Weathergotchi is an open‑source, battery‑powered temperature and humidity logger that keeps an always‑on E‑Paper display. The device records ambient conditions over time, stores readings in non‑volatile memory, and shows the current data along with a history graph. It uses an ESP32‑S3 microcontroller with deep‑sleep and an RTC timer to wake up at configurable intervals.

Hardware includes an SHT45 temperature/humidity sensor, a DS3231 real‑time clock, a 24LC512 EEPROM for logging, and a BQ27441 fuel gauge for battery monitoring. A 1.54‑inch Waveshare e‑paper display is driven via SPI, and a LTC2954 soft‑power button allows true on/off control. The PCB is custom‑designed in Ki‑Cad and the enclosure is a 3‑D‑printed, fully parametric case.

The unit runs for over 1 week on a small 400 mAh Li‑Po battery. In deep‑sleep it draws less than 20 µA, and the ESP32 wakes for ~400 ms to log a reading, update the display, and return to sleep. The DS3231 alarm triggers the wake‑up, keeping power usage minimal.

Limitations include temperature drift when the ESP32 heats up, a display low‑temperature cutoff around 0 °C, no wireless connectivity, and battery accuracy issues when the cell is near depletion. The project is fully open source, with schematics, firmware, and CAD files available on GitHub, and contributors are welcome.