Firefly Lightjar

$32.95–$48.95

The mason-jar LED that always wins — flip-on camp, emergency, and patio light you build in one evening.

FireFly — The mason-jar LED that always wins

Flip-on waterproof camp / emergency / patio light you build yourself in one evening.

No buttons. No leaks. No “dead when you need it.”
Just flip the jar upside-down and back → instant light. Hold upside-down → dim or brighten. Done.

Heart of the kit is a pre-programmed ATtiny85. Through-hole parts, PCB, and guidance included — you add batteries, a wide-mouth quart mason jar (or a wide-mouth pickle jar), and mounting bits. Regular-mouth jars are too small. The board is 68.6 mm (2.70 in) across, so it needs a jar mouth at least that wide on the inside; measure the opening of your jar to check.

Also in the family

Want the smaller MCU and beacon tricks? See FireFly10 Coming soon — same flip UX on ATtiny10, plus DoubleFlip beacon / SOS modes.

Key features

• Ultra-easy flip control — invert and return to toggle; hold inverted to walk brightness. Glove-friendly, button-free.
• Smart power — auto sleep after ~10 minutes off → months of standby readiness. Two common 14500 3.7 V Li-ion cells (not included; USB-C rechargeable; a Y-cable charges both at once).
• Beginner-friendly build — through-hole kit, pre-programmed MCU; solder in an evening.
• Adventure-ready sealing — unique flip UI enables a fully waterproof jar build (dive-tested to ~33 ft / 10 m when sealed properly).
• Fits any wide-mouth quart mason jar or most wide-mouth pickle jars. Regular-mouth jars are too small. The board is 68.6 mm (2.70 in) across, so it needs a jar mouth at least that wide on the inside; measure the opening of your jar to check.

One kit: fun project.
A six-pack: emergency stash or group build night.

In blackouts, storms, or late-night campfires — darkness retreats. Light wins.

What’s included

• Through-hole PCB + parts (pre-programmed ATtiny85)
• Assembly guidance for jar enclosure
• You supply: 2× 14500 Li-ion, a wide-mouth mason jar (or a wide-mouth pickle jar — regular-mouth jars are too small), mounting supplies

Confirm exact BOM against the Stripe SKU before shipping.

Build guide / interactive parts list

Open the FireFly interactive parts list ↗: click a part to highlight where it goes on the board, and check it off as you place it. There’s more build help on the Support page.

Board views

Isometric 3D + flat PCB plots from Mildrew. Lifestyle jar photos still welcome under static/images/products/firefly/.

Board & product views