DIY LED Hood: Prebuild Thoughts...

[GMGQ]

Hmm, well this is mainly for my chaeto down there :P Right now I'm using 2 CF bulbs, and they're growing like weeds. I just wanted to reduce the wiring/lighting clutter.

It's a small weekend project, so I'll try it out and see how it goes.

I still need to figure out the AC power requirements though...

Originally Posted by mseepman

Fair enough... One thought would be that I'm not sure that LED's are the best Fuge light. They've been known to significantly cut down on algae in tanks as they don't put off as much light in the spectrums that many algae's like. Not sure that will help grow your macro-algae either.

No extras on the BP, I just like simple and drivers are simple.

[Lampshade]

I think the cheato should do fine, the cree white's are a 6500 - 10K bulb, that's what i use on mine and they grow great. I think the reason people have problems is the intensity of the light, most algee gets nuked in VERY bright lights, and LED's have the same intensity(lumens) per watt as some of the best MH bulb available. Just keep them up a bit and don't use optics and they'll do fine.

[GMGQ]

Thanks. Plus I'll tweak the intensity with the pot.

Now do you know how I would calculate the AC power requirements?

Originally Posted by Lampshade

I think the cheato should do fine, the cree white's are a 6500 - 10K bulb, that's what i use on mine and they grow great. I think the reason people have problems is the intensity of the light, most algee gets nuked in VERY bright lights, and LED's have the same intensity(lumens) per watt as some of the best MH bulb available. Just keep them up a bit and don't use optics and they'll do fine.

[GMGQ]

The LEDs game last friday, so I spent the evening gluing them onto the fixture and wiring everything up!

DIY Aluminum Fixture:

I used 2 of the left piece side by side for the main body, and I interlocked and riveted in all 4 sides with the right piece.

Top View:


Bottom View:


Side View:


LEDs:


I was going to install a piece of plastic on the bottom as a splash guard, but I havent gotten around to getting the plastic. But now I'm wondering if it's even necessary. I'll probably hold out.

Grommets for running wires through:


Wired up (48" strip of blue LEDs as Moonlights wrapped around fixture):



Temp electrical station :P


Top view with fans (80mm Aluminum fans with blue LEDs, fitting):


Front View:


Fixture runs COOL TO THE TOUCH on full load. Blues at 800mA, Cool Whites at somewhere over 1000mA. One of my goals was to demystify the belief that you need those honking 20lbs+ Amplifier style heatsinks. Pretty cool that ALL the parts of the fixture are aluminum, from the body to the rivets, and even the 2 fans and the screws are Aluminum. I'm very happy with this LIGHT WEIGHT fixture.

I had made the 8LED Fixture, and now this. It's been really good practice. This second one took me no time at all. It's all about the planning. However, I did not anticipate building this 28LED fixture, so the big fixture for my display tank has been pushed back to next year. I just got a new order of bulbs, so they should hold me over until the next LED build (I'm thinking around 60 LEDs next year).

[Milad]

Nice job!! that looks fantastic. People never believe me when I tell them they can use U-Channel for their heatsink.

Keep an eye on the frags at the top of the tank,t hey might bleach with all the new light.

[GMGQ]

Thanks for getting the LEDs out to me man!

Yeah, just look at CPU heatsinks these days, they now have LOTS fins are literally 'paper thin.' It's all about surface area, and dissipating the heat energy from the surfaces, so that the material can continue to "sink heat" away from the LEDs.

The frags have been accustomed to LED lights, as I had my original 8LED fixture on this tank. Lots of browned out frags have started to colour up under that light, so that test run is what inspired me to do the 28LED fixture. Now I can spread out the frags along the whole length of the tank.

Originally Posted by Milad

Nice job!! that looks fantastic. People never believe me when I tell them they can use U-Channel for their heatsink.

Keep an eye on the frags at the top of the tank,t hey might bleach with all the new light.

[StirCrazy]

Originally Posted by GMGQ

. One of my goals was to demystify the belief that you need those honking 20lbs+ Amplifier style heatsinks.

I don't anyone has ever said you need a big finned heatsink, what I believe has been said is that yes with fans you can get away with smaller and cheeper forms of heat sinks, even 1.25x1.25 al tube.

what has been said though and provin is that if you have a fan failure and are not home to catch it or didn't build over temp protection into your design then that cheeper lighter heat sink puts your whole system at much more risk than a higher watt/in2 heat sink would.

got any pics of it with everything on full?

Steve

[GMGQ]

Well there's no manual of what you should or should not do. I'm just saying from what I've seen in the forums, people who jump into a DIY LED project will typically go with what everyone else has been doing, and go with the big heavy heatsinks, as that is the "norm." Even the online stores that specialize in DIY LED parts are providing these heatsinks, as that is what the market has been demanding.

Even with a massive heatsink, I dont think you can escape overheating issues. I think of heatsinks like batteries/capacitors. Once you fill it up with heat energy, it will be full, and it will not be capable of drawing any more heat from the LEDs. The LEDs are not going to stop generating heat, so the heat has to go somewhere. Therefore I think you still need fans no matter what heatsink you use.

The beauty about a smaller heatsink with more surface area is that it is easier to dissipate the heat, rather than trying to cool down a thick piece of metal. I dunno, that makes sense to me.

Again I refer to CPU heatsinks. They have passive heatsinks like this now:



Oh, and no, no pics of everything on full. It's insanely bright, and the camera just sees one big glare. The blues get totally washed out by the white, so I just turned it down to where I wanted, set it and forget it.

Originally Posted by StirCrazy

I don't anyone has ever said you need a big finned heatsink, what I believe has been said is that yes with fans you can get away with smaller and cheeper forms of heat sinks, even 1.25x1.25 al tube.

what has been said though and provin is that if you have a fan failure and are not home to catch it or didn't build over temp protection into your design then that cheeper lighter heat sink puts your whole system at much more risk than a higher watt/in2 heat sink would.

got any pics of it with everything on full?

Steve

[StirCrazy]

Originally Posted by GMGQ

Even with a massive heatsink, I dont think you can escape overheating issues. I think of heatsinks like batteries/capacitors. Once you fill it up with heat energy, it will be full, and it will not be capable of drawing any more heat from the LEDs.

see and hence the problem, people don't know how heatsinks work or how they are rated.

here is a quick and dirty explanation.

heat sinks are rated by there ability to disapate heat and it is measured in watts/square inch. so when you build a set up you are putting a heat source (the LED) in direct contact to the heat sink. by doing this tyou are relying on the ability of the heat sink to release that heat to the air.

in theory a heat sink that is rated higher than 3watts/square inch will not need any fans using 3 watt LEDs but that is under ideal conditions. humidity ambiant temp ect, all affect the rate at which a heat sink will disapate heat.

part of the rating is ambiant temp, humidity and temp differential between the heat sink and ambiant air. generaly you will see a heat sink rating at watt/square inch with the max efficiency at a 10 degree diff or some number like that. which means that to get the full watt/sq in the heat sink has to warm up to about 10 degrees above ambiant, so that is another thing to concider, as if you have a hood temp of 90 degrees the die temp will run about 100 degrees so lowering the ambiant temp will lower the die temp.

so to increase your ability to keep your LED die temp cooler you can do a few things, the easiest is to build a fan set up to force air across the heat sink surface increasing the amount of heat in can disapate.

another way is to use a hollow heat sink which you can run liquid through to adsorbe the heat. theroeticly you could run sump water though it and keep your heat sink at 80 degrees, but this could add to the heat in your tank so you may or may not get away with this unless you use a chiller or another radiator to disapate the heat somewhere else.

you could also run air through a hollow heat sink, this is what "steve's LEDs" does with his 1.25" square tube LED heatsinks.

but with out some sort of safety shutdown I would be hesident with this style as if the fan fails the LEDs have a very good chance of overheating.

the third main way is to increase the size of the heat sink to a higher watt/square inch rating. if you increase this enough you may not need fans as they heat sink will be capable of a higher rate of heat disapation than the LEDs can put in to it.

now us being over cautious we tend to do both, high rate heat sinks and fans. for instance I am using a high rate heat sink with fans and a way to monitor the temp of the heat sink, I am setting it up with a small quiet fan just to ensure a slight air flow over the fins to prevent any stagnent areas which could cause local hot spots, the second fan will kick on with a higher flow if the temp gets over a set point, and at another set temp 1/2 the lights will shut down and if temp still goes up the rest of the lights will shut down.

this seams like a lot of over kill and yes it is, but my intent is to run the LEDs at full current and keep them subcooled and prevent any premature LED faliures. could I do it with a cheep chunk of alumium flat bar.. hell ya, it would need a lot more fan cooling hence more power usage, more noise, ect but ya would be a little lighter and little cheeper.

I personaly don't care what people use to make there setups. could use tinfoil for all I care , but what I do care about is when people critisize others for what they see as overkill because they don't understand how something works. So my hope is that this clears up some of the theory of how a heat sink works and maybe helps people to understand why some people chose to go a little over kill.

there is also they other factor.. finned aluminum can just look cool also

Steve

[Milad]

Originally Posted by StirCrazy

I don't anyone has ever said you need a big finned heatsink, what I believe has been said is that yes with fans you can get away with smaller and cheeper forms of heat sinks, even 1.25x1.25 al tube.

what has been said though and provin is that if you have a fan failure and are not home to catch it or didn't build over temp protection into your design then that cheeper lighter heat sink puts your whole system at much more risk than a higher watt/in2 heat sink would.

got any pics of it with everything on full?

Steve

uh? Do you read all my posts or something, that you can say that for sure? Ive gotten flamed on other boards for saying you dont need the oversized heatsinks, you can use aluminium u-channel. I stopped saying it and started selling the oversized aluminium heatsinks but still tell people they can use the u-channel.