Solar-Powered NB-IoT Crop Sensor

Challenge: Field-deployed crop sensors that run for years on a small solar cell and LiPo, measuring soil moisture, temperature, humidity, and light, reporting over NB-IoT. Solution: STM32L433 in Stop2 mode draws under 2µA between readings. The solar MPPT charges a 400mAh LiPo that sustains the system through winter weeks with minimal sunlight. The cellular modem dominates the power budget, so the firmware batches readings and transmits in short bursts rather than maintaining a persistent connection. Results: Deployed fleet has been running reliably across multiple growing seasons.