By reading different values from the sensor, we can detect if is it light , dark or a value between them. Another element that we are going to use on this experiment is Piezo Buzzer. So what is it ?

Calibrating the system using a bowl of clean water. There is no single parameter that determines the quality of a water sample, so the pollution monitor has no less than five different sensors.

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!