I've wanted to try a high-light planted tank for a while, but I needed to upgrade my lighting first. After looking at lighting options, I really wanted LEDs. I like the idea of not replacing bulbs, but I wasn't prepared to spend a couple hundred dollars on a light fixture for a small tank. I decided to attempt to build my own LED
My design process:
I really didn't know much about LEDs. I had no idea how they compared to T5HO bulbs or even what LEDs I needed to use. I tried comparing LEDs to T5HO bulbs using lumens, but got nowhere with that. LEDs and fluorescent bulbs are too different. I found PAR is a better comparison metric, but it's difficult to find any PAR readings.
I found a rather comprehensive explanation of lighting here: Aquarium Lighting; Kelvin, Nanometers, PAR, Bulb, Watt, MH, LED, Light Basics.
The link has been edited, but there's a ton of information I also found some pretty good information reading through reef forums. This thread, DIY LEDs - The write-up - Reef Central Online Community
, finally gave me the information I was looking for: How LEDs compare to T5HO bulbs using PAR measurements. Turns out LEDs beat the T5HO PARwise, so I was sold. I started looking at Cree LEDs and I settled on the Cree XR-E Q5 LEDs.
Cooling the LEDs was my next challenge. The diodes aren't cheap and I'd hate to burn them out because of inadequate cooling. Heat sinks are blasted expensive, so I was hung up there for a while. After seeing fixtures made out of plain aluminum, I decided I'd try building mine out of aluminum and hope for the best with water cooling as a backup option.
10 Cree XR-E Q5 LEDs - DealExtreme: $5.09 Cree XR-E Q5 Emitter on Premium Star (228LM at 1A)
driver - DealExtreme: $10.70 2000mA 30W Power Constant Current Source LED Driver (85~265V)
Aluminum project box - Radio Shack
Switch - Radio Shack
power connectors - Radio Shack
Potentiometer - Radio Shack
Resistor - Radio Shack
1" square x 1/16" thick aluminum tube - Home Depot
3/4" x 1/8" aluminum bar - Home Depot
3/4" x 1/16" thick aluminum L-channel - Home Depot
1/2" 8-32 machine screws - Home Depot
8-32 nuts - Home Depot
16 gauge? wire - Home Depot
Heat sink compound - eBay
1/4" washers - my garage
power connector and cord - old computer power supply
Drill bit index
I didn't want any evidence if the project turned into a pile of smoking wreckage, so I've only got pictures of the finished product.
Inside the project box is the LED
driver. It takes in AC
line voltage and converts it to 2000mA 16-18VDC constant current. The switch simply switches one of the legs of the AC
input. The third pin is grounded to the chassis.
On this side of the box, you can see the DC
power connector and the dimming control knob. The power connector is just a nice clean way to transfer the power through the box wall. I found instructions for making the LED
driver dimmable on DealExtreme where I bought the driver. It was actually pretty simple to do. All it took was a resistor and a potentiometer. I made the mistake of using an audio pot instead of a linear pot, so the dimming control isn't very good. The LEDs really don't start dimming until the last quarter of the pot's travel.
Here you can see the LEDs all lit up. Each leg of five LEDs is wired in series and the two legs are wired together in parallel. At full brightness, each leg is using 1A of 18V power. The wiring is a little sloppy and I may clean it up or at least use some wire ties. I think I'd try to route the wires through the frame on my next fixture.