DIY Temperature and Humidity sensor using EInk display

This is a simple DIY Temperature and Humidity sensor, with a small EInk display and (future) integration with Home Assistant.

Features:

• shows the numeric value of temperature and relative humidity (measured at every 10 minutes)
• shows two graphs with the temperature and relative humidity (measured at every 10 minutes), from the last 24h
• PLANNED: Send temperature and relative humidity to HomeAssistant

Main characteristics:

• Easy DIY, OpenSource and easy repairable
• Uses the factory calibrated temperature and humidity sensor AHT21
• The display is a 1.54 inches EInk display
• The microcontroller board is the ESP32-S2, running Pyhton (CircuitPython) firmware
• The systemn runs from a USB-C cable or from some other power supply source like 3xAAA NiMh batteries, as there is a DC-DC boost converter that supports input voltage from 1V up to 5V, and outputs a fixed 5V

All the components were bought on Aliexpress.

Pictures

Pictures from prototype on 2023.02.22.

Showing the temperature and humidity values:

Details of the 3D printed enclosure:

Details of the DIY electronics:

Details of the DIY build. Black board is the 1.54 inches EInk display, the purple board is the ESP32-S2 board (Lolin S2 Mini), the blue board is the AHT21 sensor and the green board is a DC-DC boost converter module that transforms the 2.4V from the NiMH batteries to 5V to power the ESP32-S2 board and all other components:

Tecnhical information

• the 3D printed enclosure was designed in FreeCAD
• the firmware is developed in CircuitPython
• the graphs are implemented using the uplot library