Non-Contact Liquid Level Sensor 5-12V NPN

These are very cool water level sensors. Simply stick them outside a non-metal container or tank and it will switch with a signal to a microcontroller. If you supply 5V from, let's say an Arduino Uno, it will output 5V to a digital pin so you can do your magick in your coding like starting a water pump. If you use two you can set a low and high water level to start a pump when the low water level is reached and stop the pump when the high water level is reached.