LED lighting

LED Light from the frontI’ve been experimenting with these LED arrays by Bridgelux (Mfgr part #BXRA-C1202-00E00, Digikey part #976-1005-ND*). They are rated at 2 Amps max current, but so far, I am not driving them anywhere near their rated power. In the tests shown here, the LEDs installed in my homemade lamp are drawing 22 watts of power; combined. They’re 2 Amp rating with a 12.8V forward drop would equate to 25.6 watts per array, so I’m powering the 4 arrays at about 25% of their capacity. The reason for that is convenience only. I intend to bump the power supply voltage when I get a chance to build and test a constant current power supply.

In spite of the efficiency of LEDs, they still produce too much heat to operate without a heat sink. In these next photos, you can see that I have each LED array mounted on it’s own heat sink. The heat sinks I used were salvaged from old computers. They are CPU heat sinks, and they are overkill for what I’m doing, but they were in my junk box and they do the job.

LED light from the side LED light from the back

Just to give you a frame of reference for how much light these LEDs kick out, with only 22W of power, I took some photos with fixed camera settings (except I used tungsten white balance with the tungsten bulb and daylight white balance with the LED light, because the LED light temperature is much cooler than the tungsten light. i.e. the LED light is closer to daylight in color balance). So, the next two photos are brightness tests. The one on the left is the 100 watt tungsten, and the one on the right is the 4 LED arrays operating at 25% power, and consuming a total of 22 watts.

Photo with 100W tungsten light Photo with LED light

You may notice that the tungsten light bulb produces a single, fairly soft shadow. The 4 LED arrays produce several shadows, and the light is much whiter. It is also worth bearing in mind that I can get this much light from a single LED array, when it is powered at it’s full rated power.

Right now, I’m working on building lights for shooting video. I am certain that my LED lights will eventually replace my 650W halogens, and I’ll be able to power them from batteries. Obviously, they will produce much less heat and use less energy, but also, the LEDs should last a very long time and they are very durable, unlike halogen bulbs. It will probably take 6 LED arrays to generate as much light as a 650W halogen, but it would be easy to install 6 LED arrays in a single light fixture, and, given their longevity, they will pay for themselves in bulb replacements, if not in energy savings.

Of course, all of this experimentation is going to come home. I plan to wire my house for low voltage LED lighting with motion controllers that will turn the lights on where you need them and dim them where you don’t. I don’t think I’ll be using these high powered LED arrays in the house. Maybe I’ll use one or two in the kitchen. I envision a more distributed lighting arrangement with many smaller LED lights installed all over the ceiling for very even lighting. No matter how I do it, I can expect to use less than 1/2 the energy that my compact florescent bulbs use, and I’ll never have to replace another bulb. Furthermore, I like the idea of using 24VDC for the lighting because my solar panels produce DC power. By eliminating the conversion to 120VAC, I’ll get another efficiency boost. I can easily illuminate my entire house, using LED lights and power from my photovoltaics (solar electric panels).

* If you decide to purchase one or more of these LED arrays, be sure to purchase as many LED array holders (Digikey part# WM4556-ND) with them, because they are nearly impossible to wire without the holder. With the holder, they are a breeze to wire. The holder is manufactured by Molex, Inc. and the Molex part number is 1801500000. The LED arrays can be powered directly from a 12V battery with no current limiting resistor, but they will draw only around 0.6 amps at 12.5V. They still put out a lot of light at 0.6 amps, and it may be worth operating them like that, just for the pure simplicity of wiring. There are many variations of these arrays with different color temperatures, different power ratings and various forward voltage drops. If you want to go with 12V power, you might try something with a forward voltage drop of 12.5V or 12V. Be careful, though. It’s pretty easy to fry an LED if you let too much current flow through them.

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2 responses to “LED lighting

  1. Pingback: The little things | Sustainable Living

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