Automating Tent Climate with Home Assistant and a $20 Sensor
Wire a humidity/temperature sensor, an inline fan, and a humidifier into Home Assistant for hands-off VPD control.
Theo Lin·April 18, 2026·10 min read
The hardware
ESP32 board, SHT40 temperature/humidity sensor, two smart plugs (one for the EC fan, one for the humidifier), and a Home Assistant install on a Raspberry Pi or any spare PC.
The automation
Read VPD every 30 seconds. If VPD > 1.4 kPa, turn on the humidifier. If VPD < 0.8 kPa, ramp the exhaust fan. Add a 5-minute hysteresis window so devices don't flap.
Going further
Once you trust the loop, add CO₂ injection, soil moisture probes, and a Telegram alert when the reservoir drops below 30%.