This instructable shows how to design and build a very bright LED lamp for your Aquarium. What makes this instructable different from other that have gone before is that I'm using HBLEDs instead of traditional LEDs.
I found a new HBLED from Optek which are much less expensive than most high power LEDs. The Optek LED is around 50 cents in quantities of 100+. The LED is small at only 3.5mm square. But, the LED kicks out a 1/2 watt of light. There are some downsides to these LEDs. First, they are surface mount. Second, they must be attached to some kind of a heat-sink.
A couple of things that make the lamp presented here really cool. First, the lamp is made by sandwiching the LEDs between two pains of glass. The glass acts as a really good heat-sink. The glass sandwich is also sealed around the edge to make it water tight. Second, the lamp is almost totally clear being made of glass. Plus, since the HBLEDs are really small, they don't obstruct other aquarium light. This makes possible to simply add the new LED lamp and continue to use existing aquarium lights you already have.
The rest of this instructable discusses designing the 14 watt HBLED lamp for your aquarium.
Step 1: Design LED Carrier PCB
The Optek LED, being surface mount, needs to be mounted to some kind of a circuit board. I designed the following carrier circuit board to be as easy to use as possible. Also, the board needs to facilitate heat transfer. The life expediency can only be assured if the LED does not get too hot.
The carrier board is flat on the back side so that it can be thermally bound to a heat-sink. The board also allows wires to be solder along the edge of the board. Lastly, the board has large thermal pads to help wick away the heat and transfer it to the heat-sink.
Have a look at the attached pictures for more details.
Step 2: Deigning & Building Lamp
What better way to transfer heat than to use a glass plate. The glass plate transfers heat very well. The glass is also inexpensive - glass plate is less expensive than Plexiglas. I simply used some picture frame glass that I already had laying around the house. I cut two plates 18" x 3 1/2" with the idea of sealing the LEDs between the two plates. The open gap around the edge of the glass is then sealed with a bead of silicon sealant. Once sealed, the glass seems very solid - the two plates glued together makes them much stronger.
During assembly, the LED carrier boards are super-glued right onto the glass. I used 24 LEDs in total. Of the 24 LEDs, 5 are warm white and 19 are blue. This gives me 125 lumens of warm white and 114 lumens of blue.
Step 3: Design & Build the LED Current Regulator
To get the maximum amount of light from the LEDs each needs 150mA of current. Without a regulator this is hard to achieve. As the LEDs warm up their voltage sweet spot changes. So, to keep 150mA flowing, the voltage must be constantly adjusted. The alternative is to be conservative and add a big current limiting resistor. The current limiting resistor is not a very elegant design.
I ended up using six LEDs in series with a LM317 regulator. The regulator is wired/configured to regulate current in this application. Have a look at the attach sketch & pictures for more details.
Step 4: Conclusion
The design discussed here uses a 24 volt / 600mA / 14 watt wall power supply (10 bucks from Mouser). Of those 14 watts, 12 watts are delivered to the LEDs in the aquarium. The remaining two watts are consumed in the current regulators.
Using a thermometer, I measured the LED temperature to peak at about 105 degrees F. This temperature was taken on the outside of the glass. The current regulator enclosure (closed) peak at 110 degrees F and the power supply peaks at 115. So, all three temperatures are only warm to the touch. Nothing gets really hot.
I hope this helps others who may be thinking of designing applications with HBLEDs.
For more information, please visit my web site at "ph-elec.com". I'm making the HBLED carrier available to anyone who may be interested.