Want an ESP32 sensor node that never needs a USB cable dangling from it? You need three things to start: an ESP32-C6 Mini, a small solar panel, and a single lithium cell. [Narrow Studios] folded all the glue circuitry around those parts onto one compact board, so you can skip the breadboard stage and go straight to firmware.
What the board is built to do
The design targets exactly one job: solar-powered IoT. The ESP32-C6 Mini at the center carries the radios that matter for a battery-run sensor, WiFi, Bluetooth 5, Zigbee, Thread, and Matter, so a single node can join almost any home-automation mesh. That radio spread is the reason to reach for the C6 over an older ESP32: one chip talks to a Matter hub, a Zigbee bulb, and your phone without a second module. Not finding an off-the-shelf board built for this, the designer laid out his own and sent it to PCBWay, and the shared project files are public if you want to order a set.
The charging circuit and pinout
The solar part comes from a Texas Instruments BQ25186, a single-cell linear charger that sips from a panel and tops up one Li-ion cell. The solar input has reverse-voltage protection, which matters more than it sounds. Hook a panel up backwards and you let the magic smoke out of a $3 IC (embarrassing, and yes it happens). Ten GPIO pins are broken out for your sensors, plus an I2C bus on a QWIIC connector, so you can chain temperature, light, or air-quality modules without soldering a thing. The pull-ups for the I2C lines are already on the board, so a first-time sensor hookup is genuinely plug-and-read.
Build one yourself
Grab an ESP32-C6 dev board from circuit.rocks (from about PHP 450), a 5V 1W solar panel, and an 18650 or LiPo cell to follow along. Flash MicroPython or the Arduino core, wire one QWIIC sensor onto the I2C bus, and drop the chip into deep sleep between readings to stretch a small panel across cloudy days. Log the battery voltage on an analog pin so you can see how your duty cycle holds up over a week. The full write-up, schematic, and a design-walkthrough video sit on the hackaday.io project page.
Originally published on blog.circuit.rocks.
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