**Abstract**: This paper introduces the basic composition and working principle of a simple and practical automatic water level control system for a water tank, including valves. Through assembly and testing of the system, the expected results were achieved, and it was officially applied to the water supply system of a township. Practical experience shows that the design of this water level control system is reasonable, with good operational results, and has the advantages of low cost and high application value.
**Keywords**: Water level, Automatic control system
**0 Introduction**
In recent years, higher demands have been placed on urban water supply systems. The automation of water tower water level control systems has been continuously improved to adapt to social development and the improvement in living standards, ensuring timely, accurate, safe, and sufficient water supply. Currently, there are many mature products for water level automatic control systems. Control methods mainly include microcontroller monitoring, comparator circuit monitoring, and the use of PLCs and sensors to form a water tower water level stabilization control system. These systems operate reliably, enabling remote monitoring and unattended operation. In many remote areas, especially rural areas with dispersed populations, water supply problems also need to be addressed. If manual methods continue to be used, the labor intensity is high, work efficiency is low, and safety is difficult to ensure. This paper designs a simple, practical, and cost-effective water level automatic control system tailored for water supply in townships and remote rural households.
**1 Composition of the Water Tank Water Level Automatic Control System**
Considering the characteristics of remote rural areas with dispersed populations and inconvenient water access (including from wells), and taking into account the relatively low living standards of farmers, the designed water supply system must be both convenient for farmers' lives and economically affordable. The composition of the water tank water level automatic control system includes:
As shown in the diagram, the water level automatic control system circuit mainly consists of two parts: the main circuit and the control circuit. The main circuit is a water pump powered by a 220V AC power supply. The control circuit includes rectification, filtering, voltage stabilization, sensing circuits, and current/voltage limiting circuits.
**2 Equipment for the Water Tank Water Level Automatic Control System**
The equipment for the water level automatic control system only requires low-cost, safe, and reliable components.
From the equipment list, all the equipment is simple and commonly used small devices, with low costs, easy control, and maintenance. This makes it very suitable for remote areas far from cities. Traditional water level control systems often use sensors for upper and lower limit control to ensure the water level stays within the specified range. In this design, three wires replace the sensors and are placed between the upper and lower water levels. By utilizing the conductivity of water, the system achieves automatic upper and lower water level control, saving the cost of purchasing sensors and avoiding sensor failures, further reducing costs and improving system reliability.
**3 Control Principle of the Water Tank Water Level Automatic Control System**
The structure of this water tank water level automatic control system is simple, and its control principle is as follows: After the system is powered on, the AC power supply passes through rectification, filtering, and voltage stabilization. A potentiometer adjusts to obtain a 12V DC working voltage. When the water tank water level is below the lower limit, the contactor coil loses power, and its normally closed contact connects the water pump to start pumping water into the tank. When the water level rises to the upper limit, the contactor coil is energized, the normally closed contact opens, and the normally open contact closes, stopping the water pump.
V1 and V2 protect the LM317 output voltage to ensure it remains at a safe voltage, preventing damage from short-circuit currents. V3 protects the transistor and prevents electric shock accidents. The upper and lower water levels can be set by adjusting the positions of the three wires.
**4 Testing and Application**
After installation and debugging, the system was tested in conjunction with a laboratory water supply and drainage system, with excellent results. It has been officially used in the daily water supply installations of several households in a township for nearly two years without any faults. The system operates stably, fully meeting the pre-specified standards. Simply adjust the stabilized output of the control circuit between 10V-12V, and the system can be put into use. It can be powered by an AC transformer or a DC power supply.
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