The system here monitors temperature, humidity, and smoke levels and alerts you if those levels reach a certain point.

I used an LCD shield to display the current temperature and speed of the fan, but you can use the circuit without the LCD display. You also need to select the transistor by the type of fan that you ...

Adding a photoresistor (light sensor) and a thermistor (temperature sensor) and connecting them to a programmed Arduino gave me a gadget that monitors the environment of a single plant.