This is a little tutorial on how to create your own programmable, neopixel LED necklace! Adafruit has a great guide to neopixels, if you want to learn more about them. I used these neopixels from Amazon, they have little pads on the back of them to solder to.
You will need a soldering iron, solder, a measuring tape, wire cutters, and very thin, flexible, SOLID core wire, not stranded! The thinner gauge of wire you can find the better. First, I decided on a microcontroller to control my neopixels. I chose an Adafruit Gemma, for it’s small size and I could use an old rechargeable 3.7 volt li-poly battery, recycled from a cheap toy drone!
Normally I would laser cut a little jig to hold my pixels, but I can’t use the laser at my Fab Lab right now (thanks Covid19) so I just cut little squares out of cardboard to set my pixels in while soldering. The blue material is some sticky tack to secure the cardboard to my soldering surface. This jig is how I got each pixel evenly spaced.
I tinned the little pads with my soldering iron and snipped a few bridge wires. I measured with my eye for the length of the wires. You can always snip off the extra if they are longer than necessary! I didn’t worry about trying to strip off the plastic on either ends, I focused the tip of my soldering gun to the tip of the wire, and the plastic melted where I needed it to, right above each pad.
I found in practice that it was best to solder two groups, as shown above, and then solder those groups together. Always makes sure your neopixel arrows are facing the same direction. These neopixels are a polarized component and only pass along the code to turn them on through the ‘in’ and ‘out’ pads on the back.
Eventually I had a decent sized strand to test out how I planned on securing the back of the pixels. As you can see, the solder joints look pokey and rough, my solution for smoothing them, maintaining the flexibility of the necklace, and ensuring it would be comfortable around my neck, was to use this:
I’ve never tried this brand of epoxy before but I was very pleased to find it does set fast, as advertised, and it was easy to mix and apply. I used a toothpick and piece of cardboard to blend and bloop onto the back of each pixel. The trick is to blob on enough that it covers all the joints, but doesn’t spill over the sides. This epoxy was perfect!
I soldered my neopixels to my Gemma. At the end of the strand I soldered on wires, twisted them together, and poked them through the hole in the Gemma. I would like to add a proper jewelry clasp instead of the wired one, but it works for now! I used some example code from the fastLED library to test and make sure my neopixels were working properly. I love how it looks and I‘m really surprised at how comfortable and light weight it is while wearing!
