error-free, editable, and universally applicable databases of symbol, variable, or tag names. These are human-readable alphanumeric names assigned to the addresses of components (including PLCs) and improving upon the direct use of complicated register addresses — which was once standard practice. Complementing these sortable and searchable device tags are informative machine and workcell tags as well as those for common machine functions such as Auto, Manual, MotorOn, Fault, or Reset. Consider Siemens STEP 7 Totally Integrated Automation (TIA Portal) software, which includes various use-specific packages and is accessible through the Siemens SIMATIC (Siemens Automatic) software-management environment. STEP 7 software is convenient for illustrating the most common approaches to PLC programming, as it’s the most widely used software in the world for industrial automation — with copious verification of functionality and reliability. By most estimates,
legacy SIMATIC STEP 7 software to support the programming of S7-1200, S7-1500, and S7-1500 controllers — as well as ET 200SP I/O CPUs and legacy S7-300 CPUs (an enduring industry staple) along with S7-400 and SIMATIC WinAC controllers. Professional-grade and specially licensed copies of STEP 7 include additional functions, logic editors, and integration of traditional engineering software. Though beyond the scope of this article, it’s worth noting that industrial control alternatives to multi-function PLCs are configurable and programmable through complementary software. The vast ecosystem of Siemens controls provides copious examples.
1. LOGO! logic modules satisfy small and modest automation applications to bridge the gap between relays and microprocessor-based industrial controllers. They’re programmed via Siemens LOGO! software with Soft Comfort engineering software, a LOGO! Access Tool, and a LOGO! Web Editor for simple configuration and design operation 2. Process control systems employ Siemens SIMATIC PCS 7 controller products
Programming PLCs: A technical summary with Siemens examples
and complementary power supply modules, application-specific function modules, and digital as well as analog I/O modules. Of course, PLCs aren’t the only option for automation control. Relay-based systems maintain their indispensability in a vast array of applications, and programmable automation controllers (PACs) or industrial PCs (IPCs), as well as panel PCs (HMIs with control electronics), are other alternatives for many machine designs and systems needing varying degrees of distributed control. PACs and IPCs running industrial-grade Microsoft Windows OSs especially offer top design flexibility. Each of these control systems is configured and programmed with software of diverse sophistication to render all types of control design more advanced and user- friendly than ever. This in turn allows OEM machine builders and plant engineers to quickly institute system builds, upgrades, and migrations with maximal efficiency, productivity, and IIoT connectivity.
The tools to program controls — including PLCs Nearly all PLCs today are configured and programmed through PC-based software. Large vendors with broad programmable motion control, sensing, actuation, and machine-interface component offerings (in addition to general automation and PLC products) typically allow programming of all these components in their own proprietary unified programming environments — PC-based Windows-compatible software with design, configuration, programming, and even operating and management modules. That’s especially true where vendor lineups include pre-integrated offerings — such as smart motors or HMIs having PLC functionality, for example. While potentially daunting to learn, unified programming environments (once mastered) dramatically speed machine design. One benefit of such software environments is how they provide
Written by: Lisa Eitel, Contributing Author, DigiKey
programmable through SIMATIC PCS 7 system software
3. Rack (rail), panel, and box industrial PC (IPC) products
Programmable logic controllers (PLCs) are ruggedized microprocessor-based electronics essential to all modern automation, including: ■ The process-heavy industries of oil and gas, nuclear, steelmaking, and wastewater treatment ■ Industries with an emphasis on control of discrete tasks — including general factory automation, automated warehousing, packaging, food and beverage, and medical- device manufacture In these installations, PLCs are traditionally found on DIN-rail mounted or control-cabinet rack systems with slots to accept PLC modules (having CPUs to run logic and dispatch commands)
Siemens PLCs are employed in nearly one-third of all PLC installations worldwide.
With this software, engineers can create process control, discrete automation, energy management, HMI visualization, or simulation and digital-twin programming related to the functions of PLCs and other industrial controllers. For PLCs, Siemens’ STEP 7 (TIA Portal) engineering software evolved from
Figure 1: PLCs offer all the strengths of purpose-built hardware — including reliability. In contrast, PACs offer top flexibility. Some suppliers allow engineers to program both control types in the same unified software environment. Image source: Siemens
we get technical
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