Microcontrollers and PLCs are widely used in industry. Because of their different characteristics, their work focuses are also different. Let's take a look at the similarities and differences between microcontrollers and PLCs in industrial applications.
About microcontrollers
A single-chip microcomputer integrates the basic components of an electronic computer, such as the CPU (also known as the central processing unit, mainly composed of an arithmetic logic unit and a control unit), memory, bus, and input/output interfaces, onto a single silicon substrate using integrated circuit technology. Because single-chip microcomputers are very small (about the size of a finger) yet powerful (possessing the functions of a simple computer), they are widely used as controllers in electronic devices. Currently, from large-scale defense weapons like missiles and rockets to small modern household appliances like televisions and microwave ovens, single-chip microcomputers are used as controllers in virtually every device. Therefore, from a control perspective, it is often referred to as a single-chip controller.
A microcontroller's operation relies on software, specifically a pre-designed program stored in memory. While the working principle of all electronic devices equipped with microcontrollers varies depending on the specific device, their fundamental principle remains the same:
1. Receive information from the outside world through the input interface and store it in the memory.
This information mainly consists of two parts: information from sensors such as temperature and pressure;
Manual information derived from human intervention, such as the operation of switches and buttons.
2. The CPU in the single-chip microcontroller performs high-speed calculations on the input data according to the program.
3. The results of the calculation and processing are sent to the control actuator, such as a relay, motor, or light bulb, through the output interface.
This process repeats continuously: the microcomputer in the system constantly monitors various information and takes timely actions to ensure the system operates normally...
About PLC
PLCs are products built on top of microcontrollers. A microcontroller is a programmable integrated chip. In other words, a PLC is made up of a microcontroller and peripheral circuits. Microcontroller development is low-level development, which is more complicated. Programming is done in assembly language or C language. For example, when programming a delay with a microcontroller, you need to calculate from the crystal oscillator. PLCs are different. Each manufacturer provides a programming software that can be programmed using ladder diagrams. Delays only require sending a number to the time relay.
PLCs are currently largely manufactured using single-chip microcomputers. It can be said that a PLC is an application of a single-chip microcomputer in relay control systems. The ladder diagram used by PLCs is similar to relay circuit diagrams, making it easily accepted by a wide range of electrical engineering technicians.
In summary:
1. A PLC is a product built on top of a microcontroller, which is an integrated circuit. The two are not comparable.
2. PLCs are more suitable for use in harsh industrial environments and are more stable, while microcontrollers have a higher operating environment.
3. In terms of programming languages, microcontrollers mostly use assembly language, while PLCs use ladder logic.
4. Microcontrollers can be used to construct a wide variety of application systems, from micro and small to medium and large. PLC is a special case of microcontroller application systems.
5. PLCs from different manufacturers share similar working principles, functions, and specifications, offering a degree of interchangeability and guaranteed quality. Furthermore, their programming software is moving towards standardization. This forms the basis for the widespread application of PLCs. In contrast, microcontroller application systems are diverse, with varying functions, inconsistent quality, and significant challenges in learning, using, and maintaining them.
Finally, from an engineering perspective, let's discuss the selection between PLC and microcontroller systems:
1. For single projects or projects with very few repetitions, adopting a PLC solution is a wise and quick approach with a high success rate, good flexibility, and fewer follow-up issues, but the cost is relatively high.
2. For large-scale supporting projects, using a microcontroller system has the advantages of low cost and high efficiency. However, this requires considerable R&D strength and industry experience to ensure the system's stability and reliable operation. The best approach is to embed the PLC functionality into the microcontroller system. This greatly simplifies the development time of the microcontroller system, ensures performance, and guarantees profitability.
