Here is an ultra simple Arduino Night Alarm project wired around a handful of inexpensive and easily available components. One advantage of using Arduino as a security system is the flexibility!

Here is a tested Arduino project that uses 3 sensor probes as water level indicator with 3 leds and one LCD display + a simple controller that turns on a motor when the water has reached the desired ...

When the sensor detects that the moisture content is already below 30%, it sends a signal to the Arduino, which, in turn, activates a water pump to provide hydration to the plant.