The following components were used in the implementation of this project:
Arduino: The Arduino was used to process the input from the temperature sensor and determine from that input whether or not the fan should be turned on or off (if it was in "Auto" mode). It sent control signals to the relay which would then cut the DC power supply in or out of the circuit accordingly, which served to activate or deactivate the fan. In addition, the Arduino served as a driver for the LCD display.
5V DC fan: Used to simulate a house's cooling system--when the temperature sensed by the chip got too high, the fan was activated (in "Auto" mode). Also, the fan could be turned manually on or off.
TMP01FPZ: This chip outputted a voltage proportional to its temperature in Kelvins. This output was processed by the Arduino and sent to both the LCD readout and the solid-state relay in the form of a control signal.
LCD display: The LCD display was responsible for two things: showing what mode the system was in ("On", "Auto", and "Off") and what the temperature was as outputted by the chip. This display was driven by digital output from the Arduino.
DC power supply: The power supply was fed into a solid-state relay and into the fan from there. When voltage from the power supply was applied to the fan, it would spin.
Solid-state relay: The relay was needed to regulate power from the DC power supply. When a control signal was applied to the relay, the current from the power supply would be allowed to pass through it and into the fan, turning it on. The absence of the control signal would "close" the switch, shutting off the fan. This was a necessary addition because the Arduino could not power the fan from its digitalWrite() output alone--it didn't produce enough current to drive the fan. Thus, the dedicated power supply became necessary, and the relay along with it.