LM324 Water Level Sensor/Indicator

This is Hot Water Level Indicator circuit. This circuit can be used to monitor level of hot water in a tank. This circuit is simple and inexpensive. this circuit uses thermistors NTC1-4 as the sensor that is placed spread over the height of the tank. If the sensor is placed 4 inches from the top of the tank, it will indicate the height of the hot water about 8 to 10 inches from the bottom of the tank when the hot water rise the lowest sensor. Here is the schematic diagram of the circuit:

The SW1 is normally open switch that is used to monitor the hot water level. When it was pressed, the op-amps non-inverting input voltage and the voltage difference at preset and the junction of the thermistor are compared. The thermistors resistance will toggle the op-amp output to swing to almost full voltage supply depends on the heat of the water. The indicator of this circuit is the LED that shows the height of the hot water. [Circuit’s diagram source: english.cxem.net]