PLC

PLC is a highly practical technology, primarily serving industrial production, where reliability and stability are the most fundamental and crucial requirements.

Unlike computer programming, a well-designed PLC control system not only involves PLC programming but also integrates various peripheral devices such as inverters, servos, three-phase asynchronous motors, cylinders, hydraulic systems, proximity switches, encoders, and push buttons. Only by organically combining these peripheral sensors and actuators can the system function effectively. Therefore, a standalone PLC program holds no value. Similarly, a program sketched on paper or presented in a PPT is meaningless unless it is compiled in PLC programming software and downloaded to a PLC. After all, you are not Lin Zhengying; drawing a program on paper and sticking it onto a motor won’t make the motor run.

Thus, practical experience is vital for learning PLC. This contrasts with computer programming, where a computer alone suffices. For PLC learning, not only a computer but also physical devices are necessary, which can be a significant burden for beginners. Industrial products are not cheap, and after-sales service is crucial for them. Purchasing problematic products or causing damage due to various reasons can be quite troublesome.

Is there a solution? Yes, indeed. We can fully utilize PLC simulation. Simulation involves using software to virtually create a PLC to validate our programs. However, PLC simulation is not omnipotent. What can it do?

Learning Basic Elements of Ladder Diagrams

Ladder diagrams are the foundation of PLC, embodying the principles of PLC programming. For electricians engaged in equipment maintenance and repair in factories, ladder diagrams serve as the bridge between electrical control and automation. Elements like normally open/closed contacts, self-locking, interlocking, timers, and counters are the basics of PLC. No matter how complex a ladder diagram program is, it is composed of these fundamental elements. Mastering these elements is the first step. How to master them? Reading alone is ineffective; drawing on paper is useless. Practice is essential. How to validate our programs? Simulation!

For instance, using timers is a significant hurdle for many beginners. Timers can be fully validated using PLC simulation, even without an actual PLC.

Validating Programmed Code

Once we grasp the basic elements of ladder diagrams, we can attempt to write programs. No one starts by writing complex programs; it’s a gradual progression from simple to complex. Exceptions exist, but they are rare. Therefore, beginners should take a step-by-step approach. Making mistakes is not scary; repeating the same mistakes or being clueless after making them is. How to validate our programs? Simulation!

Through simulation, we can identify errors in our programs and gain a deeper understanding of the PLC’s cyclic scan principle.

Simulating Mathematical Calculations

Mathematical calculations are frequently used in PLC programming, as many process calculations require them. Some might dismiss the need for simulation in this area. This is a grave mistake. Computers differ from human brains; incorrect data types or variables in your program will yield incorrect results. Mathematical calculations are the easiest to validate through simulation.

Simulating Special Function Blocks

Certain functionalities can also be simulated, such as PID function blocks. Simulation can validate our settings and program correctness.

Simulation can resolve most of our learning queries. However, it is not omnipotent. For instance, edge triggering might not be simulatable on some PLCs, though such PLCs are becoming rarer with technological advancements.

Regarding servo control, simulation without actual servos can only validate the logic of servo control. Communication cannot be simulated, but various tools can aid in learning and troubleshooting communication issues, such as serial port tools. To some extent, PLC communication can be simulated. Siemens PLC’s TIA Portal, for example, can simulate network communications like TCP and S7, validating the structure of our programs. This is sufficient for beginners.

Simulating Inverter, Contactor, and Relay Control

Should we purchase inverters, contactors, and relays? It’s possible if you have the budget, but it’s not advisable. Buying these components is not cost-effective. Controlling these elements via an inverter essentially involves controlling output points. PLC simulation can fully simulate the control of these automation components.

What PLC can simulate are precisely what beginners should learn and master. What it cannot simulate is challenging for beginners to grasp. For example, communication and servo control are difficult to learn if you don’t understand ladder diagrams.