AIM: To design and implement an automatic water tank level control system using PLC for maintaining desired water level and preventing overflow and dry run conditions.
OBJECTIVE:
To automatically control the water level in the tank
To operate the pump based on tank level conditions
To prevent overflow and dry run of the motor
To improve system efficiency and reliability
To enable real-time monitoring and control
The PLC ladder logic program consists of the following main sections:
Start/Stop Control
The START push button is used to activate the system
The STOP push button is used to deactivate the system
A latch (A1) is used to maintain the system state This ensures the system remains ON until it is manually stopped.
Level Control using Counter (CTUD)
A CTUD (Up-Down Counter) is used to simulate tank level
CU (Count Up) increases the level (filling condition)
CD (Count Down) decreases the level (usage/discharge)
PV (Preset Value) represents maximum tank level
CV (Current Value) represents actual tank level
This method allows level tracking without using physical sensors.
Valve and Motor Control: Based on level conditions:
Motor turns ON when level is low
Motor turns OFF when level reaches maximum
Valve controls the inflow of water
Exhaust/Discharge Control
Output logic is used to control discharge valve
Water outflow is managed based on system conditions
WORKING:
In automatic mode, the system operates without manual intervention once the Auto Mode is selected. When the Auto Start push button is pressed, the process begins and the PLC continuously monitors the tank level. If the tank level is below 100%, the pump and feed valve are automatically turned ON, allowing water to fill the tank, and the level is displayed in percentage (%) on the HMI screen. A low-level indication is activated when the level falls below 10%, signalling the need for filling, while a high-level indication is activated when the level reaches 90% of the set value, indicating that the tank is nearly full. Once the tank reaches the preset level, the pump and feed valve are turned OFF, and the discharge valve is turned ON to allow water to flow out. As the water is discharged, the tank level gradually decreases. When the level reaches 0%, the discharge valve is turned OFF and the pump along with the feed valve is turned ON again. This entire cycle continues automatically until the Auto Stop push button is pressed, ensuring efficient and continuous operation of the system.
PLC LADDER LOGIC OF WATER TANK LEVEL PLANT:
APPLICATION:
Industrial water tanks
Chemical storage tanks
Boiler water level control
Agriculture irrigation system
Residential water automation systems
Smart city water management
CONCLUSION:
The PLC-based water tank level
control system provides efficient and automatic operation. It reduces water wastage,
prevents motor damage, and improves reliability. The use of a counter-based system makes it flexible and suitable for various industrial and domestic applications.