LED DIY questions (kinda long)

[evilc66]

Using the projects for a reef as a guide for this will instantly up your LED count. Most of the reason for such a dense array is for color blending. The further apart you get the LEDs, the more pronounced color banding is. With this setup being only one color, you can get away with much wider spacing.

There are some new methods and products that will make experimenting with quantity and position a lot easier. Bergquist has a thermal adhesive that makes installing LEDs a peel and stick affair. It's not quite as efficient as bolting them down, but is less permanent than using epoxy. What you could do is set it up with a 3" spacing. If you don't like it, you can add more LEDs and reposition everything relatively easily.

[Hoppy]

You could get 4 pieces, 48 inch long, 4 inch channels for about $130 from here: http://cgi.ebay.com/6061-T6-AS-Alumi...item518d8ddb40
That would make a very nice heatsink, and should be more than enough aluminum. This is a bit more than I paid locally, but mostly due to the shipping cost.

[wondabread]

A few changes. Dropped 18 leds to 42 spaced 3" apart.

Would a cree with 90 degree viewing angle be ok or should I look for something 120ish to make sure there is no spotting -- or should I just not worrying about spotting at all? Gonna mount it 22"ish inches from substrate.

I can't wait to build this!

[Hoppy]

Looks pretty good now, but be sure to allow room somewhere for the LED drivers, DC power supply, etc. You will be much, much happier if you assemble all of the light parts as one assembly, then mount that in the "box" canopy. Doing it this way makes troubleshooting much, much easier.

I'm tempted to say you need a 4th row of LEDs to get the intensity you want. I think the LEDs are too far apart in that direction. But, I could easily be wrong. I used 3 inch channel extrusions, so my spacing was 3 inches each way (as I recall). Yours would be closer to 6 inches apart front to back.

For the distance you are planning the light to travel, you can use ordinary LEDs without any lens other than the standard one that covers and protects the LED junction. That gives very uniform light intensity from all of the overlaps. But, it also makes the LEDs very visible to someone standing near the tank, unless you mount the light assembly in a deep box so the box sides shield people's eyes from the LED side light. Painting the inside of the box white adds some of that light back to the tank.

My two position switch, a DPDT switch, works very well for dropping the intensity in half when I need to. Using my driver circuit, this was pretty easy to do. Using buckpuck type drivers would require some thought to figure out how to do it, but I think it is equally easy.

[wondabread]

I was thinking about fitting the drivers (meanwell ELN-60-48P)in the channel, think the heat would be a problem? I can easily attach the three channel pieces together with scrap aluminum I have around the house and then bolt the assembly into the fixture. The biggest thing so far is what, exactly, I will be making the fixture out of. I would like to stay away from wood, I don't know where (locally) I could find aluminum to make the box, which leaves plexi-glass. I'll have to look into pricing pieces at HD/lowes.

Thanks for the advice so far Hoppy.

[Hoppy]

Based on my fixture, heat is not a problem with the aluminum channel heatsink, even with everything mounted on it. I can't feel any rise in temperature of the channels when it is in operation. Of course, running the LEDs at 700 mA would put more heat into the heatsink, but not, in my opinion, enough to worry about. As I recall, the buckpuck type drivers don't generate any significant heat.

[Dragonstar]

You don't need as much heatsink as you might think. It may seem odd, but the best resource I've found for LED DIY stuff is the Custom Saber Shop where they make lightsabers with 1, 3, 5, and even 10W leds. I use a 1" round, four-finned heatsink in my saber with a 1 watt Cree led and there is no noticeable heat whatsoever.

[Dragonstar]

Forgot to add, for my aeroponic setup I use red and blue 1 watt crees that I power via a usb hub. The reds need a resistor but the blues don't. I cut the led part off of some of those cheapie LED USB reading lights, mounted a heatsinked LED (glued with arctic alumina adhesive) instead, and then I plug the led "units" into a powered CyberPower usb hub. I can flex the lights to point them whereever, so if a plant gets taller I can adjust the light to stay above it.

[wondabread]

Originally Posted by Hoppy

As I recall, the buckpuck type drivers don't generate any significant heat.

That's good news. I will have to double check the dimensions, but I think they should fit inside quite nicely.

I will have at least 3 fans and this unit will be stored in the basement, so ambient temps are 55-65 pretty much all year.

I think my next post about LEDs will be my DIY thread in a couple weeks when I start buying hardware. Goodie goodie!

[Hoppy]

Originally Posted by wondabread

That's good news. I will have to double check the dimensions, but I think they should fit inside quite nicely.

I will have at least 3 fans and this unit will be stored in the basement, so ambient temps are 55-65 pretty much all year.

I think my next post about LEDs will be my DIY thread in a couple weeks when I start buying hardware. Goodie goodie!

I will watch for it, since it should be very interesting. Good luck!