Circuit principle:
The 12V DC voltage passes through VD1, and the R1 illuminates the LED 1 of the LED as the power supply indication, and the other serves as the working power of the system. After the power is turned on, if there is no water in the water tank, the two water level probes are connected to the positive power supply via R1 and R2, which is high potential. The 4 feet of IC1 output low level. After IC1C processing, the 10 feet output high level. This high level is added to the base of VT1 via R4, so that VT1 is saturated and turned on, the relay is energized and the pump is pumped; the other is connected to the 2 pin of IC1 via R8, because the high water level probe is also high. Ping, after the NAND gate processing, IC1's 3-pin output is low, and the IC1C is locked with the NOT gate. As the water pump continuously supplies water to the water tank, the water level in the water tank gradually rises. When the low water level probe is immersed in water, the 6 feet of IC1 become low level, and the 4 feet output high level, but at this time the NAND gate has been locked. Live, so it will not affect the output, the pump continues to pump water; as the water level rises further, when the water level hits the high water level probe, IC1's 1 and 6 feet become low level, this change to IC1's 4 feet No effect, but the 3 feet become low level due to 1 pin, the output is high level, so the pins 8 and 9 of IC1 are high level, the 10 feet output low level, the relay loses power and is disconnected, the pump Stop pumping, and this low level is added to 2 feet via R8, so that 3 feet stay high. Until the water level is again lower than the low water level probe, the above process will be repeated, thereby automatically controlling the water level of the water tank. In this circuit, a manual control circuit is designed, and when the WAR switch is pressed, the relay is forced to open.
