How to make a four-level water level indicator with full water alarm function

Working principle: This circuit is composed of a quad bidirectional analog switch integrated circuit CD4066 as the core. Each circuit has four independent switches that can control the transmission of digital or analog signals. When there is no water in the water tank, due to the effect of the 180K resistor, the control ends of the four switches are low, the switches are disconnected, and the LED does not light up. As the water level increases, due to the conductive properties of water, the 13th pin of the IC is high, S1 is turned on, and LED1 lights up. When the water level gradually increases, the LEDs light up in turn to indicate the water level. When the water is full, LED4 lights up, indicating that the water is full. At the same time, T1 is turned on, and B sounds an alarm, indicating that the water is full. When the alarm is not needed, just disconnect switch K.

The circuit components are selected with reference to the circuit diagram. Transistor T1 acts as the electronic switch of the buzzer alarm in the circuit. It is recommended to choose a medium-power tube such as 8050 with a larger amplification factor. The audio alarm B can be selected according to the actual situation and personal preference.