Instructables
Picture of The 10W RGB Color Fading Chinese Lantern
nitelantern2.jpg
My soon to be 13 year old son is a second degree black belt in Tae Kwon Do and loves all things asian. Thus his 13th birthday party was destined for an asian theme. My wife had most of the decorations covered but being the LED freak I am, I told her I had an idea...  Which normally gets a frown. In this case she was interested! I had also recently bought some 10W RGB plate emitter LED's from Deal Extreme that I had been chomping at the bit to use in something. Thus the RGB color fading Chinese Lantern was born. All I needed to do was figure out how to heat sink the LED, drive it with its rated current properly, make it color fade and mount it so I could light up the lantern.  Here is how I did it.
 
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Step 1: The LED

Picture of The LED
Step One: The LED

The heart of the project are the 10W plate emitter LED's. I got these from Deal Extreme. I have also found them available from Aliexpress although I have not ordered this particular one. I have shopped from Deal Extreme for the past 4 years and have never had an issue.

The LED consists of  nine 1 Watt Red, Green and Blue LED's with 3 of each color wired in series. The controller I am using runs off of 12 VDC so the first step was to determine the correct current limiting resistors for 12 Volts. Red LED's drop about 2.2 Volts when forward biased with green and blue 3.3 Volts or so. Each string needs about 330Ma to produce its rated power.  I measured each string with a lab power supply at 350 ma of current. The red was 6.5 Volts, the Green 10 Volts and the Blue 10.5 Volts. I selected 22 Ohms for the red current limiting resistor and 5.6 Ohms for the Blue and Green. (Makes it a little simpler and easier to buy in quantity.) What power rating should I use? Power = Current squared times Resistance. So for the 22 Ohm resistor worst case we get P=(.350ma)2 X 22Ohms = 2.7W so a 3W resistor will work. The red will dissipate the most because it is the larger resistance.

The other thing to take into account is heat sinking the LED emitter. It must have a heat sink to keep its temperature down or the LED's will fail. I found some surplus 2”X1.75” heat sinks that are about 3/8” thick with a lot of little fins on them. They were originally for graphics cards. I figured they ought to be good enough so I bought a dozen of them. After an hour of use, the emitter plate was 50C and the heat sink warm to the touch so they are big enough.

Parts List: Alternate source: http://www.aliexpress.com/item/1pc-High-Power-Super-Bright-Integrated-RGB-LED-Light-Bulb-Beads-10W-Lamp-Bulb-Free-Shipping/704083925.html
Alternate source: Mouser http://www.mouser.com/Passive-Components/Resistors/_/N-5g9n?Keyword=5.6+ohm&FS=True