Articles - LED Spot Lights
08/31/2014
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I love experimenting with LEDs. Based on my experience with the light strip above, which still works great, I wanted to try some high-power (very bright) LEDs. After extensive research, I decided on the Cree XM-L2. These are intended to be used in outdoor lighting and for other high-lumens purposes. You can buy ready-made lamps with these kinds of LEDs in them, but they are pricey (around $80). These LEDs by themselves are nearly $10 each. I bought three of them for my experimentation, and they are the "neutral white" color, which varies between 3700K and 5000K in color. They also make the "cool white" (5000-8300K, bluish), and "warm white" (2600-3700K, reddish). If you are trying to create a mood, then those are good, but I prefer to stay close to 5000K which seems to be better for layout photography.
LED Spot Lights
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Highly-recommended for these LEDs are these lens holders. Their size depends on the lens you get. In the photo below I have shown the holder from three different angles so you can get an idea of what it looks like. The four legs you see on the bottom perfectly match the openings on the Cree LED.
LED Spot Lights
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There are several lens types available at two different sizes. I bought the largest one and the "frosted" variety to try to avoid the spot/focus light effect. We'll see how this works out. I have shown the lens from above and from below in the photo. The tab you see protruding from the lens matches a hole in the lens holder, which helps keep it in place and straight.
LED Spot Lights
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These LEDs get very hot, so you need a heat-sink to help keep them cool. I bought these finned heat-sinks, which have a thermally-conductive adhesive pad on the back to which the back of the LED will be attached.
LED Spot Lights
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I was then looking into getting some high-wattage current-limiting resistors, when I came across this high-power-LED driver. These drivers eliminate the need for a current-limiting resistor. They also allow for keeping the current at a fixed value, while varying the voltage. This means the LED keeps the same brightness regardless of what power fluctuations you might have. For a controlled environment in our layout that is probably not an issue. This particular model I got also supports dimming, but that is not why I got it. I got it because it can provide 2100mA to the LED. The Cree LEDs can handle up to 3000mA (the higher the amps, the brighter the LED). The driver's dimming feature can be ignored by simply not connecting the gray and purple wires. The driver can take power from a 10- to 30-volts DC source. 12-volt is very common in model railroading, so that'll work.
LED Spot Lights
I'll now show you how these parts all fit together. LED Supply actually has an assembled photo on their web site which helped me to decide to buy these particular parts. The photo below shows how the lens fits into the lens holder (my hand also gives you an idea of how big the parts are).
LED Spot Lights
The Cree LED then fits nicely in between the legs of the lens holder. As you can see from the view on the right, the LED points down the center of the lens holder, but the way it is shown on the left is how it is supposed to fit.
LED Spot Lights
The LED would then be mounted against the finned heat-sink (cover will need to be removed, of course).
LED Spot Lights
Here the lens holder is shown on top of the LED.
LED Spot Lights
The lens goes on top of that. The lens actually snaps into the holder (there are two small lips on the black holder that hold the lens in place; no glue needed). The LED driver needs to be connected to the LED. LED Supply has a nice web site with complete documentation on the parts they carry. I received my package in a few days, even though I elected to use their free shipping offer.
LED Spot Lights
Actual hook-up could not be easier. I have a spare 13.8-volt power supply to which I hooked up the red and black wires of the BuckBlock LED driver. Be sure to give the system plenty of amperage; it needs it. Since I don't plan on using a dimmer, the purple and gray wires are simply left unconnected. They could, optionally, be connected to an on/off switch. Then it was a matter of soldering the blue and white wires to the LED itself.
LED Spot Lights
And be prepared to be blinded. It may not look it in the photo, but you cannot look into the LED; it is that bright. I did and it is kind of like having looked into the flash of a camera; it took my eyes a while to get rid of the blind spot. I then turned off all lights in the room, and this one LED lit up the room nicely. I also like the color it produces; it does indeed appear to be a neutral white. Within a few seconds of turning the LED on, the heat-sink started getting warm. I could hold the heat-sink in my hand, though. In the photo I had placed the lens holder and lens on the LED/heat-sink. It does provide a bit of a filter to the blunt light output of the LED. I actually like it better with the lens than without (too many harsh shadows without the lens). I think this will be the way I am going to light my layout in the future. You can hook any number of LEDs in series to the BuckBlock LED driver. That is one cool device, AND it is made in the U.S.A.!!!
LED Spot Lights