Fletcher made this scalemail tail a couple years ago and always dreamed of having rainbow lights inside. That was the first time they used these clear plastic scales – and they were specifically chosen to have space for the lights to shine through! Alternating black and clear scales creates a strong silhouette while still leaving space for the light to shine through.
I’ve wired LEDs before to make cosplay accessories, but I didn’t want to buy parts for them so I used what I had lying around – namely a Raspberry Pi. That was super overkill (from a processing, power, and price perspective) so for this tail, I needed something I could permanently dedicate to the build (and I needed to stop cannibalizing this one Pi for every LED project I started). I picked up a Gemma M0 and a Circuit Playground from Adafruit – I was hoping the Gemma would be sufficient but I wanted a backup plan as well. Thankfully the Gemma was plenty powerful for what I was trying to do!
The first challenge I ran into – how do I add wires to sewable pads?? I had jumper wires for breadboards, but I didn’t have any alligator clips… let alone alligator clips to jumper wires. Conveniently, we had a few alligator clip wires lying around at the makerspace so a friend of mine made me a trio of the connectors I needed – he clipped the wires on one end, stripped them back and added a prong so we had a clip on one side and jumper cable on the other. Thanks Steve!
Okay step one – attach the wires. Done! Step 2 – connect the Gemma to my laptop. This didn’t work immediately and troubleshooting it took longer than I’d like to admit. It turned out to be an easy problem, but the version on the board was out of date. I used the serial console to get more data on my board and it was a few versions out of data. I updated my controller from 2.14 to 2.19 and that did the trick – I could connect to the Gemma from Circuit Python and start the fun part of actually coding.
Except I wired it wrong, oops. This is why we use test wires! Turns out the arrows on the lights are important and are indicating the direction that data flows. Alrighty- I reversed the end of the pixels I was using, clipped my wires on, and bam, we have lights! Not pretty lights, but that comes later.
First look at the lights
Here’s a video of the first version of the rainbow lights! The tail is up and running, but I did some more work to make the lights flow smoothly and have a more natural feel. In the next post, I’ll go into more detail on how I did that!
Overall Thoughts on the Gemma M0
The Gemma M0 made this a lot easier than my experience with the Pi. Simply being able to connect to it via USB without needing to ssh or setup a spare monitor/keyboard to configure the Pi was a big win to me. Same as running code – the Gemma auto-runs its main file at the root level on the controller, so as soon as it’s powered on, the light sequence kicks off (rather than needing to set up an auto-launch script on the Pi). Apart from needing to run an update, it pretty much did everything I needed out of the box.
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