Ok So I'm Thinking about building myself a LED unit for my tank. Now my question is how much of these LED's would you guru's recomend? This is the specs: Cree LED 5W XT-E Cool White Brand: Cree Type: XT-E Forward Voltage: 2.85 - 3.4 V Forward Current: 350mA to 1500mA Colour Temperature: 5000-8300 K Viewing Angle: 115 Deg Max Temperature: 150Deg My dimensions are 80cm x 50cm x 50cm. Thinking of medium to high light. This is the tank with my 2x24w Hagen unit but i want to replace the t5's completely with LED's and looking for more light than what i have at the moment.
i have 2 18w LED bulbs so i have some experience with DIY LED. i think 4-8 of those 5w would be sufficient for a 50cm deep tank but your temp range is very wide though. your tank might end up a bit blue if i'm not mistaken, especially with a lighter substrate. also. avoid placing them too close to the glass to avoid unnecessary algae growth
How about 48 of these guys? To much? 3W LED Cool White 6000-6500K on Aluminium Heatsink: Forward Voltage: 3.2 - 3.6 V Forward Current: 700mA Beam Angle: 140 Degrees Luminance: 200-220LM Colour Temperature: 6000-6500K
3.6v x .7a= 2.5w (3w max) i would be more concerned about individual lux output vs cost effectiveness considering you'll still need a power supply though modding a pc power supply might do. honestly you'd be better off buying 2 20w LED floodlights and even then that would probably be too much light. much cheaper simpler, easier and reliable
I'd steer clear of the 5W LEDs entirely, unless you're going to go for a forced air cooling system with lots of heat sinks. The 3W chips are fine, I've been using them on my tank for almost 2 years now. I just have heat issues in summer when it gets really hot. But a single PC fan sorts that out easy. As for number of LEDs, no more than about 20 of the 3W chips. At the 20 x 3W end of that scale you better have your CO2 running at full blast otherwise you're going to have pea soup in no time!
I used 30 x 3W LED chips on my tank (70W x 60D x 65H) and I had algae issues the minute my CO2 started getting low. The only reason I used that many was to get enough light down to the substrate for carpeting plants. Recently before I broke the tank, it was down to just 20 x 3W chips and I had zero issues with plants. I didn't have a carpet at that point, so I didn't need all the extra light.
I agree with wudze. Get the 3w LED chips. Now this is what I would do. Use 30 x 3W cool whites and 6 x 3W red LEDs. Yes the red makes a big difference on plant growth. Build up 6 banks of 6 LEDs ( 5 x white and 1x red ). The 6 LEDs must be connected in series and the 6 banks in parallel. Before you connect the 6 banks in parallel you first have to current limit each bank. Anything between 250mA and 500mA.I use a LM317 with resistors to do that. For a power supply I would use a high end psu like the lambda 24 volt 4 amp. I would not use a pc power supply as thy are notoriously unreliable and insufficient. Look under "Aquascaping and members setups", go to my 2 foot low tech at work" and see what I did.
Forced cooling on LEDs is a pain in the butt (so to speak ). If it breaks down it will cook your LEDs and I don't need that kind of worry. I think it is wise to use modern power LEDs like 'CREE' or similar. Their efficiencies are high (≈40%) when compared to the older low-power LEDs at ≈25%. That prevents a lot of heating. I use those LEDs almost exclusively, but . . . I never exceed 500mA bias current and I mount them on large Alum heat sinks. That way I don't need forced air-cooling. With regard to spectrum supplementation I would recommend to install extra LEDs @ 400nm and 670nm at the strength of ±10% of the base LEDs PAR output in each band. Have fun guys.
A really nice option is also to try meanwell power supplies . they available from manteh and will go a long way to supply stable current to your LED's (make them last longer) . you could even get the 1 - 10 volt pwm controlled supplies and run them through a controller . will enable you to fade lights in and out and set min and max intencities for indevidual channels
