So, you’ve got yourself a reel of those gorgeous new pebble lights.
I don’t blame you! They are gorgeous. Coated in silicon, they are impervious to water and dust, nicely diffuse, and very flexible, so they can safely be used in costumes and stuff that will flex a lot. Each pebble is an individually-addressible 5V Neopixel (2812b), and seem happy with 3.3v data so you don’t need a level shifter.
They are, though, not a lot of fun to strip and solder. The stranded wires are thinner than anything you’ve ever seen. You might think you’ve got them soldered together, but the first bike ride at Burning Man and *blam* they fall apart, or short somewhere, or who knows what, but they just don’t work for very long and it’s your fault for soldering it wrong.
After hours trying everything I could to get the ends of these suckers onto JST connectors, I finally just designed a tiny circuit board to solve this problem.
The idea here is you can strip the wires, sploot them apart, and solder them onto copper pads on the PCBs which is much easier than soldering wires to wires. Then, you can put some heatshrink on top of the whole thing, which holds everything physically in place, prevents shorts, and protects against the elements.
Want to make some of these PCBs yourself? If you upload this gerber file directly to JLCPCB with all the default settings, they’ll make them and ship them to you.
If you want to customize something, here are KiCad files.
Here are detailed instructions.
Pre-solder the pads on the PCB
Separate the three wires from the pebbles
Use sharp scissors to start the separation, then pull the three wires apart with your fingers or needle-nose pliers.
Strip about 75% of the insulator
You are not going to be able to use wire strippers. Instead, make a tiny nick in the insulator by hooking it on your sharpest pair of scissors, then pull off the insulator using your fingernail.
Sploot out the three conductors
Here’s what it looked like under a microscope:
Notice that the bottom conductor (when the pebble is facing up) has one or two strands of copper-colored wire in there. This is the 5V conductor. The one in the middle is data, and the remaining conductor is GND.
Place the three stripped wires above the pads on the PCB. With your soldering iron, heat each of the wires for a few seconds. Once they heat up they will melt the solder below them on the pad and sink into the solder. Add a couple more drops of solder on top.
One of the pebbles will land on top of the PCB. That is intentional! We are going to sacrifice that pebble by covering it in heat shrink, which will create much more physical strength than we could get from the solder joints alone.
Solder the other side
Repeat on the other side. You might want to use a JST-SM 3-pin connector which is pretty standard in LEDs, or any other connector you like. You can also find reels of 3-conductor, 22awg “LED wires” online if you need a few more feet.
Find some heatshrink that is 1/2″ diameter, about an inch long. Look for heat shrink with a 4:1 shrink ratio that is adhesive lined, dual-wall. Slip this over the whole PCB and heat.
And you’re done!
Notice that one of the pebbles has disappeared beneath the heat shrink, but that’s worth it, because it provides a little lump that makes the whole joint stronger.