Low power WiFi temperature/humidity sensor

Features

• 9 months+ runtime on a 1200mAh Li-Ion battery
• Highly accurate Si7021 temperature and humidity sensor
• Physical case with low impact on temperature (<0.05°C)
• MQTT integration with e.g. Home Assistant directly over WiFi
• PH2, PH3 and GH2 connectors for range of Li-Ion batteries
• POGO programming header for quick flashing
• Battery voltage measurement for power management
• Technical details available on Github

PCB

• No through-hole components for easy stacking on top of Li-Ion battery
• Two-layer, 50 mm x 34 mm
• KiCad files
• Gerber files
• Partial BoM

Software

• Arduino files
• Update config.h with your settings
• Fine-tune vbatt_calibration for accurate battery voltage measurements

Case

• 3D printed case: STL, SCAD

• Analysis shows latest case design (case2) only impacts temperature readings by 0.05°C, less than the sensor repeatability (0.08°C):