Water level automatic controller composed of NE555

As shown in the figure, this is a water level automatic control circuit. The control circuit consists of a step-down rectifier circuit, a water level measurement and control switch, a bistable trigger, etc. The step-down rectifier circuit provides NE555 with a power supply voltage of VDD=12V. The NE555 in bistable working mode is used as an RS trigger. BG1 and the upper water level probe A are used as reset trigger switches; BG2 and the middle probe B are used as set trigger switches; C is the lower limit probe connected to the ground level. Using the characteristics of the RS trigger, the setting and resetting of NE555 are controlled to make the relay J attract or release, thereby controlling the operation of the pumping motor D to keep the water level between the given upper and lower limits.