PLC Programming Tutorial for Beginners

Programmable Logic Controllers (PLCs) are widely used in industrial automation systems to control and monitor various processes. They are robust, reliable, and easy to use, making them a popular choice for controlling everything from simple machines to complex industrial processes. In this quick tutorial, we will walk through a hypothetical real-world example of PLC programming for beginners.

Before diving into the programming aspect, it's important to understand the basic components of a PLC system. A typical PLC system consists of the following components:

PLC unit: The brain of the system that houses the microprocessor and memory.

Input/Output (I/O) modules: These are used to connect the PLC to sensors and actuators in the field.

Power supply: Provides power to the PLC and I/O modules.

Programming software: These are used to program the PLC.

In this quick tutorial, we will use a Siemens S7-1200 PLC, a simple and user-friendly PLC that is widely used in small-scale industrial applications. The software we will be using is Siemens TIA Portal, a powerful programming software that allows you to program, configure and diagnose the PLC.

The example we will be using is a simple conveyor belt system. The system consists of a conveyor belt that is controlled by a start/stop button and an emergency stop button. There are also sensors that detect if the conveyor belt is running, if there is an object on the belt, and if the belt is jammed.

First, we need to connect the PLC to the I/O modules. The I/O modules are connected to the PLC via a special cable called a Profinet cable. The I/O modules are used to connect the PLC to sensors and actuators in the field. In this example, we will be using a digital input module too connect the start/stop button and emergency stop button and a digital output module to control the conveyor belt motor.

Once the hardware is set up, we can start programming the PLC. The first step is to create a new project in TIA Portal and configure the PLC. In the PLC configuration, we need to define the type of PLC we are using and the type of I/O modules we have connected.

Once the PLC is configured, we can start programming. The programming language used in TIA Portal is called Ladder Logic. Ladder Logic is a graphical programming language that is easy to understand, even for beginners. It is based on the idea of electrical ladder diagrams, where contacts and coils represent the inputs and outputs of the PLC.

In the example, we will be using two programs, one for the start/stop button and one for the emergency stop button. The start/stop button program will monitor the status of the start/stop button and turn the conveyor belt motor on or off accordingly. The emergency stop button program will monitor the status of the emergency stop button and turn the conveyor belt motor off if the button is pressed.

To start programming the start/stop button, we need to create a new program in TIA Portal and add a rung to the ladder diagram. On the rung, we will add a contact that represents the start/stop button and a coil that represents the conveyor belt motor. We will also add a logic function, such as an AND function, to ensure that the conveyor belt only runs when the start/stop button is pressed and the emergency stop button is not pressed.

Once the program is complete, we can test it by simulating the program in TIA Portal. This allows us to see if the program is working correctly without having to physically test it on the conveyor belt system. After testing and making any necessary adjustments, we can then download the program to the PLC and test it on the actual system.

The emergency stop button program is created in a similar way. We will create a new program, add a rung to the ladder diagram and add a contact that represents the emergency stop button and a coil that represents the conveyor belt motor. We will also add a logic function, such as a NOT function, to ensure that the conveyor belt motor is turned off when the emergency stop button is pressed.

Once both programs are complete, we can integrate them into a single program that controls the entire conveyor belt system. We will also add additional functionality, such as monitoring the status of the sensors that detect if the conveyor belt is running, if there is an object on the belt, and if the belt is jammed.

In conclusion, PLC programming can seem intimidating at first, but with the right tools and resources, it can be quite simple. By following this real-world example of PLC programming for beginners, you should have a better understanding of how PLCs work and how to program them using ladder logic. The Siemens S7-1200 PLC and TIA Portal programming software are great options for small-scale industrial applications and are widely used in the industry. Happy programming!