Some comparisons between PLC and DDC in the field of building control

Abstract: Some comparative information of PLC and DDC in the field of building control is provided by excellent flowmeter and flowmeter manufacturers. There are many articles on the comparison of PLC and DDC on the Internet, because after reading most of the articles, I feel that PLC is good, people who sell DDC say that DDC is good... After an ABC is released tomorrow, everyone will say ABC is good. The following is an objective look at the difference between the status quo of PLC and DDC. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following are the details of some comparison articles between PLC and DDC in the field of building control. There are many articles on the comparison of PLC and DDC on the Internet, because after reading most of the articles, I feel that PLC is good, people who sell DDC say that DDC is good... After an ABC is released tomorrow, everyone will say ABC is good. The following objectively discusses the difference between the status quo of PLC and DDC! Regarding PLC and DDC, which application has more advantages in building automation system, the comparison is as follows: 1. Application field: DDC is developed from PLC, PLC is specially used in industrial automation, and almost all domestic applications The industrial production line control system, thermal power plant control system, and steel plant control system all use PLC systems. At present, a considerable number of building control systems also use PLC. Building automation DDC is developed by manufacturers from PLC according to the characteristics of building automation. The difference from PLC is only a part of the program is solidified in it, but it also lacks the flexibility of PLC and the ability to deal with complex electromagnetic interference environments. 2. Structural difference: After years of development, the current PLC is actually the same as DDC in terms of network. It also supports a variety of protocols. It is also a layered structure and can also realize point-to-point communication. Communication management can be carried out through the host computer. 3. Software features: The host computer software of the DDC system is mostly dedicated software. In fact, it is incompatible from another aspect. The software of each manufacturer is different, and many of them are in English, which is even worse for technicians. The beginning of a dream. The host computer software of the PLC system is not only a special software, but also a general configuration software. Now the domestic general configuration software is pure Chinese, and the configuration is flexible and convenient. The general configuration software can deal with complex industrial control systems, but what about building control in districts. Besides, whether it is the debugging of PLC system or DDC system, professional debugging personnel complete the configuration, and then train the owner to operate and manage, which is the same for the owner. In contrast, the configuration software can realize all the functions of professional software, but also It can realize many functions that professional software cannot achieve (such as high simulation interface, human voice alarm, user-defined functions, etc.). 4. Professionalism: Now many building control projects have applied PLC systems. Facts have proved that the above-mentioned DDC function PLC system can also be completed. The experienced PLC building control implementers have also accumulated all control process procedures, energy management and energy saving procedures. , and because it has source programs for all process programs, it can quickly make customized functions for different projects. Since there are ready-made process programs, the on-site debugging work is also very short, and at the same time, it will be more smooth than DDC debugging, because the DDC built-in program has only interface functions and is in a fixed format. , and it is uncertain whether it can be solved or not. 5. Scalability: Everyone knows that the PLC system is a universal and open system. At this stage, the TCP/IP protocol is used between most PLC systems and most DDC system operator stations, which can be accessed with a network. At present, the DDC system software charges expensive fees according to the number of users, which makes most of the completed building control systems want the sub-control operation station but dare not think about it! PLC system just has this advantage. 6. Safety: In fact, just imagine this problem: a thermal power plant is generating electricity, and suddenly a PLC module is broken. As mentioned above, the entire system must be shut down before it can be replaced. What would be the consequences? It might explode! Ha ha! It is much more serious than the consequences of building control! At present, the modules of many PLC systems are hot-swappable and hot-standby redundancy (for these functions, building control seems to have learned from PLC in recent years), PLC is developed for industrial environment, in complex industrial control environment The failure of the lower module or the shutdown of the system may cause major accidents or casualties, and the reliability requirements are higher than DDC! I don't know how the above statement came about. The PLC control core can operate reliably and fault-free in harsh environments for a long time. It is easy to wire, easy to maintain, has good isolation, and has strong corrosion resistance. It can adapt to a wide range of temperature changes. The mean time between failures (MTBF) is greater than 15 years. 7. Debugging complexity: PLC programming is now mostly used in ladder diagram language. This language is visualized, what you see is what you see, and ordinary electricians can learn it without English proficiency. The current PLC system is the same as the DDC system.All the systems can be fully debugged by a laptop and a network cable in a comfortable computer room.

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