Teapot Laboratories' BWLR1E Is an Energy-Efficient Open-Hardware Solar-Powered Environmental Monitor

Designed for air quality monitoring, this sensor includes energy harvesting and a neat 3D-printed magnetic chassis for quick deployment.

Open-hardware designer Aldwin Hermanudin, of Teapot Laboratories, has put together an environmental sensor designed to be low impact — by drawing power from a solar cell to report on local conditions over a LoRa network.

"Teapot BWLR1E is a solar-powered wireless LoRa environmental sensor capable of sensing temperature, humidity, air pressure, and air quality using the on-board [Bosch Sensortec] BME688. With [the STMicroelectronics] STM32WLE MCU [microcontroller unit] as its core and [an e-peas] AEM10941 for solar charging, the device is capable of multi-year operation with the possibility of indefinite battery-life by utilizing the solar charging capability."

The heart of the project is a RAKwireless RAK3172 WisDuo LPWAN module, which combines an STM32WLE5CCU6 microcontroller with a radio stack designed for LoRa 1.0.3 compliance. Alongside this Hermanudin has added the AEM10941 energy harvesting chip, connected to a quartet of compact solar cells housed at the base of a 3D-printed casing. The BME688 offers multifunctional environmental sensing, gathering data and transmitting it via a LoRa network at a range of over a kilometer (around 0.62 miles).

For programming, the design includes two breakouts: a UART for programming the unit via the Arduino IDE, and a serial-wire debug (SWD) for programming Mbed or via the STM32Cube environment. The boards are designed in KiCad, while the 3D-printable case — available in variants with or without room for the programming header — is built in TinkerCAD and provides protection plus four magnets for ease of mounting.

"Soldering the solar cell is better to be done manually using a soldering iron," warns Hermanudin, for anyone thinking of building their own. "Without [a] proper reflow oven, it may damage the solar cell and reduces it's efficiency."

Full details, including schematics, board design files, case STLs, and source code, are available on the Teapot Laboratories GitHub repository under the permissive MIT license.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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