The article discusses the development of a software module for controlling electric drives as part of the ModBus industrial network, which was intended for modernize the automated control system of the production line section of the "Zarya" bakery plant. Frequency converters are used to change the speed of motors in the available control system, and the operator has to manually control each converter. The rotation speed of the motors is controlled by setting the frequency value, which is inconvenient for the operator. It is impossible to simultaneously change the operating speed of all production line equipment with this control method, which leads to mismatch in equipment operation. To solve this problem, a network is being built based on the ModBus protocol, based on available equipment. The article describes the main peculiarities of the ModBus protocol, developed method, that allows the operator to specify the required system run time instead of the frequency value for each motor, and developed software module, that implements the proposed method.

Keywords: programmable logic controller, ladder diagram, ModBus protocol, controlling without feedback, frequency converter

The article deals with the imported used in the educational process controllers replacement problem. There was a need to replace imported products with domestic ones due to the withdrawal of leading import manufacturers from the Russian market, so it seems reasonable to exclude imported equipment from the educational programs of universities. The course "Digital Automation and Control Systems" is based on the study of various industrial controllers. The first place among industrial controllers in SUAI is occupied by Siemens products, which officially left the Russian market. The question of searching for similar controllers of domestic production arose, at the same time, the manufacturer should not depend on the supply of imported components. Controller PR200 by OWEN was chosen as such a manufacturer. The article compares PR200 by OWEN with LOGO! by Siemens and comes to the conclusion about the interchangeability of these controllers in the educational process. The peculiarities, advantages and disadvantages of the development environments of both manufacturers are considered in the article. It also tells about the experience of using the stand based on PR200 in the educational process, therefore, the possibility of a complete replacement of LOGO! has been proved.

Keywords: programmable logic controller, programmable relay, functional block diagrams, specialist training, substitution of imported products, development environment

The article reveals the problem, that arises as a result of generalized training of specialists according to the International Electrotechnical Commission standard 61131-3. The standard regulates the languages in which software is developed for programmable logic controllers. Training according to the standard allows a specialist to work with any controllers developed by any manufacturers, the downside of which is an insufficiently in-depth studying of the additional potentials of controllers, that are typical for the models of the particular manufacturer. Further, we consider a number of specific special functions of the FBD language using the example of programmable relays LOGO! by Siemens, which are not typical for the other devices, that work in this language, then we observe the examples of using these functions in various technological processes. Also, we get to know the abilities to transfer the parameters betweenparts of the program by using so-called link and the features of the implementationof pulse-width modulation in LOGO! controllers.And finally,we comprehend methods of working with analog signals including analog calculations and the option of non-standard using of the minimum/maximum search function as a storage element.A lot of developers ignore similar functions, because they are not covered in the training courses. Using of special functions simplifies the development of programs and provides additional capabilities for the programmer.Therefore, the necessity of a deeper studying of the capabilities of a certain controller seems to be apparent.

Keywords: programmable logic controllers, functional block diagrams, specialist training, analog signal processing, rarely used functions