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Anonymous users2024-02-06PLC is a programmable controller.
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Anonymous users2024-02-05The DDC is a direct digital controller, and the PLC is a programmable controller;
The basic application function program is solidified inside the DDC, and the basic application function can be completed without secondary development programming, and the secondary development application can also be carried out, and the basic application function program is not solidified inside the PLC, and all application function programs must be prepared by the user according to the requirements;
DDC can only complete the control of relatively simple control objects, simple to use, easy to maintain, PLC can complete ten complex field applications, learning, use and maintenance is also difficult;
DDC is a special controller to meet the needs of building automation BA system, mainly used to control air conditioners, valves and pumps in the building, PLC is to meet the needs of modern industrial automation FA can be used for logic control, process control and data acquisition of various complex machinery and equipment, production lines and test devices.
PLC can replace all the functions of the DDC system, and DDC cannot replace most applications of PLC.
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Anonymous users2024-02-04DDC can become a smart relay, PLC is the controller, that is, PLC as the main body, DDC is just a building concept with low safety performance for civil use, but its input can have analog, digital, and resistance functions at the same time, but there is no advantage over it, these PLCs can be achieved by selecting expansion modules. Therefore, DDC is a relatively low-grade relay type of equipment.
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Anonymous users2024-02-03DDC is actually a kind of PLC, DDC is more professional, but PLC should be able to achieve some professional functions through dedicated software modules. PLC originally appeared to replace relays, so the early PLC had poor processing ability for analog quantities, and the ability to regulate and control was not strong. DDC is designed to achieve some specific control functions from the beginning, so it is easy to use and more powerful for specific occasions.
But the current PLC has completely overcome the previous weaknesses. PLC also has the advantage that because it is originally designed for industrial environments, it has strong reliability and anti-interference ability, which is much stronger than that of DDCs, especially those used in building automation.
There are two kinds of general control, one is process control (such as various temperature control), this kind of control generally has little to do with time, one is mechanical control, relying on time to control (such as assembly line, etc.), DDC can only be used for process control and the switching output of DDC is only a relay, and most of the switching is transistor Due to factors such as **, and environment (the environmental requirements in the building control are not high), it is recommended to use a more professional controller - DDC.
**There are 3 control modes for the control of air conditioning and refrigeration system, the early relay control system, the direct digital controller DDC and the PLC (programmable controller) control system. Due to the high failure rate, complex system and high power consumption, the obvious shortcomings of the relay control system have been gradually eliminated, and the direct digital controller DDC has made great progress in intelligence. However, due to the anti-interference ability of DDC itself and the limitations of the hierarchical step-by-step structure, its application scope is limited.
On the contrary, the PLC control system has been gradually widely used because of its reliable operation, convenient use and maintenance, strong anti-interference ability, and suitable for new high-speed network structure.
DDC is actually a kind of PLC, but DDC is more professional, a lot of programs are solidified in DDC, when choosing according to the inherent program mode of DDC to compare with my actual application mode, if the two modes are the same, you can choose, if it is not the same, then you can not choose this kind of DDC, and PLC is different, as long as the hardware is satisfied, the software can basically be written freely according to specific requirements, that is to say, DDC is more professional, the scope of the program can be programmed is very small, And PLC can be written freely.
The DDC is called a direct digital controller, with a digital input and a high degree of integration. Stronger than PLC
PLCs are called programmable controllers, analog inputs, and have a lower level of integration than DDCs.
They can all be written. But DDC is a fixed mode.
It should be said that DDC is a developed version of PLC. Although this is not correct, it can be understood in this way, hehe!
DDC is easier to use than PLC, DDC software has a wealth of control modules, compared with PLC, it is like the difference between Windows and DOS. Moreover, many DDC software have PLC modules, and you can program freely like PLC in this module, without being restricted by software.
These two are mainstream PLCs, one made in Japan, one made in Germany, I have used both, both are very representative, it is recommended to learn both, you can learn Mitsubishi's first, because most of the programming methods of other brands of PLC are imitation of Mitsubishi, especially domestic brands, just like the Delta I use now, and Xinjie, which is almost exactly the same as Mitsubishi. Mitsubishi is what a traditional ladder looks like. And Siemens is also unique, although he also said that it is a ladder diagram, but his is a modular ladder diagram, which looks more intuitive than Mitsubishi's, and the step7 software is also very easy to use. >>>More
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