Arduino Smart Thermostat (DHT22 + Relay + I2C LCD)

Room at 19 degrees, target 21: the relay clicks on! The **DHT22** measures the temperature, and when it drops below the target the **relay** turns the heater on. Thanks to **hysteresis**, the relay does not keep clicking around the target. Two **buttons** set the target in 0.5 °C steps, and it is kept in **EEPROM**; the **I2C LCD** shows temperature, humidity and heater state. The basics of real home automation in one project.