A camping lantern with one control. It's a puck about 9 cm across and 8 cm tall, with a translucent dome on top. Twist the dome and the light sweeps continuously from a barely-there deep red, through orange and candle amber, to warm white and finally a bright neutral white. Press it to switch on or off. It always comes back where you left it.
Right way up on a table it lights the whole dome. Flip it over and six magnets in the base stick it to a car roof, a tent pole or a steel shelf, with the LEDs shining straight down and nothing in the way. A cheap LED-strip remote works too, for when it's stuck somewhere you can't reach.
On one 18650 cell it should run about 3 hours at full brightness, 13 hours at amber, and for days as a red night light. It charges over USB-C.
Where it's at
The design is at v0.3. The enclosure is down to two printed parts, a base and a dome, and the firmware is written. Next is a hand-wired prototype built from off-the-shelf modules, to settle the layout and tune the colours by eye through the dome. After that, two custom boards for a small run.
Technical details
One dial. The rotary encoder under the dome is clamped to 60 detents, three full turns, and normalised to a single level from 0 to 1. Colour and brightness are both functions of that one number, which is what makes it feel like a dial rather than a menu. The colour comes from a table of keyframes, from pure red at 0 to white with a touch of blue at 1, interpolated between. Brightness follows a 2.2 gamma curve, so the bottom of the range spends lots of detents in the useful night-light zone. Hold the press for 1.5 seconds and it flickers like a candle.
Light. A 24-LED SK6812 RGBW ring lies flat on the base, facing up into the dome, with the encoder shaft through its middle. Warm tones come from adding red and a little green to the natural-white LEDs.
The dome is the knob. v0.3 prints the dome and the column that grips the encoder shaft as one part, in the same translucent PETG, so the column glows instead of casting a shadow. The only real shadow left is a 10 mm flare at the top, about 0.8% of the dome.
Electronics. An ESP32-C3 SuperMini, a TP4056 USB-C charger, a TPS61023 5 V boost converter and an HT7333 regulator, with a 74AHCT125 shifting the LED data up to 5 V. The LEDs draw about 1 mA each even when dark, so the ESP32 cuts the whole 5 V rail when it's off and deep-sleeps at around 10 µA, waking on the encoder button or the IR receiver.
Boards. For the small run, two PCBs replace the modules. KiCad drafts exist for both: a ring board with the 24 LEDs, fully routed, and a D-shaped main board with everything else, placed but not routed.
The case is modelled in OpenSCAD and the firmware is an Arduino sketch.
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