The majority of the work for this project is getting the pixel strips soldered. As we go, we also really want to minimize the amount of loose wire hanging around. Wires can get pulled or tugged out of place really easily, so we'll spend a lot of time managing wires and sealing strips.
If you're new to soldering NeoPixels (or could use some tips on making it easier), check out our Make it Glow: How to Solder NeoPixels guide.
It is essential to test each strip connection as you go, and test again (and again) as you build out your costume. I like to keep a Circuit Playground Express loaded with test code and some alligator clips on hand. This makes it much easier to chase down any cold solder joints or crossed wires as you're building out your costume.
Wire Management
One way to keep your wires tidy is to use silicone stranded ribbon cable. This 28awg (American Wire Gauge) wire is thin and flexible, and will not break when it's flexed again and again.
I only use silicone stranded wire in my wearable projects. Non-silicone wire will break the 10th or 11th time you wear your project. No bueno. Seriously, spend the extra dollar and use good wire.
This ribbon cable has 4 wires, with a striped wire on one edge. We only need 3 wires, so pull off the 4th wire -- the one opposite edge from the striped wire.
I minimized the amount of loose wire by sliding the soldered strips out of the casing, soldering, then sliding the casing back over both the strip and the wire. It was a little fiddly to get it all in there, but it does fit when using 28awg ribbon cable, and will definitely minimize breakage down the line.
"Ooze" Sections: Side-Light Pixels
I'm using side-light strips for the top "ooze" sections because I want a diffused look with a high pixel density. If the pixels are shining right at the viewer, each individual pixel is really visible. When they're indirect and shining down on the fabric, the viewer sees the reflected light rather than the direct light from the pixels. This makes the dress look like it's glowing magically rather than full of wires and technology.
More about pixel diffusion here
These strips are available in 60/m, 90/m or 120/m densities. I found the 90/m to be dense enough to give me smooth buttery animation without overloading the project with hundreds of lights.
For the double-sided "ooze" portions (along the neckline and under the bust line) I cut two strips, one for each side of the "vee" shape. I soldered the longer side up to a long ribbon cable wire, then spliced in a wire that was long enough to reach the far end of the vee. The "drip" portion will get soldered to the "out" end of the longer strip.
Once the pixels are correctly soldered and tested, slide the silicone sheath back over both the strip and the wire to keep it managed and out of the way.
Since the data is coming from different directions, one side of your vee will need to be mounted face-down in order for all the lights to be facing the same way. No problem: the strips look the same whether they're mounted face-up or face-down.
For the Neckline
The side-light strips don't bend easily around a curved neckline. In order to get them to fit the curves, I cut the pixels in the middle of my strip and soldered about an inch of ribbon cable between the two halves. Then I re-sealed the strip using clear heat shrink and hot glue with the wire stuffed inside the silicone casing. This gave me a nice bend that follows my neckline much better.
"Drip" Sections: 60/m NeoPixels
I used regular 60/m NeoPixels for my longer "drip" sections. I did some testing, and the lights move so quickly during the "drip" that a medium-density pixel strip still looks fantastic. The code is written for a single density of strip, but I found that mixing 60/m and 90/m pixels still looks completely realistic.
There are a few benefits to using these medium-density strips rather than the delicate 90/m side-light strips or the pricey 144/m strips that are available.
- The "drip" sections make up the majority of the pixels in this project. If I use 144/m it will almost double my power usage and also nearly double the cost of the lights.
- These strips will get flexed the most, since they're crossing my waistline. I want strips that are a little tougher and that will be able to stand up to being bent or sat upon. The side-light pixels are really breakable when flexed, and I've found that these 60/m pixels really do hold up better in costumes.
Solder about 1" of wire to the "out" end of the longer side of your ooze section vee. Connect the "in" end of your drip strip.
Once each section is assembled, and the wires are managed as neatly as possible, test your strip again. It's easy to pull wires out while you're futzing around. It's much easier to fix any broken joints now than it will be when the pixels are on the dress.
"Splat" Pixels: Slim NeoPixel Dots
The little drips where the lights appear to hit the ground are maybe the coolest part of this effect. They're also the most vulnerable: any lights in your hemline are going to get stretched, kicked, stepped on and tripped over. In my design, they also need to be sewn into the dress itself instead of attached to an underlayer -- though you could add them to a slip or hoop skirt depending on your build. My dress has a slit up the front so doesn't lend itself to undergarments, so I decided to attach them permanently.
I used one strand of Slim NeoPixel Dots for this part of the project. These are really tough LEDs. Each pixel is encased in resin with super flexy wires in between. I haven't managed to break one of these strands yet. I can also leave them in the dress for washing -- a little dunking isn't going to hurt them as long as you let them dry completely before powering again.
The "splat" strand attaches to the two rightmost pins on the bottom of the controller (as well as a power wire). I soldered on a long ribbon cable wire and put a 3-pin connector on the end so I can easily detach the the dress from the underdress.
We will be able to select which LED in this strand is associated with which drip in the code, so I didn't worry too much about exact placement. I just made sure there was some slack between the pixels to minimize any pulling.
I made a little slit in the fabric and slid the whole strip inside, then sewed it into place by feel through the lining of the dress. I didn't even have to detach the lining, I was able to get all the lights in place by pushing them around through the fabric.
I plan to change this arrangement a bit because the wire from the connector shows when I wear the dress. I will add another 3-pin connector up near the microcontroller and thread the whole wire down inside the lining, so I'll be able to plug it in someplace less obvious.
Once you're 100% sure all your strips are working, and your wires are as managed as you can get them, seal up the ends of all your strips by sliding a small piece of clear 3/4" or 1/2" heat shrink over the end of the strip, covering the wire connections. Fill the heat shrink up with hot glue, then use a heat gun to shrink it down while the glue is still wet. When the glue dries, your connections will be potted in glue and covered in plastic, and are much, MUCH less likely to break when they get pulled on.
Seal every single connection before attaching it to your costume.
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