Reef Discussion

[MagicJ]

If i want an overall heatsink of 4.5 x 36, does it matter if it is made up of 1 large peice or 4 pieces of 4.5x9?

Does this effect the cooling efficience in any way?

Sorry Jonathon, I should have replied last night :(

No, I don't think it would have any significant affect on the cooling efficiency - you are reducing the number of external surfaces by joining them together which may affect the heat transfer but not enough to worry about. I have seen many builds done this way.

I used 25x50x3mm aluminium angle for my heatsink and it only gets warm with the LED's driven at 700ma - it gets a fair bit hotter at 800ma!! If you are looking to use the standard finned heatsink that many use I don't imagine you will have any trouble with heat, unless you are looking to drive the LED's at a high current.

 

[marineclass]

Thanks mate. I have gone 4 smaller good quality heat sinks so that I have 9 LEDs on each panel. I think this will give me some good spread and heat shouldn't be a problem- thanks for your advice

 

[MagicJ]

One other thing - make sure you don't put any LED's on the join between the heatsinks. They need to be on a nice flat surface to ensure the maxiumum heat transfer to the heatsink.

 

[marineclass]

It wont matter about wiring going from 1 heat sink to another will it? As long as each led is stuck onto a flat surface with no join under it and then the wire travels across to the next heat sink?

 

[MagicJ]

It wont matter about wiring going from 1 heat sink to another will it? As long as each led is stuck onto a flat surface with no join under it and then the wire travels across to the next heat sink?

No, that will be fine.

 

[nick_s_h]

Nice thread, thanks for doing all this :)

 

[MagicJ]

Thanks Nick - next post should be up this week some time

 

[DavidS]

So what does everyone do with the drivers? Where do you mount them? Do they get really hot as well?

 

[slin1977]

So what does everyone do with the drivers? Where do you mount them? Do they get really hot as well?

Drivers get mounted away from heatsinks and level. Yes they get hot. Really hot, depending how hard they driven.

 

[DavidS]

OK then - would love to see some pics of how everyone has them mounted, situated, etc., so I can get some ideas on how best to do it in my setup before I actually buy a kit.

 

[slin1977]

another quick answer if you use a nice big quality heatsink you might be able to get away without the need for cooling fans!

For that ,matt, you have to know the core temperature at the diode junction. Active cooling is almost always neccessary. If not, you not running your lights to their full potential. Just watch the second generation mazzara fixtures, they are sure to incorporate some fan system. To maintain manufactured claims of led life expectancy.....

 

[MagicJ]

So what does everyone do with the drivers? Where do you mount them? Do they get really hot as well?

This is how I have put mine together - these are located under my tank:

The drivers get moderately warm, but nowhere near as hot as my old MH supplies!!

For that ,matt, you have to know the core temperature at the diode junction. Active cooling is almost always neccessary. If not, you not running your lights to their full potential.

Not sure I totally agree ;)

The specs in the CREE datasheets are based on the LED's being driven at 350ma and a junction temperature of 25 degrees celcius. Now the relationship between current and light output is not linear - doubling the current from 350ma to 700ma only increases the lumens output by 80%, tripling the current from 350ma to 1050ma only increases the lumens by around 150%. There is also the issue of heat management as an increase in the temperature at the diode junction results in a reduction of the lumens output. I plan on putting more of this detail in future posts.

There is a balance to be reached in achieving an efficient LED light. Yes, you can drive XP-G's at 1500ma but the heat generated would be very difficult to manage; the extra light generated would not be 'efficient' and the lifetime of the LED's would be reduced substantially. At the moment, the generally accepted position is to drive the LED's at 750ma - this does not result in 'really hot' drivers nor does it necessarily require active cooling. Are the LED's being driven at their full potential - the answer is no, but I believe that there are other matters to consider.

:)

 

[Dynamic]

This may be a stupid question, but are drivers and transformers the same thing? I was always under the impression they were different.

 

[MagicJ]

This may be a stupid question, but are drivers and transformers the same thing? I was always under the impression they were different.

The Meanwells shown above combine a transformer (from 240v AC to 48v DC) and a Constant Current Driver within the same unit. Some other drivers require a seperate transformer to provide the power.

 

[Dynamic]

Oh okay. Does Meanwell do 240AC to 12vDC within the same unit?

 

[MagicJ]

The 60-48 driver shown above automatically adjusts the voltage from 24-48v depending on the number of LED's connected i.e. you can connect 7 LED's or 13 LED's and it will just work with no need to adjust anything :) Meanwell put out a range of drivers to meet your needs e.g. the ELN-60-9 outputs a voltage from 3-9v.

 

[Dynamic]

Awesome. Thank you.

 

[DavidS]

MagicJ - that looks nice and tidy, thanks for the pics. I like the method you've got of mounting the drivers themselves - I think I may steal that idea, and modify to suit ;)

 

[MagicJ]

David, the drivers do get warm - I was looking to provide as much air movement around them as I could thus the reason for the open section. The box at the top was used to house the joins in the wires going to the actual LED's together with the transistor switching circuits for the Arduino controller.

 

[DavidS]

Nice - I reckon I have a spot in the bottom of my cabinet where I can mount them where they'll have air around them, and there's nothing else down there really generating heat.
I like the box at the top - I was thinking of doing something similar, except in my case, as I have two levels of aquariums, I was thinking of running the cables from the controllers up to the top level, then putting in a junction box up there. From there I can wire out to the DDC-01 PWM controller as well. Keeps as much wiring on one level as possible, which suits me.

The only thing I really have to get my head around is how I mount the damn light. The closest explanation of I could give is that it's sort of a hood, but not, but is, so I don't have a lot of space to hang them from. Not that it isn't possible if I get creative, just awkward.