Light up the night with cheap LED strips

 

Too much flying to do and not enough daylight? Looking for a new way to enjoy your foamies?  Try some lights for night flying!  Every hobby shop sells LED strips, but they're overpriced and in single colors only.  Fortunately, RGB strips (Red, Green, and Blue) are super cheap and just as easy to use.  You can pick up a 5m (16 foot) strip on Amazon for $15.

 

The great thing about RGB strips is that you can wire them for any color you like: hook up the +12V pad, then wire ground to one or more of the three RGB pads to get red, green, blue, yellow, purple, cyan, or white.  You can even change colors in mid-stream if you like.  If that's still not enough color choices for you, there are all kinds of controllers that will let you literally dial a color.

 

Don't be intimidated by the wiring process, it's really not any harder than putting connectors on an ESC.  Some things to think about as you plan your project:

• These strips are 12V, so plan on a 3S battery to power them, whether it's your flight battery or a separate one
• You'll want to wire it so you can unplug the lights easily for longer battery life in the daytime
• You'll also need connectors on any removable pieces (wing, power pod, etc.) for easy servicing

Here's the patient for today's experiment, my good friend's Old Fogey.  It's an excellent slow flyer, and the large cross-section of the fuselage looks fantastic when lit up.

 

 

 

 

We had 2-pin JST connectors laying around, they worked perfect but pretty much anything will work.  As you lay out your connections, be sure to plan which end is male and female (voltage is usually on the female side, or in other words, females are hot), and check how long the wires will need to be in order to reach the battery, ESC, and any distant parts of the airframe like the tail.

 

 

 

LED strips come in all shapes and sizes, but the ones we're using here are called 5050 SMD after the part number of the LED.  They're found with either 30 or 60 LEDs per meter (also listed as 150 or 300 LEDs per 5m strip)  The base of the strip is a flexible PCB or circuit board, and the LEDs are pre-wired in series with resistors so that they run on 12V rather than the usual 3-5V.  The ends of the strip may already have 4-wire connectors attached, but you'll need to attach some wires of your own once you cut the strips to size.  The strip will be marked with cut lines in the middle of some shiny copper pads to attach wires.  

 

You only need to power one end of each strip, and you can chain them together if that makes your wiring simpler.  These are common anode strips, meaning that you apply +12V to one pad, and connect one or more of the three other pads to ground in order to light them up.  The current draw of a 5m strip on full white is around 3A.  Old Fogey has 120 LEDs, half at full white and half single color, for an estimated 0.8A.  You would have a hard time overloading a typical flight battery unless you're covering a Kraken.

 

 

As you lay out your lights, think about how they're going to hit the airframe: foam lights up beautifully with indirect and internal light.  The LEDs are fairly directional, so pointing them outward isn't going to produce a great result.  In fact, it may work better to attach the strips "upside down" with the lights pointing into the foam.  The strips linked below have a rounded dome of waterproof epoxy over top of them, and this produces a fantastic "leakage" effect along the edges of the strip so that you can light up both sides of a surface easily:

 

 

Mock up your layout and decide what's going where.  Your RGB strip probably came with 4-pin connectors on the end, so you can easily test with a 12V power supply or 3S LiPo.  Keep in mind that the full 5m strip can draw up to 4A if you light up all three colors.  Connect +12V (usually white or black wire, and marked with an arrow on the molded 4-pin connectors) to + (red wire on battery) and any combination of R/G/B to - (black wire on battery) to try it out.

 

 

Cut carefully down the middle of the cut lines with scissors so that you can use the pads on both sides of the cut line.  If you have waterproofed strips, you'll need to scrape away the epoxy over the pads with a hobby knife.  If you cut straight down to the flexible PCB, you may be able to pull the whole chunk away with a thumbnail.

 

Clean it up by scraping with knife or thumbnail.  The strip is pretty tough as long as you don't dig under the pads themselves.  Once the pads are uncovered, you're ready to solder.

 

 

Dab some flux on the pad, strip the end of your wire only 1mm or so, place them together and solder.  The solder should flow over the whole pad and securely anchor the wire.  If you want them to match up with the rest of your plane's wiring, you should put red wire on the +12V pad, then black wire for the color pad(s).  Double-check what color you want the strip to be before you solder the color pads.

 

 

If you want white light, strip more of the wire and lay it across the three pads, and solder it all the way across.  Make sure you use plenty of flux to get the solder under the wire.

 

 

Check that you didn't short the pads together by measuring the resistance between the wires with a voltmeter.  Add some strain relief and insulation by wrapping it with electrical tape, and you're ready for the next one.

 

Be gentle with the leads, especially if you're using stiff solid-core wires -- you can easily break the solder joint, or even rip the little copper pads off the flex PCB.

 

Whether you're using connectors with pigtails or not, you're likely to wind up with multiple wires to join.  Twist them into a little bundle, dip it in flux, apply solder, then insulate with heat shrink or electrical tape.  You could also use a terminal strip or anything else that's convenient.

 

 

Your RGB LED strip may come with 3M adhesive backing, which sticks great to paper-covered foam.  That doesn't help if you're attaching them upside down, but clear packing tape gets the job done.  If you want something more removable, velcro works as well.

 

 

Let's fly!

 

Thanks to FliteTest for building this incredible community, and my neighbor Joe for getting me into the hobby and inspiring projects like this.

 

 

$15.86 for 5m with waterproofing and adhesive backing: http://www.amazon.com/gp/product/B0085IXEYS

20 pairs with pigtails for $4.90: http://www.amazon.com/dp/B00G9TFV5A

Or buy the connectors and crimp your own (crimping tool optional)

 

Tools: soldering iron, flux, solder, scissors, wire strippers, hobby knife, small-gauge wire

 

 

Don't like to solder?  You could try these "strip clips" from Adafruit.  You'll still need to remove the waterproofing first, but they clip on to the bare pads and give you wires to connect instead of copper pads the size of a gerbil's toenail: https://www.adafruit.com/products/1004

 

Need more color choices?  Use a controller to select from millions of colors: http://www.amazon.com/dp/B0058LXB3Y

 

Ready to get really crazy?  Put a microcontroller onboard and blink/fade/animate the lights: https://learn.adafruit.com/rgb-led-strips/usage