thermostat

A thermostat is a device that regulates temperature by comparing the actual temperature of a space or object with a desired setpoint and triggering heating or cooling equipment to reduce the difference. It typically combines a sensor, a controller, and an actuator that operate a furnace, air conditioner, boiler, or valve to adjust the heat output or cooling level.

Most thermostats work with feedback control. The sensor detects temperature, the controller determines whether the current temperature deviates from the setpoint, and the actuator switches or modulates the heating or cooling device. Some systems use simple on/off control with a defined deadband, while others use more precise methods such as proportional or PID control to minimize fluctuations and energy use.

Thermostats come in several types. Mechanical thermostats rely on physical properties like bimetallic strips or wax capsules to sense temperature and engage a switch. Electronic thermostats use solid-state sensors (such as thermistors or RTDs) and a microcontroller to control outputs. Programmable thermostats allow scheduled setpoints for different times of day, improving comfort and efficiency. Smart thermostats connect to home networks, learn routines, and can be controlled remotely or integrated with other smart devices.

Historically, thermostats emerged in the 19th century with mechanical temperature regulators and evolved through electromechanical to electronic models in the 20th century. The development has continued with wireless communication and IoT capabilities, enabling greater energy management in buildings and appliances.

Applications span residential and commercial heating, ventilation, and air conditioning, as well as appliances like ovens and refrigeration units. Proper installation, calibration, and sensor placement are important to ensure accurate temperature control and energy efficiency.