Featured image of [Project] Capacitive Touch Unicorn Horn
Modern Magic

[Project] Capacitive Touch Unicorn Horn

Picture of Mika Yeap
by Mika Yeap
Jun 16, 2019
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Absolutely blank when it comes to weekend plans? We've got just the thing. Hint: it's got something to do with unicorns.

Anyone can print a unicorn horn with white PLA, but it takes a dedicated cosplay nerd to print one that lights up. But a unicorn horn that lights up via capacitive touch? That’s something else entirely.

But designer at Adafruit Erin St Blaine has done exactly that: designed a wearable unicorn horn that lights up at a human touch. It does this using a copper spiral decorating the outside of the horn, made of copper tape. But pictures probably don’t do an artifact like this justice, so let’s get down to business and make our own.

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1

Light Up Unicorn Horn Project What We Need

Tools

  • 3D Printer (optional)
  • Soldering iron & accessories
  • Utility knife
  • Needle & thread (for mounting)
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2

Light Up Unicorn Horn Project Let's Put It Together

Image of Light Up Unicorn Horn Project: Let's Put It Together
Wiring diagram. (Source: Adafruit)

We’re going to connect the Gemma M0 to the battery, Neopixel ring, and LED, using heat shrink tubing to secure connections. After that, we should be able to use the capacitive touch module on the Gemma M0 to directly trigger the LED.

Here’s a wiring table, courtesy of Adafruit, just in case you’re stuck:

Connections table. (Source: Adafruit)

Software

Here’s what you’ll need on the software side to get cracking:

  • Arduino IDE (1.8 or newer preferred)
  • Adafruit Board support for Gemma M0
  • Arduino libraries: FastLED, Adafruit_FreeTouch, Adafruit_NeoPixel
    • These can be installed from the Arduino Library Manager. Go to Sketch > Include Library >Manage Libraries… and search for all or part of the library’s name, then click “Install.” You’ll need to look for:
      • FastLED
      • Adafruit_FreeTouch
      • Adafruit_NeoPixel

After you’re all set up in the software department, flash some code onto the Gemma M0, and then we can get right along to printing the horn!

Printing Time

You could print the horn in two materials or colors if you’re being fancy, but there’s also a merged single-extruder version:

The designer recommends printing the horn with 0% infill, and no supports or raft; but printing the platform with 20%, as well as supports and a raft. Though in both cases, a skirt or brim can be helpful, depending on your setup. If you’re not sure if you need them, this basic guide might be a good starting point.

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Light Up Unicorn Horn Project Final Assembly

Assembling the unicorn horn. (Source: Adafruit)

First, assemble the little electronic contraption shown in the diagram. That’s the most difficult part. After that, all you need to do is attach the copper tape to the outside of the horn, then connect the tape to the Gemma M0 board, and you’ve got a light-up horn!

You’ll probably want to attach the horn to a headband of stiff fabric to wear it on your head – to do this, sew the platform onto the fabric using the mounting holes. Don’t forget to use a stretch strip of cloth elastic on the ends for a comfortable fit.

At this point, you might face some issues with sensitivity: the capacitive sensor’s readings may fluctuate wildly and require slight tuning before the horn can light up on command. Adafruit has provided detailed steps on this calibration process, if it becomes a problem.

Otherwise, you’re all set to be the life of the mythical animals party!

License: The text of "[Project] Capacitive Touch Unicorn Horn" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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