Four-level water level indicator with full water alarm function

working principle

The 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.