Minimalistic multichip DIY LED build

FDAWG said:
That seems light considering many 2-3w fixtures have overheating issues with a finned aluminum heatsink and fans mounted directly over the fins blowing down.

I've noticed throughout the thread that many of the projects have passive heatsinks that are undersized. I'm not talking about the fan cooled heat pipe CPU coolers, but the simple aluminum fin heatsinks like you see on 3w builds.

Maybe I'm overkill, but I thought I would mention it.
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Im running several tanks now with those 2 to 5 watt LED's and I'm using simple 1" X 2" channel allumnium without any forced air. I have no overheating issues at all. However I think the important thing is the spacing between the LED's. I space them at least 3 1/2" apart and even after 8 hours of operation the Alumnium is just warm to the touch near the LED's themselves. Another thng to consider is how the stars are mounted and that you have a good heat transfer between the LED and the Alumnium heat sink.

The next build I'm considering will be using the newer Cree 10 Watt LED's so I'm wondering if will be able to say the same thing about them. It is also rumored that soon there be 20 Watt LED's available from Cree. But the only draw back I'm finding on designing the unit with just 10 Watt LED's is there lack of available colors with the star mounts.
 
TropTrea said:
Im running several tanks now with those 2 to 5 watt LED's and I'm using simple 1" X 2" channel allumnium without any forced air. I have no overheating issues at all. However I think the important thing is the spacing between the LED's. I space them at least 3 1/2" apart and even after 8 hours of operation the Alumnium is just warm to the touch near the LED's themselves. Another thng to consider is how the stars are mounted and that you have a good heat transfer between the LED and the Alumnium heat sink.

The next build I'm considering will be using the newer Cree 10 Watt LED's so I'm wondering if will be able to say the same thing about them. It is also rumored that soon there be 20 Watt LED's available from Cree. But the only draw back I'm finding on designing the unit with just 10 Watt LED's is there lack of available colors with the star mounts.
Click to expand...

DIY 3w LEDs with aluminum fin heatsinks don't have overheating issues if you space the chips out and properly affix them to the heatsink with thermal paste/glue/tape. The issues arise once a finished housing surrounds the heatsink and limits venting. DIY projects are often hung over open top minimalist tanks with lots of passive venting. Once you squeeze a few fixtures into a canopy with high ambient temperature, it gets harder to keep cool.

A good design needs to work in the most adverse conditions.
 
TropTrea said:
The next build I'm considering will be using the newer Cree 10 Watt LED's so I'm wondering if will be able to say the same thing about them. It is also rumored that soon there be 20 Watt LED's available from Cree. But the only draw back I'm finding on designing the unit with just 10 Watt LED's is there lack of available colors with the star mounts.
Click to expand...

You must be meaning 20 watt single chip emitters, because the CXA series has been past 20w for a long time already. It's not available over 5000k and I bet the color rendering is bad but they go up to 60w for the CXA2030. These are multichip packages similar to what bridgelux produces.
 
tomservo said:
You must be meaning 20 watt single chip emitters, because the CXA series has been past 20w for a long time already. It's not available over 5000k and I bet the color rendering is bad but they go up to 60w for the CXA2030. These are multichip packages similar to what bridgelux produces.
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Yes I am refering to the single chip emitters. The multi chip I agree have out from Cree for some time now. If I reacll over a year ago they had one with 9 XP-E emitters in it that you would tink would be rated at 27 Watts however it's max was rated considerably less.

On a personal bases I realy would not want a white chip rated over 5,000K. I perfer a 3 or more Blue to White ratio and with a higher K rated chip you just do not get enough in the yellow, orange, and red part of the spectrum. Yet in the chips rated under 4,000K you get too much. But this is my personal color taste which varies considerable between individuals.
 
it's a lot cheaper to build with those 5000k leds so that's a plus

I like 10-14k with blue/rb

I used to run iwasaki only tanks, back when they came out, I tired of that look
 
So I am not sure if this is the place. But I have a problem/question. I have built a light fixture with 25 x 20w leds. After connecting the last pod of 5 lights I now get shocked if it touches the aluminum light rack and the water. I tested continuity between the wires going to the leds and the rack and am getting nothing. I tested Vac between a ground and the light rack and I am getting 25v. I disconnect one pod and it goes down to 19.x. I was wondering if anyone else is seeing any ac voltage leak from the base of the leds. My guess is no one notices it as it is so small but since I have 25 it is multiplied.
Any help, suggestions are welcome!
 
Have you any drivers attached to the light rack? Have you any else AC sources attached to the light rack. What type of fans?

Sincerely Lasse
 
Lassef said:
Have you any drivers attached to the light rack? Have you any else AC sources attached to the light rack. What type of fans?

Sincerely Lasse
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I do have 5 fans. I just checked and they all have 12v dc going to them. Also the fans are mounted on acrylic, and acrylic is nonconductive.
Mabe it is the way I am testing. I am hooking the multimeter to the - of an extentioncord and the positive to the light rack.
 
You say that you have an AC current (alternating current). Ín my mind - you cant have an AC current if you only have DC. Do you have any AC-device in the aquarium?

Sincerely Lasse
 
Lassef said:
You say that you have an AC current (alternating current). Ín my mind - you cant have an AC current if you only have DC. Do you have any AC-device in the aquarium?

Sincerely Lasse
Click to expand...
Hey Lesse,
In the tank I have 2 x mp40, skimmer, mj1200 and a snapper return pump. I turned everything off accept the driver for the lights and still got shocked (think I am starting to like it :bigeyes:). Again the AC may be the way I was testing. I tried to go from the - of one light to the light rack and got nothing.

I just tested again and I did not get shocked.. I dont know what is going on. Will have to see if It comes back and do some more testing.

Thanks for your help!

BTW, I love the way the lights look. I run them at 50%. I put the reflectors on them, but they fell off. Going to try to use 2 part epoxy to hold them on.
 
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lookout888 said:
Hey Lesse,
In the tank I have 2 x mp40, skimmer, mj1200 and a snapper return pump. I turned everything off accept the driver for the lights and still got shocked (think I am starting to like it :bigeyes:). Again the AC may be the way I was testing. I tried to go from the - of one light to the light rack and got nothing.

I just tested again and I did not get shocked.. I dont know what is going on. Will have to see if It comes back and do some more testing.

Thanks for your help!

BTW, I love the way the lights look. I run them at 50%. I put the reflectors on them, but they fell off. Going to try to use 2 part epoxy to hold them on.
Click to expand...

I do not know your electrical systems in the US but here in Sweden you can turn the plug 180 degrees in the socket (in the wall), thus changing where phase and neutral is in the system. Its a well known trick when you have problems like this. The only way i can see that you will have an AC current going from the water to the fixture (if the fixture is isolated from everything containing AC) is that you have a leak from the phase to the water and a connection from the fixture to the ground or neutral conductor. To turn the plug 180 degree you change where phase and neutral are in the AC devices. You can test it. I know that in some countries (like Great Britain) you cant turn the plug - but I do not know how it is in the US.

I use 2 part epoxy before but now I use thermal resistance silicon glue - probably you can get it from the same source you get your chips from.

Sincerely Lasse
 
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Do you have the pot very low? Is there any contact between the chip´s + or - with the coolers metal parts? Can you test with another driver? Can you measure current and voltage out from the driver? Is there any bad solder joints. Is the pot connected properly?

I have had a problem like this but in that case it was a dirty 1-10 V signal from my GHL which was haunted.

If you take away the pot - does it still flickering (the driver will put out 102 % if I remeber right in this case)

Sincerely Lasse
 
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