Turn on your heartlight
Let it shine wherever you go
Let it make a happy glow
For all the world to see

A little fire for your heart! But there’s no actual flame here, no heat…instead, LEDs and a microcontroller make a virtual flame that dances like the real thing. (In fact it’s playing a tiny video loop of a real candle.)

We planned this animated flame simply as a piece of high-tech jewelry, but other uses are possible…a fire or lantern effect on cosplay props, a safer alternative to having candles on the table or as part of a holiday display, or a unique night light for finding your way to the bathroom at night.

It’s a simple circuit that can be built either as a pendant or as a tabletop piece. Fair warning though: the pendant variant is tricky…it’s a very tight space requiring ace soldering skills and some unconventional methods. As a tabletop piece, perhaps in a glass votive, or maybe you have a cosplay prop in mind, it’s much more forgiving.

Parts from Adafruit:

• Pro Trinket 3V (the code works fine on the 5V Pro Trinket as well, but the battery will run a little longer with the 3V board)
• LiPoly Backpack Add-On for Pro Trinket
• 350 mAh Lithium Polymer Battery (required for pendant — a larger battery is OK if making a votive candle instead)
• Breadboard-friendly SPDT Slide Switch
• 16x9 Charlieplexed PWM LED Matrix Driver
• LED Charlieplexed Matrix: red, yellow, green, blue or white. White is brightest, yellow most closely matches a real candle…all depends what effect you’re after. Green Lantern, perhaps?

Other Required Items:

• Soldering iron and related paraphernalia
• Narrow-gauge wire. Especially if building the pendant…we’re huge fans of our 30 AWG silicone-coated stranded wire for tightly-packed projects like this one!
• Hobby knife and/or file.
• If making the pendant design:
• 3D printer and transparent filament
• Two (2) #2-56 x 3/8" screws (or M2 x 10mm)
• Small screwdriver
• Flush cutters
• Necklace chain or lanyard cord
• 5-minute epoxy or E6000 glue (do not use JB-Weld, it's conductive)
• If NOT making the pendant:
• Glass votive candle holder or other container

Before going shopping or committing to any parts or materials, read through the whole guide first to see what’s needed and what you might already have, or for ideas on what you might improvise.