying a tap, and hand tapper ?
Click to expand...
 
Fastslappy

Fastslappy

Well-Known Member
yeah that's all mine is
used in punched steel like in AVR & audio gear
the better PC cases have some in them but they use cheap rivets on cheap cases
just look for the less aggressive threads
that nub makes the screw self aline better when entering a pilot hole @ 3/32"
 
nevergoodenuf

nevergoodenuf

Well-Known Member
You don't need a tap. Just get the size screw you plan on using and 2 or 3 bits that are smaller than the screw. Test them out on the corner of a heatsink to make sure it isn't to tight or to loose. I don't remember the sizes I used but never stripped one or broke one.
 
Airwalker16

Airwalker16

Well-Known Member
Ya that's what I figured with aluminum. It's pretty forgiving material and as long as you've got a hole I feel like steel screws, (MUCH HARDER than aluminum) could get themselves in there no problemo. Thanks nevergoodenuf.

I know you've done a few diy heatsink cobs yourself ;)
 
S

SteadyMobbin

Member
Airwexhaust er16 said:
Ya that's what I figured with aluminum. It's pretty forgiving material and as long as you've got a hole I feel like steel screws, (MUCH HARDER than aluminum) could get themselves in there no problemo. Thanks nevergoodenuf.

I know you've done a few diy heatsink cobs yourself ;)
Click to expand...
Do i need a exhaust for a grow tote?
 
J

J-Icky

Well-Known Member
I just used the screws to tap the HS holes. My advice would be to figure out the drill bit size just below the size of your screws. Then when tapping with the screw go slow and if you feel resistance then back the screw out a little and blow off the threads. If you still have resistance then back the screw all the way out and blow out the hole. I did 6 AA64gt HS's this way and the only problem I had was that I messed up drilling one of the holes, but did not break any screws using them to tap.

Just be careful and don't crank away on the screw thinking that because its steel going into aluminum that it won't break. Even steel is delicate at that small of a size with medium torque, even in aluminum.
 
frica

frica

Well-Known Member
gresskar said:
Hi, will the following heat sink (60mm length) be able to passively cool a cxa3070 at 500mA?

www.bal-group.com/heatsink_detail/247
Click to expand...
Easily.
It would be able to handle it at 1.5A easily too.
1.8A too.

You generally want to keep the temperature of the COB under 85 degrees, it can handle more heat when driven below 2.8A but going hotter means sacrificing efficiency.
The heatsink temp increases by 0.738 °C every watt, so let's say you want to keep the temp within 50 degrees of ambient it can dissipate around 67 watts of heat.
A CXA3070 doesn't even pull 20 watts at 500mA, so it will barely heat up with that heatsink.
Also not everything in the LED becomes heat directly, it's probably 55% efficient at 500mA so the heatsink only has to dissipate less than half of what the LED pulls.

At 60mm it will be able to handle up to 2.1A easily.

Remember to use a good heat pad/heat paste
 
G

gresskar

New Member
frica said:
Easily.
It would be able to handle it at 1.5A easily too.
1.8A too.

You generally want to keep the temperature of the COB under 85 degrees, it can handle more heat when driven below 2.8A but going hotter means sacrificing efficiency.
The heatsink temp increases by 0.738 °C every watt, so let's say you want to keep the temp within 50 degrees of ambient it can dissipate around 67 watts of heat.
A CXA3070 doesn't even pull 20 watts at 500mA, so it will barely heat up with that heatsink.
Also not everything in the LED becomes heat directly, it's probably 55% efficient at 500mA so the heatsink only has to dissipate less than half of what the LED pulls.

At 60mm it will be able to handle up to 2.1A easily.

Remember to use a good heat pad/heat paste
Click to expand...
Thanks for the info :) I'll probably go for 40mm or 20mm length instead since height is a limiting factor in this build. I'm not sure how close I can get the cobs to my scrog screen at 500ma, but the more room I save, the taller I can make my DIY pots :)

I like the heatsink I posted because it comes with predrilled holes that are, conveniently, spaced 35mm apart; same as the ideal cob holder for 3070's
 
Airwalker16

Airwalker16

Well-Known Member
gresskar said:
Hi, will the following heat sink (60mm length) be able to passively cool a cxa3070 at 500mA?

www.bal-group.com/heatsink_detail/247
Click to expand...
You know, that's a cool idea
You could use multiple small short length's for each cob and just mount this style to whatever your heart desires! :)
But FYI: I'm not too sure that say, an Ideal Chip Lok style COB holder will even fit on that would it? Or do you plan on using kapton tape?
 
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