Greenhouse Climate Controller with Automatic Fan
Keep a small greenhouse from overheating: a fan turns on above your target temperature and humidity.
In the Florida sun a closed greenhouse can pass 40 °C in an hour. An ESP32 reads the BME280 and switches a 12 V fan through a MOSFET with hysteresis so it does not click on and off constantly.
Mission steps
Mount the sensor in shade
Put the BME280 at plant height, shielded from direct sun.
Wire the fan driver
12 V fan through a logic-level MOSFET module, gate signal from an ESP32 GPIO, grounds shared.
Flash ESPHome
Add the sensor and a thermostat or template switch with on above 30 °C and off below 27 °C.
Add humidity control
Also run the fan above 85% humidity to prevent mold.
Alert
Notify if the temperature still rises past 35 °C — the fan may have failed.
Questions
Can I run it on solar?
Yes — use the solar guide's math. Fans draw the most power, so size the panel for the fan's watts × hours of sun.