User:RolandWagnerKe/sandbox

A Soft-PLC or SoftPLC (programmable logic controller in software) consists of a PC - usually an industrial PC, embedded PC or box PC - a PLC software and the I/O modules or fieldbus extensions such as bus terminals.

Features

 * PLC depends on the operating system of the PC, often MS Windows with real-time extension, meanwhile also Linux with/without real-time extension.
 * possible failure in case of system crash
 * The PC CPU cannot be fully used for PLC functionality.
 * The Soft-PLC may require a real-time kernel operating system to control the computing time that the computer operating system (e.g. Windows) transfers to the PLC.
 * I/Os are accessed via plug-in cards with integrated I/Os or fieldbus connection, or via Ethernet-based fieldbus systems with industrial Ethernet.

Field of application
The Soft-PLC runs under a host operating system such as Windows, Linux or Unix and can therefore be operated like a computer. The Soft-PLC has many applications, especially in industry. Special small computers are often built on which a touch screen is mounted. With their help, processes can then be monitored at any time using appropriate software and, if necessary, rapid intervention can be taken. In addition, one has the possibility to design the circuits differently at any time.

A possible advantage compared to a normal PLC is that no additional PC or programming device is needed to change the programmed circuits, since the programming software and the control software may be located on one PC (usually only under Windows). In addition, maintenance is often considerably simplified thanks to the already integrated remote maintenance software. In addition, the available resources (CPU power, main memory/RAM, fixed memory/Flash or HD) are usually higher or significantly cheaper compared to dedicated PLC systems. Due to the system, however, such a system carries the risk that the entire control system may fail if any additional program fails. Therefore, these systems are not used in safety-critical systems. Nevertheless, they are used in many different areas of industrial automation technology, such as production systems, but are also popular for training purposes.

The applications are programmed in a similar way to a conventional PLC, usually in accordance with IEC 61131-3. With manufacturer-independent tools such as CODESYS, Soft PLC and conventional PLC can be programmed in the same way, thus creating a common code base.

Structure
A conventional PLC is constructed with elements (= modules), which are usually programmed with a computer or a special programming device. In operation, however, these controls run without this computer. An additional PC must also be used to implement process diagrams (visualization), which always show the current system status. With the Soft PLC, however, all these components are combined on one computer. One then simply controls a machine with this PC. In this way, very complicated circuits can be programmed and only very little space is required. Program changes can therefore also be carried out quickly and without much effort.