What are the characteristics of programmable controllers?

Programmable controllers are widely used, so they have great practical significance. We have heard of programmable controllers to some extent, but we may not know the major features of programmable controllers. In this article, the editor will introduce the four major features of programmable controllers. If you are interested in programmable controllers, you may wish to continue reading.

1. Rich in functions

The functions of programmable controllers are very rich, which is mainly related to its rich instruction system for processing information and internal devices for storing information.

It has dozens or even hundreds of instructions, and can handle a wide variety of logical problems and perform operations on various types of data. It can do everything that an ordinary computer can do.

Its internal relays are equivalent to intermediate relays, and there are more of them. One bit in the memory can be used as an intermediate relay, so how can there be more!

It also has many counters and timers, which is far beyond the reach of relay circuits. A small box or module can have hundreds or thousands of internal timers and counters. This is because as long as a word in the memory is used and some flags are added, it can become a timer or counter, so there are so many.

Moreover, these internal devices can be set to retain after power loss, or not retain after power loss, that is, to be cleared after power-on, to meet different usage requirements. These are also difficult to do with relays.

Its data storage area can also be used to store large amounts of data. Hundreds, thousands, or tens of thousands of words of information can be stored, and the data will not be lost after a power outage.

Programmable controllers also have a variety of external devices that can establish a friendly human-machine interface for information exchange. Programs can be entered, data can be entered, programs can be read out, and data can be read out. Moreover, reading and writing can be performed on a screen with both pictures and texts. After the data is read out, it can be dumped and printed. Data can be entered by typing, by reading cards, etc.

The programmable controller also has a communication interface, which can be linked or networked with a computer to exchange information with the computer. It can also be networked itself to form a larger and more geographically extensive control system that a single machine cannot have.

The programmable controller also has a powerful self-checking function, which can perform self-diagnosis. The results can be automatically recorded, which increases the transparency and convenience of its maintenance.

The rich functions make it possible for programmable controllers to be widely used; at the same time, they also create conditions for the automation, telecontrol and intelligent control of industrial systems.

A programmable controller has so many functions that other electrical controllers do not have; it is also incomparable to traditional relay control circuits.

2. Easy to use

It is very convenient to use a programmable controller to control the system. This is because: first of all, the control logic of the programmable controller is established by a program, which replaces the hardware wiring. Programming is more convenient than wiring, and changing the program is more convenient than changing the wiring!

Secondly, the hardware of programmable controllers is highly integrated and has been integrated into various miniaturized modules. Moreover, these modules are matched and have been serialized and standardized. The modules required for various control systems are mostly available from programmable controller manufacturers and can be purchased on the market. Therefore, the configuration and construction of the hardware system is also very convenient.

Because of this, the word "programmable" is used in programmable controllers. For software, its program can be programmed and it is not difficult to program. For hardware, its configuration can be changed and it is easy to change.

Specifically, programmable controllers are convenient in five aspects:

(1) Easy configuration: The control system needs to determine which company's programmable controller to use, what type, what modules to use, and how many modules are needed. Once determined, you can place an order on the market.

(2) Easy installation: The programmable controller hardware is easy to install and assemble. The external wiring has a connector, which is simple to connect. After it is connected once, when replacing the module, just install the connector on the new module without reconnecting. No internal wires need to be connected. Just make some necessary DIP switch settings or software settings, and compile the user program to work.

(3) Convenient programming: Although there are no actual relays, time relays, and counters inside the programmable controller, these devices do exist through the program (software) and system memory. The number of such devices is unimaginable in relay control systems. Even a small programmable controller can have thousands of internal relays, and hundreds of time relays and counters. Moreover, the contacts of these relays can be used an unlimited number of times. There are so many logic devices inside the programmable controller that users no longer feel any restrictions when using it. The only consideration is the input and output points. And even if these internal input and output points are used more, it does not matter. The number of control points of a large programmable controller can reach more than 10,000 points. How can there be such a large real system? If it is really not enough, it can be controlled through the network without any restrictions. The instruction system of the programmable controller is also very rich, and it can easily realize the control of various switching quantities and analog quantities. The programmable controller also has a memory area for storing data, which can store all the information to be saved during the control process. ...In short, due to the powerful functions of programmable controllers, the limitations on their role in control systems are no longer the programmable controllers themselves, but people's imagination or other supporting hardware facilities.

Programmable controllers have a wide range of peripherals, and there are many types of programmers, which are easy to use. There are also data monitors that can monitor the operation of programmable controllers. There are also many software for using programmable controllers, which can use not only ladder diagram languages ​​similar to relay circuit design, but also BASIC languages, C languages, and even natural languages. These also provide convenience for programming programmable controllers.

Programmable controller programs are also easy to store, transplant and reuse. Once the program of a programmable controller for a certain product is perfected, it can be used for all such products. Just make a copy for each unit produced. This is much easier and simpler than wiring and debugging each unit of relay circuits.

(4) Easy maintenance: This is because:

① The programmable controller works reliably and rarely fails, which greatly reduces the workload of maintenance. This will be further introduced when talking about the third feature of the programmable controller.

② Even if the programmable controller fails, it is very convenient to repair. This is because the programmable controller has many fault prompt signals. For example, if the battery voltage of the programmable controller that supports memory data retention is insufficient, there will be a corresponding low voltage signal indication. Moreover, the programmable controller itself can also record fault conditions. Therefore, if the programmable controller fails, it is easy to diagnose. At the same time, it is also very simple to troubleshoot after diagnosing the fault. The fault can be troubleshooted by module, and the spare parts of the module can be bought in the market, and a simple replacement is enough. As for the software, it will not fail after debugging. No matter how many more, just adjust it according to the use experience to make it perfect.

(5) Convenient for re-use: If a programmable controller is used for a certain device and this device is no longer used, the programmable controller used for it can be used for another device by simply revising the program. If the original device is quite different from the new device, some of its modules can be reused.

3. Reliable work

Using a programmable controller to control the system is very reliable. This is because the programmable controller has taken many measures in both hardware and software to ensure that it can work reliably. In fact, if the programmable controller does not work reliably, it cannot be used in an industrial environment and it will not be a programmable controller.

(1) In terms of hardware:

The input and output circuits of the programmable controller are electrically isolated from the internal CPU. The information is transmitted by optocouplers or electromagnetic devices. In addition, the CPU board has shielding measures against electromagnetic interference. Therefore, it can ensure that the program of the programmable controller is not affected by external electrical and magnetic interference and can work normally.

The components used in programmable controllers are mostly contactless and highly integrated. The number is not too large, which also provides a material basis for their reliable operation.

In terms of mechanical structure design and manufacturing technology, many measures have been taken to ensure that the programmable controller can work safely and reliably, which can ensure that the programmable controller is resistant to vibration and impact. The operating environment temperature can be as high as more than 50 degrees Celsius, and some programmable controllers can be as high as 80-90 degrees.