Make a necklace or tiara for your favorite birthday girl that proudly displays her age in shining lights. This beginner-friendly guide walks you through building a magical LED tiara or necklace that displays the birthday child's age using Adafruit's flexible LED number filaments.
These filaments run at 3V and are powered by coin cell batteries—one battery per number—making the design lightweight, wearable, and delightfully low-tech. This project requires a little easy soldering and no coding. You'll end up with a sturdy, eye-catching crown that's safe for kids and perfect for birthdays, dress-up days, and royal make-believe adventures.Â
For double-digit birthdays, use a 2-coin cell holder. For single-digit, use just one battery.
The white coin cell holder listed below is ideal, but I didn't have one on-hand so this tutorial shows how to do it with our 20mm coin cell breakout board instead. The wiring is the same, and the breakout has a slightly smaller form factor so is great for a necklace build where we're trying to keep everything as small as possible. The coin cell holder that closes is going to be a bit more robust, so it might be better if you're making this for a kid in her single-digit years.
Page last edited May 16, 2025
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