DIY LED Using 10 Watt Arrays

mike31154 · #1 05-09-2012, 05:17 PM

A little over a month now running the fixture. Not completely finished, but I've stained the wood & half attached some of the trim to make it a little nicer to look at. Still need to figure out how to cover the top without adding a bunch of weight & restricting air circulation to the heatsink/fans. Something thin & flexible I can sort of bend into a shallow dome perhaps.

Everything appears to be adjusting nicely to the LEDs, with no apparent issues, other than the green algae. Since this fixture is providing more blue light for a longer period of time, the green stuff is taking it on the chin & tank is looking better every week. All coral including several sps bits continue to grow. Will take more time to get a better idea of the rate, but just the fact that they're doing well is a good sign.

Latest photos. Fixture is dimmed down for morning dawn effect. Things get much brighter when I crank up the voltage.

reefme · #2 05-09-2012, 07:11 PM

How are you getting the reflectors and lense installed?

mike31154 · #3 05-10-2012, 02:33 AM

Quote:

Originally Posted by reefme

How are you getting the reflectors and lense installed?

I won't be using optics. Things are looking great without reflectors & lenses. I think the colours blend more effectively without lenses.

mike31154 · #4 07-21-2012, 02:35 AM

Fixture running great since beginning April. Thought an update may be in order. I've added a second power supply allowing me to run each on a different timer to give a simple dawn/dusk scenario. Still no automatic dimming other than that. Added a fourth manual dimmer to allow individual control over each of the 4 different colour LEDs I've used. Two meters provide voltage monitoring through a couple of switches I added. The top voltmeter shows volts for the two left dimmers fed by the 250 watt power supply (Royal Blue & 10000K LEDs on the outer rails). The lower voltmeter monitors the smaller 150 watt power supply (6000K & Blue LEDs on the center rail). By using the DPDT switches I can toggle between monitoring the voltage provided through each of the 4 dimmers. Here's a pic of what it looks like at the moment.

All the 10 watt LEDs should be well 'burned in' by now and the only thing that has failed is one of the heatsink fans. Easy enough to replace since I have a few spares kicking around. Still running without any constant current devices, relying on the dialed down voltage to keep things safe. Intend to do some current measurements to see how things are matched between LEDs, but it's been working so well I wonder why I should bother. If one were going to cook, it surely would have done so by now.

mike31154 · #5 10-17-2012, 08:51 AM

Update I reckon after running the fixture for almost 7 months. LEDs still going strong, no burn outs.

I finally cut the heat sink fan leads off of the LED terminals & wired them separately to the power supplies. A whole lot of cutting, soldering & running more wires to feed 27 fans, but now the 12 volt fans are getting at least 10 volts DC regardless of what I do with the LED dimming controls. The issue of giving the fans a kick start in the morning with my finger due to low voltage delivered to LEDs is now solved. Reliable start of the fans.

Note the way the emitters are wired above, with the fan leads soldered in parallel with the LED leads. All the fan leads have been cut & rewired. In the future whenever I replace a fan, I'll keep the connector on as shown on the center LED. Stripped 20 gauge solid strand wire slides into the connector nicely, no soldering.

Coral & other livestock doing well, tank looks good, saving electricity, evaporating less water. Downside I guess is the heaters need to run longer to keep the tank temp up.

Northernseacorals · #6 11-05-2012, 06:54 AM

Fantastic build man, light looks excellent.

mike31154 · #7 11-05-2012, 05:08 PM

Thanx, it's been running well since last April. Last week I finally did some additional current measurements. Been meaning to do this for some time since the only other time I measured current was before assembly. Constant voltage is not the conventional way of running a LED fixture & doing so has its risks, but I've seen instances of folks cooking their LEDs with constant current drivers as well.

At any rate, the current measurements taken at several different forward voltages revealed that I've really been underdriving the fixture. Highest I've had the voltage is around 9.5 volts which is 0.5 volts above the lowest recommended voltage for the Royal Blue LEDs. That was only for a short burst though & since putting the fixture in service I've kept the voltage at about 7.5 max.

There was a definite difference in current between a Blue & a Royal Blue at 8.5 volts, with the Blue drawing 310 mA & the Royal Blue drawing 500 mA. Both numbers are well below the 1,000 & 900 mA rated current. It took 10 volts to get the Blue up to 500 mA. By comparison, a 10,000K white was only drawing 180mA at 8 volts. Need to keep in mind that the voltage/current curve is not linear & current rises quickly once you get close to the maximum forward voltage. One of the reasons I've kept the voltages fairly low up to now.

Only checked one or two of each colour LED so I need to do more measurements to compare the current difference between LEDs of same colour at the same voltage in order to see how well (or not) balanced things are. After running for months, they have to be 'burned in' & there should be no surprises, but with electronics you never know. They're well cooled with the individual fans now running at 10 volts, so I'm reasonably confident that there should be no major disaster even if one or two burn out & I don't notice for a while.

Even at the 6 to 7 volts I've been running the LEDs at, coral growth was very good, comparable to my previous Halide/T5HO set up. Since taking the current measurements recently, I've bumped up the voltage of each colour to 8.5 and the tank looks great. Quite a bit brighter, especially the whites, so I'll need to keep an eye on things to ensure I'm not burning coral. Looks good so far after several weeks & algae is not getting out of hand either. Could probably run them all at 9 volts, which is recommended minimum forward voltage for all colours except the 10,000K whites (10 volts), but there seems no need to do that based on growth & look of the tank. Besides, that would use more power & probably shorten the life of the LEDs somewhat.