Introduction: Extremely Simple 5V Ultrabright LED Light
I was talking it over with the saikoLED team a few months ago, and we realized that there's really nothing out there for doing ultra high brightness LED work that is super cheap and has an adequate passive cooling solution. In order to deal with this, we came up with a new design that is sort of the "Honda Accord" of LED lights as opposed to a Cadillac that we've generally done before.
This light is extremely simple -- a case that has a hole pattern appropriate for a 20mm LED Star Board (either Luxeon Rebel stars or the LEDEngin 5W LEDs should work great), a hole pattern to attach a chassis mount power resistor for current limiting, and some mounting holes. In this case, the mounting holes are either three #8 screws (or eye bolts), or two 1/8" NPT holes suitable for using with the LOCLine line of flexible hollow connectors. I really like the idea of the LOCLine connectors as they are essentially super cheap plastic goosenecks that the wires can all be run inside.
After this, you simply connect up a 5V power supply to provide an attractive, cheap, and quite bright LED light fixture. By purchasing a power supply with variable voltage output, you can also easily dim the LED by varying the voltage between 3 and 5V, or use a supply that can output 5V with a PWM for brightness control. However, the goal here was simplicity, so the assumption is that this might be used to make an alcove a pretty bright color as opposed to a fading RGB light fixture.
That said, it would be relatively simple to use a RGB tri-color 20mm LED board in this fixture along with some external electronics for fading. Most of the goal here is to have a nice case and mounting option for LED lighting so that cooling is less of an issue.
Step 1: Case Design
The case is designed to be manufactured easily using eMachineShop.com. All holes are straight through, the case is 0.062" aluminum, the holes are tapped as appropriate, and after receiving them I took a lot of 40 or so to be anodized all at once for $60. The 3D structure is made using the CNC Bending option, which produces a case that has a nice 30 degree or so taper without needing any expensive internal milling.
Inside, the hole pattern for the star board is centered, and the hole pattern for the power resistor is off to the side with only four total solder junctions to worry about per light. The screws for the LED are #4-40 while the resistor uses #2-56 aerospace screws. The two larger visible holes are both tapped 1/8" NPT holes for use with LOC-Line flexible arms, but otherwise are simply the hole to allow wiring to be taken outside of the case while mounted either in a hanging fashion using #8 eye bolts, or from the side when fixed directly to a surface such as an aquarium canopy.
Step 2: Powering and Use
This is a pretty simple system -- LED has a voltage of around 3.4V, resistor is 2 ohms, supply voltage is 5V, so the current through the LED is in the ballpark of:
In practice, this batch of LEDs was more like 950mA, but as long as it's under 1A it is in the rating for the LEDs. Additionally, the thermal performance of the case should be good enough to keep the die at around 70C (it is rated to 120C or so) even at full power. However, for additional safety a 3 ohm resistor could be easily substituted. It is also possible to attach optics to the LED for a more focused beam -- my intent with these was for an aquarium light that is only a few inches above the tank so I did not choose to use them.
If anyone is interested in purchasing the cases, they can be found at http://saikoled.com/products/
If you want to manufacture your own case, I have included the design files so that you can make your own as a .ems (emachineshop.com file). It took a lot of time and effort to iterate to such a simple and functional design which is still elegant, but this instructable is published under just an attribution/share-alike license so as long as you contribute your improvements back feel free to use it in commercial stuff.