Automatic Fan and AC Control using Schneider M340 Programable Logic Conrtroller

In many places like classrooms, offices, and small halls, fans and air conditioners are often left ON even when there are no people inside. This leads to unnecessary power consumption and higher electricity bills. Also, manually switching devices ON/OFF every time someone enters or leaves is not efficient. So, there is a need for an automatic system that can control fan and AC based on the number of people present in the room.

Schematic:

The system consists of two IR sensors placed at the entry and exit door. These sensors are connected to a PLC. The PLC is also connected to output devices like a fan and an air conditioner through relays or contractors. A display unit can also be connected to show the number of visitors inside the room.

LADDER DIAGRAM:

Solution:

The solution is to design a PLC-based visitor counter system. When a person enters, the entry sensor detects and increments the count. When a person leaves, the exit sensor detects and decrements the count. If the count is greater than zero, the PLC will turn ON the fan. If the count increases beyond a certain number (for example, more than 3 people), the AC will also turn ON. When the count becomes zero, both fan and AC will turn OFF automatically.

 

PLC Program (Ladder Diagram Description):

-  Use two inputs: I0.0 for Entry Sensor and I0.1 for Exit Sensor

-  Use one counter for counting number of persons

-  Increment counter on I0.0 signal

-  Decrement counter on I0.1 signal

-  If counter value > 0, turn ON output Q0.0 (Fan)

-  If counter value > 3, turn ON output Q0.1 (AC)

-  If counter value = 0, turn OFF both outputs

 

Explanation:

In this system, PLC plays the main role in controlling the entire operation. The IR sensors detect movement and send signals to the PLC. Based on these signals, the PLC program updates the count value using up and down counting logic. This count is then used as a condition to control output.

 

When at least one person is inside the room, the fan is automatically turned ON to provide ventilation. When more people are present, the temperature may rise, so the AC is also turned ON for better comfort. When all people leave, the system automatically turns OFF all devices, saving energy.

 

This system is very useful in real-life applications like classrooms, meeting rooms, and offices. It reduces human effort, saves electricity, and increases efficiency. The project also helps in understanding PLC programming, sensors, and automation concepts in a practical way.