Heatsinks for DIY LED lamps

[Positivity]

Nice to see you messing with CPU coolers supra. Too bad on the china cob deal changing their ad..mouser has 3000k abs but at a huge markup.

CPU coolers are nice but they have some things that don't work well with cobs like the small footprint.

I'm about to build another light for my 2700k 3590s. I was debating standard heatsink or CPU cooler. Ended up choosing the CPU coolers again for this particular setup. But...I wouldn't have, if it was for a high performance flowering light. In that situation I'd use multiple cobs driven softly that only require one heatsink to mount many cobs...

With that said..I'm piecing together a build to run the 2 3590s at 1.8a. The whole 150w each. Just curious...I know the l/w will be way down and the heat way up.

 

[SupraSPL]

Very interesting build POS. Will it be dimmable? If not, have you considered the Vero29? Apparently they are very well suited for that type of application. If would allow us to build very powerful lamps relatively cheaply. I guess the advantage is a very simple lamp with a low up front cost. The disadvantage is more vertical height requirement and low efficiency as you pointed out. Great recipe for a commercial lamp that is for sure.

 

[Positivity]

Very interesting build POS. Will it be dimmable? If not, have you considered the Vero29? Apparently they are very well suited for that type of application. If would allow us to build very powerful lamps relatively cheaply. I guess the advantage is a very simple lamp with a low up front cost. The disadvantage is more vertical height requirement and low efficiency as you pointed out. Great recipe for a commercial lamp that is for sure.

It's going to be a lot like the last one I made. Just instead of a 1a driver I'm thinking of trying a 1.75a driver. If I was starting from scratch I'd use the veros but I already have the 3590s.

Yeah...it will need to be dimmable. It's more of a test rig than anything. I doubt it will run for long periods of time at 150w. It's not really a light I need so I'm just going to have fun with it. Found a driver on Ali but the shipping kinda sucks...still in the mean well price range though. It will be one hell of a cooling challenge for sure.

 

[SupraSPL]

Gotcha, so in that case you are probably better off with the 3590s because they will perform so well when dimmed. Looking forward to seeing your design.

 

[AquariusPanta]

@AquariusPanta Good question, what I am saying is that the energy consumed by the fan was technically unnecessary because if we use passive cooling we get to enjoy the full efficiency of the LED. But when we use active cooling there is a penalty and I wanted to see how much that would affect the overall efficiency. So I figure it like this:

CXA3070 3000K AB @ 1.4A = 52W @ 42% efficient (21.84 PAR W out of 52 dissipation W)
Fan power consumption at 9V = 1.6W minimum so now:
CXA3070 3000K AB @ 1.4 = 52W + 1.6W = 53.6W
So 21.84 PAR W out of 53.6 dissipation W = 40.7% efficiency (equivalent)

So this demonstrates that actively cooling is like getting 40.7% efficiency out of a 42% efficient COB. BUT if the COB is running a bit cooler with active cooling, it might make up some of that difference.

Yeah no your math isn't off, the logic backing the math appears to be though. If I'm not mistaken, your claiming that a COB+HeatSink combo, without a fan, leads to a more efficient COB.

I don't see why you would include the efficiency of the fan with the COB, even if it produces some heat. Why stop at the fan? Why not include the inline filter, the oscillating fans, the other COBs, etc. into the efficiency? They all produce heat yes?

My understanding of the COB is that it's going to be really efficient operating at 25 degrees celsius, while less efficient at 50 degrees celsius. The hotter it runs, the less efficient it's going to be. The same goes with higher currents.

This begs the question, how does one watt of heat from the fan affect the HeatSink and furthermore the output of the COB? For starters, if the COB, with a given HeatSink, runs at an average 40 degrees celsius and the surrounding temperature is 23 degrees celsius, would it be better or worse to introduce a fan that cools the hot HeatSink with cool, dry air from the environment? Would the extra ~1 watt of heat generated by the fan even be worth consideration when the COB is running at cooler temperatures?

I think not. But that's my logic. Now share yours Supra and try not to dodge the point of interest (smiles).

 

[Greengenes707]

He is not talking about the heat watts with the fans...it's just the watts to run the fan to cool the cob.
In an actively cooled situation there would be no light without the fan. The cob would burn up...and thus that wattage should be include in the necessity of producing ligh at that current.
As opposed to a passively cooled at the same current that doesn't need the extra watt of cooling to produce the same light.

 

[FrozenChozen]

I haven't put that waterblock to use yet because I'm not sure its a good idea also. I do however have a couple vero18s and my pepper cabinet should be ready in a few days. I could run it for a week or so and test it out now that I have parts and space. Maybe I will try and set it up this weekend if I'm not too busy, the problem is I will have to kapton tape them on as I have no way to attach them without puncturing the block. Anyone have any ideas on how to attach them?

Thermal adhesive... Arctic Alumina

 

[AquariusPanta]

He is not talking about the heat watts with the fans...it's just the watts to run the fan to cool the cob.
In an actively cooled situation there would be no light without the fan. The cob would burn up...and thus that wattage should be include in the necessity of producing ligh at that current.
As opposed to a passively cooled at the same current that doesn't need the extra watt of cooling to produce the same light.

Sure he is, whether or not it's explicit. Whatever wattage is produced by the fan, 1W, 2W, or 3W, is considered heat. So he may say 1W is consumed to cool the fan but he could also say 1W of heat is emitted from the fan as a consequence.

I imagine a COB wouldn't easily burn up, as their maximum temperatures (pulling from data sheets) run around 120 degrees celsius, which is pretty hot. The owner would really have to screw something up. I suppose COBs are more susceptible to burning at higher currents than over any other factor.

Altogether I understand where @SupraSPL is coming from but at the same time the benefits of cooling a HeatSink (in theory), regardless of the situation, should overcompensate for the extra power consumed to cool the COB, as it increases the efficiency to some extent. Then again, I don't have any tests or math to argue my point, so I guess I'll leave it be until someone covers it.

 

[guod]

The four myths about active vs. passive methods
http://www.edn.com/electronics-blogs/led-insights/4422914/Cooling-high-power-LEDs--The-four-myths-about-active-vs--passive-methods

All you need to know about fans
http://www.electronics-cooling.com/1996/05/all-you-need-to-know-about-fans/

 

[churchhaze]

edn.com = electronics buzzfeed?

Needs more cats...

None of those "myths" are actually myths. Fans do waste power. They aren't 100% efficient. Moving parts means less reliable than no moving parts, and no parts is more reliable than parts. They do gather dust, and they're noisy compared to no fan. They're noisy when a fan blade gets caught on the metal. They're noisy when they get dusty and the dust gets caught between the metal and the blades.

The author does not make any coherent points. He starts off by making the argument that active cooling designs are lighter and cheaper than passive, which is the only good argument he makes. (Of course none of his 4 myths are related to weight) Is he trying to sell lights or something? What a dishonest argument trying to say that a fan pushing into a heatsink will never stop turning and will never accumulate dust. BULL. Forcing air into CPU heatsinks in particular with their thin fins and spacing so close are DUST MAGNETS. After a few months, there's always a thin layer of lint between the CPU fan and the fins.

A system with a 1% chance of failure per year is actually very high chances of failure. I see some of you with as many as 20 fans. What's the chance that one of them will fail? Fans are unreliable, and to deny that is just stubbornness. Everyone knows that moving parts eventually break down and fail. It's part of the laws.

Even if he somehow came up with a deisgn to get around these "myths", they're still not myths just because you mitigate the negatives.

The four myths about active vs. passive methods
http://www.edn.com/electronics-blogs/led-insights/4422914/Cooling-high-power-LEDs--The-four-myths-about-active-vs--passive-methods

All you need to know about fans
http://www.electronics-cooling.com/1996/05/all-you-need-to-know-about-fans/

 

[bicit]

Altogether I understand where @SupraSPL is coming from but at the same time the benefits of cooling a HeatSink (in theory), regardless of the situation, should overcompensate for the extra power consumed to cool the COB, as it increases the efficiency to some extent. Then again, I don't have any tests or math to argue my point, so I guess I'll leave it be until someone covers it.

Sometimes running a fan isn't worth the cost or complexity for some users. Unless you use nice, power efficient fans the gains would be miniscule, about 0.5-2% depending on which emitter you're looking at. Sometimes a passive light is good as well.

 

[nogod_]

The point is:
Do you get enough of a bonus in the lumen/watt efficiency to justify the extra power consumed to drive the fan. The answer is probably. If you can hit 40c with a $10 cpu cooler and 1.5w operating penalty per cob, but it takes you $30 worth of heatsink to passively cool the same setup down to 40c, then how long will it take you to recover the $20 increase in startup cost with the 1.5w power savings. (A long, long time)

In my opinion passive cooling is just an insurance policy against a fan malfunction. It isnt going to save you any money (unless your fan shits the bed and you smell huevos fritos)

Sure he is, whether or not it's explicit. Whatever wattage is produced by the fan, 1W, 2W, or 3W, is considered heat. So he may say 1W is consumed to cool the fan but he could also say 1W of heat is emitted from the fan as a consequence.

I imagine a COB wouldn't easily burn up, as their maximum temperatures (pulling from data sheets) run around 120 degrees celsius, which is pretty hot. The owner would really have to screw something up. I suppose COBs are more susceptible to burning at higher currents than over any other factor.

Altogether I understand where @SupraSPL is coming from but at the same time the benefits of cooling a HeatSink (in theory), regardless of the situation, should overcompensate for the extra power consumed to cool the COB, as it increases the efficiency to some extent. Then again, I don't have any tests or math to argue my point, so I guess I'll leave it be until someone covers it.

 

[churchhaze]

It depends. If you have 1 vero 10 on a giant sink with lots of surface area, the fan's power is not justified. The power spent on running the fan will probably be greater than the power gain from running at a slightly lower Tj. Tj would be very low even without the fan.

When I run my vero 18 at 500mA on my UFO killer heat-sinks, I do not need any fans at all. It's less than skin temperature.

When I run them at 700mA like I designed, the heat sinks will warm up to 70C. In that case, the power of a small fan is justified.

I may actually sell/repurpose my 700mA drivers, buy 500mA drivers, and go totally fanless. Then I will go to edn.com and let that scatterbrained author know about how he was right about passive heat sinks being heavy.

The point is:
Do you get enough of a bonus in the lumen/watt efficiency to justify the extra power consumed to drive the fan. The answer is probably. If you can hit 40c with a $10 cpu cooler and 1.5w operating penalty per cob, but it takes you $30 worth of heatsink to passively cool the same setup down to 40c, then how long will it take you to recover the $20 increase in startup cost with the 1.5w power savings. (A long, long time)

In my opinion passive cooling is just an insurance policy against a fan malfunction. It isnt going to save you any money (unless your fan shits the bed and you smell huevos fritos)

 

[AquariusPanta]

edn.com = electronics buzzfeed?

Needs more cats...

None of those "myths" are actually myths. Fans do waste power. They aren't 100% efficient. Moving parts means less reliable than no moving parts, and no parts is more reliable than parts. They do gather dust, and they're noisy. Of course the word "waste" just means not put to use.

The author does not make any coherent points. He starts off by making the argument that active cooling designs are lighter and cheaper than passive, which is the only good argument he makes.

There are pros and cons to both methods. Everyone is going to have a different grow setup. It's evident that the industry and most DIY'ers, not all of course, incorporate fans into their fixtures for a reason and it appears to be the way to go. Although according to Supra's claim, they may have overlooked something in the process...

Sometimes running a fan isn't worth the cost or complexity for some users. Unless you use nice, power efficient fans the gains would be miniscule, about 0.5-2% depending on which emitter you're looking at. Sometimes a passive light is good as well.

Running a fan at ~2W every day for ~15 hours over a 90-period would amount to ~$0.30 @$0.12 kWh for a single grow. A single year of use, with 4x grows, would be around $1.20 in electrical costs (keeping in mind that the cost of electricity rises over time). Multiply that by additional fans and the cost in electricity increases even more so.

The question follows: Is better to pay for the larger upfront cost of a bulkier HeatSink, while running fewer COBS and at lower currents or to purchase small slabs of aluminum and run more COBs per area at higher currents despite the annual charge in paying for those fans to operate?

Of course this question requires intensive research and knowledge of any of the given variables in order to accurately answer it but it ultimately comes down to the numbers clicking.

I don't doubt your response Bicit, as I totally agree with your points and that there isn't just one answer. We should all be open to the different ideas and configurations of COB fixtures, whether it be active or passive cooling, including myself.

 

[churchhaze]

That's not what I was arguing. Only the beginning of his article talks about the actual pros and cons of each. The main cons of passive systems are they're large, heavy, and expensive. The cons of active is they're louder, less reliable, they waste more energy, and they gather dust, which are all the cons that author called busted myths.

You're making a completely separate argument, which is based on which route people commonly choose. Yes, I do lean toward designs less reliant on forced air, but that wasn't the argument I was making. I was pointing out that I think the author is a crock.

There are pros and cons to both methods. Everyone is going to have a different grow setup. It's evident that the industry and most DIY'ers, not all of course, incorporate fans into their fixtures for a reason and it appears to be the way to go. Although according to Supra's claim, they may have overlooked something in the process...

 

[AquariusPanta]

It depends. If you have 1 vero 10 on a giant sink with lots of surface area, the fan's power is not justified. The power spent on running the fan will probably be greater than the power gain from running at a slightly lower Tj. Tj would be very low even without the fan.

When I run my vero 18 at 500mA on my UFO killer heat-sinks, I do not need any fans at all. It's less than skin temperature.

When I run them at 700mA like I designed, the heat sinks will warm up to 70C. In that case, the power of a small fan is justified.

I may actually sell/repurpose my 700mA drivers, buy 500mA drivers, and go totally fanless. Then I will go to edn.com and let that scatter brained author know about how he was right about passive heat sinks being heavy.

This is a fantastic example Churchy.

The cost of a CPU fan and the PSU to power it are going to cost anywhere between $5-15 at the very minimum. Adding the cost of electricity to power the fan, it may be be better to exclude the fan/PSU combo for smaller fixtures, while rather spending that money on more aluminum.

As far as fixtures containing more than 5x COBS (like Vero 18's), I'd like to think you could find a sweet spot between a single or pair of large fans (120-140mm) running off the same PSU, with a reasonably sized HeatSink, all the while controlling the available space in the tent or closet.

That's not what I was arguing. Only the beginning of his article talks about the actual pros and cons of each. The main cons of passive systems are they're large, heavy, and expensive. The cons of active is they're louder, less reliable, they waste more energy, and they gather dust.

You're making a completely separate argument, which is based on which route people commonly choose. Yes, I do lean toward designs less reliant on forced air, but that wasn't the argument I was making.

I was rather speaking in general about there being pros and cons to both methods, as each one is going to support a given scenario differently. I understand your argument though. Maybe I overlooked it at first .

 

[Positivity]

Passive cooling leds is a little caveman..at least for higher powered setups

Dual ball bearing fans can last 100,000 hrs...just need to look at a noctua spec sheet to see how a real fan performs.

One point in the article that can't be denied is the performance increase of heatsink with a little help from a fan.

Of course you can passive cool a light... but a air cooled light will be lighter, cooler, and more enjoyable to work with.

But...I think lights may be over cooled in some instances. We aren't cooling the leds so much as the ambient temperatures. The leds can handle 80c.. Just the plants can't.

Passive heatsink with a air cooled housing. Is it still passive..

Or...under drive them. But that's an expensive option. Drive it hard and add a air cooled fitting...let the led work a little

Options options options...many good ways to get the job done

 

[churchhaze]

The main problem with passive is price to setup and size/weight.

But if you could get the passive design free, wouldn't it be better?

Passive designs also reduce system complexity.

 

[churchhaze]

I mostly got annoyed at some jackass (sorry) writing an article about how moving parts are actually reliable, don't waste energy, don't make noise, and don't get dirty.

He's a jackass because he calls what's common sense to all engineers "myths". Moving parts aren't unreliable? A failure rate of over 0 means it's going to fail, which means it's going to break if you keep running it. If you run 2 independent systems containing the same moving parts, it's twice as likely that one will fail.

 

[Positivity]

Passive heats up slowly but surely is my main problem with it.

If a 2w fan can cut your heatsink in half..AND stabilize temperatures... Wouldn't you?

Passive cooled with zero fan intervention would be limited to lower powered setups I'd think.

Still figuring this out like everyone else..