LED Array for a Pico

[pulse13]

If you don't want to do so much soldering, use Luxeon III LEDs instead of the .08 watt 5mm LEDs you are using. They run at 2.5 watts and cost $10 each from the supplier linked to from www.lumileds.com. , and they're easy to find on ebay too. Thats 35 times less LEDs for the same output.

[neanderthalman]

Looks like an interesting product pulse. I took a look around that site, and I couldn't find the physical dimensions. I can get 2.5W of light from my LED's in under one square inch of hood area, so if they're smaller than that, then you could pack even more light in a hood. Lets face it, the whole point of a new light is to get more light. If they're overly large, then you also wouldn't get a good mix of blue and white, so your tank coloration would be patchy.

 

I've got a change in my design. I was running the numbers again a few days ago, and I didn't like the results...only 18W of light from all of this. I was curious as to whether or not these LEDS could withstand 4V. The only way to know for sure is to try. I've been running my second test array with only three leds connected in series since sunday night. The light output hasn't diminished, so I'm going to wire my LEDs in groups of 3 again...the new white LEDs appear to be able to handle 4V just fine. It will also more than double the light output of my array to somewhere in the area of 42W.

 

Am I taking a stupid risk...possibly. I didn't start making this hood to only get 18W of light out of it. I say double or nothing!

[phr0Ze]

Heh. Careful with those Luxeons. Those LEDs provide the most output and are only a 1/2 inch diameter and they WILL beat anything you can put together with standard LEDs. The problem with them are they are VERY hot. They have a white paper here just to tell you how to determine how big of a heatsink you will need. And they all say you will need a heatsink. http://www.lumileds.com/pdfs/AB05.PDF

 

Also, they are pricey. Although if you work things out lummens per dollar they may end up cheaper. I would not compare wattage since they are dissapating more heat.

 

Finally some interesting points about LEDs in general. As they get hotter, they do resist less (http://led.linear1.org/what-is-thermal-runaway), they also shift color slightly, and they will actually get dimmer.

 

So even if you are running at normal spec you will get more brightness with more cooling. Even more so if you are mounting in those drilled acrylic LED holders.

 

All this information came from the 2 mentioned sources.

[neanderthalman]

That's some good information on the effect of heat on the light output of LEDs. All semiconductor devices, including resistors, transistors, whatever, will experience a reduction in resistance with an increase in temperature. The reason deals with quantum mechanics, and I'm sure nobody wants to hear about that. I am going to closely monitor the temperature inside the hood, and if it's getting unreasonably warm, I will add additional ventilation fans to the back sides.

 

I wonder what I could do with a bunch of those luxeons in my hood...mind you cooling would likely become an issue, and I don't want to have to fit heatsinks in there as well. Chances are, they won't work out to be cheaper, as you would have to add heatsinks and more cooling. Still....more light is more light...

 

I don't think the white LEDs will change color much with temperature, as the white color is the result of a phosphor coating. I do agree that it will shift the blue LEDs, although I don't know how far or in what direction. I do know that the blue ones that were damaged by overcurrent in my test fixture were green for a few seconds before going out, so that may be an indicator. Thermal runaway is the reason I left the array running for a few days, although I don't think the container they were in got as hot as this hood might - we'll have to see. It wasn't ventilated, but the hood is. Thermal runaway is also the reason my semiconductor lab sessions always stunk.

[Socalsuperhero]

Well, I finished getting the array put together and everythign wired up. All I have to say is WOW those things are bright! I was absolutly amazed at how much light they throw, and how far...I pointed it ouside and lit up the back yard. This project has actually inspired me to create a white only array to replace the halogen headlight on my bike (I do a ot of night time mountain biking in the summer). Anyways, they do get hot, and the aluminum gets very hot too, which maked me happy since i know the aluminum it helping to pull that heat away from the leds. Wish I had a luxometer, for now I can only go off my observations. At the very least, the led's are equally as bright as the 32watt pc bulb. Realistically, I'd say because of the directional nature of the led's they are at least half again as bright as the pc. I'm totally stoked on this project now that I'm looking at 70+ watts of light in my eclipse 5 corner. Also, the color worked out quite well with these, will have to test it on a tank for sure, but on a white wall the color is almost identical to the 50/50 pc--the white's crisper though.

[neanderthalman]

Congrats Socal - I hope your color improvements are as impressive as mine were. Keep up the good work, and I'd love to see those before and after pics

 

LEDs are the new MH of pico reefing, IMHO

[neanderthalman]

Well, my schedule changed, so I was able to get some work done on the array tonight. One of the things that I wasn't happy with on my first array was that the leads on the LEDs were all at different heights. Yes, I'm a perfectionist, but making electrical systems look sexy is my job.

 

I figured out exactly how long to make the leads on the LEDs, and then found a peice of wood the same thickness. I drilled two holes for the leads to go through, then used it as a jig to cut all of the leads to the same length. I then bent them against a peice of acrylic, again the exact size that I needed, so that the bends would all be at the same height, the leads would be the exact length, and the bends are all nice and square. Didn't really take much more time either.

 

I've started mounting the LEDs in the acrylic, but I'm going out to get drunk. I'll finish up mounting the LEDs and get them soldered tomorrow. Then all I'm waiting for is the next shipment of LEDs to arrive.

[pulse13]

Just be carefull that you wire the LEDs with the correct polarity if you're trimming the leads to the same length.

[neanderthalman]

Yeah, I actually screwed up the first row, looked at it, and smacked myself for being stupid. That's why I use removable silicone sealant to glue them in place. It holds them firmly enough to keep them there, but I can remove them later if I need to.

 

The longer lead of an LED is the positive lead, but there is also a flat spot on the casing. That flat spot indicates the negative side of the LED, similar to the band on a regular diode. Both the flat spot on the LED and the band on a diode are represented by the bar on the circuit diagram of a diode.

 

[neanderthalman]

Alright, I finally got around to soldering the LEDs that I already have, and here they are...wow. There's 144 of them, 12 rows of 12.

 

 

Oh, and if anyone is ever, EVER, interested in one of those cold-heat cordless soldering irons...don't bother. I'm returning it in the morning. Damn my curiosity. I'll be sticking to my 1950's soldering iron from now on.

[neanderthalman]

I got too impatient waiting for my other LEDs to arrive. Succumbing to boredom and curiosity, I attached some temporary leads and gave it 12V to measure the intensity. 9300 lux @ 8", and that's only half of my array. I don't think it will get much brighter than that, but adding the rest of the LEDs will increase the size of the spotlight it creates.

[mushroom head]

Cant wait to see how this will work out for you. I want to see how the corals like the LED lighting.

[mushroom head]

Oh and can you give my a link to buy the right LEDs. I want to use the LEDs u are using but i cant find them.

[neanderthalman]

Yeah, I can't wait to see how this all works out too. The shipping is supposed to be 5-15 business days from Hong Kong. It's been nine business days, and tomorrow doesn't count. Tomorrow is a holiday in Canada, so the mail system is out tomorrow. Hopefully I'll get them next week sometime.

 

I wasn't able to find any auctions for the LEDs this time, but they are available through the sellers ebay store. Here's the white ones and the blue ones.

 

In the second link, you can buy fifty LEDs, and specify that you, say, want thirty white LEDs and twenty blue LEDs. He'll accept any combination of colors, in groups of tens. The white LEDs are 10,000 mcd, not 12,000 mcd, however.

[neanderthalman]

It may also be a while until the corals are acclimated to the new lighting. It's going to be more than 23 times as intense, possibly even greater for my GSP on my powerhead. I'm going to have to screen them from the lights for a week or two, gradually reducing the amount of screening until they're under full intensity.

[Snoop]

how much pc lightig (watts) did u have what filter and power head do u have on your tank i have a 2 gallon and want to make it a planted marine tank

[neanderthalman]

I have a 10W PC light on my 1.6. It sucks. I hate PC. I've got a MJ400 for a PH and no HOB. Everything is in the tank, all filtration is LR, and I don't run carbon or anything.

[schaadrak]

Will the blue ones cause corals to flouresce, or do you need to get UV LEDs?

[pulse13]

Both blue and UV will cause corals to fluoresce. I have 460-470nm blue and 405-410nm UV as moonlights on my 5g eclipse. The blue will cause both green and other color pigments to fluoresce, esp. orange. The UV tend to only cause green to fluoresce, but it is much more intense. Also, with the UV, your eyes are not as sensitive so you don't get that blue look to the tank, so pretty much at night all you see is the green glow of the corals on a dark background. The lower the wavelength the more the water starts to fluoresce and turn a murky pinkish color (ie < 405 - 410 nm, so stick with the highest nm UV LEDs you can find (seen them range from 365 - 415nm). However, I only use the UV for a few minutes at a time when I'm viewing. I've read that many of the UV LEDs only have a lifetime of a few hundred hours, so if you want the UV ones only hook them up as a moon light with a separate power switch.

[neanderthalman]

I read some similar information regarding the UV LEDs, and in my original test array, an overvoltage destroyed ALL of the UV LEDs, sparing only white and blue LEDs. I find them to be just a little too sensitive, and their reliability is questionable.

 

I am still getting amazing fluorescence from my corals, and I attributed it, I guess correctly, to the blue LEDs. Funny you mention orange, Pulse, it's my orange zoos that a fluorescing like mad. My new array has no UV LEDs at all.

[neanderthalman]

In the end, I had to take a day off work to finish the damn thing, but now it's done. In the end, I got about 11500 lux at 8". That's also measured after it's been running for a couple of hours, to account for losses to heat. So far, they're running pretty cool with the ventilation fan. Here's a couple of pics of the finished product.

 

 

 

 

This last pic is a FTS with six layers of window screen filtering the light. The LEDs are so intense that I'll probably kill everything in the tank if I just change the lights right away, so I'll remove a screen every two or three days, and in about two weeks, it'll be up to full intensity. I'll post a before and after shot then.

 

[phergus_25]

so what kind of brightness is it compared to other forms of lighitng like pc ad what watts? just eye ballin it ya know

[neanderthalman]

well....it's difficult to make a direct comparison because the only other lights that I have are PC. I havent got any data to compare them to, say, VHO or MH. I can say, however, that my original 10W array was 14 times as bright as my 10W 50/50 PC.

 

The only other data I've found so far, is a comment by Fred (FAC_WNY), that a 1000W MH has an irradiance of 69000 lux at 10". My array is under 50W....so comparing the lux/W ratios,the MH scores 69 lux/W, whereas the LEDs score nearly 250 lux/W. That's not entirely accurate, nor is it a good way to judge a light. My lux measurements were taken at 8", whereas the MH measurement was 10". I also can't verify the numbers that Fred was quoting, but he has a tendency to be right about most things.

 

If the opportunity presents itself, I intend to take my own measurements of some MH bulbs at 8". That way, I can be confident in my comparison of LED to MH, but at this point, I think LEDs are doing quite well. What remains to be seen is how well corals grow and thrive under LED lighting. It is hard to argue against the effectivness of MH lighting in a reef aquarium, and so few tanks are lit solely by LED lighting at the moment.

[1105]

neanderthalman, this thread has inspired me to make an LED display for my cube that I'm making and I have most of the LED's allready, but dont know what I need to power them. The rows of LED's are 17x8, blue and white. I'd like to be able to turn both colors on/off seperatly. Any suggestions on what I should use for the powersupply(s)? Thanks

[neanderthalman]

well, I've had good luck now with a 12V power supply from an old computer, and a 12V cell phone charger. I had bad luck with a power supply from a surplus bin. I think that if the original intent for the power supply was for a high tech device, like a computer or cell phone, you'd be more likely to get a quality power supply.

 

As far as the exact power supply you should use, that depends on the specs of the LEDs you have. What is their Vmax and Imax?

 

The required voltage of your LEDs should determine how they are physically mounted. In my array, I wanted 4V across each LED, so with a 12V supply, they are wired with 3 LEDs in series. In that case, you would want to have them in dimensions that allow for groups of three to be wired easily.

 

You need to determine how many groups of three you would have, then determine what the total current draw will be. Then you can shop for a power supply.

 

As far as turning the colors on/off separately, it depends on how you want to control it. If you just want to have a couple of switches somewhere so that you can turn them on manually, you should probably use a single power supply. If you want to turn them on with a timer, perhaps for a sunrise/sunset effect, two separate power supplies would be easier.

 

Let me know the specs of your LEDs, how many you have, what your maximum dimensions are, and how you're planning to use the separate on/off feature, and I can better help you choose a power supply.