Basic types of PLC modules？

There are many types of programmable controllers, which can be classified in different ways.

4.1 According to the control scale points

Control scale mainly refers to the control of switching quantities into and out of the number of points and control of analog quantities into and out of the module, or both (closed-circuit system) the number of ways. But mainly to the switch quantity count. The number of analog channels can be converted into switching points, roughly equivalent to 8 to 16 points along the way.

According to the number of points, PLC can be roughly divided into micro-machines, small machines, medium-sized machines and large machines, super-large machines.

Micro-machine control points only a few dozen points, such as the V80 series PLC body from 16 points to 40 points, OMRON's CPM1A series PLC, Siemens Logo only 10 points.

Small machine control points up to more than 100 points. Such as the V80 series PLC of Dewson can be expanded to 256 points, OMRON's C60P up to 148 points, CQM1 up to 256 points. Siemens of Germany's S7-200 machine up to 64 points.

Medium-sized machine control points up to nearly 500 points, to a thousand points. For example, the PPC11 series of Dewson can be expanded to 1024 points, and the C200H machine of OMRON can reach up to 700 points in ordinary configuration, and the C200Ha machine can reach more than 1000 points. Siemens S7300 machine of Germany can reach up to 512 points.

Large machine: the number of control points is generally more than 1000 points. For example, the PPC22 series of Dewson can be expanded to 2048 points, OMRON's C1000H, CV1000, local configuration up to 1024 points. C2000H, CV2000 local configuration up to 2048 points.

Ultra-large machines: the number of control points can reach 10,000 points, to tens of thousands of points. Such as the U.S. GE's 90-70 machine, the number of points up to 24,000 points, in addition to the 8,000-way analog volume. Then the PC-E984--785 machine of the American Modicon Company has a total of 32k (32768) switch gauges and 2048 analog channels. Siemens' SS-115U-CPU945 has a total number of switch points up to 8k, plus 512 analog channels. And so on.

The above division is not strict, but only roughly, in order to facilitate the configuration and use of the system.

Generally speaking, according to the actual number of I/O points, where the above-mentioned different range, the choice of the corresponding models, the performance to price ratio is bound to be high; on the contrary, it must be worse.

Naturally, there are special cases. For example, the number of control points is not very much, not necessarily with the mainframe, but because of the special control unit of the mainframe, can be hot standby configuration, so the mainframe is used.

4.2 Divided by structure

PLC can be divided into two categories: box type and modular type. Micro-machines and small machines are mostly box-type, but from the development trend, small machines are gradually developed into modular. Such as OMRON, the original small machines are box type, and now the CQM1 is modular.

Box PLC power supply, CPU, memory, I/O system are integrated in a small box. A mainframe box is a complete PLC, and it can be used to realize control. Control points do not meet the needs, and can be connected to the expansion box, the main box and a number of expansion boxes to form a larger system to achieve more points of control.

Modular PLC is divided into several modules according to the function, such as CPU modules, input modules, output modules, power modules and so on. The module function of the large machine is more single, and thus the module type is relatively more. This can also be said to be the trend. At present, some medium-sized machines, the function of the module also tends to single, and the variety is also increasing country. Such as the same OMRON C20 series PLC, H machine CPU unit contains power supply, while the Ha machine is separated from the power supply, there is a separate power supply module.

Module function is more single, more varieties, can facilitate the system configuration, so that the PLC can be more useful, to achieve higher efficiency.

There are three methods of linking modules into a system by modules.

① no base plate, relying on the module interface between the direct connection, and then fixed to the corresponding rail. Dewson's V80 series PLC is this structure, more compact.

② with a base plate, all modules are fixed on the base plate. Such as the PPC11, PPC22 and PPC31 series PLC of Dewson, C200Ha machine of OMRON, CV2000 and other medium and large machines are this structure. It is more solid, but the number of slots of the base plate is fixed, such as 3, 5, 8, 10 slots, etc. The number of slots is not always equal to the actual number of modules, and there are inevitably empty slots in the configuration. This is not only wasteful, but also occupy more space, but also have to occupy the empty unit to fill the extra slots.

(3) Instead of a base plate, a rack is used, and all modules are fixed to the rack. This structure is more complex than the base plate type, but more secure. Some of the very large PLC with more for this structure.

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