How does a FC function work in Siemens PLC?

In this article, we will discuss FC Function in Siemens TIA Portal. FC Function is mainly used to create a certain logic which is repeated frequently in the PLC program.

Today, we will learn how we can create an FC function in the Siemens TIA portal and about the advantages of the FC function. For that, we will take an example of a simple motor starter.

FC Function is Siemens TIA Portal

Let’s create a Function in the TIA portal,

1. Open TIA Portal

2. Create a New Project

3. Click on Write PLC Program

4. Click on add new device and select a PLC controller.

5. Click on add new block.

6. Select a Function and name it. Here we are creating a function for motor starter, so we name it as Motor Starter. And then click on Add.

7. Add variables in the Function. Now for a simple motor starter, we have input-outputs such as Start, Stop as push-buttons, Safety as selector switch, Overload as thermal overload switch, and finally a contactor coil as motor output. So we need to add all the inputs and outputs as well as temporary logic bits used in the program.

8. The below images are showing the ladder logic of the motor starter.

Network 1: When the safety switch is in a normal position, it will give an indication that the motor is ready to start.

Network 2: Start logic for the motor.

Network 3: Stop logic for the motor.

Network 4: Motor overload logic.

9. The below image is showing the running stat of the motor.

10. The below image is showing the trip stat of the motor.

Advantages of FC Function in Siemens PLC

⇒ FC function has the main advantage that we can call it as many times as required, so a programmer has no need to write the same logic again and again in the main program.

⇒ Another advantage is that troubleshooting for the particular equipment is easy.

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