1.3 Water Level Sensor

Evaporation or leaks will cause a drop in the water level of an aquarium. If the water level gets too low, the water’s pH level will change due to increased concentration of dissolved substances contained in the water. A liquid level sensor can be used to determine the water level in the aquarium.

The Gikfun Liquid Level Sensor is a simple reed switch. The main body of the switch is a thin shaft that contains two metal contacts that are normally “open”, meaning the two do not make physical contact (see Figure 1-4). Surrounding the thin shaft is a float, which houses a thin magnetic ring at one end. When the magnetic ring is very close to the two metal contacts, the magnetic force pushes the two contacts together and creates a closed circuit. When placed in a liquid, the position of the float relative to the shaft prevents the magnetic coupling from occurring and, as the liquid level drops, the float slides down the shaft. When the water level forces the float to the bottom of the shaft, the float’s magnetic ring forces the two contacts together. The completed circuit can then be used to detect low water levels using the microcontroller.