DIY LED Using 10 Watt Arrays

[mike31154]

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]

Fantastic build man, light looks excellent.

[mike31154]

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.

[mike31154]

To provide additional flexibility to the fixture with regard to dawn/dusk effect, I've decided to add some SMD5050 RGB strips. During the longer summer days ambient daylight minimizes the effect of the sudden blast of light when the 10 watters kick in, but this time of year it's quite a radical wake up call for the livestock in a darkened room.

I scored a 5 meter reel of waterproof RGB LED strip lighting online complete with 44 key IR remote control & 12 volt DC 5 amp power supply for about $35. Had to wait a month to get it, but can't complain for free shipping & no brokerage fee or customs hit. Had an 8 foot length of the thin aluminum angle left from the 10 watt rail build, so I cut that into 2 sections & stuck the RGB strips to them. The aluminum angle will be attached to the existing center rail of my fixture using stainless #4 screws. I've threaded the holes so should be a slick & easy addition. I'll need to disconnect the fixture & take it down though, so I can drill & tap matching holes into the center rail.

Photo of the strips mounted to the alu angle. They come with a 3M sticky backing which holds well, but a zip tie at each end to support the connectors adds a bit of security.


Opposite end. The RGB control box with IR receiver attaches to the connector. Power supply plugs into the other end of the control box. Plug & play with more colour choices, dimming, flash modes than I'll ever need.


I loosely laid the two strips above the tank the other day to see how it looked & they put out quite a bit of light. The 5 meter reel of 5050 LEDs consumes 36 watts, there are 60 LEDs per meter providing 780-900 lumens/meter. Each of the strips I cut off the reel is just over a meter long (approx. 41 inches). This gives me 63 LEDs/strip, for a total of 126 for dawn dusk/tweaking or night lighting. Good thing they can be dimmed with the 44 key remote. One of the timed power bars I use for the 10 watt LEDs has the alternate day/night receptacles, so the plan is to plug the strip light power supply into one of the night jobs. Still not as good as having a controller to turn the strips off at some point during the night when I'm not home, but better than nothing I guess. When I'm away I may just set them up to be fully dimmed red all night.

[mseepman]

Hey Mike,

I scored a couple of those same ones and am planning on using them above my kitchen cabinets.

Nice way to use them on the tank!

[mike31154]

Indeed, uses for LED strip lights are almost limitless. I considered using the whole reel as Xmas lighting on a spruce tree in my front yard, but found that I probably need more than 5 meters for that! So I ended up using the crappy tire LED strings I bought a few years ago. Many of those are beginning to burn out already though & they don't have the flashing/dimming options, so I'm thinking of ordering a few reels for next year.

[Tony Ooi]

i was trying to understand the whole circuitry from all the post here.
Sorry i have few quick questions as i trying to follow these post and make sure i get the correct understanding
In the end, you didn't have any resistor in series with each LED, right?
The whole circuitry is just the 12V power go into the dimmer and from dimmer go to the LED. Please correct me if i am wrong.

[mike31154]

Originally Posted by Tony Ooi

In the end, you didn't have any resistor in series with each LED, right?
The whole circuitry is just the 12V power go into the dimmer and from dimmer go to the LED. Please correct me if i am wrong.

You are absolutely correct. The two 12 VDC power supplies have a limited range of adjustment via a small potentiometer next to the wire terminals. The adjustment range is from about 10 volts to 13 volts. Downstream of the power supplies are the manual dimmers which provide further control & enable me to dim all the way to off.

The LEDs are all hooked up in parallel, no series chains whatsoever. If one of the LEDs were to burn out, the remainder on that dimming circuit would likely run at a slightly higher current which poses a certain risk if I don't notice for a while. I mitigate that risk by having the manual dimmers adjusted to 8.5 VDC, which is 1/2 volt below the recommended minimum forward voltage of my 455nm Royal Blue LEDs (spec for them says Vf should be 9 to 10 volts). So in essence, I am slightly underdriving the Royal Blue LEDs. The whites, 10000K & 6000K as well as the 470nm blues can handle a higher Vf (up to 12 VDC) so they are underdriven even more. In addition, each LED has its own fan for cooling, which adds to the safety factor with respect to burn outs.

I opened up a couple of the dimmers to see what makes them tick since there is little info on them other than the rated input/output. Some of the vendors selling them on eBay talk about them being pwm and/or constant current capable but it sure would be nice to confirm how they really work. Aside from the potentiometer, the dimmer consists of solid state circuitry including what looks like a MOSFET transistor, so they do have some complexity. Despite the low price, the soldering & assembly are very good quality.

[Tony Ooi]

Thansk for your explanation.
Te 12V DC power supply, the potintiometer you mention , is it the the plastic which have philips screw head?
my dimmer just arrived yesterday. I have yet to open up to inspec what is inside , but it felt like almost nothing and very light wieght. I have LED which spec at 10watts(running at 10V, 1A current). Theoretically should able to handle up to 8 LED per dimmer base on the label stated there 8A. For safety reason, i might just want to keep 6-7 LED per dimmer.

[mike31154]

Originally Posted by Tony Ooi

Thansk for your explanation.
Te 12V DC power supply, the potintiometer you mention , is it the the plastic which have philips screw head?
my dimmer just arrived yesterday. I have yet to open up to inspec what is inside , but it felt like almost nothing and very light wieght. I have LED which spec at 10watts(running at 10V, 1A current). Theoretically should able to handle up to 8 LED per dimmer base on the label stated there 8A. For safety reason, i might just want to keep 6-7 LED per dimmer.

On both my power supplies the adjustment potentiometer is as you describe, located next to the power supply power "ON" indicator LED. If you look at the photo on post #46 closely, you should be able to see it on the left of the power supply front panel. It's the only adjustment that is accessible from the outside of the power supply.

Definitely a good idea to keep the number of LEDs per dimmer below 8 as you plan to do. Having said that, the dimmer controlling my 10000K LEDs is doing fine with 10 of them hooked up. Of course I don't run them at full voltage/current, but it reminds me that it might be a good idea to add one more dimmer! Seems to me when I first ran the fixture one of the dimmers had both the 10000K & 6000K on it, meaning a total of 14 LEDs plus the cooling fans! No issues, but I don't know what I was thinking & certainly wouldn't recommend that, even though I had the voltage down at 4 to 5 volts.