LED Sanity Check?

[kbb0118]

I've been collecting parts to change out my CFL scrubber for LED. I need help with the LED setup math. For my fish room I'm going to do a 5-6 cube Waterfall ATS. 10" x 7" screen lit on both sides, about 2.5" away.

-One Mean Well ELN-60-48D dimmable driver, set to 1.0 Amps
-Two Strings of 12 Exotic 660nm 3W running Parallel from the single driver (see LED specs below). That's 12 LEDs on each side. I can swap out a couple reds for Cree 3W XR-E royal blues on each side.
-Each side would have a 9" wide x 6" tall heatsink, no fans

By my calculations 1.0 Amps divided by 2 parallel strings is 500mA of current. Will this setup be ok?? Can safely I put 13 LED's on each side?

12 LEDs with forward voltage of 2.3v running at 0.5Amps is 13.8 Watts, times 2 that is 27.6 Watts total. I'm unsure of my math. Help?

Here is the Spec sheet for the driver (far right column)
http://www.meanwell.com/search/eln-60/default.htm

Exotic 660nm 3W LEDs Specs:
Wattage: 3w
Max Drive Current: 700mA (500mA recommended)
Forward voltage (@ 700 mA): 2.3v
Light Intensity: 40lm
Dominant Wave Length: 660nm
Viewing angle: 120°
Color: Deep Red
Star Size: 20mm

[tomservo]

You've got loads of headroom there - 12 * 2.3 = 27.6v, so you have another 20v headroom. In fact, I think 27v is pretty close to the minimum voltage for that driver. I'd suggest adding 2 blue leds on each side. Have you considered the LPC60-1050 ? There's no dimming function and it's a few bucks cheaper. Nice thing is you don't need to supply it with a 10v signal.

[MorganAtlanta]

Make sure you put a fuse inline in each parallel string.

[kbb0118]

tomservo - I've never set up parallel strings before and just want to clarify. I was doing two strings of 12, so 24 LEDs total on the one driver. When running parallel, on the math do I double the volts? So I end up with 55.2v total? And the driver is rated for 48v so that is the max I can have right? Am I over? That is the part that I am confused about. I happen to have a spare Mean Well ELN-60-48D from a prior project so that was the only reason. Plus I can set the amps with the integrated POT on that driver.

MorganAtlanta - thanks for the tip on fuses. I wasn't going to but I will look into it. I read something brief on a build that had fuses so I'll have to do more research.

[MorganAtlanta]

Use inline fuse holders like these http://www.frys.com/product/6578413 and a 750mA quick blow fuse like this: http://www.frys.com/product/5867843

When you run strings in parallel you should run the exact same mix of LEDs in both strings. The voltage drop is the same across both strings (27.6V), but half the current goes down one and half down the other (612mA down each string). If one string goes out, all the current (1.25A) would go down one string, which is why you need fuses to protect the LEDs from burning out if one string goes out.

[tomservo]

Morgan is right on here - you definitely want fuses. The inline holders work, but some guys (me included) are using terminal strips on the fixtures themselves.. Here's a shot of a fixture I'm working on, if you zoom in on the right side you can see what I mean. You use two terminal strips and then put an "axial" fuse between them. Axial just means it has wires coming from each end.



And here's a crop where I have a fuse installed:


If you're wondering, I got the fuses from digikey - P/N 507-1554-ND .45 ea or .32 each qty 10 and the terminal strips I used are 6 position ED2998-ND (~$1 each). Obviously other versions can be had as well.

[kerry]

Thats a nice DIY build!!! What size tank is that going on??

[tomservo]

Thanks, it's going over a 250 bowfront (78x24-30x24). It's a magnificent tank. Gotta get some acrylic to build a scrubber for him, too!

[kerry]

I figured it was a BIG tank, I am finishing my LED build for my 150 Sunday.

[kbb0118]

You guys are brilliant. Thanks for helping me out!